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Darren Forbes . Richard FosberV . Ann Fullick Viv Newman o Roger Norris . Lawrie Ryans
STUDENT BOOK
OXTORD TINIVERSITY PRESS oxford university press is a department of the university of oxford. It furthers the University's objective ofexcellence in research, scholarship, and education by publishing worldwide.
oxford University
press
oxford
is a registered trade mark
of
in the uK and in certain other countries
Published in Malaysia bv Oxford publishing (Malaysia) Sdn. Bhd. (11750g4_D) 4 Jalan Pemaju ur/r5, seksyen ul, Hicom-Grenmarie Industrial park 40f 50 Shah Alam, Selangor Darul Ehsan, Malaysia oxford Publishing (Malaysia) sdn. Bhd. (1175094-D) is a subsidiary of oxford university press Text
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Darren Forbes, Richard Fosbery, Ann Fullick, Viv Newman, Roger Norris, and Lawrie Ryan 2013
Illustrations
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Oxford University press 2015
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20 I 7
First Edition published in 2018 Essential Science for Cambridge Lower Secondary Stage 7 Student Book was originally published in English in 2015 by oxford University Press, Great Clarendon Street, Oxford, OX2 6DP' United Kingdom with ISBN 9780198399803. This adaptation is published by arrangement. Oxford Publishing (Malaysia) Sdn. Bhd. is solely responsible for this adaptation from the original works.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system,-or transmitted, in any form or by any means, without the prior permission in writing of oxford Publishing (Malaysia) Sdn. Bhd. (1175094-D),or as expresslv permitted by law, by licence, or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, oxford Publishing (Malaysia) sdn. Bhd. (rr75094-D),at the address ab,ve You must not circulate this work in any other form and you must impose this same condition on any acquirer
ISBN 978 967 2Ir3 23 2
98765432r Tlpeset in 11 point Minion pro Regular Printed in Malavsia bv Herald Printers Sdn. Bhd., S.lrneo, Darul Ehsan
Although we have made every eflort to trace and contact all copyright holders before publication this has not been possible in all cases. Ifnotified, the publisher wiit rJcti4, any errors or omissions al the earliest opportunity.
Gontents ok
Chapter
l.l 1.2 1.3 1.4
1
r.t2
Science in Contextl The story of appendicitis Living and non-living things The characteristics of life Investigating living organisms
4
Looking at cells
9
The human systems The human skeleton Muscles and joints
Summary Summative Practice
,,
Louis Pasteur: the fight against
disease Summary Summative Practice
and disease
54 56
57
l3 t4 l6 18
l9 2l 23
24 26 28
29
32
for the future
32
2.2
Bacteria Protozoa
34 36
2.3
Fungi
37
2.4
Viruses
39
2.5
Micro-organisms and food
3.1
3.2
Investigating
60 62
habitats
52
64
Abiotic and biotic components 66 3.4 Grouping organisms 68 3.5
3.6 3.7
chains Foodwebs Food
70 72
Interactions between organisms 74 Scientific Inquiryl Biological
control 3.8 3.9 3.10
3.1I
77
Interdependence between organisms and environment Human effects on food chains
Adaptation for survival
3.12
Local and seasonal adaptations Adaptation for extreme
3.13 3.14 3.15
environments Underwater adaptations Pollutions Human population growth
Summary Summative Practice
Chapter
4
Variation and classification
78
80 82 84 86 88 90 93 95
96
100
Science in Context! Variety
moths
4.1 Classifications 4.2 Animal and plant kingdoms 4.3 Classifying animals 4.4 Classif ing plants Scientific Inquiry!
50
60
3.3
in
48
environments
field Habitats
43
46
Habitats and
in the
4l
M
3
Science in Context! Working
n
Science in Context! Medicines
production Scientific Inquiry! Probiotics 2.6 Micro-organisms and decomposition 2.7 Micro-organisms and disease 2.8 Micro-organisms and disease in animals 2.9 Micro-organisms and disease in plants 2.lO Louis Pasteur: decay and food production
Chapter
J
0hapter2 Micro-organisms
2.1
2.ll
Living things
Scientific Inquiryt Cells under an electron microscope 1.5 Cell specialisation ( 1) 1.6 Cell specialisation (2) t.7 Animal and plant tissues 1.8 Organs in humans and animals 1.9 Organs in plants
l.l0 t.l I
vl
4.5
Classification
variation Summary Summative Practice Species and
f 00
lO2 lO4 106 f 09
fI
I
ll3 ll5 115
Ghapter
5
demonstrations
5.1 Gases 5.2 Liquids 5.3 Solids 5.4 Classifying everydaymaterials 5.5 Substances and mixtures Scientific Inquiryl Matter Scientific Inquiryt Separation of plant pigments
5.6 Changes of state 5.7 Using models in science 5.8 Heating and cooling curves 5.9 Investigating water
5.ll
r18
r83
122 124 126
t28
l3l 132
r33 r35 137 139
r42
Physical and chemical changes
144
Summary Summative Practice
145
6
Ghapter
8
183
Earth
186
Science in Context! Finding
120
Investigating evaporation
Ghapter
l8l
Summary Summative Practice
Solids, liquids and gases 118
Science in Context! Amazing
5.10
7.8 Uses of neutralisation
out about
Earth
186
8.1 Investigating rocks 8.2 Tlpes of rock 8.3 Weathering of rocks
f88 f 90
193
Scientific Inquiry! Moving Types of soil Four spheres ofEarth Inside Earth
rocks f95
8.4 8.5 8.6 8.7 Plate tectonics 8.8 Volcanoes,earthquakes
196
and tsunami Disaster response Evidence from the past
203
Summary Summative Practice
209
8.9 8.f0
r45
f98 199
2Ol
206 207
2to
Material properties 148
Science in Contextl Developing a new
material
6.1 Materials and their uses 6.2 Physical properties of materials 6.3 More physical properties 6.4 Testing metals and non-metals 6.5 Data on metals and non-metals
148
t54 r56 158
Scientific Inquiryl Alloy and
their properties
r60
Summary Summative Practice
r6r
Chapter
7
Acids and bases
7.1 7.2 Bases 7.3 Making indicators 7.4 The pH scale 7.5 Investigating acidic problems 7.6 Neutralisation 7.7 Preparing common salt Scientific Inquiry! Salt crystals and red cabbage indicator
effects
Science in Contextl It's a
9.1 What are forces? 9.2 Frictional forces 9.3 Dealing with friction 9.4 Forces in balance 9.5 Gravity and weight
164 164 166 168
170 172 174
176 178
212
record!
212 214 216 218 220 222
Scientifi c In quiry! Magnetic
161
Science in Context! Acids and
health Acids
Forces and their
r50 152
suspension
9.6 Moving through fluids 9.7 Stretching and squashing 9.8 Measuring density 9.9 Upthrust, floating and sinking 9.f
0
224 225
))7 229
23r
Forces at work
233
Summary Summative Practice
235 235
Ghapter
10
Energy
transformations 238 Science in Context! An
r80
energetic
day
238
10.1 10.2 10.3 f
0.4
10.5 f
0.6
lO.7 10.8 10.9
Ideas about energy
240
Investigating the energy in food Elastic and gravitational energy Exploring kinetic energy Exploring energy
242
transformations Energy transformations in cell Sankey diagrams for energy transformations
247
Wasted energy
253 255
10.r0
Conservation of energy Energy efficiency
10.11
Reducing wasted energy
r0.r2 Producing electricity 10.13
The future of energy sources
Scientific lnquiryl Lemonade or battery?
Summary Summative Practice
Chapter
ll.l ll.2 11.3
ll.4
11
Earth and beyond
Science in Context! Resources in the Solar System Earth and the Sun Scientific Inquiryl Kepler's laws The Moon The Sun and the planets
Exploring the conditions on other planets
11.5
Beyond the planets f f .6 Changes in the model of the
Ghapter
2M 245
249 251
l2.l 12.2 12.3 12.4 12,5
257 259
12
Temperature and heat
Science in Context! Ocean temperature Temperature and scales Thermometers Thermal expansion Measuring heat energy Heat transfer Scientific Inquiryt The story of the vacuum flask
Summary Summative Practice
26r
292 292 294 297 300
302 304 306 307
308
263 26s 266 266
310
Scientific enquiry* Science in Contextl History
of
length measurement The skills of investigation (1) The skills of investigation (2) The skills of investigation (3) Scientific Inquiryl Common laboratory apparatus
310
319
270
Physical quantities Measuring length
272 273 275 279
Measuring area and volume Other measurements Scientific Inquiryt Archimedes and gold crown
323
327
Summary Summative Practice
328 328
270
283 285
3t2 314
3r6 3r8 321 325
Solar System
287
Glossary
331
Summary Summative Practice
289 289
lndex
351
*Note: Scientific enquiry should be taught prior to other chapters.
About this book Amazing Science 7 provides complete coverage of the Cambridge Science Curriculum Framework for Stage 7 andprepares students for Cambridge Lower Secondary Checkpoint. It incorporates the latest National Curriculum to provide support for both teachers and students to prepare for the Ujian Nasional (UN).
Learning outcomes Clearly stated at the start of each topic
... Practical activity To develop scientific
skills
Science in Contextl Spreads at the start ofeach chapter, to put learning into realworld or historical context and to challenge students to think about
wider issues Expeft tips To avoid l .h.v-r. nhh.!ho.g.3n\h' n -'l-''ra. I idrprarion, br lJUl nb". /,r. J.{i ill - i .tr''".11'.J you cn rr a cooil il( orwhs. rfd h,l i I \6 tphn,
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Science in Contextl
Medicines for the future
Key terms
Highlighted bold in text for each topic and defined in
bilingual Glossary vl
* Summary questions
,onrept
To test and consolidate students' learning after each topic
Outlines the key concepts
map
in the chapter
Scientific enquiry A special section designed to develop students' scientific skills. This section encompasses Practical activities and also covers scientifi c measurements
Scientific lnquiryl lLelated information to cultivate higher order thinking skills
Note: Scientific enquiry should be taught prior to other chapters
Glossary Key words arranged in alphabetical order with detailed explanations in both English andBahasa Indonesia
Science rn Context!
History of length measurement
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Each discipline in Science is colour-coded
Summative Practice Prepares students for the progression test and to introduce them to Cambridge Checkpoint and Ujian Nasional style questions
Summary Summarises important concepts in the chapter vtl
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tr ilm ffi
Science in Contextt The story of appendicitfls Sometimes things in your body go wrong. Adi has been admitted to hospital with a severe stomach pain. He could have fallen and hurt himself. He might have an infection which could cause sickness and diarrhoea. He could have problems with his liver or his pancreas. What is happening in Adi's body?
Your body contains many organ systems. One common cause of bad stomach pain is appendicitis. This is an infection in the appendix, a small organ in your digestive system.
large i
ntesti
n
e
) a.
This inflamed appendix will make
Adi feel very sick
quickly once their infected appendix has been removed. They just have to recover from the effects of the operation and wait for the cells of the body to repair the damaged tissues.
If the appendix is not removed in time, it may burst. The infection then spreads from the appendix into the tissues around the organs of the body. This is called peritonitis and it is very serious. The infection can spread quickly to the
.^,
A cross section of an aooendix with acute
appendicitis
The doctors will listen to Adi's symptoms. They will examine him carefully. They may test samples of his blood and urine to see if he has an infection. When they have decided he has appendicitis they will operate to remove the infected organ.
After that, a pathologist will look at the cells under a microscope to find out what was wrong. Young patients like Adi often get better very
?o
,'
Goncept map
blood and then to all the different organs of the body. It can make a person collapse and even die. So, it is very important to see a doctor if you have symptoms like Adi's.
We can treat diseases like appendicitis because we understand about cells, tissues and orqans in the body.
In this chapter you are going to learn about living organisms. You will discover the amazing world of cells through the microscope. You will look at how these cells work together to form the organs, which make up the bodies of the plants and animals around you.
Living and non-living things After this topic you should be able to: o state what a non-living thing is o differentiate between living things and nonliving things.
a
a a a a a
a
Dwi made a visit to Gong Cave in Pacitan, Indonesia during her holidays. She was fascinated by the stalagmites and stalactites in the caves. The stalactites form columns that hang from the ceiling of the cave while stalagmites are formed on the cave floor. Do you think stalagmites and stalactites are living things?
excretion growth movement nutrition reproduction respiration sensitivity
^.
Stalagmites and stalactites in Gong Cave, Pacitan, Indonesia
We are surrounded by living things and non-living things. Sometimes, it is difficult to differentiate between them.
All living things have seven characteristics in common. These are excretion, growth, movement, nutrition, reproduction, respiration and sensitivity. We say something is a living thing only when they show these seven characteristics. Non-living things do not show these characteristics. There are two q?es of non-living things. The first tlpe of non-living things refers to materials which originated from living things. For example, a wooden chair (a non-living thing) is made from a tree (a living thing). Petroleum, another non-living thing, is formed from organisms which died millions of years ago.
r
Amethyst quartz crystals are hardened minerals formed from non-living things
The second tlpe of non-living things refers to items that are derived from materials which were never alive. Examples of these are metals, sand and glass.
ls it alive? Collect three things from your school surroundings. Decide if they are living organisms or not. . Prepare a checklist like in the previous page and fill in the information. Look at the images below - they show living things (known as living organisms) several characteristics of living things.
.
-
which exhibit
Now try question 2from the Summary questions below.
Collect 10 items that you can find tn your classroom and draw a table that has all the seven characteristics of living things. Tick the items that exhibit anv of these characteristics and cross if they do not.
Summary questions
O
lmagine you are leading a team of scientists on a missiorr to Mars. You want to find out if there is life on the planet. What would you bring to help you with your
investigation? How would you decide if you had discovered life or not? How would you convince scientists on Earth that you had discovered life? Look carefullv at oictures
@
ano @.-Reterrins
to the key terms on page 4, decide which characteristics of life you can observe in each picture.
@
eroiplanted some seeds in his garden. Are they living or non-living?
Investigating living organisms After this topic you should be able to:
.
exptarn some ways
to demonstrate the characteristics of
o
. . . . .
ilving organisms list some of the work scientists do.
carbon dioxide observation oxygen record urea
To know if something is a living thing or not, you have to work like a scientist to find out. This means asking lots of questions and looking very carefully to make observations. Scientists look, smell, listen, take photos or record sounds as part oftheir observations. They also measure things. They carefully record their evidence. Then they try to explain what they observe as well.
Respiration Living organisms respire to get energy from their food. It means they often use oxygen to break down their food and produce energF. They produce carbon dioxide and water as waste products. They also produce heat. Getting rid of this carbon dioxide is also known as excretion. Carbon dioxide is a poisonous gas. If you bubble carbon dioxide through a colourless liquid like limewater, the limewater turns cloudy white. You breathe in and out thousands of times a day. Your body gets oxygen from the air you breathe in. What do you think happens when you breathe out? Think of a way to test your idea.
Growth and reproduction Carbon dioxide turns clear limewater cloudy
Living organisms take time to grow. As living things grow, they increase in body size, weight and number of body cells. Growth is an irreversible and permanent process. It changes your body shapes and functions. Growth rate can be measured by height and weight. In human beings, the stages of growth include infancy, childhood, adolescence, adulthood and old age. Reproduction also often takes a long time. It means an organism produces offspring and thus, ensures the continuation of their population. All living things reproduce in different ways. Plants, for example, reproduce through seeds, leaves and stems. Can you tell the difference between growth and reproduction?
Excretion Excretion means removing waste products from the body. Breathing, sweating and urinating are examples of excretion. We remove carbon dioxide and water vapour when we breathe out. When we sweat, we excrete sweat which consists of water, salt and urea. Excretion is important because it prevents the body from becoming poisoned.
Nutrition All living
organisms need to make or take in food for fuel. This fuel gives them energy. Animals cannot
make their own food.
So
they eat other organisms.
Plants don't eat food. They use light, carbon dioxide and water to make their own food. They produce glucose, and also oxygen as their waste product. They absorb minerals from the soil as part of their nutrition.
Some plants trap and digest animals. These plants cannot get the minerals they need from the soil, so they eat animals instead!
Summary questions
The importance of movement Movement is vital for living organisms to survive. For example, animals need to find food, shelter, and breeding partners. They must also avoid danger. Plants need as much light as possible to
@
now maKe your answer as scientific as possible.
Sensing the world around you All living organisms can sense if there are changes in their surroundings. When they do that, they can find food and keep out of danger. The main human senses are sight, hearing, smell, taste and touch.
Testing the connection between taste and smell Your sense of smell and your sense of taste work very closely together. You can taste things much better if you can also
smellthem. Plan and carry out a scientific investigation by using flavoured snacks or different tvpes of crushed fruit. In
to question 1 on page 6. Answer the same question again - but
make food.
.
rnint about your answer
the great migration, animals such as zebras and wildebeest miqrate
to find planLs to eat Carnivores such as crocodiles, lions and hyenas
@
nri kept a plant by the window in the classroom for a month. He watered it regularly. He put another plant in the dark for a month. In the end, the plant in the dark died. This proved that the plant needed light
to make food. His friend, Budi, did not agree. He did not think the investigation was very scientific.
(a) Why did Arithink that light is needed
(b)
migrate to follow their animal prey
(c)
for plants to make food? Suggest why Budi was right to think that the investigation was not scientific. Plan a more scientific investigation to show that plants need light to make food.
Looking at cells What is a microscope?
After this topic you should be able to:
o
set up a light microscope and use it to observe cells prepare an animal
.
Cells are very small. We need a special tool called a microscope to see them.
slide
.
name the main structures seen in an animalcelland plant cell under a light mrcroscope state the similarities between animal cells
o
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A water flea (inset) cannot be seen with our naked eyes but it can be observed under a light microscope
eyepiece lens you observe through here
-
is
praceo
the focus and
microscope makes small
bigger than they really are! We can use it to see living organisms or non-living things such as crystals that we could never
+L^
condenser - focuses light on the specimen
detail of the specrmen
armllimb
diaphragm - controls the amount of
where you hold and carry the mrcroscope
-
linh+ ra.ahi^^ +h-
specrmen
cip
mirror/light source
- to hold the specimen
- raflantc li^h+ t^ tho specrmen
in place base
- Keeps the -i-'^.-^^^ "+.hl-
A
things look bigger. It is rather Iike a complicated magnifiiing glass. It can make things look 4x, 10x, 100x or even 400x
lens that
stage - where microscope slide
,^^^
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magnifies the specrmen
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coarse focus knob - brings the cnariman
body tube
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*:, * A light microscope
see
just using our
eyes.
Light from the light source goes through the material you want to look at on your microscope slide. It travels up through the objective lens and the eyepiece lens until it reaches your eye. You see a clear, magnified picture of your specimen many times bigger than it really is.
How to use a light microscoPe? Handling a microscope is not hard, and the steps below can help you. Step
l:
Step
2: Adjust the mirror to allow light to
Place the microscope on a flat surface, with the mirror facing the light source. enter the microscope.
Step
3:
Step
4: Select the lowest power
Place the slide onto the stage.
objective lens. Step
5: Look into the
eyepiece
lens.
Step
6: Turn the coarse focus knob until the specimen can be seen clearly.
Step
. . o .
7: Turn the fine focus knob to obtain a sharp image.
cell
chlorophyll microscope starch
Preparing a slide of cheek cells Now let's use a microscope to observe cells, in this
case cheek cells.
The preparation of cheek cells and onion cells are almost similar except the use of staining agent. Methylene blue is used to stain cheek cells as this makes it easier to observe the nucleus. In plant cells, such as the onion, iodine solution is used because it reacts with the starch granules in the cells. That makes it change colour, and you can then see the plant cells through a microscope.
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Place the cover slip over the specimen gently
onto a crean
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Use filter paper to absorb any excess methylene blue
methvrene brue to
Animal cells Microscopes have made it possible for us to see the cells that make up animals and plants. If you Iook at one of the simple cells that lines the human mouth through a light microscope, this is what you see. cell membrane - this
nucleus - this is the control centre of the cell. lt contains all the plans for making
is
the outer layer
ofthe cell. Substances move in and out
through the membrane
new cells and new organrsms
cytoplasm - this is the jelly-like substance where all the important jobs of the cell are carried out, such as using the substances from food for growing
vacuole - tiny spaces containing air, fluid or food particles. Animal cells have many small vacuoles
l, Animal cell
Flant cells Many of the structures in
a
plant cell are the same
as
in an animal cell. However, there are some big
differences too.
nrtnnl:cm
vacuole - a membrane-lined space filled with fluid
nucleus
cell membrane
cell wall hr\/a
chloroplasts
-
plant cells '^h
cellulose wall around
-
them, which helps the plant to stay upright, gives shape and protects the cell
small disc-like structures found in
green plant cells. They contain a ^16oh
r t^r
^i^mon+
known as
chlorophyll
A
Plant cell
1',!
Which is which? These are pictures of animal cells and plant cells photographed using a powerful light microscope.
.
Can vou tell which cells are which? Then label the main parts of each cell.
1 00Ox
Summary questions
Modelcells
.
Plan and make a model of an animal cell and a model plant cell. What materials will you use?
ofa
O
vicroscopes have changed the way scientists look at the living world. Explain
Gomparison between an animal cell and a plant cell Animal cell
why they are so impodant.
@
Plant cell
Basic units in both organisms and carry out life processes
@
Has cell membrane, cltoplasm and a nucleus
Animal cell Not fixed
Shape
Does not have a cell wall Does not have
chloroplasts Chloroplast
Usually absent but if pr"r.rri, the vacuole is small Glycogen
Cellwall
granules
,
vacuole
Foodstorage
Fixed shape Has a cell wall Has chloroplasts to make food Has
a
large central
vacuole Starch grains
Explain the similarities and differences between plant and animal cells to someone who has not studied biology.
foot
at the animal
celland plant cell models that you and your classmates have made. Decide which models are the best and explain what makes them particularly good.
Gells under an electron mlGroscope l,ook at the two pictures of pollen grains. The second picture is observed through an electron it gives you a more detailed look at the pollen grains than the first picture.
rrricroscope. So
An electron microscope gives a more detailed image compared to a light microscope. Thus, it is widely used by researchers to observe specimens. An electron microscope has a higher magnification irnd resolution power so researchers can see the finer details of cells and micro-organisms.
.r.
rr
Pollen grains under a light microscope (left) and an electron microscope (right)
chloroplast
Golgi apparatus
ritochondrion
ribosome
vacuole
lrrcncnma
rough endoplasmic reticulum
centriole
cytoplasm
nucteotus
cyroprasm
cell wall nucteus
r;ell membrane
smooth endoplasmic reticulum
cell membrane
mitochondrion
Animal cell
Plant cell
This is a diagram of an animal cell and a plant cell observed under the electron microscope. Can you explain the functions of these structures?
Gell specialisation After this topic you should be able to:
. .
explain how cells, tissues, organs and organ systems are arranged give some examples of specialised animal cells.
(1 )
Single cells are very small, often only about 0.0l mm across. Some organisms are made up of single tiny cells. We say they are unicellular. Bigger organisms such as human beings, trees, insects and mosses are multicellular. This means they are made up of many cells. For example, you are made up of billions of tiny cells all working together.
The cells that make up a body are not all the same. They are specialised to do different jobs. Nerve cells for example, carry
electrical messages
to the brain and
throughout the body.
Specialised cells have different features so they can do a particular
. . o . .
multicellular organ specialised tissue unicellular
job in the body.
Gell organisation Lots of specialised cells of the same type working together make up a tissue. A tissue carries out a special job in the body. Muscle tissue for example, contracts and relaxes for our body movement. Several tissues working together in the body form an organ. For example, muscle tissue works with other types of tissues to form the stomach, an organ. Sometimes several different organs work together to carry out a specialised job in the body. This is called an organ system, such as the digestive system and the excretory system. Organ systems are needed to form complex organisms.
Specialised animal cells When cells become specialised to carry out one job, they look very different compared to the simple animal cell you looked at on page 11. Look carefully at the cells and you will be able to see how they have changed to carry out their special job.
.r.
Cell organisation begins with cells tissrres oroans apl systems to form organisms
nucteus
Muscle cells relax
- Contract and
to enable movements of
different parts of the body
'|4
Bone cells - Suoport the softer tissues and orovide ooints of attachment for muscles.
short strands of cytoplasm (dendrites)
energy released here
head contains hydrolytic enzyme to enter the egg cell (ovum)
long strand of cytoplasm
tail (flage lum) propels through f uid
carries genetic
(axon/
(
Nerve cell (neurone)
t^-
information in the nucleus
A ^^-,^ ^^il L^^ ^ rurrg A I rerve Leil r rds d
to transfer eiectrical messages around the body.
axon
The dendrites connect to many other nerve cells.
cell membrane
no nucteus/ so short life
- Carries genetic information to the egg. It is specialised to move to the egg cell with its tail and the energy-releasing middle region, and then to break into the egg with its head Sperm cell
flexible shape to pass through small spaces
Summary questions
O
tO
(b) biconcave shape increases surface area to transport oxygen
r
Design a cellthat is
good at storing fat. Label it to explain the specialised structures. Design a cell
that is good at detecting light.
cytoplasm contains haemoglobin, which carries oxygen
Label it to explain
the specialised structures.
Red blood cell -The special shape gives a large surface area so oxygen goes into the cell. No nucleus to make more room for the special red pigment (haemoglobin) that rransporrs oxygen.
(c)
Use the Internet
or other books to look up fat cells and light-detecting cells, and see how
cilia beat to move fluids
wellyour design compares to what the real cells look like.
@
Oraw a table as below ano compare nerve, sperm and red blood cells.
nucleus
Ciliated epithelial cells - These cells are covered with tiny, hair-like cilia which beat to move things in the body, for example mucus from the lungs They use lots of energy.
15
Cell specialisation (Z) After this topic you shoutd be able to: give some examples of specialised plant cells
. .
explain how specialised plant cells are grouped together to make tissues and organs.
Specialised plant cells These strange looking plant organs carry out special jobs. The pitcher plant traps insects while the mangrove roots absorb air and water into the trees. These plant organs are made of cells organised into tissues. Several
speciarised
tirro", work togeth& to fo._
the organ. For example, the roots contain transport tissue made up of xylem and phloem cells as well as supporting tissue.
Mangroves
Cells for making food The process where plants make their own food is called photosynthesis. In the green parts of plants (the leaves and the- stems) many of the cells have special green structures called chloroplasts that carry out photosyntltesis. The green substance in these structurts, chlorophyll, capturer"light energy from the Sun, which is used Uy ihe plant to ma'ke sugar (glucose). Plant leaf cells containing rots of chloroplasts make specialised palisade tissue, which ii where most of the
photosynthesis takes place. vacuoie supports and stores nutrients
Pitcher plant
chloroplasts
ce tl
trap light
membrane
c.) C), C--cytoplasm
-r, A leaf cell 16
O cellulose cell wall for support and shape
Drawing cells Here is part of a plant leaf and a plant root under a light microscope, The cells are stained
(coloured)to make them show up more cleady.
. . .
Make careful drawings of a palisade cell from a leaf and a root hair cell as seen through a light mtcroscooe. Label as many things as you can. Look at the diagrams of the leaf cell (on the previous page) and the root hair cell (below). What don't you see in these micrographs?
Summary questions
@ r
Light micrograph of a plant (x
200)
leaf I
microscope and saw the green chloroplasts. She also looked at onion cells. Even though the onion cells had no chloroplasts she coulo still see that they were plant cells and not animalcells. (a) What are the main differences between plant and animal
Light micrograph of a plant root (x 15)
Root hair cells You find root hair cells close to the tips of growing roots. Plants need lots of water and minerals for growth. The root hair cells help them absorb water. They give the plants microscopic 'hairs' on the roots so there is a very large area ofroot surface that can take in water. Root hair cells are always found close to the transport tissue in the roots so the water can be carried up to the rest of the plant.
cells?
(b) Why do you think there are chloroplasts in some parts of the plant and not in others?
large surface area helps efficient
-
^L-^-^+i^^
dissolved substances help draw water into
-
the root
@ nucleus
.^, A root hair cell
The guard cells
- are kidneyshaped cells that control the size of stoma (opening) by changing its shape. They regulate water loss in plants. Guard cells
Siti observed the cells of a plant leaf under the
cyroprasm
vacuole
chloroplast
n
ucle us
Sore plant cells
are
adapted for taking in water from the soil and others are adapted for photosynthesis. What other types of cells might be needed in a plant? Can you find out about two more specialised types of plant cells? (Hint: moving substances into leaves or around the plant.) 17
Animal and plant tissues After this topic you should be able to:
o .
state the role of tissues in cellorganisation give some examples of animal and plant tissues.
. o . .
Tissues are built from individual cells which are similar in structure
and in function. Examples of tissues in humans are epithelial tissues, nervous tissues and muscle tissues, while vascular tissues, ground tissues and epidermal tissues are found in plants. Nervous tissues sense stimuli and send impulses to different parts of the body as a response. Impulses are electrical signals. Nervous tissues control and coordinate activities of the body. This tissue makes up our brain, spinal cord, and nerves.
impulse phloem stimuli xylem
epidermis cortex
A
Nervous tissues made from many neurone cells
The contraction
of
muscle tissue enables movement. The
movement may involve the whole body or part of it. The three types of muscle tissues are smooth muscle, skeletal muscle and cardiac muscle.
skeletal muscle
Vascular tissue consists of *yle- and phloem. Xylem transports water and minerals from the roots to other parts of the plant. Xylem also supports the plant. Phloem transports
Summary questions
@
whichis more complex:
@
npart from transporting
food from the leaves to the roots and stems.
Ground tissues consist of parenchyrrra tissues, collenchyrna tissues
^.
Vascular tissue (xylem and
phloem)
and
sclerench).ma tissues. These tissues store food. They also provide support to the plants.
cardiac muscle
human tissues or plant tissues? Explain your answer.
water and mineral salts, xylem also supporls the plants. How does xylem do that?
Organs in humans and animals After this topic you should be able to: give the positions of
. .
.
the main organs in the human body explain the functions of the mdn organs in the human body.
Humans, like lots of other animals, have many different organs inside their bodies. Plants have many different organs too. Each organ has a particular job to do. Your heart is an organ that pumps blood. It is part of your circulatory system, which transports substances all around your bodv.
Seeing inside your body Organs can be observed by cutting open (dissect) the body like the frog below. By using special machines, doctors and scientists can now see inside the human body without cutting it open. Look at the photo below of a magnetic resonance imaging (MRI) scan of a human body. What can you see?
dissect
lung
hea
11
liver pancreas
gall bladder small intestine
stomach
large intestine
A
urinary bladder
Organs {ound in a dissected frog
L An MRI scan 19
The main human organs MRI scans are not always easy to understand. However, if you know the main organs in the body, you will find it much easier to see what is going on when you look at the scan!
brain
-
controls the activities of the body
aorta
-
trachea
carries blood around the body
-
carries air in and out of the lungs
lungs
-
air is breathed in and out to give oxygen for respiration and get rid of
vena cava - carries blood back to the heart
carbon dioxide heart pumps blood to the lungs to take up oxygen and then pumps blood to all the organs ofthe body
-
liver
stomach
-
-
breaks down poisonous chemicals
breaks down food
pancreas helps break down fats
kidney
Summary questions
-
makes urine and balances the mineral salt and water content in blood
O
Make a list of attthe organs you can identify on the MRI scan using the information from the diagram of the human body.
@
Using the diagram of the human body, and
small intestine breaks down food and takes it into the blood
-
any other resources, oraw separate diagrams of the large intestine takes water back into the body and gets rid of waste
-
20
respiratory system, the circulatory system, the digestive system and the excretory system.
F
Aftar thic innin rrnr
r
should be able to: . give the position of the main organs of flowering plants - the t^^.,^^
^+^mil, ttjdvUJ, JLUt
. .
o .
. .
r'^^+^
TUULJ
Wherever you live, plants will be part of your life. People eat plants, wear materials made from plants and build houses from plant materials such as wood. All flowering plants have some structures in common.
Although plants from around the world may look very different, they all have the same plant organs.
and flowers explain the functions of the main organs of flowerrng plants make careful observations and drawings.
flower leaf root stem
D:to
Orchids
Flowering cacti
wlltin
a Photo'
n:lmc
ldentifying the main organs of a plant Collect four different complete plants from your school garden. Make sure you have permission from an adult to dig up the plants. Gently wash the soil off the roots. Spread each plant out on a piece of paper and identify the main organs. . Draw each of your plants and label the organs. o Compare the size and shape of the same organs in different plants.
Plant organs What the organs do Each plant organ has a job (function) in the plant. That is how a plant carries out the functions of living organisms. The organs of a plant keep growing all through the plant's life.
.
Leaves make food in a process called photosynthesis (see page 16). The leaves are usually green. The chloroplast traps the sunlight which the leaves need to make food. The leaves are often big and flat so they capture as much light as possible. They also let the plant take in oxygen and release carbon dioxide at night. They are therefore important for respiration, excretion as well as
photosynthesis.
.
Flowers are the reproductive organs of the plant. They may be sensitive to light and close up when it gets dark. The stem supports the plant. It holds up the flowers so that insects or the wind can bring pollen into them. The stem also holds up the leaves to the Sun so they can make food. The stem is sensitive to light and it moves by bending so that the leaves are exposed to as much light as possible. The roots grow into the soil. They hold the plant in the ground. They take up water and minerals from the soil, which the plant needs to make food. The roots may store food to help the plant
reproduce.
(
The structure of a flowering pl ant
Summary questions
O
Not allthe ptants have flowers. Explain why.
@
Sometimes the organs of plants look very strange. lt is because they have special functions in the plant. For example, the spines on a cactus look thin and hard. In fact they are leaves which help the plant
to lose less water. They also protect it from being eaten. Can you think of three really unusual plants from your country and explain the functions of their special or unusua organs.
n
I
I
I 22
rThe human systems After this topic you should be able to:
o .
state the roles of systems in humans give some examples of human systems.
When a few organs work together to perform a certain function, it is called an organ system. The systems work independently and together to form a functioning human body.
( Nervors
brain cninal
bones
system Coordinates and controls nerve
rnr.l
activities and responses.
nerves
( sk"l"t"l system
. . . . . .
(r rnnartc
circulatory system digestive system excretory system nervous system organ system respiratory system
lver
omach large ntesti ne smatl I nIesIt ne Tectum i
tha
body and provides movement.
Circulatory system Transports food substances, oxygen, carbon dioxide and waste products in
)
Respiratory system Supplies oxygen to
the body
the body and removes carbon
dioxide
Summary questions un nary
O
*nu
@
suppose one system fails, what do you think
bladder
o.
Digestive system Breaks down {ood molecules to produce nutrients.
(
Excretory system Removes waste products such as carbon dioxide, urea, water, mineral salts
do tissues usually consist of similar cells whereas the systems are made up of different organs?
happens to the rest of
the body?
The human skeleton After this topic you should be able to:
. .
r o o
explain how the skeleton gives the body supporl, protection and movement name the main bones of the body.
All living organisms move, including people. We are vertebrates with a bony skeleton inside our bodies. We use that skeleton to help us move about.
Inside the body To see the bones inside our bodies we use X-ray photographs. X-rays go straight through the soft parts of our bodies. So on X-ray photographs only the hard bones can be seen.
skeleton vertebrate X-ray photograph
cranium (skull)
cl avi cl e
(collar bone) hu merus (upper arm bone)
-^^^,,t(s ho u lder blade)
steTnum
(breast bone) rib
vertebral column
X-ray pictures let us see the bones inside a living body
(backbone) - made up of lots of small bones called
vertebrae pelvic girdle carpa
ls
(wrist bones) pnaranges (finger bones)
femur (thigh bone) patella (kneecap)
tibia (shin bone) fib
u
la
(calf bone) tarsals (a nkle) pna ranges
Itoes)
r
The human skeleton
Broken bones Look carefully at these two X-rays.
Summary questions
t
Try and work out which bones have been broken in each one.
. .
Make a sketch and labelthe broken bones. Explain how you decide which bones were broken.
Here are some names of the bones in the body. Use them to
answer the ouestions.
ribs
thigh bone backbone (vertebrae) shin bone skull toe bones
(a) Which parts of the (b)
skeleton hold the body upright? Which parts of the skeleton protect delicate organs?
The skeleton is not one single large bone. It is made up of lots of smaller bones with joints in between them. Explain why this is important.
What does the skeleton do? The skeleton does three main jobs:
. . .
it supports the body it protects delicate organs it is jointed so we can move easily.
We all need a strong support system to hold us up. Otherwise we would be giant, rubbery blobs! The bones of the skeleton are hard and strong so they can protect vital organs from being damaged.
We need protection for the delicate parts of our bodies, such as our brains and our hearts. Strong, bony'cages' like the skull and the ribs give us the protection we need. We need to be able to move about quickly and easily. The place where two bones meet is called a joint. The joints between the bones mean the skeleton allows us plenty of movement, as well as support and protection.
@
eaoies and small children have bones that are more flexible than those of an adult. This makes it possible for them to keep growing. (a) Apaft from making
growth possible, why is it a good thing that the bones of small children are quite flexible?
(b) Adults would not get on very well if their bones were as flexible as those of a small child. Why not?
Broken bones If you fall badly or meet with an accident you may break a bone. A broken bone hurts and it does not support your weight. However, broken bones do get better. Ifthey are kept still for several weeks, your body makes new bone tissue, which heals the break. A plaster or splint is put around the broken bone to keep it still as it heals. 25
I
Uuscles and ioints After this topic you should be able to:
. .
explain how the joints make it possible for you to move explain how the muscles work against each other (in antagonistic pairs)to move the bones of the
The bones of the skeleton can move, but only if you make them. The bones inside your body move thousands of times a day. Pick up your pen and lift it up to your shoulder. Which bones did you move?
Muscle power
skeleton.
a a a a
a
antagonistic muscles contract relax synovialfluid tendons
humerus
u
Riranc
enntran+c
lna
ra,hila
triceps relaxes. The biceps exerts a pulling {orce on tendons to raise the radius. The lower arm is raised
To move our bones we need muscles. Athletes train to get big, strong muscles which are easy to see, as in the photo above. Most people cannot
see their muscles quite so clearly! Muscles are bundles offibres which can contract or shorten. Each end of a muscle is joined to a
Triranc
nnntrrrtc
while biceps relaxes. The triceps exerts a pulling force on tendons to move the ulna down The lower arm straightens.
forearm straightens
26
different bone by non-stretchy tissue called tendons. When a muscle contracts. it shortens to pull a bone into a different position.
Your muscles can only pull - they cannot push the bone back to where it came from. A different muscle must contract to pull the bone back. While the second muscle contracts, the first relaxes. Muscles that work in pairs like this are called antagonistic muscles because they work against each other. ( Antagonistic
muscles working in the arm
Muscles and movement Try the arm movements shown on page 26. See if you can feel your muscles as they shorten
and stretch. o Which other parts of your body are moved by pairs of muscles working like this? Make a list of all the pairs you can think of.
Joints and movement Bones cannot be bent without being damaged. Wherever two bones meet, there is flexible connective tissue which allows movement. These places where a bones meet are called joints.
There are two tlpes of joints in our body called immoveable joints and moveable joints. The immoveable joints are found in our cranium bones and do not allow movements.
If the joint is able to move back and forth, like a hinge on a door, it is known as a hinge joint. It can If the joint can move in a circular motion in all directions, like in your shoulders and hips, the joint is known as a ball-and-socket joint. be found in your elbows and knees.
Summary questions numerus
ligaments - to hold the bones of the joint together so they move slowly
O
the diagram of joint into your book. "oOU a Label each paft of the joint and describe what it does.
cartilage .r,
synovial
fluid
Harir notices that the muscle which lifts his arm up (his biceps) is bigger than the muscle which pulls his arm down (his triceps). Can you think of a scientific explanation for this?
@
Make a poster to show the structure of a joint, the way it works and what happens when it goes wrong. Work in groups - each group can find out about a different joint.
ulna
A synovialjoint, a structure of a moveable joint
The ends of your bones are covered with tough, rubbery cartilage to protect them. In places where the bones move a lot, such as your hips, knees and elbows, you make synovial fluid. This fluid cushions and lubricates the joint. It makes sure that the bones move smoothly without grinding against each other - it is like oil
in the engine of
@
a car!
If the joints become damaged or diseased it is very painful to move. Some joint problems such as arthritis are more common in older people as all the tissues of the joint suffer from wear and tear with time. 27
ti
I
Sum ffiry All living things move, take in or make food, respond to changes in the world around them, grow, reproduce (produce offspring), get rid of waste products and get energy from their food. Non-living things do not have characteristics
such as excretion, growth, movement, nutrition, reproduction, respiration and sensitivity.
Plants use carbon dioxide, water and light to make their own food. Animals have to eat other organisms, either plants or other animals.
Bespiration releases energy from food. lt also produces carbon dioxide. you can bubble the carbon dioxide through clear limewater and it willturn cloudy.
A
microscope has an eyepiece lens, a stage, a clip to hold the specimen in place, an objective lens, a mirror or light source and focusing knobs. you need a microscope to look at most cells. A simple animal cell has a nucleus, cell membrane and cytoplasm.
A simple plant cell has a nucleus,
cell membrane and cytoplasm as well as a
cell wall, chloroplasts and a permanent vacuote.
A plant cell has cell wall, chloroplasts, a large vacuole whereas an animal cell does not.
T
I
I 5
28
Cells often become specialised
a
to carry
job in the body; for example, in animals: red blood cells, out
particular
white blood cells, nerve cells; in plants: leaf cells, root hair cells, guard cells. Tissues are important as they form one of
the building blocks in organisms. The main organs in plants are the roots, stems, leaves and flowers.
Organ systems in mammals include the resprratory system, the digestive system and the excretory system.
Systems are composed of organs which come together to make the entire human body function well. The human skeleton is made up of many bones. lt supports the body against gravity, protects the delicate organs and allows movement.
The joints allow the bones to move smoothly. They have specialtissues such
as cartilage, which absorb shocks and cushion the bones.
Muscles are special proteins, which contract and pull on the bones, making them move. Muscles can only pull in one direction so they are found in pairs that work against each other.
Summative Practice Mark(/) for non-living things and (,x)for
(c) The increase in size of the chicks. (d) Parent birds diving for fish. (e) Chicks opening their mouths when
living
things.
they
hear the parent birds approaching the
(0
nest.
Young birds making energy available the muscles to flap their
5
wings.
in
t6l
Fill in the parts of the microscope with their
functions.
t5l
Why are icicles not considered as
things?
living n
l
The seven characteristics of living things are defined below. Write the correct characteristics.
t4l
Definition
Number the correct seouence on how to use a mrcroscope.
(a) Breaks down food, releasing its energy,
Look into the eyepiece lens
(b)
(c)
often using oxygen Changes the position of all or part of the body Increases in size and stays larger
(d) Makes and removes waste
Adjust the mirror to allow light to enter the microscope Turn the fine focus knob Place the slide onto the stage
products
from the body
(e) Makes more of the same by producing
0
tr T tr tr T
offspring Makes responses to changes in the surrounding environment
Turn the coarse focus knob
t5l State one difference in preparing animal cell slides and plant cell slides. Explain your
answer.
t2l
Match the cells with the correct functions.
(g) Obtains from the surrounding sources the energy and chemicals needed to make bodies move or qrow
o Allow movement
t7l
A scientific expedition travels to a remote island to investigate birds' life. For each ot the following, state one characteristic of living things which is being shown by the birds. (a) Nest building. (b) Parent birds bringing food to their chicks.
(b)
a
Provide
supporr
t2l
ldentify the tissues based on the statements.
(a) This tissue senses stimuli and sends impulses to different parts of the body as a resoonse b) This tissue enables movement (c) This tissue transports food and water in olants (d) This tissue produces food and provides suppoft to the plant t4l
ll
10
(a)
Arrange the following from smallest to laroest:
HUman cell
Match the labelled parts of the cells with the following structures. You may use each name once, more than once or not at all.
t3l
(b) Which
of the following are plant organs?
tsl
11
(a)
13 (a)
What is the meaning of the term organ?
t2l
Copy and complete the table to compare plant and animal cells. You may use ticks ano crosses.
(b) This is an MRI scan of a oaft of the human
bodv.
(c)
see.
List the organs that you can t3l State one function of each of the following organs:
t5l (b)
Use the information in the table to draw a Venn diagram to show the features of plant cells and animal cells. Your diagram will look like this:
t6l 12 The diagrams show a plant cell from a leaf and a human cell from the inside of the mouth.
Plant
cell
Animal cell
The features that are found in both olant and animal cells will be in the middle where the two circles overlap. t1l Plant cell
A. Support and protect the organs B. Contract and relax to provide movements
Copy out this list of specialised cells. red blood cell, white blood cell, root hair cell, muscle cell, leaf cell, nerve cell
Match each cell
to a function from the
C. Transport oxygen in the body D. Receive and transmit nerve impulses
list
below. Provide your answers in a table form.
o .
18 The diagram shows two types of cells. Which of the followino statements is correct? L
protects the body against diseases carries electrical messages from the brain to the muscles carries out photosynthesis absorbs water and mineral nutrients carries oxygen around the body contracts to move parts of the bodv
o . . o
[1]
t6l t
5
(a) One of the functions
of the skeleton is to
Both cells have cell warr Starch is the food reserve found in cell K c. Chloroplast is only found in cell L D. K can make its own food but L cannot
A. B.
protect the body. Name the parts of the skeleton that protect the following parts of the body:
(i)
heaft and lungs
(ii) brain
cord
tll t7l
(iii) spinal /b.) State trruo other functions of the skeleton.
\"/
19 The diagram shows a system in the human oooy.
r2l
(c) What advice would you give to someone who has broken a
bone?
t3l
(d) What do you call muscles that work (e)
in
pairs against each other? tll Joints are found where two bones meet. Explain the way in which the following help movement at joints. muscles, tendons, ligaments, cartilage, synovial fluid
AJ
t5l
16
\N
Name the system. Respiratory system
A. B. Muscular system
The statement below shows the function of a part of a light microscope.
C. D.
A lever that controls the amount of light reaching the
specimen
Blood circulatory system Skeletal system
t1l
20
Which part of the microscope best fits the r^locnrintinn ahnrra?
A. Condenser B. Diaphragm C. Body tube
D. Fine focus tube 17 The diagram shows a structure of cells found in a human body. Which of the following is the function of the cells shown?
The diagram shows a structure in the organisation of human cells. Which of the following has the same level of cell organisation?
A. Ovary B. Stomach C. Parenchyma D. Pancreas
t1l 31
Micro-organisms and disease
Science in Contextl
Medicines for the future Scientists are always looking for chemicals that can kill bacteria, viruses or fungi but would not harm people. That isn't easy at all. Scientists have to make careful observations and ask the correct questions. They do experiments
to see if they are right and collect evidence to show to other scientists. They then develop explanations that can convince other people about their ideas.
Below are some examples of the way scientists are looking for new chemicals to
.
kill bacteria:
Many antibiotics, such as penicillin,
Scientists also want to know what diseasecausing bacteria need to live and grow. Then they use computers to try and design new chemicals that will stop the bacteria growing or kill them.
Fish have slime on their bodies and that protects them from infections. If they lose their slime, their scales get infected very quickly. Scientists have observed this and are investigating different chemicals from fish slime which may kill bacteria.
are
made by mould (fungi) that are found in the soil. So, scientists are looking into soil to see if there are moulds to make new chemicals that can kill bacteria.
The white disc on the agar contains a chemical (antibiotic) that kills the bacterial colonies in the Petri dish
I
*
a
tt
af it
tl
&
.
I't'ople in ancient Egypt used honey to help lrt'irl wounds. Modern scientists have found llrcrc are chemicals in honey which stop irrl-cctions caused by bacteria. Some honeybirsed medicines are now used in hospitals. Screntists hope to make more and better nredicines from honey.
.
Crocodiles live
in filthv water.
fight and bite each other. Although their teeth are dirty, the bites don't get infected. Scientists have looked at crocodile blood and found a chemical that kills a wide range of bacteria. They are working hard to see if this can be made into an antibiotic medicine to cure people with bacterial infections.
Thev often
In this chapter, you will explore the link between micro-organisms and disease, including the work of the famous French scientist Louis Pasteur. You will also be looking at the importance of microorganisms in food production and in the natural decay process.
Goncept map
Bacteria Decay and food Decomposition
production (Pasteurisation)
Protozoa
Viruses Animals
Plants
Fight against diseases
Bacteria After this topic you should be able to: . label a diagram of a bacterium . explain that bacteria are living organisms . list some of the ways bacteria affect people.
Organisms are classified into five main groups called kingdoms. These are Monera, Protista, Fungi, Animalia and Plantae.
your classmates. You may see plants and animals. But there are millions of tiny living organisms you cannot see. These are micro-organisms'
When you look around you can
see
Micro-organisms exist in two forms: unicellular and multicellular.
Unicellular micro-organisms are formed from a single cell whereas multicellular micro-organisms are made up of many cells. Bacteria, protozoa, fungi, viruses and algae are various tlpes of micro-organisms. Micro-organisms are sometimes called
o . . . .
microbes for short.
bacteria
colony culture kingdom micro-organisms
What are bacteria? The kingdom Monera include bacteria and the blue-green algae
(cyanobacteria). Bacteria are some of the smallest of all living organisms and come in various shapes and sizes. About 100 of the largest bacteria lined up would just about stretch across this full stop. You cannot see individual bacteria without using a microscope. Each bacterium is a single cell, hence they are unicellular organisms. Bacterial cells look different from plant and animal cells. They don't have a proper nucleus. Instead they have a loop in the cl.toplasm that carries all the information about how to make a new cell (the genetic information). Bacteria often have other small pieces of genetic information called plasmids. Bacteria are living organisms. They take in food and respire. They excrete carbon dioxide and other waste products. They can grow and reproduce by simply splitting in half (binary fission). If they have all the things they need, some bacteria can split in half every 20 minutes. Some bacteria even have flagella to move themselves about.
Useful and harmful bacteria Some bacteria cause diseases in humans and other organisms such as animals and plants, for example:
. .
Salmonellabacterta cause stomach upsets. Bean blight disease in plants is caused by bacteria.
cell membrane slime capsule cell
wall
plasmids
Many bacteria are harmless and some are very useful to us. For example:
.
cytoplasm
genetic
decay the bodies of
Bacteria in our guts and on our skin help to keep us healthy.
. We use bacteria to
material
34
to
dead plants and animals.
.
A A bacterial
Bacteria help
cell (74000x)
make
yoghurt, wine and vinegar treating human sewage.
as
cheese,
well
as
for
Plant and animal cells What do olant and animal cells look like under a microscope? . Work in small groups. Draw and label an animal cell and a plant cell to remind yourselves of what they look like Now compare your drawings with the typical bacterial cell in the previous page.
Growing bacteria If you grow bacteria on special jelly (agar) that contains all the nutrients they need, they form colonies. These
colonies are big enough to be seen without a light microscope. This makes it easy for scientists to see if a chemical will kill disease-causing bacteria. But take great care when you culture bacteria and follow these instructions carefully to avoid any risk from harmful bacteria:
)
Growing bacteria in the laboratory
Summary questions Sterilise the inoculating loop used to transfer micro-organisms to the agar. Heat the inoculating loop in the flame of a Bunsen burner until it is red hot and then let it cool. Do not put the loop down or blow on it as it cools.
U,
Dip the sterilised loop in a suspension of the bacteria you want to grow. Use lt to make zig-zag streaks across the surface of the agar in a Petri dish. Replace the lid on the dish as quickly as possible to avoid contamination.
@
Bacteria grow fast when they have just the right conditions. Write a plan to investigate the best temperature for bacteria to grow as fast as possible. You could present your plan as a series of drawings or as a flow chaft.
@
fh"
Seal the lid of the Petri dish with adhesive tape. This is to prevent micro-organisms from the air contaminating the culture or micro-organisms from the culture escaping. Do not seal all the way around the edge so oxygen can still get into the dish. This is to prevent the growth of harmful bacteria that do not need oxygen.
Make a table to compare a bacterial cell with a plant cell and an animalcell. You will need four columns one for each type of cell and one for the features you are companng.
-
diagram of the bacterial cell on the previous page is 74 000 times its actual length. Calculate its actual length and show your working.
Protozoa After this topic you should be able to:
.
o
recognise and name protozoa
describephagocytosis in Amoeba.
Protozoa are unicellular micro-organisms that are not visible to the naked eye. These organisms belong to the Kingdom Protista. They live in soil, water and even in organisms like us! Some hunt other micro-organisms such as bacteria for food. That is why they are called protozoa which means 'little animals'. Protozoa with chlorophyll like Euglena can make their own food. Protozoa can cause diseases as some of them are parasites. This means they live on and feed off other organisms. Protozoa reproduce by duplicating their contents and splitting into two identical organisms (binary fission).
a a a
phagocytosis protozoa pseudopodia
Amoeba Amoeba is a protozoa that has no fixed shape and looks like a blob of jelly with a dark speck inside it when observed through a microscope. The jelly is the cytoplasm and the dark speck is the nucleus. The cltoplasm can be pushed in any direction that the Amoeba wants to create pseudopodia, the 'false feet'. The pseudopodia are used to move and engulf food in a process called phagocytosis.
contracti e vacuote I
I
Amoeba approaching bacterium
.^.
-^.
The pseudopodia surround the
bacterium
Some common protozoa found in the environmenr
36
Food vacuole formed,
the bacterium is diqested and absorbeo
Summary questions What is the mdn difference between protozoa and algae?
Protozoa and disease Malaria is a global life-threatening infectious disease common in tropical countries like Asia and Africa. Malaria is a mosquitoborne infectious disease caused by Plasmodium,aWe of parasitic protozoa. The parasites are spread through the bites of infected female Anopheles mosqttitoes. It affects humans and other animals.
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@
What are the characteristics of protozoa that make them look like animals?
(9
Wny do cows need protozoa in digesting their food?
Fungi After this topic you should be able to: . explain that yeast and moulds are types of fungi . describe yeasts and
We do not need a microscope to all micro-organisms. Certain
see
fungi are called microorganisms while others can grow very big indeed!
moulds.
a a
fungus (pluralfungi) hypha (plural hyphae) yeast
Fungi destroy millions of tonnes of food around
the world every year
This puffball is a very large fungus. The apple gives you an idea how larqe it is
Finding out about fungi You will probably have seen fungi in market stalls or growing wild or as part of your food. Mushrooms and puffballs are the parts that the fungus uses for reproduction. Most of the rest of the fungus spreads out in the soil as very thin,
thread-like structures called hyphae. Many fungi are very useful to people. However, all fungi get their food from dead or other living organisms and so some of them cause a lot of damage. They digest crops and food and make them rot. There are many types of fungi. Some fungi are unicellular such as yeast and the rest are multicellular like bread mould. Th.y usually need moist conditions to grow. The cells of these fungi can be seen under the microscope. You will see that they look very different both from plant and animal cells and from each other.
Yeasts Yeasts are single-cell organisms. They are found all
around us. They often grow on the skins of fruits, feeding on the sugar in the fruit. They usually respire using oxygen from the air, but they can respire without oxygen too. Each yeast cell has a nucleus, cltoplasm and a membrane with a cell wall around it. They reproduce by budding, with a
small new yeast cell forming from the old one following diagram and photo.
as
you can
see
in the
There are many types of yeasts. People have used some types of yeast for centuries to make bread and drinks such as beer and wine. But some yeast cells can also cause diseases of the skin, the lungs and the brain.
-1.
Yeast cell
Scanning electron micrograph of yeast cells (1 5 000 x)
Moulds Moulds are very different from yeasts. They are made up of tiny, thread-like structures called hyphae. Hyphae are not individual cells. Look at the structure of a mould hypha in the following diagram. See how it differs from the structure of the yeast. Moulds need oxygen to respire. They get their food by digesting it outside their bodies and then taking in all the substances they need. This is why mouldy food goes very soft as it is being digested. Moulds reproduce, but they do not split into two. They make little fruiting bodies that are full of spores. Each spore can grow into a new mould.
cytoplasm
r 38
Mould hyphae
nuclel
Summary questions
O
tul
(b)
lU
Explain how we can tellthat fungi are living organisms. Draw a table to compare yeasts and moulds.
Moulds can make
food go bad. What conditions do moulds need to grow?
@
Vou want to study some yeasts or moulds under a microscope. How would you do it?
@
Wfrat is the actual diameter of the yeast cells shown in the photo? How did you arrive at the answer.
Viruses After this topic you should be able to: . describe the structure of a virus explain what a parasite is
Imagine a micro-organism that doesn't respire, feed, move, excrete or have any sensitivity, but can reproduce by taking over other organisms. It sounds unbelievable but this is what viruses do.
What is a virus?
explain why viruses are effective parasites.
a a a
acquired immune deficiency syndrome (AIDS) human immunodeficiency virus (HlV) leprosy parasite virus
Viruses look like something from outer space
^. A virus is incredibly small, about 0.000 l mm long. Viruses can reproduce, but only inside the cells of another living organism such as an animal or a plant. Viruses are unlike other living organisms. They don't respire or move themselves, feed or excrete. Under powerful electron microscopes, viruses can be seen as strange shapes, which are made of protein and genetic material. genetic material (not in a nucleus) ta il
sheath
tail fibres prorern coaT
.f.
The structure of viruses
Viruses and disease All viruses cause diseases in living organisms. Diseases caused by viruses include colds, influenza, chickenpox, measles, polio and
HIV (human immunodeficiency virus) infections or AIDS (acquired immune deficienry sydrome). Viruses cannot move themselves from one organism to another but they have found different ways of spreading around. For example, the virus that causes the common cold spreads when people cough or sneeze.
(
A single sneeze like this releases millions of viruses into the airfor other people to breathe in - and catch your coldl 39
Make a virus! Work in a group. Look for different images of viruses on the Internet or in books. Choose one virus and find out what it looks like and what disease it causes. Plan to make a model to show the structure of vour virus. Make vour model and oresent it to the class.
Viruses are parasites Viruses are parasites. A parasite is an organism that takes what it needs to live from another living organism known as the host. A parasite always hurts its host, and sometimes it will even kill the host.
Apart from viruses, other parasites include:
. . .
animals, such as tapeworms and threadworms bacteria, such
fungi, such
as
Mycobacterium leprae, which causes leprosy
as Candida,
which causes thrush.
Most parasites rely on their host for food, and sometimes protection. Once viruses get into the body they invade the cells.
Summary questions
The protein coat of the virus often stays outside the cell but the
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vo, may need to do
genetic material is injected through the cell membrane. The genetic material of the virus then takes control of the nucleus of the host cell. It uses the host to make lots of newviruses. Eventually the cell bursts and releases all the new viruses. These then spread through the body and infect more cells. They can also leave the body and infect someone else.
people think that viruses are not living organisms?
Scientists have developed antibiotic medicines which can be used to cure diseases caused by bacteria. However, we do not have
some research to answer this question. State the range of lengths in millimetres of the following:
medicines which can destrov viruses vet and so we cannot cure viral diseases.
virus, bacterium, animal cell, plant cell
@
@
t
€
.t
Draw a diagram, chart or make some models to compare the sizes of the different cells in question 2.
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Wf'y are drawings and photos of microorganisms always magnified? What is the magnification of the virus (left) shown in the illustrations on page 39? Show your working.
synthesis of virus mareflats
insertion of genetic material into host cell
@
@
attachment
Virus reproduction in a host cell
Micro-organisms and food production After this topic you should be able to:
.
. .
. . . .
explain how yeast is used in the production of bread explain the way bacteria are used to make yoghurt and
Every time you eat cheese, yoghurt or bread you are eating foods made using micro-organisms.
Bread making with yeast If
yeast cells have air, warmth and plenty of sugar, they will respire and growvery quickly, making
ANAACA
lots of carbon dioxide as
make conclusions from data collecteo in an investigation.
waste product. For thousands of years people have used this
curds lactic acid whey yoghurt
a
method to make bread that is light and airy. Flour, sugar, yeast and some water or milk are mixed together to make dough. The r dough is kept somewhere warm to rise.
The yeast in this naan bread makes it rise when it is being baked
As the yeast respires, the carbon dioxide bubbles make the dough get bigger. Its texture gets lighter.
When the bread is baked, the bubbles ofgas get bigger and the dough rises even more.
Yoghurt-making using bacteria Yoghurt is a creamy solid made by mixing bacteria with warm milk. The bacteria feed on the sugar in the milk and make a chemical called lactic acid. This gives the yoghurt its sharp, tangy taste. The lactic acid causes the milk to clot and,solidiff int*.goghRrt, gn+ the a9!iog".of.,fh9. bacteria also gives it a smooth, thick texture. Once the yoghurt-forming bacteria have acted on the milk, they stop other bacteria from growing, so the milk doesn't go bad. Many different animals including camels are used for milking. lf the right bacteria are added, the milk soon turns into' . ,
yoghurt 41
Keeping milk good Ordinary milk goes bad in just a few days. On hot days, it turns bad even fasterl Yoghurl lasts mucn tonger. Set up a investigation to show how yoghurt-forming bacteria keep milk good for a long time. o Prenare two test tr rbes. Measure out 10 cm3 of milk into each test tube. Label the tubes 'Milk - room temperature' and 'Milk - cool'. . Prepare another two test tubes. Put 10 cm3 of yoghurt into each test tube. Label the tubes 'Yoghurt - room temperature' and 'Yoghurt - cool'. . Place one milk and one yoghurl test tube at room temperature on the side of your classroom. . Place one milk and one yoghurt test tube in a cool place, such as in a fridge. . Observe all the test tubes every day and record the appearance and the smell of the contents. Once they have gone bad, throw them awayl Do not taste the milk and yoghurt . Display your results and conclusions. used in your experiment!
Using bacteria to make eheese Cheese is made by the reaction of certain bacteria with milk. It changes the texture and taste and also preserves it. Some cheeses can last for years.
Summary questions you place a @ lul lfhroad elnr rnh in
The bacteria used in cheese making produce a lot of lactic acid. This makes the milk separate into a very solid part (curds) and a Iiquid part (whey).
The curds can be used fresh, often with herbs and seasoning added. They can also be mixed with salt and other bacteria, or even moulds. They are then pressed and left to dry out. These hard cheeses can last a very long time.
(b)
remperaTure on
the bacteria that
Sometimes moulds are added to cheeses. or the cheeses are wrapped in the leaves of different plants. Both the moulds and the leaves sive the cheese extra flavour.
are used to make bread. Describe iho inrractinafinn
@ v
In cheese making, solid curds are made by the action of bacteria on milk The curds can be eaten fresh or turned into hard cheeses usinq more bacteria and salt
the fridge or if you bake immediately after making it, it will not rise. Why do you think that happens? You want to find the effect of
Wort< together in a
group and frnd out how people make cheese or yoghurt. Make a poster to explain the process. You could use your nna+ar tn nnntraci
home production with industrial production using informatron from websites.
What do yoghurt, tempe, cheese and miso have in common? They contain friendly bacteria known irs probiotics which help to flush out harmful micro-organisms that can cause infections in our i ntestines. 'Ihere are millions of micro-organisms in our gastrointestinal tract. Some of these bacteria are good bacteria. They keep our intestines healthy.
Eating fermented food has many benefits. These beneficial bacteria control the harmful microorganisms in the body and make our immune system stronger.
a
Apart from strengthening the immune system, these bacteria also improve the efficiency of the digestive tract. If we get food poisoning or diarrhoea, these good bacteria would be flushed out. So it is a good practice to take probiotics after that.
The idea of eating food with friendly bacteria is
new. Yoghurt, for example was used by nearly all the people who kept animals for milk. History shows that even as early as 1500 B.C., people in India were using yoghurt in their cooking.
, not something
drt'
We all have these friendly bacteria in our bodies. When we were born, we swallowed them as we were coming out of our mother's birth canal. Later, we got more of them from our mother's milk.
Today, we don't have the same number of these friendly bacteria in our bodies. It could be due to stress or infections in the bowels. However. we can increase these friendly bacteria by taking yoghurt, cultured drinks and probiotics. *#
43
Micro-organisms and decomposition After this topic you should be able to: . describe how microorganisms break down the remains of animals and plants
.
.
explain how decomposition by micro-organisms can be both useful and harmfulto people record observations over time.
. o .
compost decomposers sewage
What happens to a piece of fruit if you leave it too long before you eat it? It will be covered in mould and, in time, the mould will break it down completely.
Decomposition in nature Living things are always taking in materials from the world around them. Plants take minerals from the soil. These are then passed on to the animals that eat the plants. If this goes on for years and years, the resources of Earth would soon be used up! However, the mineral nutrients in the bodies of dead animals and plants, and in animal droppings, are released back into the soil by the action ofmicro-organisms. These microorganisms are known as decomposers. .l
Micro-organisms, such as this mould, quickly break down a piece of fruit
Decomposers feed on waste droppings and dead organisms. They break them down (digest them) and use some of
the nutrients to grow themselves. They also release waste products. These are nutrients broken down into a form that plants can use. When we say that things decay, they are actually being broken down and digested by these micro-organisms.
(
In a cycle of life and death, the decomposers break down dead organisms and return nutrients
' to the soil
The effect of temperature on the decomposers Work in groups to find out the effect of change in temperature on the micro-organisms that decompose living organisms. . Each group collects either whole fruit, or some plant wastes, for example fruit and vegetable peelings, grass cuttings, fallen leaves. . Divide the material into three plastic bags and lightly tie the top of the bag (black plastic bags are accepted as well). o Put one bag in the fridge, one somewhere where the temperature is about 20 oC and the last bag somewhere hot, where the temperature is about 30 "C or higher. . Open and observe the organic material after one day, three days and one week. Record your observations (photos are a good way to do this). . Compare your results with the rest of the class and make your conclusions about the effect of temperature on the rate of decomoosition.
Using decomposers The number of people in our country keeps growing. People produce a lot of bodily wastes. The more people there are, the more waste is produced! Whether we use a pit latrine or have flushing toilets and a sewage system, we rely on micro-organisms to break down our sewage and make it harmless to us and to the world around us. People also use decomposers to break down vegetable waste, dead plants and grass cuttings. They turn this waste into a rich brown substance, which is added to the soil to help plants grow bigger and better. This partially decayed material is called compost.
Decomposers as destroyers Decomposers break down dead organisms. They
Summary questions
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fo
/:\ \u
trxprarn wny tr ts so
@ will also break
down things we need. Bacteria and fungi destroy crops in the fields. They also decompose millions of tonnes of food every year. If we can stop micro-organisms from decomposing the food we want to eat, there would be more food for people in the world.
make the best compost you need warmth, moisture and oxygen. Explain why a these are needed.
impoirant that microorganisms break down waste material and dead bodies in nature. Read the Practical activity instructions carefully. Suggest what you should do to make this investigation a fair LUJ
T.
45
Microcan
After this topic you should be able to:
. .
rent able
explain how infectious diseases are spread explain how the body defends itself against
How it makes people feel
diseases. Nose, throat
. r o
Tired, with
a
headache, blocked nose
cilia infectious disease white blood cell
Infectious diseases Many diseases are caused by micro-organisms such as bacteria and viruses. They can make people feel unwell and even kill them.
Bacteria and viruses cause diseases such as tonsillitis anc tuberculosis. Th"y can get into your body through openings such as your mouth and your nose, or through cuts in your skin. Once inside they attack the cells of your body and you begin to feel unwell. But most times you don't stay ill for ever. That is because your body has its own natural defences against the micro-organisms that cause disease.
First line of defence
r
- don't let thema in!
This Salmonella bacterrum has been magnified thousands of times. Salmonella bacteria cause food poisoning
Your body works hard to prevent disease-causing organisms from getting in. Your skin covers and protects most of your body tissues. Micro-organisms getting into your mouth go straight into
ca
the acid of your stomach! The easiest place for micro-organisms to enter is your respiratory system, when you breathe air right into your lungs.
in your nose filter the air you breathe in. Also, many micro-organisms get stuck in the mucus produced in your respiratory system. The mucus is then removed by the action of cilia found on special cells (ciliated epithelial cells) that line the The hairs
airways leading to the lungs.
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o
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L)
eiliated eolr rmn:r enithelium
r Ciliated epithelial cells are ideally sr/ited for the ioh thcv have to do
lhe cilia beat to move the mucus carrying dust, bacteria and viruses away from the lungs. The cilia in your respiratory tract are beating all the time but you don't notice them. However, you see the results of their efforts when you have a cold. What happens then? When you cut yourself, your body can be attacked by all micro-organisms around you. Your blood clots to form scabs to help cope with this danger. These scabs:
. . .
stop your bleeding stop micro-organisms from entering let new skin form underneath, hence, protecting you from any further invasions.
$eeond line of detence rmwaders
- destroy the
When bacteria or viruses enter your body, cells in your blood will take over the defence. Your body has an army of white blood cells, which engulf and destroy the bacteria or viruses.
Summary questions
O
When you get an infection your body makes lots of extra white blood cells. They are made in special glands in your neck and other places around your body. This is why when you are ill, you often have swollen glands. The glands are very busy making white blood cells to fight offthe micro-organisms which are making you ill.
Draw and labela diagram to show where micro-organisms can enter your body. On the same diagram adc labels in a different
colour to show the way in which your body defends itself against diseases.
v
@
Explain why ciliated epithelial cells are ideally suited for the job that they have to do.
@
'Cigarette smoke stops the cilia on the ciliated epithelial cells in your respiratory system from beating.' 'People who smoke often get more coughs and catch colds more often than people who are non-smokers'.' Suggest a scientific explanation on how these two statements might be linked.
A white blood cell engul{ing and destroying a bacterium
47
Micro-organisms and disease in animals After this topic you should be able to: . describe a bacteriar disease in animals and explain how it can be treated and prevented o describe a viral disease in animals and explain how it can be prevented
.
o r o o o
describe a fungal disease in animals.
antibiotic polio thrush tuberculosis fl-B) vaccination
Bacteria, viruses and fungi can cause diseases in animals (including human beings). Some of these diseases kill people and livestocks
and affect the health of millions of people around the world.
Tuberculosis
- a bacterial disease
Tuberculosis (TB) is caused by bacteria. In cattle and people, it affects the lungs. TB makes animals and people cough up blood, lose weight and sometimes die. In people, TB is spread by coughs and sneezes. But you will not get this disease unless you have been in close contact with the TB patient for some time. Cattle live in herds so they easily spread the disease from one to another. People can get TB if they drink untreated milk from an infected cow. Some people do not have enough food to eat or their immune system is damaged, for example by HIV. These people have a
higher risk of catching TB. About 2 billion people (one third of the world population) are infected with TB and about 2 million of them die every year.
If
cattle are infected with TB they are often slaughtered. People may be treated. TB is caused by bacteria so it can be cured by antibiotics. It takes a very long course of antibiotics to cure TB. Sadly, people do not always finish their medicine so they become
ill
again.
TB can be prevented byvaccinations which make people immune to the disease. It can also be prevented if people are well fed and have good living and working conditions.
When cows are infected by TB they do not give much milk or meat and cannot work in the fields Many people do not get enough food as a result
mlio-aviral disease Polio is a disease caused by a virus. It attacks your nervous system and it can cause paralysis. If this affects breathing muscles, the person may die. The virus is passed on in faeces and in contaminated food and water. In the past, many people were left paralysed. Now polio exists only in three or four countries. It has been largely wiped out by a worldwide programme of vaccination.
Vaccination lets your body meet a dangerous micro-organism in a safe way. Then, if you ever meet the real micro-organisms, your body can make the white blood cells needed to destroy it before you become ill.
*'hrush
- a fungal disease
Fungi do not cause many diseases in animals but they can cause serious infections of the brain, the lungs and the heart. Thrush is the most common fungal disease in people. It is caused by a type of yeast that lives on our skin. Usually, yeast cells are harmless. However, if you have to take antibiotics or if you are seriously ill, the fungi may attack your skin. This makes your skin itchy and sore. Anti-fungal chemicals can usually kill the fungus and make you better.
Many countries have worked very hard to vaccinate their populations and help wipe out polio
Summary questions
@
Wort< in a smallgroup.
Write down allthe illnesses you can think of. Try and find out which of them are caused by bacteria, viruses and fungi.
@
tul rB is spread
more easily when people are poor and live in overcrowded
conditions - why do you think this is so? (b) Explain how TB in cattle affects people.
Why do you think that we vaccinate and treat people against TB but do not treat or vaccinate cattle?
^a. A 3-D illustration of fungi Candida albicans that cause thrush (also known as candidiasis)
@
^L
*nu
is it imporlant to vaccinate people when they are babies, and not wait tillthey are older?
Thrush is often not serious but it can be very sore and painful
49
Micro-organisms and d[sease in plants Micro-organisms infect plants and cause disease. When plants get sick and die, people don't get enough food to eat, so plant diseases can be very serious for people too.
After this topic you should be able to: . describe a bacteriar disease in plants and explain how it is spread and can be prevented . describe a viral disease in plants and explain how it is spread and how it can be prevented
.
Xanthomonas- bacterial dfrrumffi$ms
frrl
plants
There are some bacteria that cause diseases in all sorts of plants from fruit trees, such as lemons, figs and bananas, to houseplants. These bacteria all belong to the same group known by the scientific name Xanthomonas (pronounce starts with a'Z').
describe a fungal disease in plants and explain why it is so
it
as
if it
One type of this bacteria causes citrus canker. Th.y attack citrus fruits such as lemons,
senous.
oranges and limes. Th.y attack the leaves, making the leaves brown and unable to make food. They affect the fruit so they are spotty and fall offthe tree before they ripe. They can ruin a crop once they attack a citrus grove.
The bacteria ooze out of the fruits and leaves of an infected plant. They are then easily spread from one plant to another plant by water. Xanthomonas cost farmers millions of dollars every year in lost crops. This is because when plants are infected, they have to be destroyed to stop the infections from spreading.
.^.
Diseases, such as this citrus canker, can destroy farms and ruin lives
Mosaic viruses in plants There are many different viruses, such as mosaic viruses that attack and damage plants. They get into plants when the leaves are damaged, for example when insects bite the leaves. They take over the plant cells to make new viruses. The leaves of the plant develop a mosaic
pattern of different colours. This viral infection stops the plant from growing well and often stops it producing a good crop. There is no cure for plants infected with this viruses. They have to be destroyed. It is a big problem to stop the virus spreading to more plants from infection in the soil. The virus is spread by people's hands or is carried by insects that feed on plants.
(
The yellow areas in these leaves are infected with tobacco mosaicvirus. Mosaic viruses like this can damage an entire crop
Fusarium wilt
- a disease caused by fungi
Fungi don't cause many serious diseases in animals but in plants they cause terrible problems. Fusariumwilt (also called vascular wilt and Panama disease) has destroyed banana crops in almost every country where they are grown. The spores of the fungus are in the soil and they attack the small roots of young plants. They get in to the special water transport tissue (xylem) in the plant and destroy it. If the plant cannot transport water it will die. As the plant is dying, the fungus makes lots more spores. The spores fall into the soil and infect even more plants.
Anti fungal chemicals will help get rid of fungi that grow on the surface of plants. However, nothing much can be done once the fungi invade the plant tissues. It is very hard to get the spores out of the soil. The plants have to be destroyed. Our hope for the future is to breed crops that are resistant to as many diseases as possible.
'7
Millions of tonnes of crops - like these bananas worldwide every year as a result of fungal plant
- are lost diseases
d
fA
,il
4
Summary questions
@ lf
nant diseases often affect people as well as plants. Why is this?
,.
@
nice, wheat and maize are three of the world's major crop plants, Find out the names of the main diseases that attack each crop and the type of micro-organism (virus, bacterium or fungus) that causes each disease.
@
VaXe a poster that could be used to warn farm workers from spreading plant diseases from one farm
to another.
Louis Pasteur: decay and food production After this topic you should be able to:
.
.
. o
explain how Louis Pasteur helped explain
the way microorganisms break down organic matter explain the way Louis Pasteur made food safer for all of us.
fermentation pasteurisation
Vaccinations prevent serious diseases such as polio. Pasteurising or heat-treating milk helps to preserve it. Covering our food helps to keep it good. All of these methods are based on the work of one man-Louis Pasteur. He was a French scientist who lived and worked in the 19th century. Until today, his works still affect our lives.
Micro-organisms and decay For hundreds of years people thought that living things appeared from nothing. Scientists thought things went bad because moulds and other organisms appeared in them as if from nowhere (spontaneously). Louis Pasteur did not believe this. He thought that these organisms grew from some existing organisms. He set up some experiments which showed that it was micro-organisms
from the air that grew on the food (organic matter), breaking it down and causing decay.
I
Pasteur put broth in two flasks. He boiled one {lask to kill the micro-organisms he was sure were there The swan neck on each flask would stop micro-organisms in the air from getting in
not boiled
(') [1
Nothing grew in the boiled flask The broth in the flask which was not boiled went cloudy and was covered with mould.
I
Pasteur broke off the necks which trapped
micro-organisms from the air and put them in the flasks of broth. Now the boiled broth went cloudy and mouldy too as bacteria and mould soores from the air were put into it. Louis Pasteur's famous experiments with swan-necked flasks proved his ideas about the connection between micro-organisms in the air and decay. They also helped disprove the ideas of his rivals about sDontaneous oeneration
I I 52
Summary questions Explain how @ t"l naafar rriaatinn nrntontq nonnlo
against foodborne infectious drseases.
(b) What
is the
difference
between the
In many countries, the milk you drink and the milk used to make dairy products, such as yoghurt and cheese, have all been pasteurised
^^^+^,,-:^^+:^^ pdJtt ut tJclUUt
rticro-organisms and food production Louis Pasteur discovered that micro-organisms were needed to make alcohol and vinegar. They break down sugars without any oxygen to make alcohol. This process is known as fermentation. When the alcohol or vinegar went bad, it was because conditions were not right for the yeast to grow properly. Other microorganisms got in and made it decay.
that nrnr]r rnoe UHT (ultra-high
temperature) milte
@
rino out as much as you can about the life of Louis Pasteur. Present your findings as a timeline of his life, or a poster about his life and work. Work rn a group and use books and the Internet to help you. Also look at the next few pages of this book for ideas.
@
Explain why the lives of many children have improved as a result of the scientific discoveries since the time of Louis Pasteur.
Once peopleknewthis, theymade sure theydidtheir fermentations in the best possible conditions.
Pasteur also showed that if milk was heated, it killed off most of the bacteria and moulds which made it go bad. Most of the milk you buy in shops today will have been heated in this way. The process is called pasteurisation, named after Louis Pasteur. The milk lasts longer and is safer to drink because pasteurisation also kills offthe micro-organisms that cause diseases such as TB.
Pasteurisation is used to preserve many different foods now, such as fruit juice, milk, yoghurts and cheeses, wines and beers.
It has saved millions of lives over the years because it has stopped food going bad and prevented people from getting food-borne infections.
I
of milk and rne process
A change of direction For the first part of his career Louis Pasteur worked in universities and with local industries. This was n'here he discovered the scientific evidence that micro-organisms is responsible in decay and fermentation. As he got older, Pasteur became more interested in understanding some of the terrible infectious diseases he saw around him. He
had five children but three of them died young from infections such as typhoid. His youngest daughter Camille was only two when she died. Pasteur became determined to stop the spread of some of these diseases in both people and in animals. 53
Louis Pasteur: the fight against disease After this toprc you should be able to:
.
.
o
. .
explain how Louis Pasteur showed that mrcro-organisms were involved in the spread of disease describe a scientific experiment by Louis Pasteur that showed a way to help prevent orsease
talk about the importance of questions, evidence and explanations in developing new scientific ideas.
germ theory vaccine
first seen
-^^+ariA '.-, .imole light bauLlt'* were r uttt'1
through o microscoP
microscopes electron "'-*r" develoPeo'
'
I II 54
Louis Pasteur hao nrs own specially built laboratory in Paris where he did research on his germ theo'y o{ oisease
As a scientist Louis Pasteur was always asking questions. What causes infectious diseases? How do they spread? How can we prevent them? He knew the answers to these questions but he needed to prove to the other scientists that his explanations were right.
Frotecting agalnst disease Louis Pasteur knew about the work of Edward Jenner who had developed a vaccine against smallpox. After his experiments conducted on decay, fermentation and pasteurisation, Louis Pasteur was sure that all infectious diseases were caused by germs (micro-organisms) passed from one person to another. He called it the germ theory of disease. Pasteur wanted to find ways to grow these disease-causing microorganisms. His plan was to make them weaker, so he could use them as a vaccine to protect animals or people against a disease.
The battle against anthrax Anthrax is a deadly disease of farm animals and humans caused by a bacterium. It took Louis Pasteur a long time to grow the bacteria that cause anthrax in his laboratory. But he could not make it safe enough to use as a vaccine. Not all scientists accepted pasteur's germ theory of disease. One of them challenged him to prove that anthrax was caused by germs - by vaccinating some sheep against it. Pasteur's vaccine was not yet fully tested, but he took up the challenge.
The trial of the anthrax vaccine
.
25 sheep were given Pasteur's anthrax vaccine. Another 25 sheep were not vaccinated.
.
A month later, all of the sheep were injected with anthrax from infected animals.
.
Three days later, all of the unvaccinated sheep had died or were dying of anthrax. All the vaccinated sheep were still alive and well.
Pasteur had won the challenge and many more scientists then accepted his ideas about germs and disease.
This is one of Pasteur's own flasks It contains the dried soinal cord of a rabbit with rabies
Fasteur and rabies
Summary questions
in 19th century, about 100 people died in France each year from the bites of animals with rabies. When Louis Pasteur was a little boy of eight, a rabid wolf came down from the mountains and attacked people, including some from his village. He never forgot their screams as they had their wounds cauterised with red hot irons. In spite of this, eight people died of rabies. Pasteur never forgot the horror of this.
O
Pasteur knew if he could find the micro-organism which caused rabies and made a vaccine, no one could doubt his germ theory of disease. However, he could not find the germ that caused rabies. Today, we know the reason of course. We know Pasteur could not see it because it was a virus! Viruses are so small they cannot be seen with a normal light microscope. Pasteur kept trying. He worked with the spinal cord taken from rabbits with rabies to try and make a vaccine. One day a little boy who had been bitten by a rabid dog was rushed to see Pasteur. Two doctors had said he was going to die. So Pasteur tried a new vaccine treatment on the little boy and the boy did not get rabies.
Three months later he used the same method on a l5-year-old shepherd boy badly bitten by a rabid wolf. Pasteur treated him
with the vaccines and the brave shepherd boy was saved.
Now everyone accepts Pasteur's germ theory of disease. From that time onwards, scientists and doctors have worked to discover more ways of curing and preventing disease.
to
what was
Pasteur's germ theory of disease? (b) Today, we know a lot more about what causes infectious diseases than the great Louis Pasteur did. Write a letter to Louis Pasteur explaining
to him what we know about microorganisms today.
@
*nu
@
worx in small groups.
do you think Louis Pasteur tried out his vaccine on children before it had been properly tested? Would this be allowed today?
Find out as much as you can about some other important people who have helped us to understand about micro-organisms and disease. They include Edward Jenner, Lady Mary Wodley Montagu and Joseph Lister. Make a poster or a presentation of your findings. 55
The seven characteristics of livino organisms are nutrition, respiration, reproduction, excretion, movement,
reproduce by budding. Moulds are fungi made up of tiny thread-like structures
sensitivity and growth.
called hyphae. Fungi reproduce
Micro-organisms are very small living
making spores.
organisms, and can only be seen using a mrcroscooe.
People use fungi for food and to make bread but they can also cause diseases
There are various types of microorganisms, such as bacteria, protozoa, fungi, viruses and algae.
Bacteria are the most common microorganisms. They are made up of single
Viruses are incredibly small microorganisms which are made up of a protein coat and genetic material. They are parasites - they can only reproduce by taking over the cell of another living
organism and using
capsule and flagellum. Bacteria have
viruses. All viruses cause disease.
all
the characteristics of living things. Some bacteria are very useful to people,
some have no effect and some are harmful and cause diseases in people,
bV
in people, animals and pJants.
a cell wall, genetic material, plasmid, cytoplasm, slime
cells, which have
it to
make new
Micro-organisms such as bacteria and yeasts are involved in the process of decay.
animals and plants.
Bacteria, viruses and fungi all cause diseases in animals (including people)
Protozoa are unicellular micro-organisms.
and plants.
They are closer to the animal kingdom
than the plant kingdom as they don,t have cellwalls and are able to move. Fungi are micro-organisms but they can be very large. They carry out all the characteristic activities of living things.
56
Yeasts are single-celled fungi. They
One of the first people to make discoveries
about micro-organisms was the French screntist, Louis Pasteur.
Summative Practice Seven terms about micro-organisms are
The graph shows the number of cases of
listed below. Their definitions are also given. Draw out a table matchino each term with its
oolio woddwide between 1985 and 2010. Global poliovirus cases,
definition. 450000
eo
o-
1
985-201 0
400000 350000
o 300000 o o 250000 o u o o
ll
E
z
1
50000
1
00000
1985 1990 '1995 2000 2005 micro-organism composed of cells without ,^t^, ,^ ^ ^, A IIUUIUUJ
2010
Year (a)
Describe what happened to the number
of cases of polio between 1985
2010. any organism that lives in or on a host from which it obtains its food
preparation of a disease-causing organism that provides long-term protection against that disease an illness caused by a parasitic organism
2
t4l
(b)
Exolain the use of vaccination in the eradication of polio from many pafts of the world. t3l
(c)
Why
micro-organism that reproduces within the cells of its host
and
is it important to continue to vaccinate young children against polio even though the number of cases of the disease woddwide is very
low?
tsl
Explain why the following are used in cheese making:
Comolete the table.
t4l Explain why some cheeses can be kept for a long time without going t2l
'bad'.
Several children became very ill with the same symptoms. Scientists questioned their
families to find out how the children had become ill. All the families had drunk apple juice from a local farm. The scientists found that the apple juice was contaminated by soil bacteria. The farmer said that unoasteurised
apple juice tasted much better
than
pasteurised juice.
(a) Describe briefly what happens when foods such as milk or apple juice are pasteurised.
t2l
I
(b) Suggest why children and not adults
a plan to show how the two students could use their apparatus and
(c) Write
became ill after drinking the apple juice. i'!i
tl
(c) The farmer was told to change his production process if he wished to continue to sell the unpasteurised juice. Suggest three changes that he should carry out.
!:)l
John's father brews his own beer. He has made two batches. One is very good, but the other tastes foul. He thinks it has bacteria in it as well as yeast and that the bacteria have produced an acid giving the foul taste.
He takes samnlos nt bOth balcheS to
a
laboratory.
(a) Explain how he found out whether
one
batch has acid in it. l.'l (b) There are two methods to show that there are bacteria in the samples. Write some instructions for John's father to
methods. lttl briefly the process in which
materials to demonstrate experiment.
yeasts produce drinks such as wine and beer.
[:)]
Sari and Ayu have to make a presentation on
the life of Louis Pasteur. Rather than make a poster or write a biography. they decide to repeal his experiment on sponlaneous generation and show the class their results. Their teacher gives them some laboratory apparatus although he tells them that the school has no swan-necked flasks and they will have to think of another way to
I
demonstrate this parl of Pasteur's experiment Sari and Ayu staft by making some nutrient
broth that contains glucose and
some
mineral salts. These are the nutrients required by bacteria to grow. They boil the broth and pour it into some flasks that they had washed
in boiling water. They also made up some broth that they did not boil and poured that into some unwashed flasks. They covered some of the flasks with foil and left others open to the air.
(a) Explain what is meant by the spontaneous generation.
term
l2l
(b) Suggest a way in which the students could make some apparatus resembling Pasteur's swan-necked flask
t
I 'rl
58
[,:]
|
l,ii1
Ahmed and Abdul investigated the factors needed for the decomposition of leaves from the trees in their neighbourhood. They collected many leaves of the same type
and divided them into six groups, A to F. They weighed each group on a balance to make sure they were of lhe same mass. They then treated the leaves as follows:
A B C D E
washed thoroughly in a sterilising fluid and kept in a sealed container at 4 "C. similar to A, but kept at 25'C, put straight into a sealed container and kept at 4 "C. similar to C, but kept at 25'C. put straight into a perforated container
that allows air to mix with the leaves
follow for each of these
(c) Explain
Pasteur's
F
and kept at 4'C. similar to E, but kept at 25 "C.
After several weeks Ahmed and Abdul took the leaves out of the containers and weighed them again. Each group of leaves lost mass, but some lost more than others (a) Ahmed and Abdul designed their investigation to find out the effect of three factors on the decomposition of the leaves. Name these three factors. (b) Explain why they only used leaves from one type of tree and not several different Ly
(c) (d)
l.Jvo.
Suggest why they put the same mass of leaves in each container iti Predict which group of leaves, A, B, C,
D, E or F lost the most mass. Explain your answer. Make sure that you refer to
the factors that affect decomposition your explanations.
Dewi wanted
in
l,'j
to observe protozoa using
a
microscope. She took some samples from a pond and prepared a slide to see under the microscope. However, she could not see the protozoa.
Suggest ways to help Dewi prepare a better slide to observe the protozoa.
to study the effect of antibiotic concentration on the growth of bacteria. They prepared two Petri
10 Nova and his team were assigned
12
dishes containing the same volume of nutrient
agar and bacterial culture. Then, they placed different concentrations of antibiotic discs on each of the nutrient agar. They inverted the Petridishes and incubated them at 35-37 "C for 2 days. (a) Explain why they used the same volume of nutrient agar and bacterial culture. 17l (b) Predict the result of this investigation. 12/ (c) Suggest why they used the same antibiotic and not a different one. n l (d) Why did Nova and his team inveft the Petri
dishes?
n
Which of the following sequence of steps shows the process of phagocytosis?
A.
P,Q,R,S
B. S,Q,P,R C. R,S,Q,P D. Q,R,S,P
N]
13 Which of the following is an example of multicellular micro-organisms? Paramecium B. Amoeba C. Spirogyra
A.
l
11 The diagram shows some examples of protozoa. Which organism cannot be
D. Chlamydomonas
classified as orotozoa?
nl
14
These organisms differ from bread mould OECAUSE
A. they are unicellular
organisms
B. they are able to make their own food C. they have cilia D. they have chloroplasts
W
t1l
is different from Paramecium because Euglena A. cannot move B. has chloroplasts C. does not have a fixed shape D. has pseudopodia tll
15 Euglena
A.W B.X
c.Y D.Z
fil
Habitats and environments
Science in Gontextt
Working in the field Ghecking for weeds says that half of the school field is covered with weeds instead of grass. A group of students are trying to find out if that is true by using some simple equipment.
Mr Putra is the school gardener. He
.
The students marked out a transect using a long piece
of string.
.
They put a frame called a quadrat down at regular intervals.
.
They counted the numbers ofsquares ofeach quadrat where there were weeds.
.
They worked out the percentage of the field that contained weeds. It was only 32o/ol Now they can tell Mr Putra that he was wrong. The school field was not half covered with weeds!
.^.
A transect lets you take samples in an orqanised wav
Taking random samples Some students decided to do quadrats that were not on the transect lines. One group found a patch of the field
which had lots of weeds and did their quadrats there. They thought they would show Mr Putra he was right. Another group found an area with no weeds at all and decided to do quadrats there. They really wanted to prove Mr Putra wrong! However, the results of both these groups were not valid. Their results were not from the transect and they were not from random sites, so the scientific evidence they had collected was not accepted.
On average the students found eight souares out of 25 contained weeds
i.'B $nE
for living orgamlsrns
Several students wanted to find out what animals lived on the school field loo. They decided to look in the middle of the field, at the path that went through the middle and in the long grass and bushes which grew at .r'i the
sides.
lly using
. .
) Yo,
pooters,
can
the organisms living in the habitats around your school, just as this student is
nets,
pitfall traps and
doing
beating trays,
the students found many different types of insects, snails, slugs, woodlice and worms. They made a careful
record of everything they had found. They wanted to repeat their field work every month throughout the year, just to see if the living organisms around, ii them changed during the year.
.r
In this chapter you will find out about organisms live and the ways in which interact with one another. You will also about the influence of the environmt ,: humans on them.
Goncept map HABITATS AND ENVIRONMENTS
. . .
Abiotic components
Competitions Prey-predators Symbiosis
Water
I
Temperature Sunlight
Extreme environments
Balanced ecosystem
ir pollution
Water pollution Soil
Biotic components
Underwater environments
Air Soi
Local and seasonal
Producers
Consumers
Herbivores
Carnivores
Decomposers
Omnivores
pollution
After this topic you should be able to:
.
o
explain that the habitat of an organism is its home
describe some different habitats.
I fl
I
/,* ';-nd
I
, T
Habitats all around you Work in a small group. Think of as many different habitats as you can. You can starl with the ohotos below. o Write down a list of vour ideas. Share vour list with the class.
v
1:L
Pt The ice of Antarctica, the African savannah and a tropical rainforest in Borneo are three very different ha bitats
Different tlpes of animals and plants have different habitats. Dragonflies and slugs for instance live near ponds and in damp places, they could not live in a hot desert. Monkeys, that live in hot forests, would not survive in a cold treeless Northern plain.
Summary questions
O
Explain the difference between a habitat and an ecosystem.
@
Deseft animals do nol live in very cold habitats and plants from the Arctic do not grow in tropical countries. Explain why human beings can live in most of the land habitats on
Living together The type of soil, the local temperature and the weather in an area all
affect what organisms can live there. The physical conditions of an area together with the animals, plants and micro-organisms living in there are all part of the ecosystem. Animals, plants and micro-
organisms make up a community and they all need a habitat which suits them. They live in balance with the other organisms around them and the living conditions in their ecosystem.
When you look at the habitat of a particular type of living organism, think about everlthing working together. Often one organism cannot live in a habitat without another different tlpe of organism. For example, fungi need dead plants or animals to feed on, sheep need grass and bacteria in their guts and penguins need fish.
Earth.
@ ff inr< about your school and its surroundings. Describe three different habitats. What living things would you find there?
63
I
nvestigating habitats
After this topic you should be able to:
.
o . .
describe ways of investigating a habitat observe and describe living things record results in different ways, e.g. drawings, using tables make conclusions from the data collected.
invertebrate
pooter quadrat
Your school would have many different habitats. The sports field and flower beds are good examples. To study a habitat means you need to find out the different types of organisms that live there. You have to count the numbers of the organisms. Some simple equipment can be used to help you find out about a habitat.
Using a quadrat The simplest way to build a picture of a habitat is to count the number of organisms there. A quadrat will help you do this scientifically. A quadrat is usually a square frame of wood or metal with an area of either I m2 or 0.25 m2. You lay it on the ground and it outlines your sample area. You use the same quadrat every time and sample as many areas as you can. Quadrats are useful for counting organisms that do not move, such as plants or fungi. They are also used to count the numbers of slow moving animals, such as snails, barnacles or sea anemones.
Random samples When you use a quadrat it is important that you choose your sample areas at random. This means you can't choose an area which has many interesting plants - or just bare eafth! The person with the quadrat closes his eyes, spins round, opens his eyes and walks ten paces in that direction before dropping the quadrat. Repeat this for every sample. lf you use a random number generator to decide where to put down vour ouadrat it is even better.
If organisms are only partly covered by a quadrat, you can choose to count them as in or out, but you have to maintain the same method used for all your quadrats. In the diagram, you have six or seven plants per 0.25 m2 (that's 24 or 28 plants per m'z) depending on the way you choose to count them.
(
Organisms often fall partly in and partly outside a quadrat. You have to decide whether to count them in or out
[-inding animals You can easily observe large mammals and birds in a habitat by just watching out for them. Uut that habitat may also have many small invertebrate animals which are not easy to see or identi$'. There are several ways to find smaller animals:
.
A pooter: This equipment can pick up small invertebrates. It works like a simple vacuum cleaner. You suck on one tube and the invertebrate is sucked up in another tube so you don't swallow it. You then gently move the invertebrates into a collecting chamber where you can examine them. Once you have caught your organisms, a magnifting lens will help you to see them more clearly.
'I
I
Using a pooter to collect insects
A pitfall trap: Some animals, such as beetles, are too big to be sucked up with a pooter. You can make a pitfall trap. It traps beetles and other small animals that don't fit into a pooter. They are easy to make, but you must empty them out regularly so the trapped animals do not die.
A
sweep net: This is a large net which you use to sweep through long grass. You can then investigate any organisms that are caught in the net. Tree beating: Hold a white sheet or large sheet of card under a tree or bush. Then gently hit or shake the bush and collect the animals that fall out.
Summary questions
@
rino the most common organisms in a habitat in your school. Describe the habitat and the method using a quadrat in this study.
(L)
Explain how you would make a pooter from an old plastic drinking
bottle, two straws and a piece of fine cloth.
small container
A pitfall trap
@
nnimats that get caught in a pitfalltrap could be at risk if you do not check it regularly. Why?
65
Abiotic and biotlc compomwmts After this topic you should be able to: . differentiate biotic factors from abiotic factors . list some biotic factors
o
a
o o
Take a walk in your school compound. You will notice that the things around you can be grouped into living things and nonliving things. A forest ecosystem consists of living things such as micro-organisms, animals and trees as well as non-living things which include sunlight, water and temper
list some abiotic factors.
abiotic biotic humus
Living organisms are interrelated to one another and their environment
An ecosystem has living and non-living components that work together. Biotic factors are the living components that consist of all the living organisms in that community. Abiotic factors are non-living components that affect the living components.
Biotic factors The biotic components are producers, consumers and decomposers. Producers are autotrophs that consist mainly of photosynthesising plants which produce their own food from light energy meanwhile both consumers and decomposers are heterotrophs that cannot synthesise their own food but instead obtain from other orqanisms.
Abiotic factors .L Woodlice
avoids dehydration
Abiotic factors determine the conditions of the living organisms in any community. The abiotic factors are water, temperature, sunlight, air and soil.
Water Water is an abiotic factor. It is very important in ensuring that organisms survive. As most organisms consist ofwater, water is needed to carry out their life processes. Thus, water influences the distribution of animals and plants in any ecosystem. Most organisms, for example, snakes, frogs, Iiverworts and mosses prefer humid habitats. Some organisms regulate their activities to avoid dehydration. One example is woodlice which are usually found under stones and rotting tree stumps. 66
Temperature 'l'cmperature determines the type of organisms tlrat can live in a certain place. Most organisms
(an only survive within a narrow range of lcmperatures. But there are animals and plants that live in extreme conditions. Animals that live in the clesert can tolerate high temperatures during the day rnd low temperatures at night. Some animals hibernate in extremely cold temperatures as a means of survival.
Sunlight Sunlight is the most important source of energy in the ecosystem. Plants depend on sunlight to carry out
photosynthesistomaketheirfood.Differentpartsof a forest get different degrees of light. That makes it possible for different types of organisms to grow
t'
..
there. For instance, tall trees obtain a greater amount of sunlight. So they form the canopy or roof of the forest. Plants such as ferns and mosses survive in these shaddy areas. Bacteria and fungi also prefer
dark conditions.
Air Air is a mixture of gases such as nitrogen,
oxygen and carbon dioxide. Oxygen and carbon dioxide are needed for life processes such as photosynthesis and respiration. Organisms living in higher altitudes of the mountains are well adapted to the higher pressure ofair. Both camels and polar bears are well-suited to live in extTeme
Soil
conditions
Soil is an important factor for terrestrial organisms. It supplies nutrients to plants. Soil also acts as a habitat for animals like
earthworms and insects.
,
Soil is enriched
by
decomposed dead plants animals. called humus. The type of soil
Summary questions
O
List the abiotic components in the ecosystem.
@
state the differences
@
Ciu" one interaction
and
determines the tipe of vegetation that can
.' grow. For example, you
between biotic and abiotic factors.
can find coconut trees
growing on sandy beaches while paddy grows well in clay soil as it can hold water for lonq of time.
between abiotic and biotic factors in the desert.
67
Gnouping After this topic you should be able to:
.
. .
identify some ways to group living organisms explain that a habitat will contain a number of different types of
organisms use information from seconoary sources.
orsanis
$
In any one habitat you will find many different living organisms. Some of them are large, such as baobab trees, elephants, giraffes,
redwood trees, gorillas and whales. Others are small, such as ants, caterpillars, duckweeds and krill. Each habitat is different. However, the organisms found in different habitats share the same features. This means we can put them into groups. Each habitat has similar groups.
Plants make food In most places, the first group you will find
. . .
carnivore herbivore omnivore
are plants. Plants
are usually green. They have leaves, stems and roots. They make food by photosynthesis, using energy from the Sun. They are very
important. In most habitats, all the other organisms depend on the plants. This may be directly as food, or because they feed on other organisms which have fed on plants.
Decomposers In a habitat you will find other organisms growing which may look a bit like plants. They grow up from the soil or from the trunks of trees. They are not animals because they do not move around.
of a group of living organisms called fungi. Th.y cannot make their own food. They feed on the remains of other organisms. Fungi are categorised in a feeding group known as decolnposers. Other decomposers include bacteria, termites, ants, millipedes and earthworms.
These are part
{
Plants versus fungi
.a. These
Work in a group.
.
Make a poster to show the main differences between plants and fungi. Find out how they get their food. Get some good images from the Internet or other books to show the different plants and fungi that exist in the world.
l)ccomposers are responsible
lirr the disappearance of dead organisms. They break down tlcad organisms and their waste.
'lhey turn them into nutrients
and simpler substances such r.rs nitrates and phosphates, and gases like carbon dioxide. 'fhese nutrients and gases are returned to the soil or atmosphere, and plants absorb them.
'
lmagine a world without decomposers! All the dead organisms would pile up and there won't be space for the living organisms to go about their daily activities
erbivores, carnivores and omnivores
Summary questions
Many animals in a habitat eat the plants that grow around them. Some feed on grasses, others feed on the leaves of bushes or trees, and some eat flowers, fruits or berries. Animals which eat plants are herbivores.
G) v
There are many animals which feed only on other animals. They may eat insects or worms, birds or large mammals. They may eat herbivores, or they may eat animals which eat other animals. They are all known as carnivores.
(2
wnat are the main differences between a plant and a fungus?
) (a) HOW lS a Carnlvore (b)
are
(c)
different from a herbivore? In what ways do omnivores differ from herbivores and carnivores? Draw a table with
three headings herbivore, carnivore and omnivore. In each column write three examples of the type of animal.
@ til
Iti
nna thinks there will always be more herbivores than carnivores in an ^^^^,,^+^uuuJyJLvl
i; These carnivores will eat this herbivore once
they have killed it
-7ia
ll. 4la
disagrees. She thinks that there are more carnivores than other animals. What do you think? Explain your answer. 69
Food chains After this topic you should be able to:
o .
state that food chains are composed of different trophic levels explain the terms
'producer','primary consumer'and
r
'secondary consumer' draw simple food chains with three
A food chain is a way of showing how different organisms in a habitat feed on one another. Look at habitats around you, try to identift the organisms in the different food chains. The simple food chain in the picture tells us that antelopes eat grass and cheetahs eat antelopes. It doesn't tell us how many planis or antelopes or cheetahs get eaten!
Food chains show how energy can pass from one living thing to another in a habitat. The arrows show the direction in which energy is passing along the chain.
trophic levels.
.4. Grass --.) antelope --.) cheetah: a food
chain
Producers and consumers A general food chain looks like this:
The different stages of the food chain are known as trophic levels.
Plants produce their own food by photosynthesis. This is why they are called producers. Every food chain starts with a producer, and most prodr cers are plants. Animals .orrrrrir" plants or other animals, so they are known as consumers. The animals which eat plants (the herbivoies) are known as primary consumers. Some animals eat the herbivores. They are carnivores and are called secondary consumers. Omnivores can be both primary and secondary consumers because they eat both plants and animals.
In the food chain on the next page, the leaf of the plant is the producer. The caterpillar eating the leaf is the primary consumer, and the bird eating the caterpillar ii the secondary.o.rrrr-"r. Think about the living organisms you come across when studying the local habitats and write down some of the food chains. Do some extra research if you need to so you can complete them all. 70
Making three-item food chains Draw out as many three-item food chains as you can. Think of organisms you have identified in your local habitat or organisms from other habitats further away. Make large coloured drawings of the organisms in one of the food chains you have drawn up. Cut out the shapes and hang them up, with the producer at the bottom of the food chain.
oving along the chain
Summary questions
O How many antelopes do you think a cheetah eats in a week? How many blades of grass do you think an antelope would have eaten in the same week? Thousands of grass plants will only feed a small number of antelopes. Those antelopes will only feed an even smaller number of cheetahs. What happens to the food as it passes along the food chain? When an animal eats a plant, not all of the food in the plant ends up as new living material in the animal. Some of the food gets used for other things. The animal uses the food to move about and grow. Some of the food will not be digested and will be passed out of the body as waste.
When an animal itself is eaten by another animal, it only passes along the food that has become part of its body. The next organism gets only the small amount of food that was turned into the new biological material. This biological material is called biomass.
Make up three different
food chains. Use one from your local habitat, one from a freshwater habitat and one from any habitat of your choice.
@
Explain why the arrows pass from the plant onwards through a food chain.
@
Wfrat happens to the biomass as it passes along a food chain? Suggest as many ways as oossible in which it is used or lost.
Food webs After this topic you should be able to:
.
o o .
o o e
differentiate a food chain and a food web explain what a pyramid of numbers is state the characteristics of pyramids of numbers describe how energy flows in a food chain.
food web energy flow pyramid of numbers
Food webs Food chains do not reflect the complex feeding relationships that exist in most communities. There is more than one food chain in any ecosystem. Plants and animals are part of several food chains. When these food chains are linked together, a foodweb is formed.
A
food web describes the actual feeding relationships and energy flow within the community. It helps maintain a balanced ecosystem by regulating the number of organisms at each trophic level of the food chain.
Pyramids of numbers If we arrange the numbers of organisms according to each stage or trophic level in the food chain, then we have a pyramid of numbers.
In a py'amid of numbers, the organisms with the highest number is at the base of the pyramid. Plants, being the producers are always the highest in numbers and placed at the bottom of the pyramid. The primary consumers are at the second trophic level, while the secondary and tertiary consumers are at the third and fourth trophic levels. The number of organisms at each level of the pyramid decreases as we move up the food chain. The size of the organisms increases from the base of the pyramid to the top.
Plant
(producer)
Snake
.r.
A food web that is made up of several
food chains
Tertiary consumer
Secondary consumer er
{
,:r Pyramid of numbers
:r:nergy
flow in a food web
Living organisms need energy to survive. Energy
is
transferred through a food chain when an organism eats or is eaten. A food chain starts when plants absorb light energy from the Sun and convert it into chemical energy which will be stored in them. Plants use this energy for various life p such as growth, reproduction and excretion.
.
When plants are eaten by primary consumers, the stored chemical energy is transferred into primary consumers. However not all the energy is transferred as some energy will be dissipated as heat to the surroundings while another fraction of the energy will be used for activities such as moving and eating. From the primary consumers, the energy flows to secondary consumers and lastly, to the tertiary consumers. There is a loss of energy from one level to the next, and the amount of energy decreases along the food chain. Very little energy is transferred to the next level and this explains why the pyramid of numbers seldom exceeds four levels. Since the energy decreases from the lower level to the higher level, the organisms at the higher level have to eat a large amount of food to get their energy supply. So, the number of organisms at the lower level is always more than the next trophic level.
Food chains and food webs
Seals are carnivorous animals and need a lot of food to obtain
energy
Summary questions
O
State the differences between a food chain
and a food web.
@
fhe number
of trophic levels in a food chain is generally not more than
four. Why is that?
@
*nu
does the amount of
energy decrease along the food chain?
Work in groups. . Make as many food chains in a tropicaljungle you can think of. . Use the food chains to create a food web. . Once the food web rs completed, turn it into a poster.
73
After this topic you should be able to: o qtaia tho irrnoc nf
interactions between
o
organrsms
differentiate the types of interactions between organisms.
Interactions between organisms are proof that no living being can survive on its own. Organisms have to interact with one another and with their environment. Interactions between living organisms help the organisms obtain food, shelter, protection and breeding partners. It also regulates their population size and maintains the balance of nature.
The relationships between organisms can be grouped into competition, prey-predator and symbiosis. Symbiotic is relationship consists of commensalism, mutualism and parasitism.
a
commensalism
a
competition mutualism parasitism prey-predator symbiosis
a a a
a
l,):i 'tj,:,,,,r, ,,. ',. :: ,:
,
Competition is an interaction in which organisms compete for the same resources such as food, territory and breeding partners. Competition usually occurs when the resources are limited. The result of this competition has a negative effect on the weaker organism. This interaction can be ftrrther grouped into intraspecifi c competition and interspecifi c competition.
Intraspecilic competition is a competition between the same
species while interspecific competition exists among
lntrasPecific
members of different species. A herd of deer competing for food
is an example of
intraspecific competition. A lion and a hyena fighting over a carcass of deer is an of interspecific competition. .,example
h
i I t I
ts
I !
The birds are showing intraspecific interaction while the lions and the hyenas show i nterspecific interaction
i,; i i5]lry
,i%j,..4---r
r:,.*
A predator capturing its prey
A prey is the organism that is hunted and eaten whereas the predator hunts and eats the prey. Usually, the predators are carnivores and larger than the prey. However, the predator can also be a prey to a larger predator than itself. For instance, a snake eats a rat but the snake can be eaten by an owl. Predators are well adapted to kill their prey. They possess good vision, sharp claws, strong beaks, a good sense of smell, powerful jaws and sharp teeth. They can run faster than their prey. Their bodies are sometimes camouflaged so that their prey cannot see them. The prey also have sharp eyes to detect the presence ofpredators. Th.y have the ability to run and escape from their predators. Some prey give out unpleasant smells or harmful chemicals. Some can mimic the colours or smell of other stronger animals to frighten or confuse the predators.
Symbiosis means a close interaction between two different species which live together and interact with each other for an extended period of time. In a symbiotic relationship, one species will benelit while the other species may be unaffected or might be harmed.
Commensalism Commensalism is a relationship between two organisms from different species in which one gets benelits (commensal), and the other does not benefit and is not harmed (host). Commensalism usually occurs between a larger organism and a smaller one. The larger organism is the host and the commensal will be the smaller organism. An example of this relationship is the .*r* remora fish and shark.
Mutualism Mutualism is a relationship between two organisms from different species in which both benefit. A good example of this interaction is the clown fish and sea anemone. A clown fish gains protection from predators by living amongst the poisonous tentacles of the sea anemones and by feeding on the food remnants of the sea anemones. Meanwhile, the clown fish chases anemone-eating fish away.
,.'
Mutualistic relationshio between a clown fish and sea anemones
Parasitism Parasitism is an interaction between two organisms of different species in which one gets benefit (parasite) and the other is harmed (host). Usually, the parasite is smaller in size compared to its host and they reproduce at a higher rate. A parasite takes food and shelter from the host. Parasites are divided into ectoparasites, which live outside the host's body, and endoparasites, which live inside the host's body. Mosquitoes and fleas are ectoparasites while viruses and tapeworms are endoparasites.
Interactions between organisms Work in groups. . Make a folio on different types of interactions between organisms that you have learned. . Give one example for each interaction complete with pictures.
Summary questions
@
state tne difference between commensalism and mutualism.
@
rhe host
@
Cive one example of (a) mutualism
Rafflesia, the world's largest flower is a parasite that feeds on the vines of Tetrastigma plant The Rafflesia plant has no stem, root and leaves and is not visible until the flowers bloom The Rafflesia flower looks maqnificent but emits a foul smell
in
commensalism is larger whereas the host in parasitism is smaller. Why is that?
(b)
interspecific competition
(d)
commensalism
parasitism
@
Describe the prey-
predator relationship between a rat and an owt.
II
Biological control living organisms interact with one another, we should be able to control the population of a particular pest by using another organism that feeds on or kills the pest. Using a living organism to manage the population growth of another organism is known as Since we know how
biological control.
;', Owls play an important role
in
eliminating pests, such as rats, on oil palm plantations. Rats pose a major pest problem on oil palm plantations, causing monetary losses to the owners. Chemical-based baits can be used to lure the rats away, but that chemical is toxic enough to kill cattle,
so plantation owners
have
had to look for other solutions.
They experimented with snakes as snakes are natural predators to rats but that was also unsuccessful. Then, they tried using cats but the cats fell for the poisonous baits which were used for rats. The planters then decided to use owls and the plan worked!
Nowadays, planters rear barn owls to keep rats in check. This method is environmentally friendly, and also keeps a natural balance in the ecosystem. The planters only have to invest in making nests for the owls which can be easily made from wooden boxes and the problem ofrats is taken care of. The method employed by these oil palm planters is known as biological control. It is when a natural predator is used to kill a pest which happens to be its prey. By using the natural enemy, only its prey is targeted. This method does not cause health problems to the handlers unlike the chemical pesticide, which can pollute the environment. Pesticides can kill many other organisms besides the intended pest. Thus, biological control is safer than using pesticides to solve the problem of pests in agriculture.
nterdependence between organisms and the environment I
After this topic you should be able to: o state the imoortance of a balanced ecosystem . describe how interdependence in a pond ecosystem WOTKS.
o o o o
Balanced ecosystem In an ecosystem, various organisms live together and are interdependent for their survival. They interact with one another as well as the environment to create a balanced ecosystem. A balanced ecosystem is a system that does not change very much over a period of time. The size of the population remains the same through a steady supply of basic needs like oxygen, food, shelter and breeding partners. A balanced ecosystem helps to puri$r and recycle gases, water and minerals. It even helps to control climate.
balanced ecosystem dispersal
Pond ecosystem
pollination reproduction
A pond is a quiet body of water which is shallow and allows sunlight to penetrate to the bottom. This creates a variety of vegetation such as submerged plants, floating plants and pond edge plants.
Aquatic plants obtain energy to make food from sunlight during photoslmthesis. They obtain carbon dioxide from the respiration of aquatic animals and minerals from the soil at the bottom of the pond. The animals, in return, obtain their supply of oxygen from the plants which release oxygen during photosynthesis.
Animals cannot make their own food. They depend on other organisms for food. They eat plants or other animals in their
ake
consumer) Drro
(secondary and tertiary consu mer)
Trog
/"...
(seconda
consumer large fish consu me r)
snail
(primary
a
oucK (secondary consu mer)
lgae
roducer)
(secondary consumer)
'lacler
a
;decomposers)
zoop anKton
A ba anced pond ecosystem
environment. Some pond animals depend on aquatic plants for shelter and protection. They cling to parts of the plants such as the leaves, and are able to camouflage themselves to match the colours of the parts of the plants they are attached to.
Aquatic plants and animals depend on non-living components of the environment and other organisms for reproduction. The plants rely on water, wind, insects and birds for pollination and dispersal. Meanwhile, the animals rely on favourable climatic conditions and the abundance of water to find breeding partners and disperse their eggs. Plants provide opportunities for the animals to attach their eggs or their young ones.
Summary questions
o @
The forests of Indonesia are an example of an ecosystem. can you explain why? ls an aquarium without any plant considered a balanced ecosystem?
whv?
Decomposers like bacteria in the soil help break down dead organisms and release minerals into the soil. These minerals supply nutrients for the plants.
In the pond ecosystem, the non-living factors such as water, air, temperature, oxygen content, rainfall, light intensity and other factors influence the distribution of organisms.
The interdependence among living organisms and their environment creates a balanced ecosystem. The amount of food and the availability of shelter, breeding partners and space keep the population of each organism in check.
79
l i I
After this topic you should be able to:
. .
expiain how the activity of people can have a negative effect on food chains
explain how people can have a positive effect on food chains.
i
i
Supplying water in regions where the soii is very dry alows many more plants to grow so more food chains can develop
I
Wher-r we keep aninals
for food, we are managing a food chtrin. When we manage a forest to grow tir-nber, we change the food chains and focld webs that are there. Someti'es there is a soocl ellect, but sometit-nes our eft-ect is a neqtrtive one.
There are nany clifferent ways
in
which
people can calrse problems in food chains. One good example is the story of clichlorodiphenyltrichloroethane (DDT). DDT is a powerful pesticide. It kills the insect pests that destroy crops and spread diseases such as malaria.
Unfortunately DDT does not break down in the bodies of animals. It is simply stored in their fat. Not long after farmers itarted using DDT, many large water birds such as herons failed to reproduce successfully. Th.y started to lay eggs with very thin shells. When the parent bird sat on the nest, they broke.
I
|,
I
We sometimes put chemicals in rivers without knowing what they will do to the food chains there When things go wrong, the bigger fish will suffer most
I
I 80
Why did the herons start to die out? Look at the food chain below. Why do you think the herons were so badly affected by DDT? . Write down your ideas. Read on to see if you are right.
%X-; prll'
anrmal plankton
DtanKron
heron
r-...-^
DDT in the food chain
Summary questions
When DDT is sprayed onto fields, it also gets washed into streams and rivers by the rain. It got into the bodies of the tiny plants and animals in the water. These organisms take in only small amounts of DDT, so they are not harmed.
O
All the DDT will stay in the bodies of the small fish. Then big fish eat lots of these little fish. The big fish now has more DDT in their body fat. Still it is not enough to hurt them. Then herons eat lots of the big fish. There is now enough DDT in the heron to affect
Describe the positive effect on food chains when water is supplied io dry regions.
@
Here are some of the ways people affect food chains. For each ofthe following statements, decide whether it has a good or bad effect on food chains and the environment. Explain your answer. . Emptying sewage into the sea
the strength of their eggshells, so the number of herons decreases.
When people realised the terrible effect of DDT, it was banned in many countries. Now it is only used where pests do so much damage that it is worth the risk of using DDT, for example to kill the mosquitoes that cause malaria.
Other ways of affecting food chains People cause pollution in many different ways, through body waste (sewage), pesticides, industrial waste, car fumes and more. We pollute the oceans, rivers, lakes and the land. All of this can have a bad effect on food chains. We have also polluted the air. We have destroyed part of the ozone layer which protects us from UV radiation and this is affecting life
on Earth. We have changed the climate by producing too much carbon dioxide - and this means food chains are affected too. But we are also doing many good things. We conserve habitats
o
Planting grasses,
o o
sucn as marram grass, on sano dunes Putting factory waste into rivers Setting up nature
.
Stopping whale
.
reseryes hunting
Spraying crops with pesticides
that are threatened. We take water to dry areas and prevent erosion of soil. We replant areas with new forests. We create food chains. Find out more in tooics 3.14 and 3.15.
81
The ways in which organisms fit into their habitat and survive are known as adaptations. By looking at the adaptations of an animal or plant, you can get a good idea of where and how it lives.
After this topic you should be able to:
o
. . a
describe some habitats of organisms explain how organisms are adapted for survival communicate your ideas supported by evidence
SurwivinE Living organisms are adapted in many ways to survive in different conditions. For example, plants have adaptations of their roots and leaves to cope with different conditions. Here are some examples of the ways living organisms are adapted to their particular way of life.
mrko anr{ nroqont
conclusions by bringing tnoothar avir-lcnno f69p6 different sources.
.
'w7
adaptation
The habitat of the Venus flytrap has soil containing very few minerals. The leaves of the plant are adapted to catch and digest insects. The plant gets minerals from the insects in order to grow ano reproouce
ts
The long neck of a giraffe aJlows it to feed on the leaves from the
I
tnnc
n{ trooc
th:+
few other animals can reacn
.l
*:. II
R,
aa"'4r-
ftr
The cactus has:
. . . .
p
thick stem with lots of water-storing cells tiny spines as leaves a thick waxy outer layer verf deep roots. a
The barn owl has:
. . . .
excellent hearing large eyes a sharp beak and claws
light bones and feathers. A cheetah has:
. . . .
The rabbit has:
. . . .
long ears large eyes strong hind legs
flat grinding teeth.
ver/ small ears spotted fur sharp pointed teeth verY long legs.
Summary questions '! $
u,
'li'rii:ll1; ;r1
survive?
Working out the adaptations Look at the fact files of the four oroanisms vou have been grven aOove.
.
For each one write a paragraph explaining how the organism is adapted to its habitat and way of life. Do some research usinq different books and the lnternet.
rvrany antmats can
cnange corour or have colours which blend in with their background. This is '{t^^ ^^il^/-l ^^,-^' 0aileu carrouilage. How does this help them to
@
Wort< in a small group.
Think of four habitats. Write down at least one organism from each. Make a fact file to show how each organism i+^ l--^1,-i+^+ ^,-l^^+ +^ oudlJL LU tLJ ttdutLdL.
After this topic you should be able to:
o
o . .
describe the adaptations of some animals and plants to their habitats describe some adaptations for the day and for the night in living organisms describe some seasonal adaptations in different animals and plants communrcate your ideas suppoded by evtdence.
Animals and plants have to be adapted to changes in their environment to survive.
Day
an'nd rufrgffnft un vfr
ff"mfr.i,wtmrs
Habitats change every 24 hours. Daltime is usually much warmer and brighter than the night-time. Some organisms are adapted to be most active during the day. For example, most plants open their flowers during the day when insects are flying around to pollinate them. Many animals use their eyesight to find food in the light. Amphibians and reptiles are cold-blooded and need the warmth of the day to be active. Some animals are nocturnal. They are active during the night. Sometimes this is to avoid being eaten, although there are some predators that hunt at night. These nocturnal animals usually have Iarge eyes which use as much of the dim light as possible. Some flowers open at night. They are pollinated by nocturnal animals such as moths or bats. They often have a strong scent to attract the moths, which can smell with their feathery antennae.
Seasrommfl
mwfimml:W.a:';,tr,ilr,-tt,ff\1ffi
In some parts of the world, near the equator, the weather is very similar all year round. But in many other places it changes a lot through the year. In temperate regions such as Northern Europe a tree might get l6 hours of sunshine and a temperature of around 20 'C in the summer. But in the winter these change to around eight hours of light and 5 "C. There isn't enough sunlight for the leaves to make the food the tree needs and theywould all be killed by frost. So the tree becomes dormant. It loses its leaves and slows down all the processes of life.
;tll
l: l
-t Bybecomingdormantinwinterthistreecansurviveuntil thewarmerweatherandlongerdaysofspring
Investigating adaptations Using the techniques in topic 3.2, collect a selection of animals and plants from your local habitats. Look at their adaptations and use them to help you decide where they live and whether they are active in the day or during the night.
Many small plants can also become dormant. They survive the winter as seeds, or as bulbs below the ground.
Animals have to survive these changes in conditions too. Some animals change their behaviour. Some change the way they look and others change the way their bodies work. Hedgehogs and polar bears for example hibernate in cold weather. They eat a lot and build up fat in the summer. Then their bodies slow down to save energy through the winter in a sheltered hiding place. They become active again when the days get longer and warmer. Some animals migrate. They leave bad conditions and move to good conditions. Some birds and mammals travel thousands of miles every year. Swallows spend the summers in Europe and winters in Africa. In the great migration in Africa, big herds of wildebeest and zebra move across the continent. The herds follow the rains to eat the new grass which grows because of the rain.
Summary questions
O
Describe three adaptations in an organism that is active during the daytime and two adaptations in organisms that are active at night.
@
*nu do many
Many animals develop thick, shaggy coats to keep warm through the colder part of the year. They lose their thick coats in the spring
animals
in temperate countries
grow thick coats before winter?
@
Before a polar bear hibernates it: builds uo as much body fat as possible makes a den to hide in under the snow, When it hibernates it slows down all of its body processes. Exolain how these adaptations help the oolar bear to survive the winter.
o o
After this topic you should be able to:
.
describe how animals anA nlan+a pranrs aoapl ^,-J^^+ +anu Io ^\/+r'^m^ exLr er
|e
Many parts of the world have extreme conclitions, ranging from very hot and dry to very cold ancl dry. For an orgauism to survive in extreme conditions, it must have special adaptations.
h^^+ I
^^i ]u coto leaI at
in their environment.
In many places arollnd the world the daily temperatllre gets very high. Often water is in short sr-rpply as well. This rnakes lif-e hard for animals and plants. Deserts are the nost extreute hot environments. Desert plants often have roots that spread widely or go deep clown into the ground to reerch water. The leirves are ofteu smtrll and have thick waxy outer layers to recluce water loss. Desert plants often store water in their stems, their lcaves or their roots. Many plants growing in hot and dry conclitions also hirve sharp spines to protect thernselves from animals thart want to eirt them. Plants aclapted to hot conditions are callecl xerophytes. Cacti are the best known extrmple.
These Euphorbia survive hot and dry conditions with the r fleshy leaves, deep roots and the spiny thorns that protect them from being eaten
)
Mammerls that live in hot clinrates usually have very little fr-rr arnd big, thin ears to help them lose heat. Some nnimals such as desert rirts can store all the water in the food they eat so they harclly need to drink. Many clifferent types of anin-rals also adarpt their behaviour. For example, when it is very hot they hide in the shade of rocks or in burrows which they dig.
Plants that survive in very cold conditions are often very small. They may have hairy leaves to trap a layer of air to keep them warm.
;,
'' Some have special antifreeze chemicals in ',:' their leaves, so they don't freeze in the low temperatures. Elephants have large, thin ears, wrinkled skin and very little hair in order to help them lose heat
Animals also have special adaptations for living in cold places. Many mammals have a thick layer ,rl'fat (blubber) beneath their skin to insulate them from the cold. Their thick fur keeps them warm. Itirds have extra layers of soft feathers to keep them warm. Reptiles and amphibians do not live in very t old climates as they cannot get their bodies warm enough to move about. Many animals hibernate or hide away through the coldest weather. Polar bears retreat to a den under the snow for the winter. liven cold climates have summers and winters. The landscape changes colour completely when the snow and ice come. Many animals rrclapt for the change of seasons with a change in their colour rrs well as the thickness of their fur. Their colour change nreans they are camouflaged all through the year (see the photos of the Arctic fox).
Adaptation to altitude When animals live at very high altitude they have to be adapted to cope with less oxygen in the air
as
well as cold temperatures. Special
ardaptations for altitude include:
. . .
extra red blood cells to carry more oxygen
bigger lungs to take in more air
more blood vessels in the lungs to take more oxygen from the air.
.:,rP You can clearly see the difference in the colour and the thickness of the fur of the Arctic fox in summer and winter - and how well thev are camouflaqed in the
different seasons
Summary questions ..:ti. .}-:
:,,.il ''::ral
itti :,1.
.
O
Foreach ofthefour organisms listed below describe: (a) where it lives (b) how it feeds (c) its adaptations to live in its habitat . tiger
. . .
camel polar bear retndeer
87
After this topic you should be able to:
.
describe some of +A^ ^/]^^+^+i^^^tD ul ^+ U tu auoPtouut
living organisms [o lile
un0erwaler.
a
gills
a
phytoplankton
r
tt
.
What are the main problems for organisms living underwater? Mention three ways in which fish adapt to underwater life. I nnk rt tha nhntn nf Loln rnri iha nhntn nf tho coq annlor fieh
Make a poster about ^,-J^^+^+i^^^ r- +^rur l,+^ ilru dudvLoLrur
underwater
89
t: rli:::l::iil :lri,: ..':' ii
,..:i
:.
'
. .::.::'::""
.
:'t
i
'l';,,,;.''
I
After this topic you should be able to:
. .
.
state what pollution is describes the types of pollution
Air pollution
list the causes of
nitrogen cycle. Some common air pollutants are carbon dioxide, carbon monoxide, sulfur dioxide, soot, dust, chlorofluorocarbons (CFCs), and lead compounds. These are dangerous to human beings and the environment.
pollution
.
describe the effects of pollution.
acid rain algal bloom chlorofluorocarbons (CFCs)
haze smog
soot
occurs when contaminants are into the air and cannot be removed through natural cycles like water cycle and released
Sources of air pollution include emission from vehicle exhaust,
forest fires, quarries
and
industries like cement, timber
""
and asbestos.
I
\"J*dilslu
Smoke from forest lires can cause haze which reduces visibility. Sometimes, smog occurs as well. Haze alrd srnog blurs visibility. They can also cause breathing difficulty, especially for people with asthma. When there is haze, heat is trapped making the temperature rise. As for pltrnts, the stomata on the leaves are blocked by soot and this hinders photosynthesis. Balinese statue in Bali, Indonesia showing w-^atherin g and danage due lo acid rain
When we burn fossil fuel, carbon monoxide is formed. This reduces the ability of red blood cells to carry oxygen to the cells. When we do not have enough oxygen, we can get headaches and dizziness. We may even die if we breathe in ltrrger doses of carbon
monoxide. Carbon dioxide is also released fiom the burning of fossil fuels. It causes the greenhouse effect.
Sulfur dioxide and oxides of nitrogen are released from factories and power plants running on fossil fuels. When they dissolve in rainwater, they cause acid rain. Acid rain lowers the pH of ponds and lakes, making the water acidic. This is dangerous for the organisms living in the water. Crops and livestock are also affected by acid rain. Acid rain is corrosive. It damages buildings and structures especially those made from limestone and marble. Objects made from iron such as vehicles and bridges rttst even faster because ofacid rain.
Wrrys to oYercome air
. . .
pollution:
lot of smoke, smog and soot Fix catall'tic converters on all motor vehicles to convert harmful exhaust gases into carbon dioxide, nitrogen and water Use unleaded petrol to prevent the release of lead particles into Avoid using fuels that release
a
the atmosphere
. .
Use CFCs-free products
Avoid open burning of rubbish and allow the government to build incinerators
.
Fix a filter on the smoke ducts of chimneys in factories to trap pollutants before smoke is released into the surrounding air
.
Educate the people on the effects of air pollution and ways
An incinerator ln the national park with garbage bags waiting
to be disposed
of
reducing them
.
Take legal action against owners of factories or vehicles which pollute the environment.
Water and soil pollution Water pollution is caused by domestic waste and
i
littering, industrial waste, agricultural activities, logging, mining, increased sediment from soil erosion and oil spills. Water pollution can occur in any body of water such as rivers, oceans and underground water. When the different sources of water flow together, the
pollution spreads. Domestic waste is waste from kitchen, bathroom and laundry such as garbage, detergents and waste from food preparations. This waste, especially untreated !w; sewage, can cause serious health problems. Sewage ..r* A dead bird becomes a victim of oil spill refers to wastewater that contains urine and faeces. disaster in the Gulf of Mexico Sewage disposal is a major problem in developing countries as many people do not have clean water and do not live in sanitary conditions. Too much application of pesticides as mentioned in topic 3.9 can also cause water pollution as these substances leach into the underground water which will later flow into ponds and rivers. Over usage of chemical fertilisers will contribute to algal bloom with dangerous results for aquatic life in ponds and rivers. Sometimes, untredted factory waste is discharged into waterways, causing serious pollution. Water pollution ce& spread even to those rivers from which people get their drinking water.
Accidents can happen at sea involving tankers, pipelines, refineries and illegal cleaning of oil tankers at sea. The result is not only tbgoil spills which we can see, but much more damage and danger that we cannotsee. The oil washes up.the shoreline and covers the beaches with black and sticky oil. It iffects seabirds arid other marine organisms. The reproduction rate of aquatiqlife slows down due to water pollution. The food chains are also
91
Soil is a thin layer of organic and inorganic material formed on
the upper layer of Earth. Soil pollution is the contamination of land that is used for agriculture, habitation and wildlife or forest reserves.
Soil pollution is caused by the use of excessive fertilisers and pesticides, deforestation, seepage from a landfill, household dumping and discharge of industrial waste into the soil. Seepage from landfill especially heary metals can end up in a food chain, with serious results. Deforestation means chopping down large areas of trees. The result is soil erosian because there are no more trees to anchor the soil with their roots and no more leaves to soften the impact of hear,y rain. Soil pollution leads to lowyield of crops, loss of animals and plants
and their habitats, soil erosion and water pollution.
To prevent soil pollution, there could be forest replantation programmes, adopt the 3R-reduce, reuse and recycle-as a way of life and stop using chemical fertilisers and pesticides.
All the types of pollution are interconnected. For instance, factories using fossil fuels to run their operations release pollutants into the air. This causes air pollution. When the pollutants dissolve in rainwater, they return to Earth as acid rain and increase water and soil pollution. We must all be prepared to change our lifestyle to curb the problem before it gets worse.
Pollutions Write an essay of about 300 words on pollution. Discuss the effects of pollution and steps to reduce the impacts.
v
We can reduce household wastes by recycling
Soil pollution due to copper mine exploitation
Summary questions QD
State the effects of pollution.
lo* does acid rain @ damage buildings, especially those made of limestone and marble?
@
How do excess fertilisers which flow into lakes cause the
death of aquatic
I
antmals and plants?
@
Wf'at happens if untreated sewage is discharged into the rivers?
I
hluman population growth After this topic you should be able to:
. .
describe how the human population nas grown explain how the
increasing number of people has had positive and negative effects on the environment.
. o . o
climate change extinct greenhouse effect ozone hole
Human beings have been living on Earth for less than a million years. But our activity has changed the balance of nature on the planet enormously.
The growth of the human population For thousands of years there were only a few million people scattered all over the world. So our actions had only small, local effects on the environment.
In the last 2 000 years or so, the human population has grown very quickly. There are now over 7 billion people on Earth. Now the things we do can really affect the environment and even the whole planet.
Normally when a population of organisms grows really fast, it is quickly reduced by predators, lack of food, a build-up of waste products or disease. But human beings have discovered how to grow plenty of food to eat. We can cure or prevent many killer diseases. We have no natural predators. Because of all these, the human population has grown very fast.
)
The growth ofthe human ^^^,,l^+;^^ PvPu,oL,v,
The oreenhorrse elfee I is a natural process which keeps Earth warm enough for life to exist But extra carbon dioxide (COr) means extra warming, which may not be a good thing
I
:o o
i+ o o.J o ol 0
_o1 E
ln
z
B'7'6'5'4'3'2'1 Thousands ofyears ago
Negative effects More people on Earth means we use more of Earth's resources.
As a result, we are a negative influence on the environment. The negative effects are:
.
We burn fossil fuels, such as coal, oil and gas, to make electricity and heat buildings. We burn oil products in vehicle engines, producing carbon dioxide. 93
This adds to the carbon dioxide which is already in the atmosphere. Carbon dioxide and gases such as methane and nitrogen dioxide are known as greenhouse gases. The increasing amount of carbon dioxide in the atmosphere traps extra heat energy from the Sun. So the surface of the Earth gets even warmer. This is known as the enhanced greenhouse effect. Greenhouse effect is actually natural and necessary to support life on Earth. But we are producing too much greenhouse gases, causing an imbalance in the environment.
r
The ozone hole as seen from space
As a result, the climate seems to be changing all over the world. Climate change means a big change in temperature, precipitation and, wind patterns for an extended period of time. It affects the habitats of animals and plants in different parts of the world. Some animals and plants are in danger of becoming extinct. The polar ice caps are melting at a very fast rate, and glaciers such as the Alps, Andes, Himalayas and Alaska are retreating faster. The sea level is rising and low lying areas are at risk of flooding. Many places have seen changes in the pattern of rainfall which has caused floods, droughts or heat waves. We cut down very large areas of forest to grow crops such as oil palm, and to raise animals, such as cattle. This destroys a rich habitat and it means that hundreds of types of Iiving organisms are becoming extinct every year. Chemicals such as CFCs used in fridges and aerosol sprays have built up in the atmosphere and destroyed some of the ozorre, a form of oxygen. The ozone in the atmosphere protects Earth from ultraviolet (UV) light from the Sun. The ozone hole is where the ozone layer has become thin and is allowing more UV Summary questions through. This can damage many living organisms by causing more cancers to happen. The good news is that people are now t-ist the reasons why producing fewer CFCs and the ozone layer is getting thicker the human population has grown so much in agaln. recent years.
@
@
Positive effects As people become more aware of the problems, they are working
hard to protect the planet by:
94
. r .
planting more trees
. .
finding alternatives to fossil fuels, for example biofuels
preventing further destruction of more rainforests protecting areas where rare plants and animals are found the numbers can grow reusing, recycling and replacing resources.
so
wort< in a group.
Make two posters. In one, explain people's negative effects on the environment. In the other, show the positive effects people can have on the environment. Compare the posters and decide whether humans are good for Earth or not.
;ffirus
nnary
Remember that the habitat of an oroanism is its home.
Humans can have a negative effect on food chains, for example by using
There is a wide variety of different habitats
pesticides such as DDT.
around the world.
Organisms are adapted to their habitat. They are well suited to the place they live and the way they feed.
You can investigate a habitat using simple
apparatus such as quadrats, pooters, sweep nets and pitfalltraps. An ecosystem has biotic and ablotic
Organisms may be adapted to be active during the day or during the night (if they
components that work together.
are nocturnal).
Biotic components include producers,
Organisms may be adapted
consumers an0 0ecomDosers.
Abiotic components include
water, temperature, sunlight, air and soil. Plants are green organisms which make their own food by photosynthesis. Fungi are not green and they feed off other organisms which may be alive or dead.
Herbivores eat plants, carnivores eat other animals and omnivores eat both plants and animals.
A plant is a producer, a herbivore is a primary consumer and a carnivore is a secondary consumer. Organisms are linked together in feeding relationships known as food chains. Interactions between organisms maintain the food web and control the size of the population of the organism. Competition, prey-predator and symbiosis
are types of
interactions between
organisms.
Symbiotic relationships consist
of
io
survive
seasonal differences in the weather conditions and the amount of food available.
Organisms
have many
different
adaptations which make it possible for them to live underwater and in extreme
conditions of heat, cold, altitude and depth under the ocean. Pollution happens when contaminants are released into the surroundings and cause damage to the environment.
Environmental pollutions include air pollution, water pollution and soil pollution.
The enormous growth of the
human
population is having negative effects on the environment such as increased global warming and the thinning of the ozone layer (ozone hole).
Climate change refers to significant change in the components of climate such as temperature and rainfall.
As people become aware of
the
commensalism, muiualism and parasitism.
problems, they are finding solutions to have a more positive effect on the
Interdependence between organisms is
environment in some parts of the world.
vital for the survival of the organisms.
95
Summative Practice Copy and complete these sentences using
The students called them species 1, 2, and
key terms from this chapter.
so on, and recorded the colour of each type. (a) Explain the way the two groups could present the results to their class. t3l
The place where an organism lives is called its
are animals that eat
onlv
(b) Suggest why there were fewer on type B
pranrs.
A
diagram that shows the flow of energy between three or more different orqanisms is
(c)
trees.
animals
t3l
t4l
Explain why most of the animals were green or orown. t2l Their teacher said that the two groups should use exactly the same method when collecting the animals. They should use the beating tray and pooters.
Some students are investigating the animals that live on the trees in the school ground. The school gardener told them that there are two types of trees:
(a) Complete this food chain to show the
called a
is a olace where different oroanisms interact with one another and their
An
envrronment.
in which the two groups could improve their method of investigation. t4l
(d) Suggest ways
feeding relationships among these three
organisms found
in an African nature
reserye:
gqqg anlelope cheetah
t2l
(b) The food chain has three trophic
levels.
State the trophic level for each organism in the food charn. t3l
(c) Vultures are scavengers that will eat the bodies of dead antelope and dead
cheetahs. (i) Add vultures to the food chain you nave orawn. t2l (ii) What are omnivores? t2l
The diagram below shows three types of interactions among living organisms.
The class are divided rnto two groups to collect animals from the trees. Nisha's and Dino's groups think there are different types of animals on the two types of trees. They used a beating tray and pooters to make their collections. The figure shows some of the animals collected by Nisha's group from trees of type A. Dino's group found fewer animals on tvoe B trees.
Fill in the spaces provided using the correct words for the following statements. (a) An organism which hunts and feeds on another organism: (b) A relationship between two organisms where both benefit: (c) Consisting of many species of organisms interacting with one another and with the physical factors around them: _. (d) A mosquito sucking blood from the human body: t4l
cogon9rass
Photos X and Y show interactions between
Name the type of interactions shown in
(a) P (b) o (c) R
5
orqanisms.
tsl
The diagram shows a part of the oil palm plantation.
a food chain found n tne plantation. t2l (b) What is a food chain? t2l (c) A sample of soil from the plantation was (a)
Construct
examined under
a microscooe.
Name
the organisms found in the soil and state their function. t2l (d) What will happen if the workers kill all the snakes in the plantation? t2l tal The plantation owner increased the amount of ferlilisers for the oil palm trees. After sometime he noticed plenty of fungi growing on the stems and roots of the trees. The fungi can eventually damage the oil palm trees. What is the role of the fungi? How are the oil palm trees affected? t3l
Y
(a) Name and explain
the type of interactions
shown in photo
(i) x (ii) Y (b)
t4l
the forest, living organisms compete to obtain basic needs. What is the difference In
between the types of competition between animals and competition
between plants in forests? t2l How is the prey-predator interaction
(d)
beneficialto man? t2l The vegetable plants in Rahman's farm are attacked by caterpillars. Suggest the fastest way to overcome the problem.l2l
97
8
Which of the following
A. Autotrophs
rs
not an abiotic faclor?
B. Temperature C. Sunlight D. Soil
(c) The diagram shows a food web.
t1l
An interaction between two organisms in which one benefits and the other neither benefits nor harmed
Which interaction best depicts the relationship based on the statement above? Parasitism
A.
B. Competition C. Symbiosis D. Commensalism
10
ti I
Which of the following is not true of a pyramid of numbers? A. The base is occupied by producers B. The number of organisms decreases from the base to the top C. Energy flow increases from the base to the top D. The size of organisms increases from the base to the top
tll
11
The diagram shows a pyramid of numbers.
\o/
What levels do P and Q represent in this
food
chain?
t2l
(b) What conclusion can be made concerning
the organisms in a pyramid of numbers?
t2l
(i)
What type of interaction rs shown by the caterpillar and the chicken? tll
(ii) What is man's role in the food chain? t2l (iii)
What will happen when man has
chickens? t1l are plants important in a food web? t2l 12 Animals are adapted to the habitats in which consumed all the
(iv) Why
they live. Explain what is meant by the term adaptation.
t2l 13 The photo shows a red slender loris, which is a nocturnal animal that lives in the forests of Sri Lanka.
(a) Suggest three ways in which the (b)
red
slender loris is adaoted to a nocturnal life in forests. tsl Describe three ways in which the flowers on some plants attract animals. tsl
14 The environmental conditions in desefts are
very extreme. Deserts provide a habitat for
16 The graph shows the increase in the human population of Brazil between 1550 and 2012. Population of Brazil
I o o
many types of plants and animals.
o
(a) Describe the extreme conditions that
€
plants and animals experience in deserts.
E
t4l
.9
(b) (i) Name a type of plant and a type of
g
animal that are adaoted to survive in deserts. t2l
o-
o
(ii) Explain the adaptations of each of these organisms the deseft.
to
'1
550 650 750 1850 1950 '1
'1
the conditions in
t6l
15 Sperm whales are mammals and have lungs
(a) Describe what happened
to
the
population of Brazil between 1550 and
2012.
for breathing air. They hunt squid and fish. They spend about 90% of their lives at great depths and are rarely seen at the surface of the oceans.
205
Year
(b)
t4l
Why has the human population increased
so much?
t4l
(c) Suggest some problems that Brazil will have if its population continues to Increase.
(d)
Lvl
Suggest ways in which the government of Rrazit marr
.r^p
itS population inCreaSing. 15/
(e) Some scientists believe that the human population will continue to increase, then it will peak and then rapidly decline. What are their reasons for this prediction? tsl
17 Which of the following gases is associated with global warming? A. Chlorofluorocarbon B. Nitrogen dioxide C. Carbon dioxide D. Sulfur dioxide (a)
What are the problems that sperm whales experience in hunting food at great depths in the
(b)
sea?
t4l
How are sperm whales adapted to survive and feed at great depths in the sea?
t4l
18 Which of the following is not an ozone depletion? A. Reduced immune system B. Lung cancer C. Cataract D. Melting of ice caps
usually
t1l effect of
Itl
Uariation and classification
Science in Contextt
Variety in moths foko collected 25 moths from the bark of trees in the woods. They were all the same tlpe of moth but they had different colours. Some moths were pale grey, some were dark grey while some were greeny-grey colour. He made a tally table to show the different qpes he had collected.
|oko's teacher wanted him to show his results in a way which made it easier for other students to see what he had found. Joko displayed his data in a bar chart and a pie chart. Which
do you think works best?
.
Is it possible to find out if the sample of moths foko caught is typical of the moths in the wood?
.
Why are there fewer dark moths than moths of the other colours? What might happen to the colour of the moths if the wood became polluted by factory smoke?
I
E
bo o
_o
E4 zJ
A bar chart to show the different colours of the moths
al 1r,
.#
i
Eo
-r, A pie
chart to show
the different colours of the moths
il"he
history of the peppered moth
to investigate variety in the colour of moths. Many years ago in the United Kingdom, scientists noticed that the peppered moth
Joko is not the first person
- one pale and one dark. Peppered moths were usually found on the pale coloured bark of trees. There were fewer dark moths than light moths came in two varieties
because birds could see dark moths easily and them (see the first photo on the right).
would eat
After the British Industrial Revolution, the smoke from factories made the bark of many trees dark and dirty. After a time, scientists noticed that there were many more dark moths than pale-coloured ones. Birds could now see the pale moths more easily than the dark ones and so the pale moths were being eaten (see the second photo on the right).
In recent years the air and the woodlands have been cleaned up. Now pale peppered moths have become more common in British woodlands once aqain. In this chapter you will find out about the importance of classification in the animal and plant kingdoms and how biologists classift living things. These photos show the two varieties of the peppered moths on different coloured tree trunks
Goncept map VARIATION AN D CLASSI FICATION
Glassifications After this topic you be able to: r state what is
o .
should
classification list the levels in the
If you walk
a grocery store, you will n e that the goods -into are arranged tc resemble a library of foods. In the canned food aisle for example, you'll see all types of canned food. When you walk along that aisle, you will see that the canned food islsoited again into a few categories, like canned tuna and canned chickenl The canned tuna will be further categorised into flaked tuna, tuna chunks, tuna with chilli and so on.
hierarchy of classification explain that we classify living organisms by In the same way, scientists classify all known living organisms placing them into into groups. groups.
Classification helps scientists
. . . . o . o
v
""u,'
class family genus order phylum species taxonomy
Carl Linnaeus (1707
to
identi$z individual
species
accurately wherever they are. For example, the local name of cobra in India and Thailand would not be the same, thus by using
scientific Classification organisms, to the
n avoid confusion-. ntiate the types of type of organisms,
prevent confusions, and provide the precise names for organisms.
Carl Linnaeus is known as the father of taxonomy. Taxonomy is the science of naming and classifting organisms based on their similar characteristics. Scientists use a common classification to group these organrsms.
1778)
The hierarchy of classification starts from general to specific. There are seven levels in the hierarchy of classification with each level arranged in increasing specificity. The first and largest rank is called kingdom and it is divided into smaller units called pyla (singular: phylum). A phylum is divided into classes, a class into orders, an order into families, a family into genera (singular: genus), and a genus into species. A species is a group of organisms that many common characteristics ui" capable of ,have interbreeding to produce viable offspring. "rra
dae
Homo
Species
sapien
The hierarchy of classification Example, the classifications of human (Homo sapien)
lhere are five kingdoms, each having its own characteristics.
Characteristics
. . . .
unicellular organisms that lack
a nucleus and
membrane-bound organelles
are known as prokaryotes
examples are bacteria, blue-green algae (refer topic 2.1) organisms that have a nucleus and membrane-bound organelles (eukaryotes)
or fungr
a
not classified
a
examples are algae, protozoa llke Amoeba, Paramecium (refer topic 2.2)
as animals, plants
unicellular and multicellular organisms cannot photosynthesise examples are moulds, mushrooms, yeast (refer topic 2.3) all multicellular and photosynthetic plants examples are mosses, ferns, conifers, flowering plants all multicellular animals examples are mammals, birds
ilinnaeus binomial nomenclature sy$tem Carl Linnaeus made the scientific naming of organisms simple by using a method called Linnaeus binomial nomenclature. He created and implemented binomial nomenclature, in which every organism is given a name consisting of two Latin words. The first word is the genus and the second word is the species. The scientific name should be tlped as italics or underlined if written down. When writing a binomial name of an organism, the first letter of the first word is capitalised and the second is not. Maize is scientifi.cally named Zea maysjust as humans are Homo sapiens. You may also see an abbreviation of this name as H. sapiens where the genus is only represented by the first letter.
y
The scientific name of Komodo dragon, the largest lizard in the world is Varanus komodoensis
Summary questions
fi)
state the importance of the classification of
organisms.
@) What are the levels in the hierarchy
of classification of organisms?
@
oiu" two main characteristtcs of the organisms that belong to the kingdom Monera.
103
Animal and plant kingdoms After this topic you should be able to: . describe the main classification of animals into veftebrates and invertebrates o describe the main classification of plants into flowering and nonflowering plants.
. . o .
classify external skeleton internal skeleton nerve
There are millions of living organisms of different tlpes around us. Scientists put living organisms into groups or classify them by looking at the differences and similarities between them.
Sorting things out Two of the main groups of organisms are animals and plants. Look at the pictures below and divide the organisms into these two groups. Do they all fit in?
Animals and plants When one scientist talks about arr animal, it is very important that scientists all over the world know exactly what is meant. Members of the animal kingdom feed on other living organisms, whether plants or other animals. They are relatively fast moving, move their whole bodies about, and have nerves to coordinate their bodies. Animals can be very big like an elephant or very small like a tiny beetle, but they all have these characteristics. Plants are very different from animals. They are food producers. They make sugar using energy from the Sun and store it as starch. Plants are green. They don't move their whole bodies around. If any of their parts move, it does so very slowly by growing. Plant cells have cell wall made of cellulose.
This mushroom is neither a plant an animal, so it does not
Listing animals Work in a small group. . Make a list of as many different types of animals as you can in three minutes. Think of local animals and animals vou have heard about from other countries.
ffiJlore
about animals
To identi4r the thousands of types of animals in the world we put them into groups. We look for things that are similar and things that are different to decide where an animal belongs. The greatest difference is between the vertebrates (animals that have backbones) and the invertebrates (animals without backbones).
The vertebrates Vertebrates have a hard, bony internal skeleton inside their bodies. Th"y all have a backbone - made up of lots of little bones - which supports the body, allows it to move and protects the spinal cord and other delicate organs inside the body.
The invertebrates Invertebrates come
in all shapes and
Summary questions sizes. They do
not have a
backbone with a bony skeleton. Many of them have soft bodies. They may have shells outside their bodies or a tough external skeleton (exoskeleton) on the outside of the bodv.
r
What do we mean by classifyi ng organisms?
@
In what way do vertebrates differ from invertebrates?
@
t-oot< at the list of animals you made in the Practical activity. Draw a table with two
columns: vertebrates and invertebrates. List as many animals as you can under each column.
The cat is a vertebrate
r
The locust is an invertebrate
More about plants As we classifu animals, we can classify plants into groups too. We Iook for things that are similar and things that are different to help us decide where the plant belongs. We can classifr plants into two
big groups: non-flowering plants and flowering plants.
Glassifying animals After this topic you should be able to:
o
describe different ways of grouping organisms including the main groups of inverlebrates and vertebrates.
Some characteristics such as height or weight vary during an animal's life. It depends on how much food it can find. Scientists classi$, animals using characteristics which can be counted or measured or which are always the same, such as the number of Iegs or whether an animal lays eggs in water.
The invertebrates There are more invertebrates than any other type of animal. They range from simple jelly-like blobs to large and intelligent animals. Invertebrates can be divided into eight main groups (phyla). Phylum Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, and Echinodermata. Phylum Porifera, Cnidaria and Echinodermata can be found in sea while the other phyla can be found both on land and in water.
^r'
Phylum Cnidaria
-Jellyfish jelly-like sea anemones have haos fnr hoclies Thev n3ys
and
r
Phylum Echinodermata Include organisms such -as starfish and sea urchins. Starfish L-..^ ^ ^+-- ^L^-^! ^^ttern with ,oPEu |.Jo five 'arms' and spiny skin
.r,
Phylum Platyhelminthes Flatworms have simole flattened bodies. They are unsegmented
tentacles covered with stinging cells to catch their fooq
.r,
.1.
Phylum Nematoda - smooth, Roundworms have thin, rounded and unsegmented bodies
r
Phylum Porifera
.t
Sponges are
- that are non-moving animals usually found in marine waters.
Phylum Annelida - Segmented worms, e.g. earthworms, have long bodies divided into segmenTs
Phylum Arthropoda
Insects,
crabs and centipedes- are part of a group called arthropods.
All arthropods have jointed legs and a hard external skeleton.
.l
Phylum Mollusca
Snails,
- all have squid and octopuses very muscular bodies and a shell either inside or outside their bodies
Classifying the vertebrates Work in groups of five. . Each group looks at one of the groups of vertebrates on page '108 and find out as much as you can about the animals in this group (provide examples). In turn, present your findings to the rest of your class.
We can also divide invertebrates by observable characteristics such as with jointed legs and without
jointed legs. Invertebrates with jointed legs have a segmented body and a hard exoskeleton. Th"y may have three,
four, or more than four pairs of legs. Invertebrates without jointed legs can have worm-like bodies or non-worm-like bodies. Some wormlike organisms have segmented bodies while others do not. Some non worm-like invertebrates may have shells while others don't.
Invertebrates with
Invertebrates
jointed legs
without jointed legs
Three pairs oflegs
Four pairs oflegs
. . .
. . .
butterflies grasshoppers ants
scorplons spiders
ticks
More than four pairs oflegs
. . .
millipedes shrimps crabs
Worm-like bodies
. . .
earthworms flatworms
roundworms
Not worm-like bodies
. . .
jellyfish snails starfish
The vertebrates thorax
neao
Although there are fewer vertebrates than
aDoomen
one parr
invertebrates, they are much bigger and more noticeable. They can grow larger, even on land, because they have skeletons inside the body to hold them up.
of wings
Vertebrates are classified into five smaller groups (classes): fish, amphibians, reptiles, birds, and mammals.
Fish, amphibians and reptiles all have a body temperature which is the same as their of
r
jointed legs
The body parts of an insect
surroundings. Birds and mammals have their own warm body temperature which stays the same whatever the weather.
107
Birds are warm-blooded animals They breathe with their lungs wings and most of them can fly They have beaks and lay eggs with hard shpLls ThFy orten core [or their young
I
I I
Mammals aTe warm blooded animals Most of them live on land, but some mammals like whales and dolphins live in water Mammals breathe with their lungs They have hairy skin and can sweat The young develop in the body of the mother and are born alive instead of hatching The mother makes milk in her body to feed them
Glassifying plants fust as the animal world can be divided into smaller groups
After this topic you should be able to:
.
(phyla), so can the plant kingdom. Plants can be divided into nonflowering and flowering plants.
explain how plants are classifred into
. o
Thinking about plants
different groups describe some of the main plant groups present results in the form of a bar chart.
Make a list of as many different plants as you can think of,
both local plants and ones from other parts of the world that you have heard about. How will you divide these plants into groups?
. o
dicot monocot
Non-flowering plants Non-flowering plants can be divided into three small phyla: Phylum Bryophyta, Filicinophyta, and Coniferophyta. capsure
stalk stem-like srrucru re
leaf-like stTUctu re
,,{
\
@ ln/u-
Bryophyta Bryophlta include plants such as mosses and liverworts. Mosses are small plants which need damp places to live. This is because they have thin leaves which do not have a waterproof covering and no
-
transport system for water in the plant. They do not have true roots, stems and leaves. Mosses reproduce by making spores; they do not make seeds.
Moss and its structure fronds
@ fftgrr-
Filicinophyta - The phylum includes plants such as ferns. Ferns are much bigger plants than mosses. They have strong stems, roots and leaves and their leaves are waterproof. Ferns also have a transport system for water; so they don't have to live in damp places. Ferns reproduce by making spores; they do not make seeds.
Fern structure
@ lngo-
Coniferophyta
-
Conifers have thin, needle-like
leaves which they shed a few at a time all through the year.
They have a water transport system and waterproof leaves. Conifers produce seeds which are formed inside cones. They have true roots and stem.
^,
Leaves and cones of conifers
109
Plant sorting Take a walk around your school compound. o Find and identify as many different types of plants as you can. ' Make a bar chart to show how many times flowering plants, conifers, ferns and mosses showed uo in vour lists.
Flowering plants Flowering plants are grouped under Phylum Angiospermophlta. They reproduce by having flowers. The flowers produce seeds inside fruits. They have a water transport system and usually have broad waterproof Ieaves.
o{ flowertng monocots These names
The seeds of flowering plants can be divided into three parts the plumule, the radicle and cotyledons. The plumule will
-
develop into a shoot, the radicle will develop into a root, while the cotyledons are known as seed leaves. The flowering plants are divided into two main groups based on the number of coty'edons, namely monocotyledons and dicotyledons.
Monocots are not usually woody. Their leaves have parallel veins. The flowers
theY have' have one' Monocots two' have Oicots
flower petals usuallv in multtples
are usually green or brown, although some can be very
Summary questions
colourful. The roots are fibrous
and they produce seeds with
seed
with one
one cotyledon. Most monocots are herbaceous plants that can live for one or two years.
@
cotyledon I
pa ra llel VEINS
{# '\r'
@
fibrous root
L Monocots
Dicots are often
woody.
Their leaves have a network of veins, and the top and bottom surfaces of the leaf are different. They often have very brightly coloured and scented flowers which attract insects to pollinate them. They have taproots and produce seeds with two cotyledons.
ntants can belong in more than one group. Name the groups.
flower
varsfres are wet places wnere mosses grow well. Hillsides are drier places where many flowering plants grow but mosses do not. Explain these observations.
multiples of four or five
@
loot< again at the first list of plants you made and put them into groups, What percentage of the plants you thought of came from each of the four main groups of plants?
Glassifications
Echinodermata
.
earthworm
Nematoda
Mollusca
Insecta
.
grasshopper
Chilopoda
. .
centipede
Diplopoda
snail
. millilede ,,rlJ
roundworm
jellyfish
nae
Dicotyledonae
.
hibiscus
Bryophyta
.
fern
.
pine tree 111
Dichotomous key A dichotomous key is used to identify, classiS'and name unidentified organisms. We can list the observable characteristics of the organism and match them to a particular group. Observable characteristics include numbers of joints, body segments and others. Make a list of the observable characteristics you can use to classifli the organisms. A dichotomous key is made up of a pair of statements that can be numbered as I, 2,3 and so on. Each number has a pair of particular observable feature statements which are opposite to one another. For instance, has shell or no shell. The numbering continues until the organism is identified. Since there are many observable characteristics, we can build more than one dichotomous key fgr a set of organisms.
An example of a dichotomous key for animals:
Scales...
goto2
(b) No scales................
go to 4
(a) (a)
Has legs.................. go to 3
(b) No (a)
legs................... snake
Shell.....
(b) No
shell..................
tortoise
lizard
.,#
(a) backbone............... bat (b) No backbone......... Go to (a)
8Iegs..........
5
spider
(b) 6 legs ...................... ant
An example of a dichotomous key for plants:
i
I I
i
\ \\
veins........... orchid plant (b) No parallel veins............ grape tree (a) Has roots ........... ............ fern (a)
Has parallel
(b)
Does not have roots.......................... moss
ectes After this topic you should be able to:
.
o .
describe what is meant by a species discuss reasons why a species has or could become extinct measure variation
between members of a species and present the data in different ways.
. . .
characteristic fedile variation
arl
vanflatlon
The smallest group in the classification of living organisms is a species. We put organisms into different species based on variations between them.
What is a species? The members of a species can breed and produce offspring which,
in turn, can also reproduce. If two animals or two plants cannot successfully reproduce and have fertile offspring, they must be from separate species. For example, horses and donkeys look quite similar and can produce offspring called mules. But mules are not fertile - they cannot reproduce. This tells us that horses and donkeys are two separate species. Each species has its own characteristics which are passed on from parents to offspring. Many species have become extinct, or are in danger of becoming
a species disappears from Earth completely. This happens when there are changes in the environment where a species lives. Each species is adapted to its own environment. If there is a change in the environment and a species of plant or animal cannot change to cope with the new conditions, it will die out. One species cannot breed with another species to help it survive. extinct. Extinction means that
The dodo was a flightless bird that lived in Mauritius. 100 years after sailors discovered the island, all the dodos were gone. The sailors had eaten them! In modern times, climate change
means the ice at the polar regions is melting. The number of polar bears is falling fast. They are adapted to living in the ice and snow, and their numbers will continue to fall in areas where the sea ice is melting fast.
y
Horses and donkeys
Looking at variation Look at the Harlequin ladybirds. They are all members of the same species.
o
List as many of the differences and similarities between them.
Variation within a species You have seen that there is variation between different groups of living organisms. There is also variation between different members of the same species. For example, all of your classmates are members of the same human species - but you all look different. There is variation among you. Investigate several different specimens of the same type of plant or animal. you will find many similarities - but they will also have differences which you can observe, record and measure.
If
Summary questions
@
species? are common among the different types of horses? (c) Do some research and list some
there is a change in the environment, some members of the
variations in different breeds of
the others. They may be able to breed successfully and continue the species even if most of the rest die out. So variation is very environment changes.
horses.
@
Investi gating variation Some types of variation can be easily observed such as attached and unattached earlobes, and dimples when you smile. Some types of variation can only be seen clearly when you measure them, like. hand span, height and body mass. . Work with your classmates and measure easily observed variation in people, e.g. earlobes or dimples. Draw a bar chart, or a pie chart or a table to show your results. . Do the same for the variation which needs to be measured, e.g. hand span or height. Work in a group. Collect a number of seeds, leaves, pods or flowers from different members of the same species of a local plant.
o
List the features which vary. Measure as many examples as you can and choose the best way to display the data
vou collect.
What do scientists mean by the term
(b) What characteristics
species may have a variation. This means they survive better than
important for survival of the species, particularly when their
tul
Cive an example of an organism that shows clear variation
among the members of the species. Why is this important in any species for survival?
@
Find out why scientists think the following organisms became extinct:
passenger pigeon, great auk, quagga, sabre-toothed tiger, mammoth.
Summary Classification is sorling organisms into groups based on their common characteristics.
Invertebrates can be divided into several other groups including different types of worms, molluscs and arthropods.
Taxonomy is the science of naming and classifying organisms of the world based on their similar characteristics.
Veftebrates can be divided into five groups: fish, amphibians, reptiles, birds
The hierarchy of classifications, in order, is kingdom, phylum, class, order, family,
Plants are divided into mosses, ferns. conifers and flowering plants. Flowering plants are divided again into monocots
genus and species.
A scientific name consists of two
Latin
and mammals.
and dicots.
words. The first word is the genus and the second is the species. The scientific
The smallest group in classification is a
name should be written in italics.
which all breed successfully with each other to produce fertile offspring. Variation between organisms is used to
Living organisms can be classified into groups based on the differences and similarities among them.
Plants, animals, fungi and microorganisms are some of the main groups.
species. A species is a group of organisms
put them into different species. Extinction is when all the members of a species die out.
To place living organisms into groups you make careful observations and
When
a
species cannot respond to
changes in its environment it may become
measurements of their characteristics.
extinct. Breeding between species to
Animals are divided into invertebrates, which do not have a skeleton inside their bodies, and vertebrates, which have a
help them survive is not possible.
Variation between
hard, bony skeleton inside their bodies.
extinct.
species can help
the organisms in a to stop them going
Summative Practice Six groups of animals and their features are listed below. Draw a table matching each group with its feature.
moist skin covered in scales
skin with hair on most or some of the bodv moist skin with no scales backbone made of bone or cartilaqe
Which of the following statements is not
2 (a) Two fins on the upper sudace
correct? All birds can fly. All amphibians have four limbs.
A B C
D
(b)
Some mammals lay eggs instead of giving birlh to live young.
Some fish have a backbone made of
cartilage.
F
Biologists used to divide all animals into two groups - vertebrates and invertebrates As they learnt more about organisms they realised that this division was too simple However, we still refer to vertebrate ancr invertebrate animals as it is a useful way to start learning about classification. The many thousands of animal species can all be classified into these two groups. (a) In what way do inveftebrates differ fronr vertebrates?
(b) Explain what is meant by the
spectes.
3 (a)
l
tll
term
pl
ofthe body; sharp teeth Sphyraena barracuda Many small, sharp fins on the upper surface Aulostomus maculatus Tailfin is long and thin Dasyatis americana
(b) Tail fin has two tong, thin projections
Balistes vetula
(b) State two features of fish that would not be useful in this identification key. Explain each of your answers. t4l
All domestic cattle belong to the same species which is known as Bos taurus. ln the wodd, there are many different types (or breeds) of cattle. Four of these breeds are shown below.
The drawings show four different species ol fish found in the Caribbean.
A
The breeds differ from one another in several
ways. For example, they are of differenl heights.
(a) Look carefully at the drawings of
Biologists use keys
to help them
identify
different species. (a) Use the identification key to name the four different types of fish. t4l
1 (a) (b)
Body shape is long and thin:
goto2
breed.
(c)
Body shape is not tong and
thin:
go to 3
the
heads of the four breeds of catfle. List four features that vary among the catfle. t4j (b) Suggest three ways in which the breeds may differ from one another. t3l In some countries each cow in a herd is identified by a tag in its ear. Most farmers keep herds of cows that are all the same
(d)
Suggest three ways that a farmer can tell the difference between individualcows in a herd if they are not tagged. lsl Explain why cattle from all over the wodd are classified in the same species. l3l
6
180-189 mm; 190-199 mm and so on. (See page 100 to remind yourself how to do this.) t3l (d) Use the data in your tally table to draw a histogram to show the variation in hand span in the class. (A histogram is like a bar chart but there are no gaps between the bars on the tsl fa\ Suggest three reasons for the variation in
The drawings show three arthropods.
graph.)
Copy and complete the table to compare these three arlhrooods.
hand span in the
class.
tsl
Which of the following sequence shows the
Presence of
hierarchy of classification?
A. O,S,U,V,T,P,R B. S,Q,R,V,T,P,U
C. V,T,P,S,U,Q,R D. U, T, Q, P,V, S, R
The characteristics of classification change
(a) You may use ticks and crosses for the first three features in the table. tsl (b) State two features that all afthropods have in
7
common.
as they go down along the hierarchy of classification. Which of the following statements is an incorrect characteristic?
t2l
30 students were studying variation.
A. The number of organisms increases
B. The number of organisms decreases C. The number of similar features of arr
Sam
and Sara are looking carefully at everyone's earlobes. They discovered that 25 had free earlobes and 5 had attached earlobes. (a) Draw a bar chart to show these results.
t5l The class then measured the span of the left hand in millimetres. They did this by stretching
organrsm Increases
D. The organisms are arranged in increasing
specificity
largest
hand spans in the class? tsl (ii) Use your answers in (i) to calculate the range in hand span within the class. t2l (c)
Organise the data by making a tally table
using the class sizes: 170-179 mm;
l
11
t1l
Choose the field of science that names and classifies organisms based on their similar characteristics. Ecology
B. Zoology C. Genetics D. Taxonomy
(i) What are the smallest and
n
B. Fungi
C. Chordata D. Protista
A.
(b)
an
10 Which of the following is not a kingdom? A. Monera
out their fingers on a piece of paper and measuring the distance between the tip of the thumb and the tip of the little finger. Sam and Sara collected the data as follows:
t1]
nl
12 Which of the following statements
about classification of organisms is incorrect? A. lt makes the study of organisms easier. B. lt enables predictions of the organisms.
C. lt names the D.
organisms using
a
standardised system.
lt sorls organisms into one group only. t1l 117
Solids, liquids and
gases
Science in Contextt
Amazing demonstrations Otto von Germany. law at the
November, 1602 inMagdeburg,
the age of 15, and then siudied en. Whilst at Leiden, he also studied engineering and was especially interested in building
fortresses.
However, Otto will be best remembered for his famous demonstrations about the pressure caused by gases in the air. In 1650, he invented the air pump. With that, he was able to create a vacuum. He could remove the air from a container
and show the great force that air pressure could produce. Two of his experiments are shown here.
^.
Otto von Guericke
(
In this experiment,
a group of 20
I
I
I
I
I
men used a pulley a piston upwards, as one man tried to pull it downwards by
to pull
sucKtng atr out
of the cylinder. People were amazed when the
'one man'(plus the help of air
I I
pressure) won the
tug of war
In a second experiment, Otto had two halves of copper sphere made so that they fitted together perfectly. Some helpers used a pump to suck the rrir out of the sphere. On his signal, two teams of horses pulled and pulled, but they could not separate the two halves of the sphere. ir
When the horses stopped pulling, Otto returned to the copper sphere. He released a valve and a hissing sound could be heard. As the air rushed
back inside the sphere, it suddenly fell apart into two halves. The crowd were amazed and delighted!
Otto's demonstrations continued to be a great success as he toured around Europe, performing rt several royal courts.
In this chapter, you will find out about the particle theory of matter and the properties of solids, liquids and gases, including changes of state.
-L
Two teams of horses could not separate the two h:l',ac
^l
pressu re
h^-"' '"^ ^{ .i" rha .nnnar c^h-"^ L' 'q LUPPs' rP"c'e - "ll
Goncept map SOLIDS, LIQUIDS AND GASES
Gases After this topic you should be able to:
.
o
.
explain that gases are
made up of parlicles describe how the particles in gases are, on average, spread widely apart and how they move explain the properties nf nacac rrcinn tho
particle model.
. o .
Gases are all around us. The air is made up mainly of nitrogen gas and oxygen gas. Other gases you might know are:
. . . .
chlorine
gas
hydrogen helium
gas
, n
gas
carbon dioxide
gas.
) fnir airship is filled with
helium gas This gas has very low density
a
collide particle theory random
Exploring gases Blow up a rubber balloon so that it is full of air and tie inwards, then release. . Describe what happens.
it
up. With both hands press it gently
Fill a plastic syringe with air up to its maximum reading and then press your thumb over the nozzle.
o . o .
What is the volume of gas in the syringe? Now press the plunger downwards, without letting any air escape. What is the new reading on the syringe? By what percentage has the volume of the air in the syringe decreased?
Watch your teacher warm a boiling tube of air as shown below: I
o I I
Describe what happens
Particles in gases
Summary questions
Scientists believe that all matter, including gas, is made up of particles. The arrangement of particles and their movement in solids, liquids and gases is described by the particle theory. The particles are too small to see, but using this theory we can explain the properties of materials.
@
Name five common gases.
@
Describe the
[.ook at the box below showing the particles of a gas.
@
arrangement and movement of the particles in a gas. Include a dragram in your answer. Explain why gases: nave a very low
(a)
(b)
density spread out to nnnr rnrr thoir
container.
@
There is a lot of space between the particles in a gas. Therefore, a gas is not rigid and the forces of attraction between the gas particles are negligible. The gas flows much more easily than a liquid and diffuses rapidly. The particles in a gas are free to move irround rapidly in any direction. We say that they move in a random manner. They collide with each other and with the walls of their container.
.
When we compress a gas, its particles are pressed closer together. So there is less space within the gas and its takes up a smaller volume.
.
When we heat a gas, its particles galn energy and move around
more quickly. Hot gas has a greater volume than the same mass of cool gas (at the same pressure).
(
The brown vapour of
bromine gas
Explain why a hot air balloon rises.
Liquids After this topic you should be able to: . describe how the particles in a liquid are arrangeo describe how the
You get a good idea of the properties of a liquid when you go for a swim or walk through a stream. Is it easier to move through air or water? What does this suggest about the spaces between the particles in a liquid compared with a gas?
par.ticles in a liquid
move explain the properties of liquids using the particle model.
.
expand
A Water isthe mostcommon liquid on Earth Viewof Biting Rivertaken from Badegan, Ponorogo, EastJava, lndonesia
Particles in liquids The particles in a liquid are arranged randomly. There is no fixed pattern. There is very little space between the
particles. The particles can slip and slide around each other.
Look at the diagram of the particles in
.
a
liquid:
We cannot compress a liquid to any extent because its particles are touching the neighbouring particles.
.
Therefore, a liquid is less rigid than
a solid. The forces of
attraction
between liquid particles are weaker than those in a solid.
i
A liquid can flow because its particles are free to move around. Liquids flow to take the shape of their container.
Summary questions
When we heat a liquid, its particles gain energy and slip and slide over each other more quickly. This causes the liquid to expand when it is heated so that it has a slightly greater
O @
volume.
*nU can a liquid flow? Explain the results of
the Practicalactivity 'Exploring liquids', using the particle model.
Exploring liquids
a)
@ Fill a plastic syringe with water up to its maximum reaorng and seal the nozzle with vour thumb.
Vercury is a silvery liquid used in the thin
tube inside some thermometers. Explain the way in which a mercury thermometer WOTKS.
Now press the plunger downwards, without letting any warer escaoe. o Does the volume of the water in the syringe decrease? Compare this with the result of the same experiment using a syringe of air.
.^, A mercury thermometer
b) Warm a flask of coloured water which has a verv narrow
glass tube inserted as shown: o Describe what happens.
thin glass tube
coloured water
Mercury is a metal which is liquid at room temperatu re
Solids After this topic you should be able to: o describe the arrangement and movement of the particles in a solid . explain the properties of solids using the nartinla Hs, (,v,v
o .
You already know about the properties of solids, such as wood, plastic and metals. Each solid material is different
but they all have certain things in common. For example, all solids have a fixed shape. They cannot flow like liquids and gases.
mndal
evaluate vibrate
)
C"ta
is one of the most expensive solid materials l+;^rs a - ---^ ^ rL rare meLar -^+-l+L^+rnaL people use to make jewellery because of its beautiful, shiny appearance Gold is a dense, hard metal
Exploring solids Take three equal-sized blocks of different solid materials, such as iron, wood and plastic. Place each block in a olastic container filled with some water.
.
What happens?
Dry each block and then find its mass using an electronic balance. Record your results in a table. All solids are made up of particles. Discuss the results of the experiments. Think of ideas about these oarticles that could explain the results.
. .
t
electronic balance
I I
Modelsolid Make a model to show the particles in a solid using polystyrene balls.
The balls should all be the same size and you can use glue to stick them to one another. o Evaluate your model. In what ways is it a good model? What are its drawbacks?
Particles in solids The particles in solids are arranged in regular patterns. They are fixed in their positions, touching the particles next to them. The particles cannot move around like those in liquids or gases, but they do vibrate. The hotter the solid, the more the particles vibrate. Look at the diagram of the particles in a solid.
Summary questions
We cannot compress a solid because its particles are touching their neighbouring particles. The forces of attraction are stronger between the solid particles
compared to liquids and gases.
A solid cannot flow because its particles other in fixed positions. So solids have
a
are touching each
fixed shape.
When we heat a solid, its particles vibrate more quickly and more vigorously. This causes a solid to expand when it is heated.
O
*nu do solids have a
@
sotios cannot be compressed. Explain why in terms of the particle theory.
@
fne density of a solid
fixed shape?
is
mass oer unit volume of the solid, which has the unit g/cm3. Why do different solids have different densities?
-r
Glassif frrx mveryday materials After this topic you should be able to:
Solid, liquid and gas are called the three states of rnatter. Look at the comparison betweelr the three sttrtes of martter below:
o rccnnniqo ih:i cnrqg materials are difficult +^ ^^ a ^ -^ti, ru ^t^^^ii, urilssily as soilo.
.
liquid or gas
display results in a
mass shape
Solid
Liquid
Gas
definite
delinite
definite
definite
not definite;
not definite;
takes the shape of the
takes the shape ofthe
container
container
definite
not definite;
table.
o
. .
Q€IS
volume
definite
takes the
liquid solid
volume of the container arrangement
particles
of
particles closely
are
packed
rigidly arranged
and
particles are closely packed
particles
not closely
but less rigid; there is more
packed,
space between
empty space
a
oarticles
lot of
between
particles
compressibility incompressible forces
of
very strong
highly
almost incompressible
compressible
strong
very weak
attraction between particles
fluidity diffusion
flow
flow cannot diffuse diffuses slowly cannot
can
can flow
diffuses
rapidly
Look at each of the materials listed in the following table and classify them as a solid, a liquid or a gas. Explain your reason for each choice. You can use a microscope to help you. . Record your results in a table similar to the one that follows.
126
Summary questions
O
sugar
Copy and complete the
toothpaste
g
8 fr € Eh.6
,^,^il^^^^. vvoilpqpsr ^-^+^ vqDLv
5
talc
FE
te fr #e
SAUCE
cling-film
Solid hair gel
Liquid
narr spray
Gas
sponge
@
wet clay
Now share your ideas with another group.
table.
Agree on a final version of your table before discussing your results as a class.
petrol; oxygen; nitrogen; concrete; engine oil; iron; carbon dioxide; perspex; vinegar
Now try the next activity.
Making a key
o
Using the properties of solids, liquids and gases, make a key to help classify substances.
Classify the following substances as solids, liquids or gases at room temperature. Put your answers into a suitable
@
Name one materialthat is difficult to classify as a solid, a liquid or a gas. Explain why.
Try out your key on some of the materials in the previous Practical activity box.
But some materials are difficult
to classify.
Would you classif' this jelly a solid or a liquid? Why?
as
127
Substances and mixtures After this topic you should be able to:
.
explain the
.
classification of matter classify examples of matter.
Matter is made up of particles called atoms, molecules or ions. Matter can be classified into two types based on its composition: substances and mixtures.
Substances A substance is a matter that has a fixed composition. There two kinds of substances
-
are
elements and compounds.
An element is the simplest type of matter that consists of only one type of atom. An element cannot be broken down into a
o o o o o . . . .
atom
centrifugation chromatography distillation filtration ion
metal molecule non-metal
simpler form by any physical or chemical methods. The particles in an element may consist of atoms or molecules. For example, all metals and inert gases are made r.rp of atoms. Elements of hydrogen (H,), oxygen (O,), nitrogen (Nr) and sulfur (Sr) are made up of molecules. These molecules consist of atoms of the same type of element that are combined by chemical bonds. A molecule is a neutral particle.
A compound consists of two or more different elements that are combined by chemical bonds. The particles in a compound can be from either ions or molecules. A compound that is formed from a reaction between the metallic element and non-metallic element consists of ions. For example, a reaction between sodir.rm metal
(Na) and chlorine gas (Cl,) will form
a
compound chloride
of sodium chloride (NaCl). Sodium
consists of a positively charged ion (Na') and a negatively charged ion (Cl ).
A compound that is formed from a reaction between non-metallic elements consists
of molecular particles. The molecules in this compound comprise two or more atoms of different non-metallic elements that are chemically bonded. For example, a molecule of water (HrO) consists of one atom of oxygen and two atoms of hydrogen. Another characteristic of a compound is that
it
cannot be
separated by physical methods, but a compound can split into simpler substances by chemical methods. For example, oil is burnt into carbon and hydrogen.
.l.
Sulfur powder is an example of an ^l^-^^+
+A^+ ;.
--,-l^
, m^l^."1-" (rP '^ v, ^f ,, v,sLU,cr
't A
2 [A
3 4 5 6 7 A I r0',t1 tB tVB VB VtB VIB VilB ViltB VilB tB
I I
metals
12 13 14 15 .t6 [B iltA tVA VA VtA
17
VIA
l8 vilA
atomic weight
semi metals
symbol
non-metals
element name
A periodictable consists of all known chemical elements arranged in a table. lt is divided into metals, non-metals and semi metals. The last column is the inert qases which are chemicallv inactive
Mixtures A mixture consists of elements and or compounds that are mixed physically. The properties of the components in a mixture do not change and the components can be separated by physical separation methods. There are two kinds of mixtures: homogeneous and heterogeneous mixtures. A homogeneous mixture consists of two or more substances that are uniformly mixed. Salt water is an example of a homogeneous mixture. A heterogeneous mixture consists of two or more substances that are not uniformly mixed. For example, oil and water, granite and concrete.
The separation method is based on the physical properties of the components in the mixture such as magnetic property, boiling point, melting point, solubility, and others. There are several methods of mixture separations that are commonly used. These include
solid and liquid
filtration, distillation, centrifugation, and
chromatography.
Filtration Filtration is based on differences in particle size of the components in a mixture. It is used to separate a solid from a liquid. In filtration, a mixture of solid and liquid is poured into a filter paper. The Iiquid passes through the filter paper and the solid is retained.
A Filtration of a mixture ro seoarate two comoounds
0bserving the differences between mixtures Put a spatula of sugar into a glass of tap water. Stir until the sugar dissolves. Label the glass X. Put a spatula of sand into a glass of tap water. Mix and label the glass Y. Observe glass X. Can you identify the sugar and the water in that sugar solution? Explain your observation. Observe glass Y. Can you differentiate the sand from the water in that mrxture? Explain your observation.
. .
Compare glass X and Y. Discuss the differences.
Sublimation Sublimation is based on substances in the mixture that can change from solid to gas, while another substance in the mixture cannot do so. For example, when a mixture of iodine and salt is heated, the solid iodine directly changes to gas. The salt remains in the container.
Distillation Distillation separates liquid components with different boiling points. A mixture is heated until the substances boil, and the component is collected after condensing. The liquid with a lower boiling point is collected first, followed by the liquid with a higher boiling point.
L Distillation apparatus to separate m
a
ixture
Chromatography Chromatography is widely used in various activities to separate a mixture of gas or liquid. The mixture moves over the surface of another substance with a different physical state. The components in the mixture spread out at different speeds and are separated on the stationary phase. There are several types of chromatography, such as paper chromatography, thin layer chromatography, and gas chromatography.
Summary questions
@
an example.
@
Wtrat are the
@
Cbssity the following.
Gentrifugation Centrifugation is used to replace the filtration method if the size of solid particles is too small. This method is widely used to separate red blood cells and white blood cells from blood plasma. The sediments of red blood cells and white blood cells will settle to the bottom, while blood plasma will be retained at the top.
Wf,at is the simplest form of matter? Give
differences between mixture and substance?
ls it an element, a compouno, a
homogeneous mixture or a heterogeneous mixture?
sea water
( A high mi.hih6
i
speed centrifuge ic |coal
this solution
+n c^;n
down
aluminium foil table salt chicken soup
Matter
Elements
Homogeneous mixtures
.
. .
substances that are made up
ofonly one type ofatom
.
also called solutions made up of two or more substances
that are mixed uniformly
e.g.gold, carbon,
.
oxygen gas
e.g. salt water, water,
pure air
@W
t Compounds
Heterogeneous mixtures
.
o
.
two or more elements that are chemically bonded e.g.water, carbon dioxide, sodium chloride
made up of two or more substances that are not
uniformlymixed
.
e.g. oil and water, granite,
concrete
A simple diagram that summanses matteT and its components
-
-
Separation of plant pigments In the early 1900s, Mikhail Tswett the Russian botanist separated plant pigments through a chalk column. He called the technique chromatography, translated from Greek - chroma means colour and graphei,', means to write. What is the importance of chromatography? Chromatography is used to separate substance mixtures into their individual components. Paper chromatography is a quick and inexpensive technique.
How does it work?
In paper chromatography,
substances are distributed between a stationary phase and a mobile phase. The mobile phase is the solvent, while the stationary phase is the chromatography paper that is submerged in the solvent. The solvent passes through the
.a.
Mikhail Tswett
chromatographypaper, carrying the substance in the mixture. The substance is separated into their individual components based on
their solubility in the solvent and also adhesion to the paper. Let's look at the activity on the separation of pigments in leaves. a quarter cup of spinach leaves. Pour a solution of isopropyl alcohol just enough to cover the leaves. Tape a strip of filter paper to a pencil. Rest the pencil on the cup that contains the solvent. The filter paper should touch the solvent. Wait and watch the pigments separate. You will see that different colours of pigments are separated at different distances. Some pigments travel farther than the others.
Grind
7
The spinach leaves are ground usino a mortar and oestle
v
I
I
The green liquid from the spinach leaves is spotted on a filter paper. The filter paper is placed in a solvent to separate the pigment
Ghanges of state What happens when we heat butter in a pan? The solid butter will turn into a liquid. We say that the butter melts. Melting is an example of a change of state - a solid changes to a liquid.
After this topic you should be able to: . name each change of state
o
These are the changes ofstate:
explain what happens in changes of state using the particle theory.
.
solid ...) liquid is called
melting
.
liquid
"')
solid is called
freezing or
a
boiling
a
boiling point condensation condensation point evaporation freezing freezing point melting melting point sublimation
a
o a a a a a a
solidifting liquid "')gas is called
(or evaporation when it
below point) o gas "')liquid
a
An everyday .,'. examDte oT a cni of state - bu
meltins in
boiling
a
is called condensation
solid "')gas
is called sublimation Some solids turn directly into a gas without
melting into Changes of state on temperature line
'l'
takes
place
. y
" ,\
boiling
a
liquid.
Most substances can exist as solids, liquids or gases depending on their temperature. Look at the temperature line below:
@@ @ Liquid
t
melting point freezing point
f
Increasr n9 remperaru re
I
boiling point condensation point
Notice that substances melt and freeze at a particular temperature. They also boil and condense at a certain temperature. Scientists often use melting points and boiling points to identifii unknown substances. A melting point is the temperature when a solid melts into liquid. A boiling point is the temperature when a liquid boils and turns into a gas. The temperature at which a liquid solidifies is its freezing point. The process of cooling a liquid until it turns into a solid is called freezing. Condensation is the process of a gas changing into a liquid. The temperature at which a gas liquefies is its condensation point.
Observing some changes of state Watch your teacher heat the following solids at room temperature: butter ice wax sulfur (in a fume chamber) Your teacher will measure the temperature at which each substance changes from a solid to a liquid. This is the melting point of the substance.
. .
Record the results in a table. What happens to hot liquids when they are allowed to cool down again?
Your teacher will place a test tube containing a little ethanol into a beaker of hot water.
o
What hapoens?
Watch your teacher warm a few crystals of iodine in a test tube. o What happens? . What is the name given to this change of state?
Particles and changing state Look at the particle boxes below:
freezing/
condensation
solidi{ying
.L
Summary questions
Changes of state
O The particles
in a solid
are packed closely together and are
vibrating. As we heat up a solid, its particles start to vibrate more and more vigorously. Eventually the particles vibrate so much that they break free from one another and are able to move about. This is when the solid melts.
As we heat up a liquid, more particles gain enough energy to escape from the attractive forces of their neighbouring particles. The liquid starts to evaporate more quickly. Eventually, the liquid reaches its boiling point. At this temperature, particles are leaving the liquid readily and you see bubbling within the liquid.
Define the following words: (a) condensation
(b) (c) (d)
@
melting boiling freezing
wr'at do we call the change when a solid changes directly into a gas?
@
Explain what happens when a substance melts, using the particle theory.
using models in science After this topic you should be able to: . explain why scientists use models o recognise that models change over
.l _= L'
:
time.
Scientists use models to help them explain the way the world works. A scientist's model might be a theory, a mathematical equation or a computer simulation that explains our observations. We can then use the model to make predictions in new situations.
If the prediction
proves to be .orr..t, then the model is more likely to be accepted as a good one by other scientists.
Changing models Ansignt Greeks were the first people to suggest that everything about the critus, put torward his model to explain the The particles he wrote about were so small that you couldn't The
.
model
is made of tiny particles. They world they lived in. A Greek phil
see
theq.
He imqgingd that the particles were hard and could not
be
destroyed.
Our w61d 'atoms' comes from the Greek 'atomos'. It means indivisible (something that cannot be broken down). Democlilqs explained the properties of materials by saying that thell particles were different. For example, a runny liquid must be made up of smooth, round particles so that they can iumble over each ot\g1.
How convenient for your theory that we can't actually see all these individual particles do you really expect me to -believe that!
t
Scientists use physical models like this to help explain the
woflo
Modelling particle theory lmagine that you and your classmates are particles in a solid, a liquid and a gas.
Discuss a way that you could model the behaviour of the particles changing from a solid to a liquid to a gas.
. r
Try out your ideas. Evaluate your model. In what ways is it a good model and what are its drawbacks?
On the other hand, hard solids must be made up of particles that are sharp, jagged and hard. These particles get stuck in position. That's
why they don't flow. Democritus liked this model because
it
was logical. However,
another famous Greek philosopher called Aristotle had suggested that all materials were mixtures of earth, air, fire and water, and the Greek people believed him.
In his model, Aristotle said materials were different because they contained different proportions of earth, air, fire or water. This was a powerful theory, too, as people could use to explain many observations.
it
Eventually, over 2 000 years later, scientists developed a theory of particles that is still useful today. This theory does not accept everything that Democritus suggested, but accepts ... the facts about particles.
Experiments carried out around 1800s played a big part in refining our ideas about particles.
Democritus was a Greek philosopher, born in 460 BC He has been commemorated on Greek stamps and a large research institute near Athens is named after him
Summary questions
i
I
l. I
The Bohr's atomic model, as proposed by the scientist, Niels Bohr, is currentlv the accepted model for atom
O
*nu
@
St"t" a difference
@
are modets
used in science?
between the Democritus model of a solid and the one you have used in the pafticle theory introduced in this chapter.
*nu do modets change over time?
Heating and cooling curves After this topic you should be able to:
.
describe what happens to the temperature of a solid when it is heated beyond its melting point
.
describe what happens to the temperature of a liquid when it is cooled below its freezing point.
. o
cooling curve heating curve
You have seen how solids melt when we heat them and how the resulting liquids solidi$' when they cool down. In this topic we will see what happens to temperature during changes of state. A suitable substance to investigate is stearic acid.
Investigating melting Solid stearic acid will melt when heated in a beaker of hot waler.
Set up the apparatus as shown in the diagram. Using a thermometer, take the temperature of the stearic acid every 30 seconds.
thermometer
clamp stand
Do not remove the thermometer from the stearic acid throughout the experiment. Keep taking readings untilthe temperature reaches about
70'c.
.
Record the results in a table. ftime should be in the first column, and temperature second column.)
rn
the
Now carry out the next experiment as quickly as possible.
Investi gati ng freezing Use the clamp stand to lift the tube of molten stearic acid from the hot water.
thermometer
clamp stand
The tube of stearic acid will start coolino down when removed from
the hot water. Take the temperature every 30 seconds.
. o .
Record the results in a table. Draw a line graph for each set of results in the two experiments. What patterns do you see on the graphs?
^+^^-i^
^^i!
cooling down
Explaining heating and cooling curves The line graph below is obtained from the Practical activity 'Investigating melting'on the previous page. The line on the graph is called a heating curve. Look at the graph:
Summary questions
O
merrn9 (or freezing) por nt
solid melts
U
tul what
difference between a heating curve and a cooling curve? (b) From which part of a heating curve can we tell
the melting point of a
o
l
energy is being used here to separate particles
rc c)
o
from their neighbours
E
(c)
P
freezing point of the
substance.
@
curve
You can see a flat (horizontal) section on the line. The temperature stays the same for a while even though the substance is still belng heated. At this point, both solid and liquid are present in the tube. This temperature is the melting point of the solid substance (which is the same as its freezing point). The temperature remains the same until all the solid is melted as it takes energy to separate its particles from each other.
The line graph below is obtained from the Practical activity 'Investigatingfreezing'on the previous page. The line on the graph is called a cooling curve.
liqu idlsolid
U
3CJ
I
l o 0
o E
O
-
potltsit-
nydroxrcle
nrtrate
+
*"1",
Adding acid to alkali Use a dropper pipette and a small measuring cylinder to collect 5 cm3 of dilute sodium hydroxide solution in a test tube. Place the test tube in a test tube rack and add a few drops of a Universal Indicator.
o
What is the pH value of the solution?
Add 4 cm3 of dilute hydrochloric acid to the same test tube. a What is the pH value of the solution now? a
What does this tellyou about the solution?
Now use a clean dropper pipette to add dilute hydrochloric acid to the test tube, a drop at a time. After each addition, shake the tube from side to side. Add only enough Universal Indicator to turn the mixture green. You will have to be very carefulto do this successfully.
o .
What is the pH value of the solution when you have added equal quantities of acid and alkalitogether? What happens to the pH of the solution if you add too much acid?
lf you add too much acid, you don't have to start the whole
experiment again. What can you do
Make sure you wear eye
to make your solution neutralwithout having to staft all over again?
I Sodir. chloride also known
as
table salt
protection.
-
a common salt
Adding alkalito acid Using a dropper pipette and a small measuring cylinder, repeat the previous experiment but start with 5 cm3 of dilute hydrochloric acid. Then you can add sodium hydroxide solution a little at a time to the acid. Make sure you wear o What do you notice about the pH change when the point of eye protection. neutralisation is reached in both exoeriments?
Treating acidic soil Collect two soatulas of acidic soil in a beaker and half fill it with distilled water. Filter into a conical flask and test the pH with Universal Indicator.
o
What is the oH value of the soil?
Repeat this experiment but mix powdered limestone with the acidic soil before adding the water and then filtering.
.
What is the pH value after treating the soil with powdered limestone?
Repeat a second time but this time add powdered lime to the acidic soil.
. .
What is the pH value after adding powdered lime? Which powder would you recommend to the farmer?
Make sure you wear eye protection.
Neutralising acidic soil
Summary questions
As you saw on pages I74 and I75, the pH of a farmer's soil makes a big difference to the crops that can be grown.
O
Many farms suffer from soil that is too acidic so the farmer needs to increase the pH of the soil. The cheapest, most easily applied substance is powdered limestone or lime. Both react with acids to
When the right amount of acid and alkali with each other, we get a _ solution formed, with a pH value
neutralise them.
You can try neutralising soil
.7
as
in the Practical activity above.
Farmers spread lime or limestone on acidic soil
Coou and complete: When we add an acid to an alkali, the pH value of the solution goes
to raise its pH value
of
@
ciue one use of a neutralisation reaction that can be helpfulto farmers.
@
Stetcr, a graph to show the pH of the solution changing when an acid is added to an alkali, as in the first experiment on the previous page.
After this topic you shoukj be able to:
s
prepare a sanrl:tle of salt, iollowirg a
-cut ll s.l. ,r" Iu-ruLiut nxP lit r the seLr.rr; rliut of crystar s of sa t frort r
,,
r
iLs
solution
ln tlri:
iitr;t c.)ipcrinrcirt on paqc l7(r, 1,orr ncutralisecl iut ircicl \vith ilil(ilii" tr1-i,41t, .t'"'- gei silttt{ bv a ltetc, )/otl itright ltet grirlcl'Lrl litr tllrtI icle lionl
ilxr
'i1re i'c:tr--iiort irr-'Irlttn sorlitr rrr it),rllov rlc iurd hl,tl rochlrrr.1r
r , rar lr
lrJrc So,
bc Jtl
with bicar[ronate of soda (a wea< a
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