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ge Checkpoint Science Coursebook 8

Description

This captivating Coursebook provides coverage of stage 8 of the revised Cambridge Secondary 1 curriculum framework

It is endorsed by Cambridge International Examinations for use with their programme

The series is written by a highly experienced author team

The Coursebook is easy to navigate,

with each learning topic covered by a double-page spread

Concepts are clearly explained and followed by stimulating activities and questions to test students’ understanding

Answers to the questions are included on the Teacher’s Resource CD-ROM 8

Other components of Cambridge Checkpoint Science 8: Workbook 8 ISBN: 978-1-107-67961-0 Teacher’s Resource 8 ISBN: 978-1-107-62505-1 Completely Cambridge – Cambridge resources for Cambridge qualifications Cambridge University Press works closely with Cambridge International Examinations as parts of the University of Cambridge

We enable thousands of students to pass their Cambridge exams by providing comprehensive,

To find out more about Cambridge International Examinations visit www

org/cie for information on our full range of Cambridge Checkpoint titles including e-book versions and mobile apps

Fellowes-Freeman and Sang

The Coursebook contains: • language accessible to students of a wide range of abilities • coverage of the Scientific Enquiry section of the syllabus integrated throughout the text,

with activities designed to develop all necessary skills • questions throughout each topic to reinforce understanding • questions that ask students to think about applications and implications of the concepts are indicated on the pages • end of unit questions to help prepare students for the Progression test • a student reference section,

including advice on carrying out practical work and recording results

Mary Jones,

Diane Fellowes-Freeman and David Sang

Cambridge Checkpoint

Science

Coursebook

Coursebook 8

Fellowes-Freeman and Sang: Cambridge Checkpoint Science Coursebook 8 Cover

C M Y K

Mary Jones,

Diane Fellowes-Freeman and David Sang

Cambridge Checkpoint Science

Cambridge Checkpoint Science Coursebook 8

Mary Jones,

Diane Fellowes-Freeman and David Sang

Cambridge Checkpoint

Science Coursebook

University Printing House,

Cambridge cb 2 8 bs ,

United Kingdom Cambridge University Press is part of the University of Cambridge

It furthers the University’s mission by disseminating knowledge in the pursuit of education,

learning and research at the highest international levels of excellence

org Information on this title: www

org/9781107659353 © Cambridge University Press 2013 This publication is in copyright

Subject to statutory exception and to the provisions of relevant collective licensing agreements,

no reproduction of any part may take place without the written permission of Cambridge University Press

First published 2012 5th printing 2014 Printed in the United Kingdom by Cambrian Printers Ltd

A catalogue record for this publication is available from the British Library isbn

Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this publication,

and does not guarantee that any content on such websites is,

References to Activities contained in these resources are provided ‘as is’ and information provided is on the understanding that teachers and technicians shall undertake a thorough and appropriate risk of assessment before undertaking any of the Activities listed

Cambridge University Press makes no warranties,

representations or claims of any kind concerning the Activities

To the extent permitted by law,

Cambridge University Press will not be liable for any loss,

liability or damage of any kind resulting from the use of tha Activities

Introduction Welcome to your Cambridge Secondary 1 Science course

! This book covers the second year,

Stage 8,

of the Cambridge Secondary 1 Science curriculum

At the end of the year,

your teacher may ask you to take a test called a Progression Test

This book will help you to learn how to be a good scientist,

The main areas of science The book is divided into three main sections,

each one dealing with one of three main areas of science

These are: Biology – the study of living organisms

Chemistry – the study of the substances from which the Earth and the rest of the Universe are made Physics – the study of the nature and properties of matter,

There are no sharp dividing lines between these three branches of science

You will find many overlaps between them

Learning to be a scientist During your course,

you will learn a lot of facts and information

You will also begin to learn to think like a scientist

Scientists collect information and do experiments to try to find out how things work

You will learn how to plan an experiment to try to find out the answer to a question

You will learn how to record your results,

and how to use them to make a conclusion

When you see this symbol SE ,

it means that the task will help you to develop your scientific enquiry skills

Using your knowledge It’s important to learn facts and scientific ideas as you go through your science course

But it is just as important to be able to use these facts and ideas

When you see this symbol A+I ,

it means that you are being asked to use your knowledge to work out an answer

You will have to think hard to find the answer for yourself,

using the science that you have learnt

(A+I stands for Applications and Implications

Contents Introduction

Biology

Chemistry

Unit 1 Plants 1

2 Leaves 1

4 Roots 1

Unit 6 States of matter 6

Unit 7 Elements and compounds 7

1 Atoms 7

Unit 8 Mixtures 8

Unit 9 Material changes 9

Unit 2 Food and digestion 2

5 Teeth 2

Unit 3 The circulatory system 3

3 Blood 3

Unit 4 Respiration 4

Unit 5 Reproduction and development 5

Contents

Physics

Reference

Unit 10 Measuring motion 10

1 How fast

Making better measurements Measuring instruments Improving accuracy Anomalous results Understanding equations

Glossary and index

Unit 11 Sound 11

Unit 12 Light 12

Unit 13 Magnetism 13

Acknowledgements 188

Plant organs Photosynthesis

Where do you get your energy from

? Your energy comes from the food that you eat

Energy is passed from one organism to another along a food chain

Every food chain begins with a plant

Plants capture energy from light,

and transfer some of the energy into the food that they make

When we eat food,

In this unit,

we will look at how plants use energy from light to make food

The arrows in a food chain show the energy passing from one organism to another

Making with light ‘Photo’ means to do with light

‘Synthesis’ means ‘making’

So ‘photosynthesis’ means ‘making with light’

Photosynthesis is the way that plants make food,

This forest in New Zealand is a giant food factory

Questions

What does each of your words mean

at which point does photosynthesis take place

1 Plants

CUP CP Bio 8 plant schematic

Photosynthesis

What else do plants need for photosynthesis

? • Plants use water in photosynthesis

They get the water from the soil

• Plants use carbon dioxide in photosynthesis

They get the carbon dioxide from the air

You already know that plants make food by photosynthesis

But they also make a very important gas – oxygen

We can summarise photosynthesis like this: Water and carbon dioxide are changed into food and oxygen,

Biomass Plants use the food that they make in photosynthesis to make new cells and tissues

Material that is made of living cells and tissues is called biomass

Activity 1

You are going to find out what happens to plants that do not get light

Leave them in a warm place to germinate

Make sure that they do not dry out

put one set into a dark cupboard,

or into a closed cardboard box

Leave the other set in a light place

Keep giving them both a little water

Try to make sure that the temperature is the same for both sets of seedlings

compare the appearance of the two sets of seedlings

You could also make labelled drawings of a seedling from each set

Questions

A1 Explain why it was important to keep one set of seedlings in the light

A2 Explain why it was important that the temperature was the same for both sets of seedlings

Summary Summary • There is still a lot that we do not know about the human • Photosynthesis is the way that plants make food,

• Some of the food that is made becomes new biomass in the plant

• Many diff erent kinds of scientists do research into the human • Plants use water and carbon dioxide in photosynthesis

to fi nd out things that we do not yet know or understand

• Plants make food and oxygen by photosynthesis

1 Plants

In most plants,

the leaves are the organs that carry out photosynthesis

Chlorophyll Most leaves are green

This is because they contain a green pigment called chlorophyll

(A pigment is a coloured substance

) Chlorophyll is essential for photosynthesis

Chlorophyll captures energy from light

The leaf can then use this energy to make food

Leaves capture energy from light

Questions

What is the name of the part of a plant cell – also beginning with ‘chloro’ – that contains chlorophyll

? 2 Suggest why leaves are green,

where you grew some seedlings in the dark

What happened to the chlorophyll in them

A+I A+I

The structure of a leaf The picture shows the different parts of a leaf

The veins carry water to the cells in the leaf

They also help to support the leaf and hold it out flat

The leaf looks green because its cells contain chlorophyll

The leaf stalk attaches the leaf to the plant

Most leaves are very thin,

so light can reach all the cells inside them

How a leaf is adapted for photosynthesis

1 Plants

A waxy layer on the leaf surface stops the leaf cells from drying out

The upper epidermis protects the cells inside the leaf

The palisade layer contains cells that do most of the photosynthesis

Leaves are so thin that it is difficult to imagine they contain several layers of cells

It is the cells in the middle of the leaf that carry out photosynthesis

A vein carries water to the cells in the leaf

The lower epidermis protects the cells inside the leaf

The spongy layer has lots of air spaces

The cells in the spongy layer do a small amount of photosynthesis

A stoma (plural: stomata) is a tiny hole in the lower epidermis

These holes let carbon dioxide from the air get into the leaf

Activity 1

Take a fresh,

Push the leaf into some warm water

Watch carefully to see where air bubbles appear on the leaf surface

Questions

A1 On which surface of the leaf did most bubbles appear

? A2 The bubbles contained gas that came out from inside the leaf

Which part of the leaf do you think the gas came from

? (Look at the diagram of the inside of the leaf above

) A3 Suggest how the gas got out of the leaf

A4 Use what you know about the effect of heat on gases to explain why the gases came out of the leaf when it was put into warm water

Summary • Leaves are adapted to carry out photosynthesis

• Leaves are green because they contain the green pigment chlorophyll,

which absorbs energy from light

• Leaves have tiny holes in their lower surfaces,

which allow carbon dioxide to get into the leaf from the air

1 Plants

Investigating photosynthesis

How can we tell if a leaf is photosynthesising

? One of the simplest ways is to check if it is giving off (releasing) oxygen gas

This is easiest to do if the leaf is under water,

because the oxygen gas makes bubbles

Activity 1

3A Collecting the gas produced in photosynthesis SE

The diagram shows the apparatus you need to set up for this experiment

You can use any plant that grows under water

You can usually get pond weed at a pet shop,

because people buy it to put into fish tanks

If you live near the sea,

Leave the apparatus in a place where the plant will get plenty of light

If it is very warm and sunny,

you may see the gas collecting quickly

If it is colder and not so bright,

you may need to leave it for a day to give time for the gas to collect

beaker pond water upside-down funnel water plant block to support funnel

When you have collected about half a test tube of gas,

you can test it to see if it is oxygen,

like this: 1 Put your hand into the water in the beaker,

and hold the test tube near its opening

Put your thumb over the opening,

taking care to keep the test tube under water

then blow it out so that it is just glowing

to let the water fall out of the tube

quickly but carefully put the glowing splint into the tube

Try not to touch the wet sides,

it will make the glowing splint burst into flame

Questions

A1 Explain why you needed to use a water plant for this experiment

A2 Explain why you needed to leave the apparatus in a light place

1 Plants

Investigating photosynthesis

Activity 1

3B Investigating the rate of photosynthesis SE

You are going to plan and carry out an experiment to investigate this question: Is there a correlation between light intensity and the rate of photosynthesis

? A correlation is a relationship

If there is a correlation between light intensity and photosynthesis,

then we would expect that changing the light intensity will result in a change in the rate of photosynthesis

Here are some ideas you can use

• You can use a water plant like the one that you used for Activity 1

• To measure the rate of photosynthesis,

you can measure how much gas the plant gives off in a certain length of time

For example,

you can measure the depth of gas that collects in the test tube in one hour

For a quicker experiment,

you can count how many bubbles the weed gives off in one minute

If you do that,

then you don’t need a funnel or test tube to collect the gas

• To give the plant a high light intensity,

you can place a lamp close to the plant

For a lower light intensity,

• Think carefully about all the variables that you must keep the same in your experiment

• Decide whether you should do several repeats for each light intensity,

so you can calculate a mean for each one

Make changes to your plan if you think you can improve it

and compare your results with your predictions

Summary • A good way to fi nd out if a water plant is photosynthesising is to see if it gives off bubbles of oxygen

• If photosynthesis is happening at a faster rate,

then more oxygen is given off per minute

1 Plants

Roots are usually underground,

so we often do not notice them

the roots take up just as much space as the above-ground parts of the plant

Functions of roots The roots of a plant have several functions

• Roots absorb water and minerals from the soil

These are then transported to all the other parts of the plant

• Roots anchor the plant firmly in the ground,

so it is not pulled out when the wind blows strongly,

or when an animal pulls on the leaves

• Some plants store food in their roots

• When conditions are difficult – for example,

or a dry summer – some plants allow their aboveground parts to die

Only the underground roots continue to live

New shoots (above-ground parts) grow from the roots when conditions become better

For a plant,

its roots are just as important as its leaves

Activity 1

4A Roots for food We make use of many roots that store food

The plant stores the food for its own use,

Choose two different roots that humans eat as food

For each root,

find out what the complete plant looks like

Make a labelled drawing of the plant

Describe how we use the root for food

How roots absorb water and minerals Soil is made up of tiny rock particles

There is usually water in the spaces between the particles

There are minerals dissolved in the water

You may remember that special cells called root hairs grow out of the surface of roots

Root hair cells provide a really big surface through which water and minerals can be absorbed

1 Plants

Roots are good sources of food for humans

A root hair cell

Questions

A+I A+I

Activity 1

This photograph of a root was taken using a microscope

You can see that it is covered with thousands of tiny root hairs

CUP CP 8 2011 1

4E bean gas jar

Which way up

Roll up a piece of strong absorbent paper so that it fits inside the jar

Add a little water and allow it to soak into the paper

Carefully put them between the paper and the side of the jar

Place each one a different way up

Check it each day to see if it needs more water – it is important to keep the seeds moist but not too wet

Questions

A1 What do you notice about the directions the roots have grown in

? A2 Suggest how this would help a bean plant to survive

Summary • Roots absorb water and minerals from the spaces between soil particles

• Roots anchor a plant in the ground

• Roots can store food for the plant

• Roots can sometimes survive harsh conditions that kill the above-ground parts of the plant

1 Plants

Transporting water and minerals

We have seen that the roots of a plant absorb water and minerals

How are these transported from the roots to all the other parts of the plant

Activity 1

5A Transport in a celery stalk SE

If possible,

choose one that has some leaves at the top

Stand the celery stalk in the dye

Make sure you stand the stalk the right way up

You should be able to see the coloured dye moving up inside it

(This can sometimes happen very quickly and sometimes very slowly,

!) 4 When the dye has reached the top of the stalk,

take the stalk out of the dye and wash it in clean water

Look at the cut end using a hand lens

Make a drawing of what you can see

Questions

A1 Suggest why it is important to wash the celery stalk before cutting across it

A2 Flowering plants,

contain long tubes called xylem vessels

(You pronounce the ‘x’ in xylem as though it is a ‘z’

) These vessels transport water and substances dissolved in the water

Use your results to describe where the xylem vessels are in a celery stalk

Activity 1

5B How does temperature affect the rate at which water is transported in a celery stalk

You are going to plan and carry out an experiment to try to answer the question in the title

Think about the following questions

What variable will I change

? What variables will I try to keep the same

? How will I keep them the same

? Are there any safety risks in my experiment

? How will I record my results

what will I put on the graph axes

? • What do I think the results will be

When you have written your plan,

After you have done your experiment,

identify the trends and patterns you can see

Compare your results with your predictions

1 Plants

Transporting water and minerals

Xylem vessels When you did Activity 1

you saw that the coloured dye did not soak into all of the celery stalk

It stayed inside the xylem vessels

Xylem vessels are long,

hollow tubes that carry water and minerals from the roots of the plant to its leaves

In a tree,

the xylem vessels reach all the way up the trunk and to the very tips of the branches

The xylem vessels continue inside the leaves

The position of xylem vessels in a root

Xylem vessels are very tiny

The spots that you saw in the celery stalk each contain several xylem vessels

The diagrams show where the xylem vessels are in a root,

The dark blue areas show where xylem vessels are found

Xylem vessels have very strong,

This means that they help to support the plant,

as well as transporting water and minerals

The positions of xylem vessels in a stem

The wood in a tree trunk is made up of xylem vessels

If you are working at a wooden desk,

you may be able to see the xylem vessels that make up the wood

The positions of xylem vessels in a leaf

In a leaf,

the xylem vessels are inside the veins

This is a piece of wood seen with a powerful microscope

Each hole is the cut end of a xylem vessel

Summary • Water and minerals are transported from a plant’s roots to its leaves inside long,

hollow tubes called xylem vessels

• The veins in a leaf contain xylem vessels

• Wood is made up of xylem vessels

1 Plants

Unit 1 1

End of unit questions

The words below all have something to do with photosynthesis

Choose the correct word to match each description

You may use each word once,

air carbon dioxide chlorophyll chloroplast oxygen palisade layer soil stomata veins a b c'd'e f

This gas is used by plants in photosynthesis

This gas is made by plants in photosynthesis

Plants get their water for photosynthesis from here

This green pigment absorbs energy from sunlight

This tissue in a leaf is where most photosynthesis takes place

These tiny holes in a leaf allow gases to move in and out

The photograph shows the upper surfaces of leaves from two different plants

The leaves are both shown life-size

Construct a table that you can use to compare the structure of the two leaves

Then complete your table to show at least five differences between the leaves

1 Plants

End of unit questions

Anurag did an experiment to compare the rate of photosynthesis of two types of seaweed

The diagram shows the apparatus he used

measuring cylinder beaker seawater upside-down funnel seaweed

a What variable should Anurag change in his experiment

? b List three variables that Anurag should keep the same

c'What should Anurag measure in his experiment

b Describe how water is transported to the leaves of the plant

[2] [2]

1 Plants

Nutrients

Everyone enjoys eating tasty food

Food gives us pleasure

It also gives us the nutrients that we need to stay healthy

Nutrients are substances in food that the body uses: • to provide energy • to provide materials for making the chemicals that are needed to make cells and other parts of the body

Different kinds of food contain different nutrients

These foods are good sources of protein

Protein,

carbohydrate and fat The nutrients that we need to eat in the largest quantity are protein,

Protein is used for making new cells

Protein is also used for making many important chemicals in the body,

such as enzymes (see pages 28–29) and antibodies (see page 37)

Cells can use protein to supply energy

Carbohydrate is used to provide energy

Starch and sugar are two kinds of carbohydrate

These foods are good sources of starch (a type of carbohydrate)

Fat also provides energy

Fat can be stored in the body

Fat stores underneath the skin provide insulation

Fat is needed to make new cell membranes

Vitamins and minerals Vitamins and minerals are nutrients that we need in only very small quantities

They do not provide energy

There are many different kinds of vitamins and minerals that we need to eat

Fruit and vegetables are a good source of some of them

There is more information about two vitamins and two minerals on page 20

These foods contain a lot of fat

Fibre and water Fibre (roughage) helps to keep food moving easily through the digestive system

We get fibre from fresh fruit and vegetables,

and also from foods made from whole seeds such as brown rice or wholemeal bread

Water is sometimes considered to be a nutrient

Between 60% and 70% of the body is made up of water

These foods contain a lot of fibre

Nutrients

Questions

List them all

Activity 2

Starch and sugar are two types of carbohydrate

You can find out if a food contains starch using iodine solution

You can find out if a food contains sugar using Benedict’s solution

1 First,

• Put a small amount of the food onto a white tile

• Add a drop or two of iodine solution

If the iodine turns blue-black,

2 Next,

• Chop or crush a small amount of the food,

and put it into a boiling tube

Add a little water and stir or shake it well

• Add enough Benedict’s solution to make the mixture look blue

• Put the boiling tube into a water bath at about 80 °C

Leave it for about 5 minutes

• If there is sugar in the food,

the colour will no sugar change as shown on the right

Add as many more rows as you need

Colour with iodine solution

Did it contain starch

Colour with Benedict’s solution

Did it contain sugar

Summary • We need to eat seven diff erent types of nutrients – protein,

• Diff erent kinds of foods contain diff erent combinations of nutrients

A balanced diet

Your diet is the food that you eat each day

Your diet should provide you with enough of each kind of nutrient

It should also give you the right amount of energy

pasta and rice contain a lot of starch and some protein

Fruit and vegetables contain a lot of fibre and vitamins

A diet that provides all the different kinds of nutrients,

and the right amount of energy,

Nutritional deficiencies If a person does not eat enough of a particular nutrient,

their body may not be able to work properly

They may have a nutritional deficiency disease

For example,

a child who does not have enough protein in her body may not be able to make enough new cells

She will not grow properly

The table shows information about two vitamins and two minerals,

and the deficiency diseases that develop if they are lacking in the diet

Nutrient Example Good sources vitamins vitamin C citrus fruits

Dairy foods contain a lot of protein and fat

Sweet things contain a lot of sugar

This photograph shows approximately how much of your diet should be made up of each of the five food groups

Function in the body helps to make strong skin vitamin D'dairy products needed to make bones and teeth minerals iron red meat,

dark green needed to make vegetables haemoglobin,

which carries oxygen in the blood calcium dairy products,

fish needed to make bones and teeth

nuts and pulses contain a lot of protein

Deficiency disease scurvy – the skin becomes weak,

so sores develop rickets – the bones are weak,

so the legs may become bent anaemia – the blood cannot carry enough oxygen,

and the person feels very tired the bones and teeth become weak

Too much sugar can make your teeth decay

Too much fat in the diet can increase the risk of developing heart disease when you are older

Eating too much fat and carbohydrate may mean that you take in more energy each day than you use

The body stores these extra nutrients as fat

Everyone needs some fat stores,

but it is not good to have too much

Being seriously overweight can cause damage to joints,

and increase the risk of developing heart disease and diabetes

What should I eat

? These students are giving some good guidelines for eating a balanced diet

A balanced diet

Don’t eat too much ‘fast food’

Don’t eat too much food containing a lot of fat

Make sure you eat enough food to keep you strong and fit

Eat plenty of fresh fruit and vegetables

Eat a wide variety of foods,

including something from each of the food groups in the photograph,

Question

Match each reason with the piece of advice

a This means you will get some of each kind of nutrient,

including the different vitamins and minerals

b These contain fibre and lots of vitamins

c'This often contains a lot of fat,

and very few vitamins or minerals

It is fine to eat some of it,

as long as you eat plenty of other kinds of foods as well

d'Not eating enough food will prevent the cells,

tissues and organs in your body having enough energy to keep healthy

it can increase your risk of getting heart disease or diabetes

Summary • A balanced diet contains some of all the types of nutrients,

and about the same amount of energy that your body uses each day

• A diet that is missing a particular nutrient can cause a nutritional defi ciency disease

• A good diet has plenty of foods containing protein,

Digestion and absorption

The alimentary canal Your mouth is the entrance to a long tube called the alimentary canal

The other end of the tube is called the anus

The diagram summarises what happens to the food that an animal eats,

as it travels through this tube

tiny food particles are able to get out of the canal and into the body

This is called absorption

What happens inside the alimentary canal

Absorption and digestion The food inside the alimentary canal can only reach your body cells if it can get out through the walls of the tube

This process is called absorption

Protein,

starch and fat are important nutrients

Each of these nutrients is made up of large molecules

A molecule is the tiniest particle of a substance that can exist

Molecules of protein,

starch and fat are so big that they cannot get through the walls of the alimentary canal

in order to get these nutrients to your cells,

the big molecules have to be broken down into much smaller ones

Then the small molecules can be absorbed

This is what digestion is

Digestion is the breakdown of large molecules into small ones,

A starch molecule can be broken into many sugar molecules

Digestion and absorption

Activity 2

Visking tubing is similar to the walls of the alimentary canal

It has tiny holes in it – much too small for you to see – that will let small molecules go through,

Moisten it with water

Rub it between your fingers until it opens up into a tube

fill your Visking tubing with a ‘meal’ of starch solution and sugar solution

When it is nearly full,

use cotton to tie it very tightly around the top

to wash off any starch or sugar that got onto the outside of it

Add enough water to the beaker to cover the tubing

Leave it for about 15 or 20 minutes

Record your results

Record your results

Visking tubing

Questions

A1 A2 A3 A4

Explain why it was important to tie both ends of the tubing very tightly

Explain why it was important to wash the outside of the tubing

Which nutrients – starch or sugar – were able to get out of the tubing

? Use what you know about starch molecules and sugar molecules to suggest an explanation for your results

A5 Imagine you have eaten a meal containing starch and sugar

Do both of these nutrients need to be digested inside your alimentary canal

Summary • Nutrients cannot be used by body cells until they have been absorbed through the walls of the alimentary canal

• Only small molecules can pass through the wall of the alimentary canal

• Digestion is the breakdown of large molecules of nutrients to small molecules,

The human digestive system

The diagram shows the human digestive system

The digestive system is made up of the alimentary canal,

oesophagus liver stomach gall bladder pancreas large intestine small intestine

An X-ray image of part of the alimentary canal

Can you work out which parts are shown

The human digestive system

Questions

food moves along through the space inside the alimentary canal

Write down,

the name of each part of the alimentary canal that food passes through as it travels from the mouth to the anus

that food does not pass through

The human digestive system

Functions of organs in the digestive system Mouth Teeth chew food into smaller pieces

Saliva starts to break down starch to sugar

Oesophagus Food just passes through here without changing

Large intestine All the food that could not be digested and absorbed passes through here

A little more of the water in it is absorbed

The undigested food collects up and forms faeces

Stomach Hydrochloric acid kills micro-organisms in the food

Stomach juices begin to break down protein to amino acids

Liver The liver makes bile

The bile is stored in the gall bladder

Bile flows into the small intestine,

where it helps with fat digestion

Small intestine Juices from the pancreas finish breaking down starch,

protein and fat to small molecules

These small molecules are then absorbed through the walls of the small intestine

vitamins and minerals (which are already made of very small particles) are also absorbed

Pancreas The pancreas makes pancreatic juice

Pancreatic juice flows into the small intestine,

where it helps to digest protein,

Summary • The alimentary canal is a long tube that runs from the mouth to the anus

• Inside the alimentary canal,

nutrients are first digested and then absorbed

• Digestion happens inside the mouth,

Absorption happens inside the small intestine and large intestine

The mouth is the first part of the alimentary canal

Inside your mouth there are four different kinds of teeth – incisors,

Incisors are chiselshaped,

They are used for biting off small pieces of food so that you can take the food into your mouth

Canines are more pointed than incisors

In humans,

they are used in the same way as incisors

Molars are like premolars,

They are also used for crushing and grinding food

Premolars have broad surfaces with ridges on them

They are used for crushing and grinding food when you chew

The four kinds of human teeth

Questions

What do dogs use their canine teeth for

? 2 Explain how the shape of incisors helps them to carry out their function

The structure of a tooth The diagram shows what an incisor tooth looks like if it is cut in half

The diagram also shows the gum and jawbone

Teeth are held in the jawbone by strong fibres

enamel – a very hard covering,

dentine – a layer containing living cells,

not as hard as enamel gum pulp cavity – containing blood vessels and nerves

fibres – help to hold the tooth in the jawbone jawbone blood supply to the tooth

The structure of an incisor tooth

Caring for your teeth The enamel on your teeth is very strong

However,

If that happens,

you may get a hole in your tooth

This can be painful when the hole reaches the pulp cavity,

This means that drinking lots of acidic fizzy drinks (like cola or lemonade) can harm your teeth

Even if you don’t eat or drink acidic things,

you may still get acid in your mouth

This is because bacteria in your mouth break down food remains left on and between your teeth – especially sugary things

The bacteria make acid when they break down the food remains

To avoid getting holes in your teeth: • Don’t drink fizzy drinks,

• Clean your teeth thoroughly after breakfast and before you go to bed

• Use a toothpaste containing fluoride

Fluoride helps to strengthen the enamel on your teeth

CUP CP CB8 2011 2

3D Visking tube beaker

Activity 2

How do fizzy drinks affect teeth

You’ll only be able to do this activity if you can find two teeth

Your teacher may be able to provide these

long enough to hang over the edge of a beaker

Tie the other end around a small stone or weight

Pour the same depth of tap water into the other beaker

and the other tooth in the water

Write down your observations and conclusions

Summary • Teeth break down large pieces of food into small pieces

• Humans have four types of teeth – incisors,

• Teeth have an outer covering of very hard enamel,

Inside the tooth are the dentine and the pulp cavity,

• Enamel can be dissolved by acids

Enzymes

We have seen that large molecules of nutrients must be broken down into small molecules,

Teeth break down big pieces of food into small pieces

But they don’t have any effect on the molecules of the different nutrients that make up the food

The large nutrient molecules are broken down into small molecules by chemicals called enzymes

Digestion as a chemical reaction Digestion changes a substance made up of large molecules into a new substance made up of small molecules

When one substance is changed into a different substance,

we say that a chemical reaction has taken place

The diagram shows a chemical reaction that happens during digestion

Starch is changed to sugar by a chemical reaction

Questions

Catalysts The enzymes inside the alimentary canal make these chemical reactions happen

The enzymes are not changed themselves

They just help to speed up the reactions

A substance that speeds up a chemical reaction,

So enzymes are biological catalysts

Part of a starch molecule

The starch molecule slots into the enzyme molecule

The enzyme molecule makes the starch molecule split apart into sugar molecules

How an enzyme makes starch molecules break down to sugar molecules

The sugar molecules leave the enzyme molecule

The enzyme molecule has not been changed

Enzymes

Questions

Suggest how this can help enzymes to digest the food faster

Draw a series of diagrams showing how an enzyme digests protein molecules to amino acid molecules

Use the diagram at the bottom of the previous page as a starting point

Activity 2

The enzyme that digests starch is called amylase

Add 5 cm3 of water to tube B

Leave both tubes in a warm place for about 20 minutes

take a small sample of liquid from tube A

Put it onto a white tile,

Write down the result

take another sample from tube A

Put it into a boiling tube,

and add some Benedict’s solution

Place the boiling tube into a water bath at about 80 °C

Leave it for two or three minutes,

starch solution and amylase solution

Summary • When one substance is changed into a diff erent substance,

a chemical reaction has taken place

• Digestion is a chemical reaction in which a substance made of large molecules is changed into a substance made of small molecules

• Enzymes are molecules that act as biological catalysts

Enzymes help reactions to take place quickly

The enzymes are not changed themselves

Unit 2 2

End of unit questions

Copy and complete these sentences,

You may use each word once,

Teeth break down large lumps of food into smaller

of the nutrients in the food into small

This allows the nutrients to pass out of the alimentary canal through the wall of the

The table shows the carbohydrate content of ten foods

Food apple banana beans biscuits bread grilled chicken coconut egg fish mutton rice

Carbohydrate content / g in 100 g of food 9 20 17 66 45 0 4 0 0 0 30

Which food contains the most carbohydrate

? Bolormaa ate 50 g of biscuits

How much carbohydrate did she eat

What kind of carbohydrate does rice contain

? What do the four foods that do not contain carbohydrate have in common

End of unit questions

Name parts A and D

a b Give the letters of two labelled parts where protein digestion takes place

c'Give the letter of one labelled part where digested nutrients are absorbed

These were her results

spaghetti – went blue-black with iodine solution,

went blue with Benedict’s solution honey – went orange-brown with iodine solution,

turned brick red with Benedict’s solution a Describe how Rhianna tested the foods with Benedict’s solution

b Construct a results table and fill it in to show Rhianna’s results clearly

c'What conclusions can Rhianna make from her results

Amylase is an enzyme that makes starch molecules break down into sugar molecules

P Q • Nakula put some amylase solution into two boiling tubes,

P and Q • He boiled the solution in tube P

He did not heat tube Q

• He waited until the solution in tube P had cooled down to room temperature

• He added equal volumes of starch solution to tube P and boiled amylase amylase tube Q

and starch and starch • After 10 minutes,

he tested both tubes for sugar

• Nakula found that there was sugar in tube Q,

a What was the variable that Nakula changed in his experiment

? [1] b State two variables that Nakula kept constant in his experiment

[2] c'Nakula wrote this conclusion to his experiment: ‘My results show that boiling destroys amylase’

Explain how Nakula’s results support his conclusion

The human circulatory system

Sit very still and quiet

Put your fingers on your neck,

Can you feel your pulse

? Each pulse that you can feel is caused by one beat of your heart

All through your life,

pushing blood around your body

The blood travels round the body inside tubes called blood vessels

The diagram shows the basic plan on which the blood vessels are arranged

The heart and blood vessels together make up the circulatory system

vein from rest of body heart digestive system other organs other organs The human circulatory system

Questions

Look at the diagram to answer these questions

? 2 In which direction do veins carry blood – away from the heart,

? 3 The circulatory system is like a one-way traffic system

Describe two different routes by which blood in the left side of the heart can get to the right side of the heart

(Remember – the person in the diagram is facing you

A+I A+I A+I

The human circulatory system

Oxygenated and deoxygenated blood One of the most important functions of the circulatory system is to supply oxygen to all the cells in the body

Oxygen enters the blood as the blood passes through the lungs

The oxygen diffuses from the air inside the lungs,

When blood contains a lot of oxygen,

We say that the blood is oxygenated

Oxygen leaves the blood as the blood passes through tissues where the cells are using up oxygen

The oxygen diffuses from the blood,

When blood has lost most of its oxygen,

We say that the blood is deoxygenated

Question

Which side of the heart contains oxygenated blood

You can see blood vessels inside the elephant’s ear

Activity 3

Your model should include something to represent: • the heart,

with the two sides joined together but not allowing blood to move directly from one side to the other • the blood vessels that run between the heart and the lungs • the blood vessels that run between the heart and the tissues in the rest of the body

You might be able to add something that moves to your model,

such as red and blue beads to represent the blood

Summary • The heart and blood vessels make up the circulatory system

• Blood flows out of the heart inside arteries,

and back into the heart inside veins

• Blood picks up oxygen as it passes through the lungs,

and releases oxygen as it passes through the tissues in the rest of the body

The heart

The diagram shows where your heart is

It is just under your ribs,

slightly to left of centre of your body

Your heart is about the same size as your clenched fist

It is made of very strong muscle

The muscle in the heart contracts and relaxes over and over again,

However tired you are,

your heart still keeps beating

The structure of the heart The diagram shows what the inside of the heart looks like

lung and ribs removed to show the heart

The position of the heart in the human body

vein from body vein from lungs upper chamber valve

lower chamber deoxygenated blood right side

The structure of the heart

Question

and an upper and lower chamber on the right

a Into which chamber does blood from the lungs flow

? b Out of which chamber does blood flow,

on its way to the rest of the body

? c'Which two chambers contain oxygenated blood

How the heart works The heart is made of muscle

This muscle contracts and then relaxes

When muscle contracts,

This makes the walls of the heart chambers squeeze inwards

This pushes blood out of the heart

There are valves between the upper chambers and the lower chambers

The valves only let the blood flow from the upper chamber to the lower chamber

There are 34

These valves only let the blood flow out,

This is what happens during one heart beat: • The heart muscle contracts,

pushing blood out into the arteries

allowing blood to flow into the heart from the veins

The heart

How the heart pumps blood

Activity 3

it sends blood surging through your arteries

You can feel this surge of blood if you put your fingers on a place where there is an artery near the surface of the body

The diagrams show two good places to try

Each surge of blood is called a pulse

Your pulse rate is the number of pulses in one minute

Draw a results table,

ready to write in your results as you collect them

Ask them to sit very still and relaxed for a few minutes

Then count their pulse rate

Your teacher will suggest a good exercise to do

Summary • The heart is made of muscle,

which contracts and relaxes to pump blood around the body

• The heart contains valves to make sure the blood always flows in the right direction

Everyone knows that blood is a red liquid

But if you look at blood under a microscope,

The liquid part of blood is not red at all – it is a very pale yellow colour

What makes blood red is the cells that float in this liquid

red blood cell white blood cell

Question

a Approximately how many red blood cells are there for each white blood cell

? b Describe two ways in which white blood cells look different from red blood cells

platelet plasma This is what human blood looks like under the microscope

The white blood cells have been stained with a dye,

Plasma Plasma is the liquid part of blood

It is mostly water

Plasma contains many different substances dissolved in it

For example,

sugar is transported around the body dissolved in the blood plasma

The sugar is absorbed into the blood in the small intestine,

and is carried all over the body to the cells that need to use it for energy

Red blood cells Most of the cells in the blood are red blood cells

Red blood cells are unusually small cells

They are red because they contain a red pigment called haemoglobin