New editions with teaching support

Endorsed by University of Cambridge International Examinations

Complete

Sciencefor Cambridge IGCSEComplete Biology, Chemistry and Physics are now comprehensive science courses – complete with teaching support and revision materials.

What do you get with the new Complete Science?

✓ A challenging IGCSE programme that will stretch your students and develop their critical thinking skills, while still supporting your lower-ability pupils

✓ Brand new teaching support – in print and digital – that you can easily customise to make sure you teach exactly what you want

✓ Flexible learning options with a free student CD-ROM designed to strengthen exam preparedness

✓ Up-to-date and internationally-focused content endorsed for the newest Cambridge IGCSE syllabus

✓ Support for your EAL students with page-by-page vocabulary support

2

Look inside to see how you can use the new Complete Science

Worried about covering the entire syllabus? Use the grids on the Teacher’s CD-ROMs to map each area of the syllabus to specific

pages in the Student Book, to ensure nothing is missed.Want to help students gauge their learning? Use the summative tests for each unit on the Student CD-ROM for an instant progress-check.

Download a ready-made PowerPoint and customise it with your own data, images and web links for an effective and hassle-free lesson

Find the digitised version of any of the print worksheets in the Teacher’s book and adapt it so it works exactly how you want

Refer to the syllabus matching grid to make sure you’re covering everything in the most recent Cambridge syllabus

Distribute the mock IGCSE questions, so students get used to answering real questions taken from past exams

Biology

Complete Biology for Cambridge IGCSE

4.3

O R G A N I S M S A N D T H E I R E N V I R O N M E N T

252

O

Pyramids of numbersLook at the food chain on page 248. Two things should be clear:■ The organisms tend to get bigger moving along

the food chain. Predators, such as the cat, need to be large enough to overcome their prey, such as the mouse.

■ Energy is ‘lost’ as heat on moving from one trophic level to the next, so an animal to the right of a food chain needs to eat several organisms ‘below’ it in order to obtain enough energy. For example, a rabbit eats many blades of grass.

Food chains and food webs provide qualitative information about an ecosystem – they show which organism feeds on which other organism. How do we show quantitative information, for example how many predators can be supported by a certain number of plants at the start of the chain? We can use a pyramid of numbers or a pyramid of biomass, as shown in the diagram below.

Pyramids of energyA pyramid of biomass describes how much biomass is present in a habitat at the time the sample is taken. This can be misleading, because different feeding levels may contain organisms that reproduce, and so replace themselves, at different rates. For example, grass in a fi eld would replace itself more quickly than cattle feeding on the grass, so when the pyramid of biomass is constructed there would be more ‘cattle biomass’ than ‘grass

OB J EC T I VES

■ To be able to describe pyramids of numbers, biomass and energy

■ To understand how data can be gathered to make ecological pyramids

Feeding relationships: pyramids of numbers, biomass and energy

Pyramid of numbers – a diagrammatic representationof the number of different organisms at each trophic levelin an ecosystem at any one time

Note1 The number of organisms at any trophic level is

represented by the length (or the area) of a rectangle.2 Moving up the pyramid, the number of organisms

generally decreases, but the size of each individualincreases.

Producers

Top carnivore

Small carnivore

Herbivore

Butwait!

Problemsa The range of numbers may be enormous – 500 000

grass plants may only support a single top carnivore –so that drawing the pyramid to scale may be verydifficult.

b Pyramids may be inverted, particularly if theproducer is very large (e.g. an oak tree) or parasitesfeed on the consumers (e.g. bird lice on an owl).

So …

Pyramid of biomass – which represents the biomass(number of individuals × mass of each individual) ateach trophic level at any one time. This should solvethe scale and inversion problems of the pyramid ofnumbers.

Biomass expressed asunits of mass per unitarea (e.g. kg per m2)

Bird lice

Tawny owl

Blue tits

Insect larvae

Oak tree

Bird lice

Tawny owl

Blue tits

Insect larvae

Oak tree

Ecological pyramids represent numerical relationships between successive trophic levels.The pyramid of biomass is useful because the biomass gives a good idea of how much energy is passed on to the next trophic level.

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O R G A N I S M S A N D T H E I R E N V I R O N M E N T

253

biomass’ and the pyramid would be inverted. To overcome this diffi culty a pyramid of energy can be constructed. This measures the amount of energy fl owing through an ecosystem over a period of time. The time period is usually a year, since this takes into account the changing rates of growth and reproduction in different seasons. It is even possible to add an extra base layer to the pyramid of energy representing the solar energy entering that particular ecosystem.

Pyramid of energy: energy values are expressed as units of energy per unit area per unit time (e.g. kJ per m2 per year)

GATHERING DATA FOR ECOLOGICAL PYRAMIDS

To construct a pyramid of numbers or of biomass, organisms must be captured, counted and (perhaps) weighed. This is done on a sample (a small number) of the organisms in an ecosystem. Counting every individual organism in a habitat would be extremely time-consuming and could considerably damage the environment.

The sample should give an accurate estimate of the total population size. To do this:

■ The sampling must be random to avoid any bias. For

example, it is tempting to collect a large number of

organisms, by looking for the areas where they are

most common. To avoid this, the possible sampling

sites can each be given a number and then chosen

using random number generators on a computer.

■ The sample must be the right size so that any

‘rogue’ results can be eliminated. For example, a

single sample might be taken from a bare patch of

earth, whereas all other sites are covered with

vegetation. The single sample from the bare patch

should not be ignored, but its effects on the results

will be lessened if another nine samples are taken.

A mean value can then be used.

Sampling plants and sessile animalsOnce the organisms in a sample have been identifi ed and counted, the population size can be estimated. For example, if 10 quadrats gave a mean of 8 plants per quadrat, and each quadrat is one-hundredth of the area of the total site, then the total plant population in that

area is 8 � 100 � 800.

Wire

1 m

1 m

20 cm 20 cm

Wing nut

Metal or wooden frame

� A quadrat is a square frame made of wood or metal. It is simply laid on the ground and the number of organisms inside it is counted.

A quadrat is used most commonly for estimating the size of plant populations, but may also be valuable for the study of populations of sessile or slow-moving animals (e.g. limpets).

913876_IGCSE_BIO_CH04.indd 253 09/10/2010 14:51:41

Clear, uncomplicated language with highlighted keywords to

support your EAL students

Flip to the sectionquestions to further consolidate

learning and help students measure their progress – these questions are

also on the Student CD-ROM

Step 2 – Exploit the digital resources

67

2.3 Transfer of thermal energy

KEY IDEAS✓ Heat is transferred in solids by the vibrations of the molecules. This is conduction✓ Heat is transferred in liquids and gases by the movement of the molecules. This is

convection✓ All objects emit and absorb heat through infrared radiation✓ Black surfaces are the best emitters and the best absorbers of infrared radiation✓ Silver surfaces are the worst emitters and the worst absorbers of infrared radiation

Conduction

An experiment to show that copper is a good conductor of heat

copper bar

blob of waxdrawing pin Bunsen flame

If a copper bar is heated at one end with a Bunsen fl ame, the drawing pins fall off one by one, beginning with the pin closest to the Bunsen fl ame. This is because as the metal conducts the heat from the hot end of the bar to the cold end, each of the blobs of wax melts in turn.

electrons with themost vibrational energy

hot endcold end

metal ions

electrons with the lowestvibrational energy

Metal atoms that have lost their free electrons are called ions. Sometimes metals are described as a lattice of metal ions in a “sea” of free electrons. Other solids are not usually good conductors of heat because they do not have free electrons to transfer heat energy from one molecule to another.

At the hot end of the metal bar, the ions gain energy and vibrate faster. The ions in a metal are close together and so these ions pass on their vibrations to neighbouring ions, which in turn start to vibrate faster. In this way, heat is transferred from the hot end to the cold end of the solid bar.

915436_ch02_050-079.indd 67 9/10/09 08:20:51

Refresh students’ memories and focus their attention with the clearly outlined learning objectives

Help pupils more effectively absorb information via the concise and focused explanations

Cambridge Physics IGCSE Revision Guide

Physics

68

IGCSE Revision guide: Physics

Metals also have free electrons in their structure which gain kinetic energy at the hot end of the bar. These free electrons pass on their kinetic energy through collisions with other electrons and metal atoms as they randomly diffuse through the metal. In this way, energy (heat) is conducted from the hot end of the bar to the cold end.

An experiment to show that water is a poor conductor of heat

bunsenburner

boiling waterboiling tube

metal gauze

ice

Ice is trapped at the bottom of the boiling tube with a piece of metal gauze. When the water at the top of the boiling tube is heated strongly, it boils. The ice at the bottom of the tube does not melt. This shows that water is a poor conductor of heat. However, if the ice is allowed to fl oat normally, it melts quickly when the water is heated at the bottom of the test tube. This is because the water molecules can move, so the water heats by convection.

Water, like other liquids and non-metal solids, is a poor conductor of heat energy because its molecules do not have free electrons to easily pass on their kinetic energy to their neighbours, so the heat can only be transmitted through the vibration of the particles. Gases are very poor conductors of heat energy because their molecules are very far apart so kinetic energy cannot be transmitted from one molecule to another.

Materials that are poor conductors are called insulators. For example, air is an insulator.

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Use the diagrams and visual aids to

make sure that everyone understands, supporting

all types of learners

Remember to support pupils with the highlighted vocabulary

words which could challenge your EAL students

Step 3 – Help students revise

We’ve developed Complete Science for international science teachers and it’s designed to meet your core priorities:

✓ Quick and easy planning which doesn’t compromise lesson quality

✓ Flexible, straightforward resources that let you choose how you use them

✓ Thorough and comprehensive material that will fully prepare students for exams

✓ Clear, uncomplicated language with support for EAL students

✓ Exact match to the most recent Cambridge IGCSE syllabus

Ways to teach with Complete Science

Step 1 – Use the Student Books

Chemistry

Complete Chemistry for Cambridge IGCSE Teacher’s Resource Kit CD-ROM

Flip to this back of this leaflet to see a linked practical activity from the Teacher’s Resource Kit

Case studies aid comprehension and are

linked to practicals in the Teacher’s Kits - helping

students put theories into practice

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Practicals and worksheets to support your lessonsThe Teacher’s Resource Kits are loaded with useful practicals and worksheets in print and digital form that are linked to lessons in the Student Books. Plus all the worksheets are fully customisable so you can tweak them however you please, to ensure effective teaching.

Biology

Complete Biology for Cambridge IGCSE Teacher’s Resource Kit

P R ACT I CA LP R ACT I CA L

© OUP: this may be reproduced for class use solely for the purchaser’s institute 49

Name:

Handling experimental observations and data: estimating the size of a population

You need:■ plain paper ■ pen or pencil ■ bag or small box

Method:You are provided with a bag with some pieces of paper in it� The pieces of paper represent animals in a population, and the bag is the environment in which they live� The investigation looks at a ‘capture-recapture’ technique for estimating their population size�

1 Remove between 15 and 20 ‘animals’ from the habitat (the exact number does not matter) and record this number in the table�

2 Mark all the pieces of paper with a small number 1 and put them back in the bag� Shake for 1 minute to mix up the ‘animals’�

3 Remove 15–20 ‘animals’ from the bag and write down this number in the table�

4 Count how many of this second sample have got a number 1 written on them (remember to look on both sides)�

5 Estimate the size of the population using this formula:

No� in first sample 3 no� in second sample

________________________________________ No� in second sample marked with a 1

6 Repeat steps 1–5 a further 4 times but mark the captured ‘animals’ in the second step with a 2 the second time, a 3 the third time, a 4 the fourth time and a 5 the fifth time� Ignore any other numbers from the earlier samples�

7 Display all the readings in the form of a table� Work out a mean value for the estimate of the population using your five sets of results� Record the mean value�

8 Tip out all of the ‘animals’ and count the actual population size� Record this value�

9 Present your results in a bar chart that shows all five of the estimates of the population and the actual value clearly�

10 Calculate the percentage error in your estimates compared with the actual value�

913879 COMPLETE BIOL IGCSE TG.indd 49 10/29/10 1:38:17 PM

Title ISBN Price I/C* Qty TotalStudent BooksComplete Biology for Cambridge IGCSE 978 019 913876 0 £20.00Complete Chemistry for Cambridge IGCSE 978 019913878 4 £20.00Complete Physics for Cambridge IGCSE 978 019 913877 7 £20.00Teacher’s Resource KitsComplete Biology Teacher’s Kit 978 019 913879 1 £45.00Complete Chemistry Teacher’s Kit 978 019 913881 4 £45.00Complete Physics Teacher’s Kit 978 019 913880 7 £45.00 Revision GuidesCambridge Biology IGCSE Revision Guide 978 019 915265 0 £11.50Cambridge Chemistry IGCSE Revision Guide 978 019 915266 7 £11.50Cambridge Physics IGCSE Revision Guide 978 019 915436 4 £11.50 Subtotal **P&P #Less discount (if applicable) Grand total

Instructions take a step-by-step approach, minimising the

potential for confusion

Practicals help students apply their learning and connect it to real-world situations