KS3 Science Now Learn and Practice

KS3 SCIENCE NOW Learn and Practice Book Tracey Baxter, Amanda Clegg, Karen Collins and Ed Walsh

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William Collins’ dream of knowledge for all began with the publication of his first book in 1819.

A self-educated mill worker, he not only enriched millions of lives, but also founded a flourishing publishing house. Today, staying true to this spirit, Collins books are packed with inspiration, innovation and practical expertise. They place you at the centre of a world of possibility and give you exactly what you need to explore it.

Collins. Freedom to teach.

Published by Collins An imprint of HarperCollinsPublishers The News Building, 1 London Bridge Street, London, SE1 9GF, UK HarperCollinsPublishers 1st Floor, Watermarque Building, Ringsend Road, Dublin 4, Ireland Browse the complete Collins catalogue at collins.co.uk © HarperCollinsPublishers Limited 2022 10 9 8 7 6 5 4 3 2 1 ISBN 978-0-00-853152-2 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the Publisher or a licence permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd, 5th Floor, Shackleton House, 4 Battle Bridge Lane, London SE1 2HX. British Library Cataloguing-in-Publication Data A catalogue record for this publication is available from the British Library.

Authors: Tracey Baxter, Amanda Clegg, Karen Collins and Ed Walsh Publisher: Katie Sergeant Product manager: Joanna Ramsay Product developer: Holly Woolnough Development editors: Jessica Ashdale, Gillian Lindsey, Julie Thornton Copyeditor: Aidan Gill Proofreader: Julie Gorman Answer checker: Life Lines Editorial Services Illustrator: Ann Paganuzzi Cover designer: Happy Designers Internal designer: Ken Vail Graphic Design Typesetter: Jouve and 2Hoots Production controller: Alhady Ali Printed and bound by Grafica Veneta in Italy

This book has been endorsed by The WISE Campaign for gender balance in Science, Technology, Engineering and Maths (STEM) WiseCampaign.org.uk

to ensure responsible forest management.

For more information visit: www.harpercollins.co.uk/green

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Contents 1 Cells and organisation

4

2 Reproduction

30

3 Health and human systems

56

4 Respiration and photosynthesis

84

5 Ecosystems and interdependence

114

6 Inheritance and evolution

138

7 The particulate nature of matter

166

8 Pure and impure substances

188

9 Periodic table

208

10 Chemical reactions

226

11 Materials

252

12 Earth and atmosphere

270

13 Forces

292

14 Energy

318

15 Waves

334

16 Electricity and magnetism

356

17 Matter

374

18 Space physics

388

Answers

402

Acknowledgements

458

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1 Cells and organisation

1 Cells and organisation road map Where are you in your learning journey and where are you aiming to be?

1.3 Studying cells • identify microscope parts • describe observing cells • interpret evidence

1.2 Comparing plant and animal cells • describe structures • explain functions • compare

human skeleton and muscles human circulatory r system ry classification of organisms human digestive system adaptation and evolution

1.1 Organisation of multicellular organisms • define terms • explain organisational structure • compare strengths and weaknesses

KS2

KS3

4

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1.4 or

•r •d •c

ts

Road map

1.4 Unicellular organisms • recognise organisms • describe differences • compare adaptations

1.5 Specialised cells • classify specialised cells • describe examples • explain link between structure and function

1.6 Movement in and out of cells: diffusion

eukaryotes y and prokaryotes p y animal and plant cells cell specialisation microscopy

• define processes • describe examples • explain factors affecting diffusion

KS4

Maths and practical skills describing the development of scientific methods and theories over time, including publishing results and peer review carrying out scientific enquiries to test predictions observing and measuring, including the evaluation of repeatability interpreting observations and data presenting reasoned explanations using SI units and chemical names deriving and using simple equations

5

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1 Cells and organisation

1 Cells and organisation All living organisms are made of cells – they are the building blocks of life.

Cells cannot be seen except under a microscope; this is why it took so long to discover them. Some organisms are made of only one cell; most are made of millions of cells working together.

How many cells?

Look at these living organisms. Do you think they are made from one cell or more? Which do you think are the most complex?

bacterium

sponge

moss

human

Seeing cells Have you ever been to hospital? Think about the ways doctors and scientists can explore what is happening inside our bodies.

Micrographs of viruses (left) and red blood cells (right)

The development of microscopes has meant that we can see individual cells.

The most powerful microscopes can even see viruses. What differences would it make to our lives if we did not have this technology?

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Unit opener

Using your science skills Could you be a pathologist?

You make accurate decisions while being thorough because your advice could save lives.

Doctors, nurses and surgeons rely on your judgements and advice in treating patients with cancer and other diseases.

Strength and resilience are needed because there will be times when, sadly, the team cannot cure the patient.

Being a pathologist means working with the latest

technology to study cells, tissues and diseases. This means that you need to recognise what a wide range of cells and their parts should look like so that you can identify quickly and reliably when things are not normal. You also need to be able to link cell structure to function to help with making a diagnosis. You are part of a team of dedicated professionals, all working to improve the lives

of patients. Pathologists also play a critical role in researching and developing more accurate diagnoses and treatments, improving lives not only now but also in the future.

Pharmaceutical researchers study the effects of drugs on cells and organisms.

Researchers need to understand how well drugs diffuse in and out of cells as this affects how well they work as medicines. This research is a hugely important step in the process of licensing medicines for human use.

Microbiologists study microorganisms such as bacteria, viruses and fungi.

Some study diseases caused by microbes while others study how we can use microbes to help us. They work all around the world studying how microbes help us in medicine and food production.

Botanists are plant biologists. Some study plant structures to try and find useful chemicals produced by plants. Lots of medicines originally came from plants, such as aspirin and morphine.

Others may study plant genetics and development to improve crop yield and agriculture.

Zoologists study animals, their behaviour and their interactions with their surroundings.

This allows us to understand how animals are adapted to their environment, which is key to wildlife conservation. This helps us to learn how organisms have adapted to their environment. Some zoologists work in the outdoors, all over the world, whereas others work in a laboratory or a zoo.

Fertility scientists may study sperm cells to try and help people who would like to have a baby.

Microscopes are used to check whether enough sperm cells are produced, and to look at the sperm cells in detail to observe any abnormalities.

Ophthalmic laboratory technicians make lenses for glasses and contact lenses and also for equipment such as microscopes and telescopes. Microscopes are vital to allow us to study cells and microorganisms. Laboratory technicians usually learn these skills on the job as they use very precise and high-technology machinery in their work.

7

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a Cells and Organisation 1 Cells and organisation

Knowledge organiser ‘Multi’ means many; ‘uni’ means one.

Multicellular organisms contain many cells; unicellular organisms are made of only one or a single cell.

Organelles are parts of cells that have specific functions (jobs).

Cells are the building blocks of living things.

Groups of similar cells form a tissue.

A light microscope is used to magnify objects that are too small to see with the unaided eye. With a light microscope, we can observe microscopic organisms, such as bacteria, and inside cells to see the cell parts and organelles. eyepiece lens – lens that you look through; it magnifies the image of the sample objective lens – magnifies the image of the sample further; a microscope usually has more than one objective lens, to provide a choice of magnifications

stage – holds the slide focusing wheel – moves the stage so you can bring the sample in and out of focus

Different tissues work together to make up an organ.

Organs work together to make an organ system.

Organ systems work together to form organisms.

slide – thin piece of glass that holds the sample; a coloured stain is sometimes added to make it easier to see details of the sample

light source or mirror – illuminates the sample so you can see it

Electron microscopes allow much greater magnification than light microscopes. They are bigger and more expensive than light microscopes. They use a beam of electrons to form a very detailed image of a sample.

Organisms can be classed into two groups based on how their genetic material is stored.

Eukaryotes: Prokaryotes: • usually bigger and more complex than • thought to be the first organisms on Earth prokaryotes • all are unicellular • some are unicellular, most are multicellular • don’t have a nucleus • genetic material is stored in a nucleus • have very few organelles • have other organelles, such as mitochondria • example: bacteria.

• examples: animals, plants, fungi, amoeba.

8

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Knowledge organiser unit title Unicellular organisms are simply a cell with organelles working together.

Unicellular organisms are adapted in different ways. Examples are: • bacteria – there are many types of bacteria but all have no nucleus • algae – these are plant-like and contain chloroplasts to make their own food • yeasts – these are fungus-like and absorb nutrients from their surroundings.

Bacterium capsule

cell membrane cell wall genetic material

Animal cells and plant cells have some cell parts or organelles in common but some differences too.

This is because the cells have different functions.

Key vocabulary algae

a unicellular organism that has a nucleus and contains chloroplasts for photosynthesis

bacterium

a simple unicellular organism; some bacteria can cause illness

capsule

structure that covers the outer layer of the cell wall of a bacterium

cell

the ‘building block’ that all living things are made from

cell membrane

the layer around a cell that controls substances entering and leaving the cell

cell wall

the tough outer layer of a plant cell

chloroplast

a structure in plant cells where photosynthesis takes place

cytoplasm

the main component of a cell; the place where reactions take place

electron microscope

an instrument that produces a magnified, detailed image of a sample using a beam of electrons

eukaryote

an organism whose cells store genetic material in a nucleus

genetic material

material that transmits information from one generation to the next during reproduction

light microscope

an optical device used to see magnified images of tiny objects and structures

magnify

to make something look bigger

mitochondria

the structures in a cell that produce energy (by respiration)

mitochondria

cell membrane

multicellular

cytoplasm nucleus

nucleus organ

vacuole nucleus Animal cell

dria

cell membrane

organelle

chloroplasts vacuole cytoplasm

nucleus

al cell

Plant cell

the part of a cell that contains the genetic material

cell membrane chloroplasts

a collection of tissues that work together to perform a function

a structure in a cell with a specific function (job)

cytoplasm

a living thing

organ system

organs that coordinate with one another in body processes

prokaryote

a unicellular organism that has no nucleus

tissue

a collection of body cells that work together to carry out a task

unicellular

made of one cell

vacuole

a bubble of water and nutrients in a plant cell

yeast

a unicellular fungus

Plant cell

cell membrane

of many cells

organism

cell wall nucleus

cellmade wall

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1 Cells and organisation

1.1 Organisation of multicellular organisms You are learning to: • define the terms cell, tissue, organ, organ system and organism • explain the organisational structure in multicellular organisms • compare the strengths and weaknesses of unicellular and multicellular organisms.

1

Name the building blocks that all organisms are made from.

2

A group of similar specialised cells working together are called .

3

What is the name given to a group of different tissues working together?

4

Match each organ to the system it is part of. heart brain stomach lungs

5

Match each organ to its function. heart brain kidneys stomach lungs

6

digestive system nervous system breathing (respiratory) system circulatory system

controls many functions of the body pumps blood around the body transfer gases between the blood and air filter waste from the blood digests some foods

a Describe what ‘unicellular’ means as in ‘a bacterium is a unicellular organism’. b

Apart from bacteria, name two other examples of unicellular organisms.

Worked example Using the nervous system as an example of a human organ system, name an example of: a a cell b a tissue c an organ that form part of that system.

This is asking for one example of each type of structure and all from the nervous system. Think about what makes up the nervous system. a brain cells b brain tissue c brain The nervous system includes the brain; the brain is made of brain tissue; brain tissue is made of brain cells.

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Questions Using the human circulatory system as an example, name one example of each of the following involved with this system:

7

a

a cell

b

a tissue

c

an organ

d

an organ system

e

an organism.

Unicellular organisms are very successful and make up most life on Earth. Suggest why they are so successful.

8

Worked example Multicellular organisms have organs such as a brain and heart. Explain why unicellular organisms do not have organ systems.

This question asks you to explain. The first step when answering an explain question is to state a fact.

Unicellular organisms are made of only one cell.

Then explain why that fact means that unicellular organisms do not have organ systems.

Therefore, cells do not work together as tissues, there are no tissues to form an organ and no organs to form an organ system.

9 Multicellular organisms are able to carry out more complex processes than unicellular organisms. Explain why.

10 The earliest organisms were unicellular. Some of these gradually evolved into multicellular organisms, with tissues and organs. Describe how this may have happened.

Worked example Yeast is a unicellular organism used in making bread. Bakers need to allow time for the yeast cells to reproduce during the process. Yeast can multiply every 90 minutes.

How long does it take for the number of yeast cells to increase to 8 times the original number?

Assume you are starting with one yeast cell, and calculate how many cells would exist after each 90 minutes.

1 to 2 cells after 90 minutes 2 to 4 cells after 180 minutes (90 + 90) 4 to 8 cells after 270 minutes (90 + 90 + 90) Therefore, after 270 minutes, there are 8 times as many yeast cells.

11 Some bacteria can reproduce as rapidly as every 20 minutes. Starting from one single bacterium, calculate how many bacteria would exist after 2 hours.

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1 Cells and organisation

1.2 Comparing plant and animal cells You are learning to: • describe the structures found in plant and animal cells • explain the functions of structures in plant and animal cells • compare plant and animal cells.

1

To observe cells in a classroom, we need to use a piece of equipment called a .

2

Choose three parts of a cell that are found in both animal cells and plant cells: cell wall cell membrane nucleus chloroplast cytoplasm

3

On the diagram below of an animal cell, choose from the words to identify the labels a, b and c: b

cytoplasm nucleus

a

4

cell membrane

c

On the diagram below of a plant cell, identify the labels a, b, c, d and e. a

d b

e

c

5

Describe the function of each of these parts of a cell: a

nucleus

b

cell membrane

c

chloroplast.

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Questions 6

All cells contain cytoplasm. Explain why.

7

This light microscope image shows cells from inside the cheek of an animal.

8

a

Identify the cell parts i, ii and iii.

b

Name another organelle present in these cells that we cannot see in this image because it is too small.

ii iii

i

Describe the key difference between red blood cells and other animal cells.

Worked example Charlotte and Abel are trying to decide what type of cell they are looking at.

Charlotte says this must be an animal cell because it doesn’t have any chloroplasts and animal cells do not have chloroplasts.

Abel says it must be a plant cell because it has a cell wall and a cell membrane.

Suggest who is correct and explain why.

It is important in questions where two or more opinions are given, that you explore each statement thoroughly. There is not usually a completely correct or completely incorrect opinion.

Abel is correct that this is a plant cell as it has a cell wall.

cell wall vacuole

nucleus cell membrane

However, both plant and animal cells have cell membranes, so this feature does not help us to decide.

Charlotte is correct that animal cells do not have chloroplasts.

However, some plant cells do not contain chloroplasts either: only those cells where photosynthesis takes place contain chloroplasts (as these contain chlorophyll).

9

Dev says that plant cells hold their shape because of their cell wall. Kristi says that it is the vacuole that supports the plant cell, and the cell wall controls what moves in and out of the cell. Suggest who is correct and explain why.

The normal range for a red blood cell count is between 4.1 and 5.5 million/microlitre.

The graph shows the red blood cell count for a patient being treated for a low red blood cell count.

Use the graph to calculate: a the red blood cell count at the start of the treatment b

how long after treatment began that the patient reached the normal range for red blood cell count.

red cell count (millions / microlitre)

10 In a condition called anaemia, patients have a lack of red blood cells. Doctors take blood samples and the ‘red blood cell count’ is measured.

6 5 4 3 2 1 0 0

2

4 months

6

8

15

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