Le a r n an d P r ac ti ce B o o k T r acey B a x t e r , Aman d a Cl e gg , K a re n Colli n s a nd Ed Wa ls h S C IEN C E N OW K S 3
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 to ensure responsible forest management For more information visit: www.harpercollins.co.uk/green This book has been endorsed by The WISE Campaign for gender balance in Science, Technology, Engineering and Maths (STEM)WiseCampaign.org.uk
Contents1Cellsandorganisation 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
l i c n o s u di s v y te io d e o u skele n a m s l s u c c a ory s 1.1 Organisation of organismsmulticellular • de ne terms • explain structureorganisational • compare strengths and weaknesses 1.2 cellsplantComparingandanimal • describe structures • explain functions • compare 1.3 Studying cells • identify microscope parts • describe observing cells • interpret evidence 1 Cells and organisation road map Where are you in your learning journey and where are you aiming to be? 4 1 Cells and organisation
eukaryotes and prokaryotes 1.4 Unicellular organisms • recognise organisms • describe differences • compare adaptations diffusion mal d pl t s e l spec a isat o oscopy p 1.5 Specialised cells • classify specialised cells • describe examples • explain link between structure and function carrying out scienti c 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 describing the development of scienti c methods and theories over time, including publishing results and peer review Maths and practical skills 5 Road map
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)
mossbacterium humansponge
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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.
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? Cells and organisation
Look at these living organisms. Do you think they are made from one cell or more? Which do you think are the most complex?
6 1 Cells and organisation
Seeing cells
How many cells?
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 agriculture.croptodevelopmentandimproveyieldand
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. 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. 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 theirmachineryhigh-technologyandinwork.
Using your science skills Could you be a pathologist?
7 Unit opener
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.
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.
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.
‘Multi’ means many; ‘uni’ means one.
Groups of similar cells form a tissue. Cells are the building blocks of living things. Organelles are parts of cells that have specific functions (jobs).
Cells8 and Organisation1 Cells and organisation
• have other organelles, such as mitochondria
• all are unicellular • don’t have a nucleus
Organs work together to make an organ system. Different tissues work together to make up an organ.
• have very few organelles
• genetic material is stored in a nucleus
• thought to be the first organisms on Earth
• example: bacteria. Eukaryotes: • usually bigger and more complex than prokaryotes • some are unicellular, most are multicellular
Multicellular organisms contain many cells; unicellular organisms are made of only one or a single cell.
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.
Knowledge organiser
Prokaryotes:
• examples: animals, plants, fungi, amoeba.
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 light source or mirror –illuminates the sample so you can see it 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 stage –holds the slide focusing wheel –moves the stage so you can bring the sample in and out of focus Organ systems work together to form organisms
nucleus Plant cell membranecell cell chloroplastscytoplasmmembranevacuolenucleus cell wall 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.
cell wall capsule
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 microscopeelectron 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 materialgenetic material that transmits information from one generation to the next during reproduction microscopelight 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) multicellular made of many cells nucleus the part of a cell that contains the genetic material organ a collection of tissues that work together to perform a function organelle a structure in a cell with a specific function (job) organism 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
nucleus Animal cell Plant cell cytoplasmmitochondriamembranecell cell chloroplastscytoplasmmembranevacuolenucleus cell wall
unit title9Knowledge organiser
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.
cellmaterialgeneticmembrane Bacterium
2 A group of similar specialised cells working together are called
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
112Cells and organisation
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.
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.
• compare the strengths and weaknesses of unicellular and multicellular organisms.
3 What is the name given to a group of different tissues working together?
6 a Describe what ‘unicellular’ means as in ‘a bacterium is a unicellular organism’.
1 Name the building blocks that all organisms are made from.
4 Match each organ to the system it is part of. heart digestive system brain nervous system stomach breathing (respiratory) system lungs circulatory system
5 Match each organ to its function. heart controls many functions of the body brain pumps blood around the body kidneys transfer gases between the blood and air stomach filter waste from the blood lungs digests some foods
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.
Worked example
10 The earliest organisms were unicellular. Some of these gradually evolved into multicellular organisms, with tissues and organs. Describe how this may have happened.
7 Using the human circulatory system as an example, name one example of each of the following involved with this system: a a cell b a tissue c an organ d an organ system e an organism.
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Multicellular organisms are able to carry out more complex processes than unicellular organisms. Explain why.
Questions13
Unicellular organisms are very successful and make up most life on Earth. Suggest why they are so successful.
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.
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.
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 cytoplasmchloroplastnucleusmembrane 3 On the diagram below of an animal cell, choose from the words to identify the labels a, b and c: a c b 4 On the diagram below of a plant cell, identify the labels a, b, c, d and e. a c b e d 5 Describe the function of each of these parts of a cell: a nucleus b cell membrane c chloroplast. cellnucleuscytoplasmmembrane114Cells and organisation
Charlotte says this must be an animal cell because it doesn’t have any chloroplasts and animal cells do not have chloroplasts.
7 This light microscope image shows cells from inside the cheek of an animal. 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.
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.
6 All cells contain cytoplasm. Explain why.
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. 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). cell cellnucleusvacuolewallmembrane
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. 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. ii iii i microlitre)/(millionscountcellred 654321
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2 months4 6 8 Questions15
8 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.
