OCR AS BIOLOGY BIOLOGY Frank Sochacki Hodder Education, an Hachette UK company, 338 Euston Road, London NW1 3BH Orders Bookpoint Ltd, 130 Milton Park, Abingdon, Oxfordshire OX14 4SB tel: 01235 827827 fax: 01235 400401 e-mail: [email protected] Lines are open 9.00 a.m.–5.00 p.m., Monday to Saturday, with a 24-hour message answering service. You can also order through the Hodder Education website: www.hoddereducation.co.uk © Frank Sochacki 2012 ISBN 978-1-4441-7967-5 First printed 2012 Impression number 5 4 3 2 1 Year 2017 2016 2015 2014 2013 2012 All rights reserved; no part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without either the prior written permission of Hodder Education or a licence permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd, Saffron House, 6–10 Kirby Street, London EC1N 8TS. Cover photo reproduced by permission of peter_waters/Fotolia Typeset by Datapage (India) Pvt. Ltd. Printed in India Hachette UK’s policy is to use papers that are natural, renewable and recyclable products and made from wood grown in sustainable forests. The logging and manufacturing processes are expected to conform to the environmental 2 8 21 regulations of the country of origin. P Get the most from this book Everyone has to decide his or her own revision strategy, You can also keep track of your revision by ticking off but it is essential to review your work, learn it and test each topic heading in the book. You may find it helpful your understanding. These Revision Notes will help to add your own notes as you work through each topic. you to do that in a planned way, topic by topic. Use this book as the cornerstone of your revision and don’t My revision planner hesitate to write in it — personalise your notes and check your progress by ticking off each section as you Unit F211 Cell, exchange and transport revise. Revised Tested Exam 1 Cell structure ready ■ ■ ■ 7 Microscopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .■ . . . . . . . . . . . . . . . . . .■ . . . . . . . . . . . . . . . . .■ 8 Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Cell membranes ■ ■ ■ Tick to track your progress 14 Structure of cell membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .■ . . . . . . . . . . . . . . . . . .■ . . . . . . . . . . . . . . . . .■ 17 Transport of substances across membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use the revision planner on pages 4 and 5 to plan your 3 Cell division, cell diversity and cellular organisation ■ ■ ■ r●●●e●●●virtpcseeihrovsaetnicsce,te kditds o yey paodoniu uctdr rh b saueeyn nl efstdxwoeapermirscst . o qaTounicdedks at cei ootaomncphsp i aclbenotdex gtwhohen eeqn uo yincolkiun q ehu taiozvze e:s BVBTVmaSDIVPranerre 4 5 6 2222233344445toueibteenar elsl1347915603683suusr npatercsuETTimcch t ull4teaomtehrrrrxeu.atises4iaa iltgmr.CSTETBCTBTXTTn occ aaceIamThnnrrrntinxhhlgherilhy/a staaaaerohsmef ac rsleelpssnciiieaiennnnlmesshouatsouigu app r gemdaghssssanpeadtaetnelhd cppllctuhoorasicaenols igo hev oorvoiei,itsaarresngrcicn ni eoeeelsrokaittarne elvagiTtsnotrns st rotned sas .yii soigioICddCcCvPrsudd . .eeabnnonone aow . .ruuoo oohsap sflsed . .lnesgngl ben ww s . . .nnuey r nsxpuntrhe . . . apodye ss ttmfphsnn4ci . . . . . . furrt sralau . . . . . .tiexx aawa n.t lroae4ra . . . . . .csdpe shtccaecacy . . . . . .ata .a tte t . . . . . .i evcaemihi tavgs rini . . . . . .omnfn otdn ame i . . . . . .nesot aafanes . . . . . .ndksdyns d tecn . . . . . .i n s ed nrap . . . . . . . . . (tistfd aorn . . . . . . . . . ieoa uiign p i . . . . . . . . .oelulc salma . . . . . . . . .scarlsh leretns . . . . . . . . .hnah egwnt n . . . . . . . . .o a i cbtae . . . . . . . . .into vlshaad . . . . . . . . .oesesi idgey . . . . . . . . .fnereta lnn . . . . . . . . . dso d ssgto . . . . . . . . .cc rt s. w h . . . . . . . . .tu iabir) aibs . . . . . . . . .Ineg voetr . . . . . . . . .y r ii ar . . . . . . . . . mtn rnbsd . . . . . . . . .ny ee . . . . . . . . .gt iso . . . . . . . . . .fa e a . . . . . . . . . . .ri pe . . . . . . . . . . .nnm . . . . . . . . . . .tsh ERoRtCvPrs . . . . . . . . . . . hoihop . . . . . . . . . . .rrxeresdh se . . . . . . . . . . .g aeel llipfue . . . . . . . . . . . .aasrii gassa . . . . . . . . . . . .osaisx xmn n . . . . . . . . . . . .mrluta tte l . . . . . . . . . . . .a xsa iebhr . . . . . . . . . . . .scgo te n . . . . . . . . . . . .i uao eaia . . . . . . . . . . .d . ndo vnvi . . . . . . . . . . . .nnn ai e . . . . . . . . . . . .endt aadds . . . . . . . . . . . .iy erli . . . . . . . . . . . . na (ld i . . . . . . . . . . . . .orrtet sid . . . . . . . . . . . . .neenmh wx . . . . . . . . . . . . .p d e . . . . . . . . . . . . . eceh o uta . . . . . . . . . . . . .uh t x . . . . . . . . . . . . .hastshi ce . . . . . . . . . . . . .nphph leee . . . . . . . . . . . . .si htei . . . . . . . . . . . . .sn t re . . . . . . . . . . . . .ra e d agiic . . . . . . . . . . . . .rln br . . . . . . . . . . . . .tvca)i u . . . . . . . . . . . . . cie vooc . . . . . . . . . . . . .p io . . . . . . . . . . . . .ast n . . . . . . . . . . . . .ygbt l . . . . . . . . . . . . . i aey . . . . . . . . . . . . .. l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RE . . . . . . . . . . . . . . . . . . . . . . . . . . x . . . . . . . . . . . . .TeDiVr . . . . . . . . . . . . .ne ao . . . . . . . . . . . . .evr hf■■■■■■■■■■■■ maranaiewcsltsiihi ninh la . . . . . . . . . . . . .ioagie . . . . . . . . . . . . . enft . . . . . . . . . . . . . vnalg . . . . . . . . . . . . .rioeo . . . . . . . . . . . . .n’ . . . . . . . . . . . . . w stnfd . . . . . . . . . . . . .ahu . . . . . . . . . . . . . tce . . . . . . . . . . . . .eclml . . . . . . . . . . . . .ih x . . . . . . . . . . . . .patmeah . . . . . . . . . . . . .ii . . . . . . . . . . . . .arraa . . . . . . . . . . . . .v tnl . . . . . . . . . . . . .ir in . . . . . . . . . . . . .sitnk . . . . . . . . . . . . .o t sg . . . . . . . . . . . . .bt■■■■■■■■■■■■ y,h. dryeeeoa Rs . . . . . . . . . . . . .autc . . . . . . . . . . . . .ehl . . . . . . . . . . . . .vrvwi . . . . . . . . . . . . .ienbi . . . . . . . . . . . . .soi . . . . . . . . . . . . .glee . . . . . . . . . . . . .ll i . . . . . . . . . . . . .d.na . . . . . . . . . . . . . . . . . . . . . . . . . .ne . . . . . . . . . . . . .de . . . . . . . . . . . . . . . . . . . . . . . . . .d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .■■■■■■■■■■■■ 4 Exchange surfaces and breathing atmospheric pressure pressure to describe all the volume and Features to helpA Uir mnyoivte mFoe2n1t2 uMoAhiiglr ehise cprs uuastlmheeoudss p,inh tbeor iilcuco pndrgessi csbvuyre eresAhiiigrt hyise ,epr upfsroehseosddu droeu itan o anfl vldueno glhis ebya lthpressure changes accurately. T7id Bali ovloolugmicael amndo lveictuall ecsapacity Revised TesteRdevised rEexaadmy ■ ■ ■ Ti 5d6a l vWolautmere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .■ . . . . . . . . . . . . . . . . . .■ . . . . . . . . . . . . . . . . .■ Examiner’s tips and summaries TbrVerii s5666edtta8024a atit llh vi.cs oT aACLTulhepiuasmpeusamr itatbidciilneldnioyst oa igy .hsal . b .vtya f .hoo d .oc e .ul iur .r dt .vam . bo0s .t . e.l ei5u .a o . cs mdn . lh . .m o . .de a . . g n . .3 o . ..p gi . .f c . .e r . .aa so . .i . .rla t . . cb . .em . .c r . .i eon . .o . .ar . .sdtl . .e h . . .i n . . .ec . . .g du . . . . . . tl . . .i oen . . . . . . s . . .ta . . . h n . . . . . . . .e d . . . . . . . . n . . . .t . . . .eh . . . . ee . . . . . . . .dn . . . . s . . . . o . . . . o . . . . u . . . . f . . . .t . . . .t . . . .ih n . . . . . . . .e . . . . o . . . .b . . . .n . . . .o e . . . . d . . . . . . . . y . . . . . . . . . . . . .A . . . . . . . .t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TbbVv . . . . o . . . .rrii dee■■■tluaaaamttll hh cve . . . ..ea . . . . od . . . .op . . . .l f . . . .uia n . . . .amc . . . . . . . .iiar . . . .te n . . . .yt . . . . dh i . . . .si a . . . .s t . . . . tth . . . .t h . . . .hcee . . . .aen . . . . ■■■n v mo obulaue . . . .tx . . . .m . . . .iifmn . . . .oe . . . . r . . . . uoc . . . .omne . . . .f . . . .de . . . . a . . . .oi . . . .r . . . . u . . . . . . . .t . . . . . . . .■■■ Expert tips are given throughout the book to help you polisVhi8ta lNy cuaopcaluceitiryc isae tchixed masamximu mt veolucmhe onf aiirq thaut cean bien fo rcoed rodut aeftrer toaft emr a deaepx briemath.ise your taking a deep breath. Vital capacity is typically 4.5 dm3 in young men and ■ ■ ■ chances in the exam. S3i.n0 66 gd68em rs3 aiDTnnh dNye oaA utgh naelgenn twedeso toRmicfNte ecnAno. Vdh . .ia .etv .a .ela . .can .a . l .dpa .ar . g .cp .ei .tr .yov . .ictt .a .ea .ln i .cn . .ba . pe .s . ay .inc .n .ict .try .he .. .ae .s .se .i .ds . . t . .h . . . .r . .o . . . .u . . . .g . .h . . . . . .t . .r . .a . .i . .n . . .i .n . . . .g . .. . . . . . . . . . . . . . . . . . .■ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .■ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .■ 9 Enzymes ■ ■ ■ The summaries provide a quick-check bullet list for each topUi 7sc1in .gE an zsypmireo macteivtietry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R . .e .v .i .s .e . .d . . . . . . . . . 1 The subject should wear a nose clip to ensure that no oxygen escapes 4 Exafmro mp rtahec tsiycsete man asnwd enors a dadnitdio qnaul iacirk i sq auddizezde.s at www.therevisionbutton.co.uk/myrevisionnotes 2 The subject breathes through the mouthpiece. 3 As the subject inhales, oxygen is drawn from the air chamber, which Typical mistakes 79675_01_NBiologo4y_ 1-tA1wh3s0e .itrnehdd feo trs4eu ebdjeescscte etnxdh sa.yles,o theu airr chsamebelr frises again. 23/08/12 6:51 PM 5 Air returning to the air chamber passes through the canister of soda The author identifies the typical mistakes Thlimee, swehic hs abhsoorbsr ctarb, okn dnioxoidew. ledge-based questions provide the 6 The movements of the air chamber are recorded by a data logger. candidates make and explains how you can avoid first step in testing your learning. Answers are at the them. back of the book. Unit 1 Cell, exchange and transport 31 Definitions and key words 79675_0R1_Bioelogy_v1-130i.insdd i 31on activities 23/08/12 6:59 PM Clear, concise definitions of essential key terms are These activities will help you to understand each provided on the page where they appear. Key words topic in an interactive way. from the specification are highlighted in bold for you throughout the book. Exam practice Online Practice exam questions are provided for each topic. Go online to check your answers to the exam Use them to consolidate your revision and practise questions and try out the extra quick quizzes at your exam skills. www.therevisionbutton.co.uk/myrevisionnotes My revision planner Unit F211 Cells, exchange and transport Revised Tested Exam 1 Cell structure ready ■ ■ ■ 7 Microscopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 8 Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Cell membranes ■ ■ ■ 12 The structure of cell membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 15 Transport of substances across membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Cell division, cell diversity and cellular organisation ■ ■ ■ 19 Cell division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 21 Stem cells and differentiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 22 Tissues, organs and organ systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Exchange surfaces and breathing ■ ■ ■ 24 Exchange surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 26 The gaseous exchange system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 28 Breathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Transport in animals ■ ■ ■ 31 Circulatory systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 32 The heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 36 Blood vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 38 Transport of oxygen and carbon dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Transport in plants ■ ■ ■ 41 Xylem and phloem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 43 Transpiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 48 Translocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unit F212 Molecules, biodiversity, food and health Revised Tested Exam 7 Biological molecules ready ■ ■ ■ 50 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 51 Amino acids and proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 53 Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 55 Lipids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 57 Testing for biological molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes Revised Tested Exam ready 8 Nucleic acids ■ ■ ■ 59 DNA and RNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 61 The genetic code and protein synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Enzymes ■ ■ ■ 63 Enzyme activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 65 Factors affecting enzyme activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 68 Practical skills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Diet and food production ■ ■ ■ 70 A balanced diet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 72 Availability of food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Health and disease ■ ■ ■ 77 Health and disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 79 Defence against disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 83 Immunity and vaccination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 85 Cigarette smoking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Biodiversity ■ ■ ■ 89 Species, habitat and biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 89 Measuring biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 92 Global biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Classification ■ ■ ■ 94 Systems for classifying organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 96 Modern classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Evolution ■ ■ ■ 98 Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 99 Adaptations of organisms to their environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 101 Natural selection and evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Maintaining biodiversity ■ ■ ■ 104 Reasons for conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 105 The importance of maintaining biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ■ ■ ■ 106 Approaches to conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 Now test yourself answers Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes My revision planner 5 Countdown to my exams 6–8 weeks to go One week to go ●● Start by looking at the specification — make sure ●● Try to fit in at least one more timed practice of you know exactly what material you need to an entire past paper and seek feedback from your revise and the style of the examination. Use the teacher, comparing your work closely with the revision planner on pages 4 and 5 to familiarise mark scheme. yourself with the topics. ●● Check the revision planner to make sure you ●● Organise your notes, making sure you have haven’t missed out any topics. Brush up on any covered everything on the specification. The areas of difficulty by talking them over with a revision planner will help you to group your notes friend or getting help from your teacher. into topics. ●● Attend any revision classes put on by your ●● Work out a realistic revision plan that will allow teacher. Remember, he or she is an expert at you time for relaxation. Set aside days and times preparing people for examinations. for all the subjects that you need to study, and R evised stick to your timetable. ●● Set yourself sensible targets. Break your revision down into focused sessions of around 40 minutes, divided by breaks. These Revision Notes organise The day before the examination the basic facts into short, memorable sections to make revising easier. ●● Flick through these Revision Notes for useful reminders, for example the examiner’s tips, R evised examiner’s summaries, typical mistakes and key terms. 4–6 weeks to go ●● Check the time and place of your examination. ●● Read through the relevant sections of this book ●● Make sure you have everything you need — extra and refer to the examiner’s tips, examiner’s pens and pencils, tissues, a watch, bottled water, summaries, typical mistakes and key terms. Tick sweets. off the topics as you feel confident about them. ●● Allow some time to relax and have an early Highlight those topics you find difficult and look night to ensure you are fresh and alert for the at them again in detail. examination. ●● Test your understanding of each topic by working R evised through the ‘Now test yourself’ questions in the book. Look up the answers at the back of the book. My exams ●● Make a note of any problem areas as you revise, and ask your teacher to go over these in class. ●● Look at past papers. They are one of the best AS Biology Unit F211 ways to revise and practise your exam skills. Date: ............................................ Write or prepare planned answers to the exam practice questions provided in this book. Check Time: ............................................ your answers online and try out the extra quick quizzes at www.therevisionbutton.co.uk/ Location:......................................... myrevisionnotes AS Biology Unit F212 ●● Use the revision activities to try different revision methods. For example, you can make notes using Date: ............................................ mind maps, spider diagrams or flash cards. ●● Track your progress using the revision planner and Time: ............................................ give yourself a reward when you have achieved Location:......................................... your target. R evised 6 Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes 1 Cell structure Microscopes Types of microscope Revised Three types of microscope are commonly used, as shown in Table 1.1. Table 1.1 Types of microscope Type of Examiner’s tip Magnification Resolution Use microscope For the resolution of light and Light 1000–2000× 50–200 nm Viewing tissues and cells transmission electron microscopes, just remember the figure 0.2 and Scanning 50 000–500 000× 0.4–20 nm Viewing the surface of electron cells and organelles provide the unit appropriate to each type of microscope, e.g. 0.2 μm for Providing depth/three- light microscopes and 0.2 nm for dimensional images transmission electron microscopes. Transmission 300 000–1 000 000× 0.05–1.0 nm Detailing organelles electron (ultrastructure) Now test yourself Tested 1 Explain why a light microscope will not usually magnify images to greater than 1500×. 2 How can you tell the difference between an image created by a scanning electron microscope and one created by a transmission electron microscope? Answers on p.108 Advantages and disadvantages Light (optical) microscopes allow us to see living things, but unfortunately their resolution is limited. Resolution is the ability to distinguish two separate points that One advantage of using a scanning or transmission electron microscope are close together. is that the resolution is better, which means it is worth magnifying the image more as the image will show more detail. The main disadvantage is that the sample must be dried and is therefore dead. This may affect Revision activity the shape of the features seen. Another disadvantage is that the image is Draw a table to show the advantages in black and white only, but colours may be added later using computer and disadvantages of the three types graphics. These images are called false colour electronmicrographs. All of microscope. The table should electron microscopes are large and expensive. have three columns headed Type of microscope, Advantages and Disadvantages. Magnification and resolution Revised Magnification is the ratio of the image size to the actual object size (size of image/size of object). Resolution is the ability to distinguish between Magnification is the ratio of the two objects that are close together — the ability to provide detail in the image size to the object size. image. Unit F211 Cells, exchange and transport 7 e Use the magnification triangle Revision activity r u I t where: Make up an acronym to help c you remember the magnification u r I is the Image size A M triangle. t s l A is the Actual size of the object l e C M is the Magnification 1 Examiner’s tip This means that: Almost every biology examination I = A × M paper is likely to include a calculation. This will often be to do or: with magnification or image size. I You need to be able to calculate the A = M magnification, but you also need to be able to manipulate the formulae. or: If you can remember how to do the I M = calculations, these are easy marks. A Now test yourself Tested I 3 Using the magnification triangle M = , rearrange the letters to give the formulae for I and for A. A 4 Explain the relationship between micrometers (μm) and nanometers (nm). Answers on p. 108 Staining Revised Staining is the application of coloured stains to the tissue. It makes objects visible in light microscopes and increases contrast so that the Revision activity object can be seen more clearly. Draw a mind map to show the Stains are often specific to certain tissues or organelles. In an electron reasons for staining cells and tissues. microscope, the stains are heavy metals or similar atoms that reflect or Include the names of any stains you absorb the electrons. In a transmission electron microscope, the heavy may have used such as methylene metal covers the organelles whereas in a scanning electron microscope blue and iodine. the heavy metals cover the whole surface. Cells Organelles Revised Cells are the basic unit of living organisms. All eukaryotic cells share a similar basic structure containing membrane-bound organelles. Each Revision activity organelle, whether membrane-bound or not, has its own function within the cell, as shown in Table 1.2. From memory, make a list of all the membrane-bound organelles and note Now test yourself Tested one function next to each. Make a separate list of the organelles that are 5 Explain why organelles such as mitochondria do not always look the not membrane-bound. same size and shape. Answer on p. 108 8 Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes Table 1.2 Organelles and their functions e r u Organelle Function Diagram t c Centrioles Involved in the organisation of the microtubules that u make up the cytoskeleton r t Form the spindle used to move chromosomes in nuclear s division l l e C Chloroplasts Site of photosynthesis 1 Cilia Small hair-like extension of cell surface membrane containing microtubules Large numbers work in synchronised fashion Able to move whole organism or to move fluid (mucus) across a surface Cytoskeleton A network of microtubules and microfilaments Provides support and structure for the cell Enables movement of organelles inside the cell Enables movement of the whole cell Flagella Large extension of cell surface membrane containing microtubules (in eukaryotes) Able to beat to enable locomotion or move fluids Golgi apparatus Modifies proteins made in the ribosomes Often adds a carbohydrate group Repackages proteins into vesicles for secretion Lysosomes Small vacuoles containing hydrolytic or lytic enzymes Mitochondria Site of aerobic respiration Nuclear membrane/ The nuclear envelope separates the genetic material envelope from the cytoplasm Controls the cell activities Nucleus Contains the genetic material (chromosomes) The nuclear pores allow molecules of mRNA to pass from the nucleus to the ribosomes in the cytoplasm Nucleolus Assembles the ribosomes Ribosomes Site of protein synthesis Rough endoplasmic Holds the ribosomes reticulum (RER) Provides a large surface area for protein synthesis Smooth endoplasmic Associated with the synthesis, storage and transport of reticulum (SER) lipids and carbohydrates Unit F211 Cells, exchange and transport 9