Table Of ContentMary Jones
cambridge university press
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Cambridge University Press
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acknowledgements
Project management: Sue Kearsey
Picture research: Vanessa Miles
Page layout, illustration and preparation of interactive pdfs: Geoff Jones
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Contents
Introduction v Unit F212: Molecules, Biodiversity,
Food and Health
Acknowledgements vi
7 Biological molecules 105
Unit F211: Cells, Exchange and Water 105
Transport Proteins 108
Carbohydrates 116
1 Cell structure 1 Lipids 119
Microscopes 1
Cells 8 8 Nucleic acids 124
Structure and function of organelles 13 Polynucleotides 124
Prokaryotic cells 19
9 Enzymes 131
2 Cell membranes 24 How enzymes work 131
Structure of cell membranes 25 The course of a reaction 134
Cell signalling 26 Measuring reaction rate 136
Movement across cell membranes 29 Enzyme inhibitors 138
3 Cell division and cellular 10 Diet and food production 143
organisation 36 Nutrition 143
The cell cycle 36 Diet and the cardiovascular system 146
Differentiation 40 Sources of food 151
Tissues, organs and organ systems 44 Selective breeding 152
Another type of cell division 47 Increasing food production 157
Microorganisms and food 160
4 Exchange 50
Exchange surfaces 50 11 Health and disease 166
The mammalian gas exchange system 53 Parasites and pathogens 166
Measuring lung volumes 58 The immune response 174
Controlling infectious disease 183
5 Transport in animals 62 Smoking and health 189
Types of transport system 62 Evidence for the effects of smoking on
The mammalian heart 65 health 194
Blood vessels 73
Blood plasma, tissue fluid and lymph 77 12 Biodiversity 199
Blood 79 Measuring biodiversity 199
Sampling 200
6 Transport in plants 87 Species evenness 206
Plant transport systems 87
Water transport in plants 88
Translocation 99
iii
13 Classification 209
Classification and taxonomy 209
The five-kingdom classification 214
The three-domain classification 217
14 Evolution 219
Variation 219
Charles Darwin and the theory of natural
selection 221
Speciation 227
The evidence for evolution 228
15 Maintaining biodiversity 233
Threats to biodiversity 233
The importance of maintaining
biodiversity 235
Conservation 236
Answers to self-assessment
questions 244
Glossary 257
Index 268
iv
Introduction
Cambridge OCR Advanced Sciences
The new Cambridge OCR Advanced Sciences The content of the chapters is arranged in the
course provides complete coverage of the revised same sequence as in the specification.
OCR AS and A Level science specifications The book is designed to be accessible to
(Biology, Chemistry A and Physics A) for teaching students who have studied Double Award Science
from September 2008. There are two books for at GCSE, or who have a separate qualification in
each subject – one covering AS and one covering biology. The language is kept simple, to improve
A2. Some material has been drawn from the accessibility for all students, while still maintaining
existing Cambridge Advanced Sciences books; scientific rigour throughout. Care is taken to
however the majority is new. introduce and use all of the specialist terms that
The course has been developed in an innovative students need to acquire during their AS biology
format, featuring Cambridge’s new interactive studies. In the text, key terms are highlighted in
PDFs on CD-ROM in the back of the books, and bold.
free access to a dedicated website. The The depth and breadth of treatment of each
CD-ROM provides additional material, including topic is pitched at the appropriate level for OCR
detailed objectives, hints on answering questions, AS students. The accompanying CD-ROM also
and extension material. It also provides access contains some material that goes a little beyond
to web-based e-learning activities (A Level the requirements of the specification, which should
and background revision from GCSE) to help interest and stretch more able students.
students visualise abstract concepts, understand Some of the text and illustrations are based
calculations and simulate scientific processes. on material in the endorsed text Biology 1, which
The books contain all the material required for covered the earlier OCR specification, while some
teaching the specifications, and can be used either is completely new. All of it has been reviewed and
on their own or in conjunction with the interactive revised, ensuring that relevant new findings relating
PDFs and the website. to particular topics are included. In addition to
In addition, Teacher Resource CD-ROMs, with the main content in each chapter, there are How
book PDFs plus extra material such as worksheets, Science Works boxes, describing issues or events
practical activities and tests, are available for each related to the biological material, which begin to
book. These CD-ROMs also provide access to the explore the relevance of these aspects of biology to
new Cambridge OCR Advanced Sciences Planner individuals and to society.
website with a week-by-week adaptable teaching Self assessment questions (SAQs) in each
schedule. chapter provide opportunities to check
understanding and to make links back to earlier
Biology 1 for OCR – the AS biology text work. They often address misunderstandings
This book covers the entire OCR AS Biology that commonly appear in examination answers,
specification for first examination in 2009. and will help students to avoid such errors. Past
Chapters 1 to 6 correspond to Unit F211, Cells, examination questions at the end of each chapter
Exchange and Transport. Chapters 7 to 15 allow students to practise answering exam-style
correspond to Unit F212, Molecules, Biodiversity, questions. The answers to these, along with
Food and Health. Each chapter covers one of the exam-style mark schemes and hints on answering
numbered sections within the two Modules in Unit questions, are found on the accompanying
F211, and within the three Modules in Unit F212. CD-ROM.
v
Acknowledgements
US Department of Energy/Science Photo Library;
pp. 144b, 160 Gustoimages/Science Photo Library;
We would like to thank the following for permission to
p. 147 Adam Hart-Davis/Science Photo Library; p. 148
reproduce images:
© Peter Cavanagh/Alamy; pp. 153, 161r, 226 © Holt
Cover Daniel Cox; p. 3 Richard Kirby (Timeframe Studios International Ltd/Alamy; p. 154t Nigel Cattlin/
Productions Ltd); pp. 4, 8, 9, 13l, 17r, 18, 79t, 79b, Holt Studios International/Science Photo Library;
96c, 157l, 172l, 191, 225 Phototake Inc; pp. 5, 89 Dr p. 154b Herve Conge, ISM/Science Photo Library;
Jeremy Burgess/Science Photo Library; pp. 7l, 140 p. 156 © Peter Llewellyn/Alamy; pp. 157r, 221 © David
Pascal Goetgheluck/Science Photo Library; p. 7r Steve R. Frazier Photolibrary, Inc./Alamy; p. 161l Owen
Allen/Science Photo Library; pp. 10, 11t, 20 Dennis Franken/Corbis; p. 162l Cordelia Molloy/Science Photo
Taylor; pp. 11bl, 13r Dr Gopal Murti/Science Photo Library; p. 162r © Jeremy Hogan/Alamy; pp. 168, 171,
Library; p. 12 Anton Page, Biomedical Imaging Unit, 173 World Health Organization; p. 169 Dr Klaus Boller/
University of Southampton; p. 14 Biology Media/ Science Photo Library; pp. 172r, 174 Andy Crump,
Science Photo Library; p. 15l Dr Kari Lounatmaa/ TDR, WHO/Science Photo Library; p. 186 © Sally and
Science Photo Library; pp. 15r, 167 CNRI/Science Richard Greenhill/Alamy; p. 188 Roger De La Harpe/
Photo Library; p. 16 ISM//Science Photo Library; Africa Imagery; p. 189 © Photofusion Picture Library/
p. 17l Don W. Fawcett/Science Photo Library; pp. 19l, Alamy; p. 190l Richard Fosbery; p. 192 Colin Cuthbert/
55t, 73, 99, 190r Biophoto Associates/Science Photo Science Photo Library; p. 195 Nick Sinclair/Science
Library; p. 19r Marilyn Schaller/Science Photo Library; Photo Library; p. 203tl © FLPA/Alamy; p. 203tr ©
p. 39l David M Dennis; pp. 39r, 55bl, 55br, 175 John Alistair Scott/Alamy; p. 203bl © Martin Shields/Alamy;
Adds; p. 40 Microfield Scientific LTD/Science Photo p. 203br © Chris Howes/Wild Places Photography/
Library; p. 43l Duncan Shaw/Science Photo Library; Alamy; pp. 205, 241b © NHPA/Nick Garbutt; p. 210r
p. 43r © Travelshots.com/Alamy; p. 44 Sidney Moulds/ Konrad Wothe; p. 211tl Liz Bomford; p. 211cl Berndt
Science Photo Library; p. 45 M.P. O’Neill/Science Fischer; p. 211bl Survival Anglia; p. 211 greenfinch,
Photo Library; p. 47 L. Willatt, East Anglian Regional chaffinch Mark Hamblin; p. 211 goldfinch David Tipling;
Genetics Service/Science Photo Library; p. 49 OCR; p. 212tl © JUPITERIMAGES/Brand X/Alamy; p. 212tr
p. 51 Claude Nuridsany & Marie Perennou/Science Juniors Bildarchiv; p. 222 © John Carnemolla/Corbis;
Photo Library; p. 56b Brian Bell/Science Photo Library; p. 223t © NHPA/Stephen Dalton; p. 223b © John
p. 58t Photo Insolite Realite/Science Photo Library; Howard/Cordaiy Photo Library Ltd/CORBIS; p. 224
p. 65 Science Photo Library; pp. 66, 74, 92r Biophoto John Durham/Science Photo Library; p. 233 PLI/
Associates; pp. 68, 97br, 150, 152, 159, 204, 210l, Science Photo Library; p. 234l Mike Powles; p. 234r ©
235r, 242, 242 extension Geoff Jones; p. 70 Zephyr/ Paul Glendell/Alamy; p. 235l © Avico Ltd/Alamy; pp.
Science Photo Library; p. 84 © Olivier Labalette/ 236t, 238 © NHPA/Martin Harvey; p. 236b © NHPA/
TempSport/Corbis; pp. 92l, 97bl Andrew Syred; p. 95 Robert Thompson; p. 237t © ScotImage/Alamy; p.
NASA; p. 96t Ian West; pp. 96b, 97tr Andrew Syred/ 237cl © Organica/Alamy; p. 237cr © Mike Read/
Science Photo Library; p. 97tl Dirk Wiersma/Science Alamy; p. 237b © Susan & Allan Parker/Alamy; p. 239l
Photo Library; p. 106 Richard Wehr/Custom Medical © NHPA/Peter & Beverly Pickford; p. 239r © NHPA/
Stock Photo/Science Photo Library; p. 108 Hermann Andy Rouse; p. 241t © NHPA/Martin Wendler
Eisenbeiss/Science Photo Library; pp. 113, 217, 231
Eye of Science/Science Photo Library; p. 114 J. Gross, We would like to thank OCR for permission to
Biozentrum/Science Photo Library; p. 115 Prof. P. reproduce questions from past examination papers,
Motta/Dept. of Anatomy/University ‘La Sapienze’, and IUCN and the World Health Organization for
Rome/Science Photo Library; p. 128 Kevin Curtis/ permission to reproduce URLs.
Science Photo Library; p. 137 Simon Fraser/Science
Photo Library; p. 138 James King-Holmes/Science
Photo Library; p. 144t Oak Ridge National Laboratory/
vi
Chapter 1
Cell structure
All living organisms are made of cells. Cells are
eyepiece
the basic units of living things, and most scientists Eyepiece lens magnifies
and focuses the image
would agree that anything that is not made of a cell
from the objective onto
or cells – for example, a virus – cannot be a living the eye.
organism.
Some organisms, such as bacteria, have only
light beam
one cell, and are said to be unicellular. Others have
millions of cells. Any organism that is made up of
more than one cell is said to be multicellular.
objective
All cells are very small, but some of them are Objective lens collects
light passing through the
just large enough to be seen with the naked eye.
cover slip specimen and produces
The unicellular organism Amoeba, for example, a magnified image.
can just be seen as a tiny white speck floating in glass slide
liquid if you shake up a culture of them inside a
glass vessel. These cells are about 0.1 mm across. Condenser lens
condenser
focuses the light onto the
However, this is unusually large. Human cells are
specimen held between
iris
usually somewhere between 10 μm and 30 μm in the cover slip and slide.
diaphragm
diameter (see the box on page 3 for an explanation
of ‘μm’). Bacterial cells are much smaller,
light source Condenser iris
often about 0.5 μm across. To see most cells, a diaphragm is closed
slightly to produce a
microscope must be used.
narrow beam of light.
Microscopes Figure 1.1 How a light microscope works.
The first microscopes were invented in the mid
17th century. They opened up a whole new world The specimen to be observed usually needs to
for biologists to study. Now biologists would see be very thin, and also transparent. To keep it flat,
tiny, unicellular organisms whose existence had it is usually placed on a glass slide with a very
previously only been guessed at. They could also thin glass coverslip on top. For a temporary slide,
see, for the first time, that large organisms such as you can mount the specimen in a drop of water.
plants and animals are made up of cells. To make a permanent slide, a liquid that solidifies
to produce a clear solid is used to mount the
Light microscopes specimen.
The early microscopes, like the microscopes The slide is placed on a stage through which
that you will use in the laboratory, were light light shines from beneath. The light is focused onto
microscopes. Light microscopes use glass lenses to the specimen using a condenser lens. The light then
refract (bend) light rays and produce a magnified passes through the specimen and is captured and
image of an object. Figure 1.1 shows how a light refracted by an objective lens. Most microscopes
microscope works. have three or four different objective lenses, which
provide different fields of view and different
magnifications. The greater the magnification, the
smaller the field of view.
1
Chapter 1: Cell structure
The light rays now travel up to the eyepiece lens.
Worked example 1
This produces the final image, which falls onto the
retina of your eye. The image can also be captured Calculation of the magnification of a drawing.
using a digital camera or video camera, and viewed
size of image
or projected onto a screen. magnification =
real size of object
Many biological specimens are colourless when
they have been cut into very thin sections, so a Below is a ‘real’ spider and a drawing of this
stain is often added to make structures within the spider.
specimen easier to see (Table 1.1). Different parts
of a cell, or different kinds of cells, may take up
(absorb) a stain more than others. For example,
a stain called methylene blue is taken up more by
nuclei than by cytoplasm, so it makes a nucleus
look dark blue while the cytoplasm is pale blue.
Methylene blue is taken up by living cells, but
many other stains cannot get through the cell
membrane of a living cell and can only be used on Step 1 Measure the length of the ‘real’ spider.
dead cells. You should find that it is 10 mm long. The
length of the spider in the drawing is 30 mm.
Magnification
Using a microscope, or even just a hand lens, we Step 2 Now, substitute these numbers into the
can see biological objects looking much larger equation above:
than they really are. The object is magnified. We
30
can define magnification as the size of the image magnification = = × 3
10
divided by the real size of the object.
size of image Notice the ‘×’ sign in front of the number
magnification =
real size of object 3. This stands for ‘times’. We say that the
For example, we can calculate the magnification magnification is ‘times 3’.
of the drawing of a spider in Worked example 1.
Stain Use Colours produced
methylene blue staining living cells dark blue nucleus, light blue cytoplasm
(in bacteria, the whole cell takes up
the stain)
iodine solution staining living plant cells very dark blue starch grains
acidified staining lignin (the substance in the cell bright red
phloroglucinol walls of xylem vessels)
acetic orcein staining nuclei and chromosomes red
eosin staining cytoplasm and some organelles pink
(it stains dead cells only and so can be
used to distinguish between live and dead
sperm cells)
light green staining plant cell walls green
Table 1.1 Some stains commonly used in light microscopy.
2
Chapter 1: Cell structure
SAQ Worked example 2
1 A person makes a drawing of an
incisor tooth. The width of the Calculation of magnification and conversion of
actual tooth is 5 mm. The width of the tooth in units.
the drawing is 12 mm.
Calculate the magnification of
the drawing.
Units of measurement
In biology, we often need to measure very
small objects. When measuring cells or parts of
cells, the most common (and useful) unit is the
micrometre, written μm for short. The symbol
μ is the Greek letter mu. One micrometre is one
thousandth of a millimetre. Let us say that we know that the real diameter
Even smaller structures, such as the of a red blood cell is 7 μm and we have been
organelles within cells, are measured using even asked to calculate the magnification of the
smaller units. These are nanometres, written nm above diagram.
for short. One nanometre is one thousandth of
a micrometre. Step 1 Measure the diameter of the cell in the
diagram. You should find that it is 30 mm.
1
1 μm = mm
1000
Step 2 We have been given its real size in μm,
This can also be written 1 × 10−3 mm, or
so we need to convert the 30 mm to μm. There
1 × 10−6 m.
are 1000 μm in 1 mm, so 30 mm is 30 × 1000 μm.
1
1 nm = μm
1000 Step 3 Now we can put the numbers into the
This can also be written 1 × 10−6 mm, or equation:
1 × 10−9 m. size of image
magnification =
real size of object
30 × 1000
Often, we are dealing with small units, such =
7
as μm. It is important to make sure all your
measurements are in the same units. It is often best = × 4286
to convert everything into μm before you begin
your calculation, as shown in Worked example 2.
SAQ
2 This is a photomicrograph – a photograph taken
using a light microscope. The actual maximum
diameter of the cell is 50 μm. Calculate the
magnification of the photomicrograph.
3
