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Learner Guide
Cambridge International AS & A Level
Biology
9700
Cambridge International Examinations retains the copyright on all its publications. Registered Centres are permitted to copy material from this booklet for their own internal use. However, we cannot give permission to Centres to photocopy any material that is acknowledged to a third party even for internal use within a Centre. © Cambridge International Examinations 2015 Version 2.0 Updated: 16.02.16
Contents
How to use this guide ....................................................................................................... 3Section 1: How will you be tested?Section 2: Examination adviceSection 3: What will be tested?Section 4: What you need to knowSection 5: Useful websitesSection 6: Appendices
Section 1: How will you be tested? ..................................................................................... 5About the examinationsAbout the papersAbout the practical papers
Section 2: Examination advice ............................................................................................. 7General advice Advice about the questionsAdvice about the papers
Section 3: What will be tested? .........................................................................................32
Section 4: What you need to know ...................................................................................34How to use the table
Section 5: Useful websites ................................................................................................ 72
Section 6: Appendices ....................................................................................................... 75Mathematical skillsMore information about the examination
2 Cambridge International AS and A Level Biology 9700
How to use this guide
3Cambridge International AS and A Level Biology 9700
How to use this guide
The guide describes what you need to know about your Cambridge International AS and A Level Biology examination.
It can be used to help you to plan your revision programme for the theory examinations and will explain what we are looking for in the answers you write. It can also be used to help you revise by using the table in Section 4, ‘What you need to know’, to check what you know and which topic areas of biology you have covered.
The guide contains the following sections:
Section 1: How will you be tested?This section will give you information about the different types of theory and practical examination papers that are available.
Section 2: Examination adviceThis section gives you advice to help you do as well as you can. Some of the ideas are general advice and some are based on the common mistakes that learners make in exams.
Section 3: What will be tested?This section describes the areas of knowledge, understanding and skills that you will be tested on.
Section 4: What you need to knowThis shows the syllabus content in a simple way so that you can check:
• the topics you need to know about
• the contents of each part of the syllabus
• details about each topic in the syllabus
• how much of the syllabus you have covered
Section 5: Useful websites
Section 6: AppendicesThis section covers the other things you need to know, including:
• information about the mathematical skills you need
• information about terminology, units and symbols, and the presentation of data
• the importance of the command words used in the examination papers
How to use this guide
4 Cambridge International AS and A Level Biology 9700
Section 1: How will you be tested?
5Cambridge International AS and A Level Biology 9700
Section 1: How will you be tested?
About the examinationsThere are three ways you can gain a Cambridge International Advanced Level qualifi cation.
• take the Advanced Subsidiary (AS) qualifi cation only
• follow a staged assessment route to the Advanced (A) Level by taking the AS Level papers and the A Level papers in different examination sessions. Usually this means taking the AS Level papers at the end of one year of study and the A Level papers at the end of a second year of study.
• take all the examination papers in the same examination session leading to the full A Level
AS LevelYou will be entered for three examination papers, two theory papers and one practical paper.
You will take Paper 1 Multiple Choice (theory), Paper 2 (theory) and Paper 3 (Advanced Practical Skills).
A LevelYou will be entered for two further examination papers, Paper 4 A Level Structured Questions (theory) and Paper 5 Planning, Analysis and Evaluation.
About the papersThe table gives you information about the examination papers.
Paper number
How long and how many marks?
What’s in the paper? Weighting %
AS A
1 1 hour (40 marks)
40 multiple-choice questions. You choose one answer you consider correct from a choice of four possible answers.
31 15
2 1 hour 15 minutes (60 marks)
Structured questions. You should write your answers in the spaces provided. The paper tests the AS syllabus only.
46 23
3 2 hours (40 marks)
A practical test set and marked by Cambridge. It will include experiments and investigations based on the AS syllabus.
23 12
4 2 hours (100 marks)
Structured questions, totalling 85 marks plus one free response question that carries a further 15 marks. Based on the A Level syllabus, but a knowledge of the AS syllabus is required.
– 38
5 1 hour 15 minutes (30 marks)
A written paper that tests the practical skills of planning, analysis and evaluation. It will include information about experiments and investigations from both AS and A Level.
– 12
Section 1: How will you be tested?
6 Cambridge International AS and A Level Biology 9700
About the practical papersTwenty-three percent of the marks for Cambridge International AS Biology are for practical work.
In Paper 3, you will have to handle familiar and unfamiliar biological material and will be expected to show evidence of the following skills:
• manipulation, measurement and observations
• presentation of data and observations
• analysis, conclusions and evaluation.
When unfamiliar materials or techniques are involved, you will be given full instructions. One question will require the use of a light microscope.
No dissection will be set in Paper 3.
If you continue to a full A Level, after AS, the mark you obtained in Paper 3 will contribute twelve percent of your overall mark and Paper 5 will contribute a further twelve percent.
In Paper 5, there will be questions in which you will be expected to design an investigation and write out a plan that you will not carry out, as well as analysing and evaluating experimental data. To do this confi dently you need plenty of experience of practical work in the laboratory.
Questions involving an understanding of the use of the t-test and the chi-squared test may be set. You will be provided with the formulae for these tests.
Section 2: Examination advice
7Cambridge International AS and A Level Biology 9700
Section 2: Examination advice
Much of this advice is given in response to the types of answers that learners have written in the past. It is presented under various subheadings to help you to prepare for your examinations. Some examples of questions and answers are included to illustrate some of the advice.
• Make sure that you read all the general advice. These can be important in any of the papers that you take.
• Have a copy of the syllabus to look at as you read through this section. Note that in Section 4 the fi rst part is the AS Level syllabus and the second part is A Level.
• Make sure that you know the examination papers that you are taking before you look at the advice for the different papers.
• At AS Level, you will take
– Paper 1, which is a multiple-choice paper.
– Paper 2, which consists of short-answer questions.
– Paper 3 which is the practical paper.
There are different versions of each paper; for example, Papers 11, 12 and 13 are all multiple-choice papers.
• At A Level, you will take
– Paper 4, which has a short-answer section for 85 marks and an essay for 15 marks.
– Paper 5, which tests your skills of planning, analysis and evaluation. It is not a practical paper like Paper 3, but does require a lot of experience of practical work.
General advice • Use your syllabus all the time while you are revising and preparing for the examination papers. You must
know which topics you will be tested on.
• Make sure you have all the equipment you will need for the exam in a clear, plastic container. You need two pens, pencils (preferably HB or B), a clean eraser, a ruler (which measures in mm), a pencil sharpener and a calculator.
Answering questions• The questions are designed to test your knowledge and understanding and your ability to apply the skills
you have gained during the course. When you are writing your answers remember that another person has to be able to read them.
• Do not waste time by writing out the question before you start to answer.
• Keep your handwriting clear and legible.
• Keep your answers on the lines on the question paper. Do not write in the left hand or right-hand margins of the paper.
• If you wish to change an answer, cross out your fi rst answer and rewrite. Do not write over what you have already written.
Section 2: Examination advice
8 Cambridge International AS and A Level Biology 9700
• If you have to cross out something, put a line through it; do not scribble over it.If you run out of space, use white space on another part of the exam paper for a continuation answer; do not try to squeeze in your answer by using very small writing.
• If you have to use a different space for a rewritten answer or to continue an answer, put a note to tell the Examiner where it is, e.g. “see page 5” or “see back page”.
• Always try to write accurately using the correct biological terms. This often helps you to give a better answer.
• If you want to use the word “it” or “they” – think “what is it?” or “what are they?” and then phrase your answer more precisely.
• If you want to use the word “affect” or “effect” – remember to write “how they affect” or “what effect do they have?”
Example 1
Question
Chronic obstructive pulmonary disease (COPD) is a progressive disease that develops in many smokers. COPD refers to two conditions:
• chronic bronchitis
• emphysema.
(i) State two ways in which the lung tissue of someone with emphysema differs from the lung tissue of someone with healthy lungs [2]
Correct answer for two marks
1 There are fewer alveoli than in a healthy lung.
2 The surface area for gas exchange is much smaller.
From the wording of the question it is clear that the answers refer to the lung tissue of emphysema.
Ambiguous answers for no marks
1 There are many air spaces.
2 There is less diffusion of oxygen and carbon dioxide.
3 There are fewer capillaries.
Both types of lung tissue have many air spaces. The technical term alveoli should be used as in the correct answers. Even though the third answer is correct, it will not be marked as the question asks for two ways.
• Do not write the fi rst answer that comes into your head. You are unlikely to think of exactly the correct phraseology or have all the necessary detail to answer the question. Plan what you intend to write before you start writing.
• Remember to read the question carefully, plan an answer, write the answer clearly, re-read the question, re-read your answer and then make any additions or corrections clearly. Always re-read your answers to check them against the question.
• During your course you will probably have seen many mark schemes from past papers. Do not learn them. If you write out a mark scheme that you have learnt, it is unlikely to gain you many marks and
Section 2: Examination advice
9Cambridge International AS and A Level Biology 9700
often none at all, as it is very unlikely to be relevant to the exact question you were supposed to be answering
• Be prepared for questions on aspects of practical biology; they can appear on all the papers, not just Papers 3 and 5.
TermsThese are the technical words used in biology. Many of them are given in the syllabus. These terms will be used in questions. You will give a better answer if you can use them correctly in your examination. Ask your teacher if you are unsure of the meanings of the biological terms used in the syllabus and in any textbook you are using. You will notice that many terms you need to know are stated in the syllabus, so that is a good place to start when making your own dictionary. It would be a good idea to write concise defi nitions for yourself and use them to start your own biological dictionary using your class notes, websites and the glossaries from the back of textbooks.
• Try to use the correct spelling. If you cannot remember how to spell a word, write it down as best you can. The examiners will probably recognise what word you mean; if the spelling is too far out or ambiguous, then they cannot allow you a mark.
• Some biological terms have very similar spelling. Make sure you write clearly and always try to spell as accurately as you can.
• Do not try to mix the spellings of two words when you are not sure which of them is the correct answer. For example, you might write “meitosis” when you are not sure whether the answer is mitosis or meiosis. This answer will not get a mark.
Writing in your own wordsYou often have to write two or more sentences to answer a question.
• Use short sentences. If you write long sentences you can become confused and your meaning is lost. You might also write something contradictory. It is hard for the examiner to fi nd correct statements in a muddled answer.
• You are often asked to write down something you have learned. Make sure you have learnt the meanings of the common terms used in biology, e.g. active transport, osmosis, photosynthesis and respiration.
• During your course take every opportunity to read and write as much as you can to improve the way you express yourself.
Advice about the questionsThe marks• Always look to see how many marks are available for each question.
– In Paper 1 there is one mark for each question.
– The number of marks is printed on the examination papers for Papers 2, 3, 4 and 5. The mark available for each part question ((a), (b), (c)(i), etc.) is printed in square brackets, e.g. [2]. The number of marks helps you decide how much to write. The total number of marks for each question is printed at the end of the last part question, e.g. [Total: 12].
– The number of marks is a guide to how long to spend on each part of a question.
Section 2: Examination advice
10 Cambridge International AS and A Level Biology 9700
• Do not waste time and write a long answer for a question which has one or two marks. You will not get any extra marks even if your answer is full of many correct and relevant statements.
• If there are two or more marks do not write the same thing in two different ways, e.g. “The leaf is very large. The leaf has a large surface area”. Notice that the second sentence is more accurate and is preferable to the fi rst one.
The instructionsThese are called command words and tell you what to do.
• You can fi nd all the command words in the Glossary of command words used in science papers in the syllabus.
• If a question asks you to ‘name’ or ‘state’ two things only the fi rst two will be marked. Use the numbered lines for your answers if they are given on the question paper. If you write more than two and the fi rst is correct, the second one is wrong, and the third one correct, you will only get one mark (see Example 1).
• Some questions have two commands in the question, for example ‘predict and explain’. This means that you have to say what you think will happen AND then say why you think it will happen. Usually the word and is printed in bold type to help you. See the section below for advcie about answering questions that have two command terms and require an extended answer.
• Make sure you know what you should do in response to each command word.
Example 2
Question
A learner investigated the effect of increasing the concentration of sucrose on the rate of activity of sucrase. The results are shown in Fig. 4.1.
The graph in Fig. 4.1 shows that as the substrate concentration increases the rate of activity of sucrase increases to a constant level.
Describe and explain the results shown in Fig. 4.1.
It is quite easy to forget that there are two parts to this question. Before writing your answer it is a good idea to write description at the beginning of the fi rst of the answer lines and then explanation about half way down. You could write these in pencil and rub them out when you have fi nished your answer. Alternatively, you may choose to write a description of the fi rst part of the graph (activity increases) and then explain it followed by a description and explanation of the plateau on the graph. That is also a perfectly acceptable way to answer the question.
The questions• Make sure you know which part of the syllabus is being tested.
• Read the whole of a question carefully including all the stimulus material and parts (a), (b), (c) (i) and (c) (ii), etc. before you begin to answer. Some of the parts may have similar answers so you need to work out the differences between them. If you write exactly the same thing in different parts of the same question, the answer cannot be correct for both parts.
• There is often stimulus material for each question. This might be a photograph, diagram, drawing, fl ow chart, table of data, graph or just some text. Read all of this information carefully and study any pictures, tables or graphs that are included. All of it is relevant to the questions.
Section 2: Examination advice
11Cambridge International AS and A Level Biology 9700
• The stimulus material is often about something you have not studied. Do not panic. There will be enough information in the question for you to work out an answer. You are being tested on your ability to apply your knowledge to new information.
• All the different parts of a question may be about the same topic, e.g. cells structure from Section 1 or blood from Section 8, but you should be prepared for questions that test different topics, e.g. the structure and function of white blood cells (phagocytes and lymphocytes) involving sections of 1, 8 and 11.
• Look for clues in the wording of the questions.
• If you are only given a Latin name or a name you do not recognise, e.g. impala, look to see if you are told anything about it. If in a question on Section 18 you are told that impala are herbivores, then you know they eat plants.
• Answer each question as far as you can. Do not spend a long time staring at a question.
• If you do not know the answer or how to work it out, then leave it and come back to it later. It is best to put a mark by the side of the question so you can fi nd it easily. An asterisk (*) is a good idea or a large question mark against the letter of the part question. Not all part questions have answer lines. You may not realise that you have left out a part question when you check through your answers towards the end of the examination.
• Try not to leave blanks. Always check through your answers towards the end of the examination. When you come back to a question you may remember what to write as an answer to a question that you left out earlier in the exam.
• Do not waste time by writing about things unrelated to the question.
Command words and phrasesExaminers use command words to help you to understand what they are looking for in your answer. This table explains what each of these words or phrases means and will help you to understand the kind of answer you should write. The list of command words is in alphabetical order. You should remember that the meaning of a term may vary slightly according to how the question is worded.
• You can fi nd out more about command terms in the Glossary of command words in the syllabus. These notes should help you respond to each of the command words.
Command words What you should do in response to each command word
Defi ne Give a defi nition – these should be concise defi nitions
What do you understand by the term .....? Give a defi nition or a fairly brief explanation of what the term means. You can use an example to illustrate if this seems appropriate
State Give a brief answer – maybe one word or a phrase
List A number of brief answers should be given; usually you are asked for a specifi c number of points. You do not gain extra marks by writing more than the number stated
Describe You may have to describe the steps in a process or describe the appearance of a biological structure.
You may also have to describe some data given in a table or a graph. Make sure you have the correct vocabulary for such a description. For example, use the words increase, decrease, constant, peak, maximum, minimum, etc.
Section 2: Examination advice
12 Cambridge International AS and A Level Biology 9700
Command words What you should do in response to each command word
Explain This is not the same as describe. You should give an answer that has some reasons. You may have to explain why something happens or how it happens
Discuss You may be asked to discuss advantages and disadvantages – so make sure you give some of both. Much depends on the type of question, but ‘discuss’ usually means you should give different sides of an argument
Outline This is not the same as describe. You should give the main important points without any detail
Predict This means you should state what you think will happen. You may be asked to justify your prediction or explain it; explanation is not required if all the question says is “predict....”
Suggest This is often used when there is no single correct answer; you should look through the information you have been given for some clues as to what to ‘suggest’ in response to the question. Many problem-solving questions use this command word
Calculate This is obvious; make sure you know how to calculate means, percentages, percentage changes, rates and ratios (e.g. for genetics). At A Level, you should also know how to use the formulae for standard deviation, standard error, the chi-squared test and the t-test. Always give your working even if not asked. Always make sure you use the correct units
Measure You should use a suitable measuring instrument to take a reading. Often this involves using a ruler to measure to the nearest mm. Make sure you write down the unit after the numerical answer
Determine This is not the same as ‘measure’. Often this means that you should explain how an experiment could be set up to take measurements and how you calculate the answer from the results.
Estimate You do not have to give an accurate answer – but your answer (which is usually numerical) should be approximate
Sketch This is usually used about graphs. You should put a line (straight or curved) on a pair of axes. This may be a graph that has a line on it already or it may be a pair of axes printed on the exam paper without a line or curve
Deduce This is used in a similar way to predict, except you will need to support your answer with a statement e.g. referring to a principle, or theory, or including reasoning with your prediction.
Section 2: Examination advice
13Cambridge International AS and A Level Biology 9700
Command words What you should do in response to each command word
Find This is a general term which can mean several similar things, such as calculate, measure, determine, etc.
Give a reason/reasons See ‘Explain’.
Meant (what is meant by the term…) See ‘Understand’.
Understand(what do you understand by the term...)
You should (i) defi ne something and (ii) make a more detailed comment about it. The amount of detail depends on the number of marks awarded; e.g. explain what you understand by the term transcription.
The style of questionsWe use a great variety of different styles of questions. If you answer plenty of past papers during your course you will gain lots of practice at these. Here are some:
• Putting ticks and crosses in a table to make comparisons. For example, comparing the properties of different biological molecules.
• Completing tables of information by writing in single words, numbers or short phrases, e.g. what happens to the four valves in the heart during different phases of the cardiac cycle.
• Completing a passage of text with the missing terms.
• Writing defi nitions – make these as concise as you can; there is no need to use any examples unless asked.
• Making a list – answers should also be concise; detail is not required.
• Matching pairs from two lists, e.g. matching the names for the stages of mitosis with descriptions of what happens inside a cell during this type of nuclear division.
• Putting stages of a process into the correct sequence, e.g. the stages of protein synthesis.
• Labelling a diagram – label lines may already be on the diagram or you may have to add them yourself.
• Completing a genetic diagram (Paper 4).
• Describing and/or explaining data from a table or a graph.
• Explaining aspects of an investigation, e.g. a learner investigation that you might have carried out or a piece of research that has been adapted from a scientifi c paper.
• Adding information to a fl ow chart.
• Writing a fl ow chart from information that you are given, e.g. drawing a food web from written descriptions of the feeding relationships in a community.
The information in the question • Questions may ask you to “Use examples from...” or “Use only the information in ....” or “With
reference to Fig. 6.2”. If you read instructions like these, fi nd out what you are expected to use as examples or take information from. You will not get any marks if you use examples from somewhere else. The information can be given to you in different ways:
– a diagram, such as a food web, a set of apparatus or a biological structure;
Section 2: Examination advice
14 Cambridge International AS and A Level Biology 9700
– a graph, which could be a line graph, a bar chart or a histogram – always check the headings and units carefully;
– a table – always read the headings of the columns and/or rows carefully and look for any units.
Tables and graphsThe stimulus material may be in the form of a table, line graph, bar chart or histogram.
• Always read the introductory text very carefully before you study the table or graph. Underline key points in the information that you are given. In Papers 4 and 5, there may be quite a bit of introductory text explaining how the information was collected.
Tables
• Look at the column and row headings in a table and make sure you understand them. If you have read the introduction carefully, then you will.
• Find the units that have been used. Make sure that you use the units if you give any fi gures in your answer.
• Use a ruler to help read the table. Align the ruler with the fi rst column. This should be the independent variable and should increase in steps. Now put the ruler to the right of the next column and look at the fi gures in this second column that should be the dependent variable. Look for a pattern or trend in the fi gures. Identify the pattern or trend fi rst before thinking of an explanation. Move the ruler across to the right of the third column if there is one and continue in the same way. It may help to sketch a little graph on the exam paper to help you identify any pattern or trend.
Line graphs
• Look carefully at the x-axis which is the independent variable and make sure you understand what has been changed. Look carefully at the y-axis which is the dependent variable. Both variables should be described in the introduction to the question.
• Put your ruler against the y -axis and move it gradually across the graph from left to right. Follow the pattern or trend of the line (or each line if there is more than one). Mark on the graph where something signifi cant happens. For example, the line might show that the dependent variable becomes constant (gives a horizontal line).
• Use your ruler when taking fi gures from the graph. If the graph is plotted on a grid, then the examiners may allow ± one small square or half a small square in taking your readings. If you use a ruler and rule lines on the graph, you should take exact readings.
Bar charts and histograms
• Look carefully at the x-axis and the y-axis to see what has been plotted. Again, it is a good idea to move a ruler across the bar graph or histogram from left to right to help you concentrate on one aspect at a time. You can identify the highest and lowest fi gures and see if there is any pattern.
• You should make yourself some notes about the table, graph or histogram before answering the questions.
Calculations
If you are asked to do a calculation you may have to fi nd the fi gures from a table or graph.
• Write out all the working for your calculation. If you make a mistake and give the wrong answer, you may well be awarded marks for showing how to do the calculation.
• Make sure that you show the units in the calculation.
Section 2: Examination advice
15Cambridge International AS and A Level Biology 9700
• Make sure you include the units if they are not given on the answer line.
• Always express your answer in the same way as other fi gures provided, e.g. in a table. If the other fi gures are 5.6 and 4.6, then your answer should be given to one decimal place, e.g. 2.0 and 7.0, not 2 and 7.
• Round up or down the result on your calculator – do not copy all the fi gures after the decimal point.
Making comparisons• If you are asked to compare two things make sure you make it clear which thing you are writing about.
• The question may ask you to compare two structures or two processes that you have learnt about. Sometimes you may be expected to do this on answer lines in which case you must make clear the items that you are comparing (see Example 4).
• You may be given a table to complete. This may be blank and you have to fi ll it in, or it may already have some entries and you complete it.
• If you are given lines to make the comparison, it is perfectly acceptable to draw a table for your answer.
Section 2: Examination advice
16 Cambridge International AS and A Level Biology 9700
Example 3
Question
State two ways in which arteries differ from veins. [2]
Correct answer:
1 Arteries have thicker walls than veins.
2 Veins have semi-lunar valves, but arteries do not.
Ambiguous answer:
1 They have thick walls.
2 They don’t have valves.
No marks would be given to the last two answers as the comparisons have not been made.
Question
Complete the table to compare the structure of arteries with the structure of veins. [2]
Correct answer
arteries veins
have thick walls have thin walls
have thick muscle layer have very thin muscle layer
Incorrect answers as the comparisons are not made between the same features
arteries veins
thick wall thin elastic tissue
no valves small amount of muscle
In cases like this, it is much better to have an extra column that gives the features to be compared:
feature arteries veins
thickness of wall thicker thinner
valves absent present
This extra column makes sure that you make direct comparisons in each row of the table. You can always add a fi rst column if it is not included in the question.
Section 2: Examination advice
17Cambridge International AS and A Level Biology 9700
Extended writing• You are required to write longer answers to questions that have four or more marks. There are more
of these questions in Paper 4 than in the other papers. You do not have to write your whole answer in prose. You can use labelled and annotated diagrams, fl ow charts, lists and bullet points. However you present your material, you should write enough to make your meaning clear.
Example 4
Question from Paper 2
Explain, in terms of water potential, how water moves from the xylem in a leaf to the air outside a stoma. [4]
This question requires a sequence, i.e. from xylem to cell walls of mesophyll cells; from walls to air spaces inside the leaf; from air spaces through the stoma to the air outside the leaf. The movement of water in each stage needs to be explained in terms of cohesion-tension, evaporation and diffusion. Writing out the pathway on its own does not get any marks.
Question from Paper 4
(a) Explain how changes in the nucleotide sequence of DNA may affect the amino acid sequence in a protein. [7]
(b) Explain how natural selection may bring about evolution. [8]
[Total: 15]
In (a), you may fi nd it easier to use some examples to show how changes in nucleotide sequences lead to changes in amino acid sequences. You do not need to know the genetic code, but you can use changes in DNA triplets to show what will happen, e.g. AAA changes to TAA. In (b), you should have learnt several key points about natural selection that you can write down in a logical sequence.
Question from Paper 4
(a) Describe the part played by the proximal convoluted tubules in the functioning of the kidneys. [8]
(b) Explain how the collecting ducts in the kidneys may reduce the loss of water from the body. [7]
[Total: 15]
A diagram of a cell from the proximal convoluted tubule might help your answer to (a). You can label and annotate your diagram to illustrate your answer. A feedback loop (a type of fl ow chart) would be a good way to illustrate part (b).
– When you answer these questions always use full sentences if you can. If you fi nd it helps to write bullet points, then make sure that each bullet point is a full sentence. If you abbreviate your answer too much by writing notes, then you may not convey enough information to gain the marks.
– If you are giving a sequence of events (as in Example 5), then you should make sure they are in a logical order. If you are explaining a biological principle or making comparisons, then give the main points fi rst.
– If you are describing something that moves from one place to another as in the Paper 2 question from Example 5, then make sure you include the direction of movement. For example, ‘water moves by osmosis’ is unlikely to gain a mark unless you include the direction; ‘water enters the mesophyll cell down the water potential gradient’ is a much better answer.
Section 2: Examination advice
18 Cambridge International AS and A Level Biology 9700
Advice about the papersPaper 1 Multiple Choice• You have about one minute to read and answer each question. Each question may test one topic or
several topics from different parts of the AS syllabus.
• Some questions test what you know and understand.
• Some questions test if you can apply what you have learnt to understand new data. These questions will often have a diagram, graph or table to use.
• Some of the choices can be very similar; read carefully and underline words that make each choice distinct from the other three.
• Try to decide what the question is testing as you are reading it. The sequence of questions usually follows the sequence of topics in the syllabus. Therefore you can expect the early questions to ask about cells and biological molecules and those at the end to be on infectious disease and immunity.
• Do not try to fi nd a pattern in the order of your answers (e.g. A, B, C, D, A, B....)
– The same letter could be the correct answer for several questions in a row.
– Letter A might be the correct answer for more questions than B, C or D. Or there could be fewer correct answers shown by letter D than any of the others.
– Do not let what you have chosen for the previous questions infl uence which letter you choose.
• Some questions may ask about aspects of practical work, for example about different variables: independent, dependent and controlled.
• It is important to understand how to use terminology, e.g. how to apply water potential terminology to problems on cells and osmosis.
Paper 2 AS Level Structured Questions• This paper has a mix of short-answer questions and those requiring slightly longer answers. There is no
essay.
• Longer answers will need four or fi ve sentences with two or three different ideas. Always look at the number of marks for each part question to help you decide how much to write.
• Look at the number of command words: ask yourself ‘do you have to do one or two things?’. See Example 2.
• Use the lines given. Stick to the point and do not write too much.
• Only give the number of answers that are asked. Use the numbered lines and give one answer per line.
• There will only be a few parts of questions that need extended writing. These will have four [4] or fi ve [5] marks. These questions will often be related to some information you are given. You will need to write four or fi ve sentences in a sequence that makes sense. You can think of it as “telling a story with a beginning, a middle and an end”. Remember to refer to any information you are given.
Paper 3 Advanced Practical SkillsGeneral advice
Success at Paper 3 requires you to do plenty of practical work during your course and have several attempts at past paper questions to fi nd out how to complete everything in the time available. During the practical exam you will have to make some decisions; if you practise plenty of past questions you will fi nd out what
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sort of decisions to expect. As you revise, make sure you know exactly how to carry out the practical procedures described in the AS syllabus. You will be assessed on your skills at:
• manipulating apparatus to collect results and make observations
• data presentation
• analysis of results and observations
• evaluation of procedures and data.
You should make decisions, such as:
• identifying variables
• standardising the control variables
• how to change the independent variable
• choosing the number of measurements to take
• deciding the intervals between the values of the independent variable
• choosing a control experiment
• identifying any risks and stating appropriate precautions.
During the examination
• Read through the questions carefully, looking to see how many marks are given for each question.
• Read the instructions to the end; do not start a practical procedure without reading carefully all the steps involved.
• As you read, check that you have the apparatus and materials described. If not alert the supervisor.
• Think about the apparatus that you will use for each step and imagine using it in your mind.
• Make sure that you have a sharp pencil to use for making drawings and for drawing graphs and charts. Do not draw in ink because you cannot make changes as you can when using a pencil.
• Make sure you have a good, clean eraser for rubbing out your pencil lines if necessary. Do not press too hard when using a pencil for making drawings, graphs or charts. Sometimes it is hard for an examiner to tell which is your fi nal line.
Following the instructions
• Follow the instructions for practical methods exactly. If you make a change in the method it may alter the results.
• Do not take short cuts.
• Always label test-tubes and other containers to help you remember which is which.
• If you are told to “Wash the apparatus thoroughly after each use” make sure you do. If there is anything left in the apparatus the next stage may not work.
• It is a good idea to put a tick by the side of each instruction when you have completed it. This helps you to fi nd the right place in the instructions, so that you do not leave out a step or repeat a step when it is not required.
• Keep your exam paper on a part of the bench which you can keep dry. Do not pour liquids or use syringes or pipettes over your exam paper. If you keep your exam paper away from the ‘wet’ part of your bench you are unlikely to spill anything on it.
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Recording your measurements and observations
You are expected to make observations and record them.
• You can record your observations:
– as statements in writing
– in tables
– by using drawings
– by constructing tally charts.
You will take readings from different apparatus. You must make the measurements as accurately and reliably as you can. Numerical readings will normally be collected and presented in a table.
• Follow the instructions below about drawing tables.
• Make clear descriptions of colours and colour changes; refer to ‘blue’, ‘orange’ and ‘purple’ when describing reagents used in biochemical tests. You may want to refer to slight differences, so use words like ‘pale’ and ‘dark’.
• Make your measurements as accurate and reliable as possible.
• Accurate results are close to the actual or ‘true’ values; reliable results are those that are repeatable.
• If you can take repeat readings, then do so. There is not always enough time to do this.
• You can process your observations by:
– carrying out calculations, e.g. percentages and percentage changes
– plotting graphs – line graphs, bar charts and histograms.
• Use all the space available on the paper for your observations.
• Do not write an explanation until the question asks for one.
• Use a sharp HB or B pencil. It can be rubbed out easily if you need to correct a mistake. Use a good eraser so that is clear to the examiner which is your fi nal line.
• Do not forget to include headings for the columns and the rows in tables.
Drawings
These will be from microscope slides or photographs.
• Read the question carefully, the drawing may have to be an accurate size e.g. twice the original.
• Make each drawing as big as the space allows without writing over the text of the question and making sure that you leave enough space for labels and annotations, if asked for.
• Use a ruler for labelling lines.
• Draw and label in pencil.
• Use one clear continuous outline not an artistic drawing. Do not shade.
• Observe details carefully, such as the relative number of chloroplasts in different cells and the thickness of cell walls in different cells in a vascular bundle. Show these accurately on your drawing.
A plan diagram shows the distribution of tissues in a section. It also shows the proportions of the different tissues. Although called a low power plan diagram you may use high power to identify the different tissues
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and to be sure you are putting the boundaries of those tissues in the right place. You should not draw any cells in a lower power plan diagram.
When you make a plan diagram, follow these simple rules:
• make the drawing fi ll most of the space provided; leave space around the drawing for labels and annotations (if required by the question)
• use a sharp HB or B pencil (never use a pen)
• use thin, single, unbroken lines (often called ‘clear and continuous lines’)
• show the outlines of the tissues
• make the proportions of tissues in the diagram the same as in the section
• do not include drawings of cells
• do not use any shading or colouring.
Add labels and annotations (notes) to your drawing only if you are asked for these in the question. Use a pencil and a ruler to draw straight lines from the drawing to your labels and notes. Write labels and notes in pencil in case you make a mistake and need to change them. You may leave your labels and notes in pencil – do not write over them in ink.
High power drawings should show a small number of cells and they should be drawn a reasonable size so you can show any detail inside them. When you make a high power drawing, follow these simple rules:
• make the drawing fi ll most of the space provided; leave space around the drawing for labels and annotations (if required by the question)
• use a sharp HB or B pencil (never use a pen)
• use clear, continuous lines (see above)
• draw only what is asked in the question, e.g. three cell types or one named cell and all cells adjoining it
• show the outlines of the cells
• the proportions of the cells in the drawing must be the same as in the section you are drawing
• plant cell walls should be shown as double lines with a middle lamella between the cells; the proportions of cell walls should be drawn carefully.
• show any details of the contents of cells – draw what you see, not what you know should be present; for example, in plant cells you may see nuclei, chloroplasts and vacuoles
• do not use any shading or colouring.
Taking measurements of specimens and photographs
Using an eyepiece graticule
An eyepiece graticule is a scale that fi ts inside the eyepiece on your microscope. It allows you to take measurements of the specimens you view with the microscope. You can measure simply in graticule units, but you may be asked to make an actual measurement which involves calibrating the graticule using a stage micrometer. This is done by lining up the graticule with the divisions on the micrometer.
• Make your measurements as accurate as you can. You will probably be able to measure to the nearest division on the graticule.
• You may be asked to take several measurements and then calculate a mean.
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Taking measurements from photographs
You may have to measure an object on a photograph and calculate the actual size of a structure or the magnifi cation of an image.
• Always measure photographs in millimetres, not centimetres.
• If you have to use your measurements in a calculation, write neatly and show your working. The person marking your paper might be able to give you marks for knowing what to do even if you make a mistake or do not fi nish the calculation.
Presenting data and observations
Tables
Before you start to draw a table, decide what you wish to record. Decide on how many columns and how many rows you will need. Make sure you have read all the instructions before you draw the table outline. Follow these rules:
• use the space provided, do not make the table too small
• leave some space to the right of the table in case you decide you need to add one or more columns
• make the table ready to take observations or readings so that you can write them directly into the table rather than on another page and then copy them into the table (tables need to show all the raw data you collect)
• draw the table outlines in pencil
• rule lines between the columns and rows
• rule lines around the whole table
• write brief, but informative headings for each column
• columns headed with physical quantities should have appropriate SI units
• when two or more columns are used to present data, the fi rst column should be the independent variable; the second and subsequent columns should contain the dependent variables
• entries in the body of the table should be brief – they should be single words, short descriptive phrases or numbers
• data should be recorded in the table in the order in which it is collected – this is because the table is prepared before the data collection. For example, if the instructions state that results from the highest temperature or highest pH is to be recorded fi rst then these go at the top of their respective columns. It is more usual to arrange the values of the independent variable in ascending order (e.g. from 0 to 100) so that patterns are easier to follow and that is how data in tables for Papers 1, 2, 4 and 5 is usually presented
• numbers written into the body of the table do not have units (units only appear in the column headings).
You may have to process your results by calculating rates of reaction, changes in length, percentage changes or means of repeat readings. These processed results can appear in the same table with the raw data that you have collected or can be in a separate table with the independent variable.
The solidus or slash (/) meaning ‘per’ should not be used in units. For example, if you have to include concentrations as in a table you do not write g per 100 cm3 as g/100 cm3. It should always be written out in full using ‘per’ or, better, as g 100 cm–3. The negative exponent, cm–3, means ‘per’.
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Note that the solidus is used to separate what is measured from the unit in which it is measured. You may notice that text books and examination papers use brackets around the units in tables. This is also an accepted convention, but the solidus is the convention used in Cambridge International AS and A Level Biology.
Correct and incorrect ways of showing units in tables and graphs
Correct Incorrect
either:rate / mm cm–3
or:rate (mm cm–3)
rate mm/cm3
either:concentration / g 100 cm–3
or:concentration (g 100 cm–3)
concentration g/100 cm3
A note on the uses of ticks and crosses in tables:
Do not use ticks and crosses in tables of results which should show observations, such as the colours obtained in biochemical tests.
Ticks and crosses may be used in tables of comparison if there is a key to explain what they mean,
e.g. = present; = absent.
You may want to show anomalous results in tables. If so circle them and put a note underneath the table to explain that they are anomalous results.
You may be asked to compare specimens viewed in the microscope and/or in photographs. These comparisons must be organised into a table. Draw your table so that it has a fi rst column for the features that you have observed. You can then present both similarities and differences:
Feature Specimen A Specimen B
Similarities
Charts and graphs
Bar charts have separate columns that do not touch – there are gaps in between; histograms have columns that do touch each other. Bar charts are used to show data on discontinuous variables, for example blood groups, eye colour, etc.; histograms are used to show data on continuous variables, e.g. length, mass, speed, volume, etc.
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Bar charts
Bar charts should be used if the independent variable is qualitative. If you are investigating the rate of respiration of yeast when given different substrates, the independent variable is the type of substrate, e.g. glucose, maltose, sucrose, etc. In this case there is no continuous scale for the independent variable and a bar chart is the appropriate way to present the results. The dependent variable is continuous as it is the rate of respiration and would be measured in units such as ‘rate of carbon dioxide production/cm3 s–1’.
Rules for drawing bar charts:
• use most of the grid provided, do not make the chart too small
• draw the chart in pencil
• bar charts can be made of lines, or more usually, blocks of equal width. There must be space between the lines or bars. They do not touch
• the intervals between the blocks on the x-axis should be equidistant
• the y-axis should be properly scaled with equidistant intervals; the scale should usually start at 0 and this should be written at the base of the axis. If all the numbers are large a displaced origin may be used but the start number should be clear at the base of the y-axis
• the y-axis should be labelled with the headings and units taken from the table of results
• the lines or blocks should be arranged in the same order as in the table of results
• each block should be identifi ed; there is no need to shade the blocks or colour code them.
Histograms
Do not confuse bar charts with histograms. A histogram is drawn for continuous data that is subdivided into classes. A good example is collecting data on continuous variables, such as linear measurements or mass. Sometimes the intervals can be whole numbers, for example the numbers of seeds in fruits. If you are analysing data then you may wish to draw a frequency histogram to see if the data shows a normal distribution.
Histograms are used when the independent variable is numerical and the data are continuous. They are sometimes referred to as frequency diagrams.
First the raw data needs to be organised into classes.
• The number of classes needs to be established. This will largely depend on the type and nature of the data.
• The rule for determining the number of classes is 5 × log10 total number of readings.
• The range within each class needs to be determined; this is usually the total range divided by one less than the number of classes.
• There should be no overlap in the classes, e.g.4.01 to 5.20 or 4.01 < 5.215.21 to 6.40 or 5.21 < 6.41 (< = less than)
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The data should be organised using a tally chart and drawing ‘fi ve bar gates’ as in //// = 5
Follow these rules when drawing a histogram:
• use most of the grid provided, do not make the histogram too small
• draw the histogram in pencil
• the x-axis represents the independent variable and is continuous. It should be labelled clearly with an appropriate scale
• the blocks should be drawn touching
• the area of each block is proportional to the size of the class. It is usual to have similar sized classes so the widths of the blocks are all the same
• the blocks should be labelled, e.g. ‘3.0 to 3.9’ which means that 3.0 is included in this class, but 4.0 is not. 4.0 will be included in the next class: 4.0 to 4.9
• the y-axis represents the number or frequency and should be properly scaled with equidistant intervals. It should be labelled with appropriate units.
Line graphs
Line graphs are used to show relationships in data which are not immediately apparent from tables. The term graph applies to the whole representation. The term curve should be used to describe both curves and straight lines which are used to show trends.
Follow these guidelines:
• use at least half the grid provided, do not make the graph too small
• draw the graph in pencil
• the independent variable should be plotted on the x-axis
• the dependent variable should be plotted on the y-axis
• each axis should be marked with an appropriate scale. The origin should be indicated with a 0. The data should be examined critically to establish whether it is necessary to start the scale(s) at zero. If not, you may have a displaced origin for one or both axes, but this must be made obvious by labelling the displaced origin very clearly
• each axis should be scaled using multiples of 1, 2, 5 or 10 for each 20 mm square on the grid. This makes it easy for you to plot and extract data. Never use multiples of 3
• each axis should be labelled clearly with the quantity and SI unit(s) or derived (calculated) units as appropriate, e.g. time/s and concentration/g dm–3; the axes labels and units must be the same as those in the table
• plotted points must be clearly marked and easily distinguishable from the grid lines on the graph. Dots in circles ( ) or small, neatly drawn crosses (x) should be used; dots on their own should not. If you need to plot three lines, vertical crosses (+) can also be used
• label each line carefully or use a key. Use a pencil for both lines; do not use a blue or black pen or different colours
• in Paper 3 there are usually fi ve or six results to plot.
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After plotting the points you need to decide if any of them are anomalous. Ask yourself the question ‘do they fi t the trend?’. But what is the trend? You should know something about the theory behind the investigation so you should be aware of the likely trend. If you think one or more of the results are anomalous, then it is a good idea to ring them. Put a circle on the graph away from the line and put a key to state that the circled point(s) represent anomalous result(s). The next thing to decide is how to present the curve.
• It may be obvious that the points lie on a straight line; for example, the effect of enzyme concentration on the rate of an enzyme-catalysed reaction. If you have a result for the origin (0, 0) then that must be included and you can place a clear plastic ruler on the grid and draw a straight line from the origin making sure that there is an even number of points on either side of the line. If you do not have a result for the origin, then start the line at the fi rst plotted point. Do not continue the line past the last plotted point.
• You should only draw a smooth curve if you know that the intermediate values fall on the curve. You may be expecting the relationship to be a smooth curve and if the points seem to fi t on a curve then draw one. Again decide whether the origin is a point and, if not, start at the fi rst plotted point. The curve should go through as many points as possible, but try to make sure there is an even number of points on either side of the line. Do not continue past the last plotted point.
• In the practical examination you may only have fi ve or six results. These are likely to be single results rather than means of replicate results. Therefore you cannot be sure of the relationship and should not draw a straight line or a curve as described above. You should draw straight lines between the points. This indicates uncertainty about the results for values of the independent variable between those plotted.
• If a graph shows more than one line or curve, then each should be labelled to show what it represents.
Bar charts, histograms and line graphs should normally have informative titles. There is no need to give titles in the exam as it is obvious what they are. In all other circumstances give informative titles.
If you have times in minutes and seconds, never use minutes as the unit on a graph. It is very diffi cult to use a scale with each small square representing 3 or 6 seconds. Always plot results in seconds unless the unit for time is whole minutes.
Analysis, conclusions and evaluation
As part of analysis you should be able to:
• identify anomalous results. Anomalous results are those that do not fi t the trend
• process your results to calculate means, percentages, changes in mass or length, calculate percentage changes and rates of reactions
• fi nd unknown quantities by using axis intercepts or estimating from colour standards using known concentrations
• describe the pattern or trend in data
• make conclusions to consider whether experimental data supports hypotheses or not.
Processing results
You should be prepared to calculate:
• means
• percentages
• percentage changes
• rates of reaction by calculating 1/t or 1000/t; the unit used is s–1.
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You should know how to use line graphs to:
• fi nd an intercept – where a line you have drawn crosses a key value on the x-axis; for example, fi nding the water potential of a tissue using percentage change in length of plant tissues
• fi nd the rate of a reaction by calculating the gradient of a line you have drawn.
As part of evaluation you should be able to:
• identify systematic and random errors
• systematic errors are those that affect all the results in the same way
• random errors do not affect all the results in the same way
• identify the signifi cant errors in your investigation
• estimate the uncertainty in measurements. The actual error is half the smallest division on the apparatus you are using
• assess how effective you have been at standardising variables
• suggest improvements to the procedure you have followed
• suggest ways in which the investigation might be extended to answer a new question.
Estimating uncertainty in your results
You may have to estimate the uncertainty or error in your results. For particular apparatus, the error is half the smallest graduation on the apparatus, e.g. if the smallest division is 1.0 cm3 then the uncertainty would be ±0.5 cm3. So if you start your measuring at 0 the uncertainty applies where you take your measurement – say at 6.3 cm3. So the result is expressed as 6.3 ± 0.5 cm3. BUT if you have to start at a measurement other than 0 (for example when taking readings from a burette) the uncertainty applies at both ends, so it is multiplied by two as there is an error at each end, e.g. 7.5 ± 1.0 cm3. Similarly, if using a ruler then there would be an error at each end unless you start at 0. The same applies to measuring a quantity in a syringe by sucking up from empty. The error would be half the minimum measurement. But when you take two readings from the syringe (say delivering 2.0 cm3 by moving the plunger from 6.5 cm3 to 4.5 cm3) the uncertainty is multiplied by two.
Percentage error is calculated as the error expressed as a percentage of the actual reading. For example if the reading is 7.5 ± 1.0 cm3, then the percentage error is 1.0/7.5 × 100 = 13.3%.
Conclusions
• Conclusions are brief statements supported with explanations using your knowledge from the AS syllabus.
• Use your own results for your conclusions.
• Before planning what to write for a conclusion, turn back to the beginning of the question and read the introduction. You may have forgotten what you were told about the investigation you have just carried out. Think about the theory and apply it to the results you have obtained.
• Sometimes you are expected to make conclusions about some other data, not the data you have collected.
• Do not write the conclusion you have learned from a class experiment or from theory.
• You should also consider the confi dence that you have in your conclusions. For this it is a good idea to consider whether:
– the standardised variables have been kept constant
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28 Cambridge International AS and A Level Biology 9700
– there were any other variables that were not standardised
– there were any anomalous results
– any replicate results were similar or not.
• If you are unsure about any aspect of the practical you have carried out, then you can say that you do not have confi dence in your conclusions and give a reason or reasons.
Suggesting improvements
You may be asked to suggest modifi cations or improvements that will increase the accuracy and reliability of the results. As you carry out the practical procedure you should think critically about it and make some notes. If asked to suggest improvements, then look back to these notes for ideas. You can suggest:
• ways to improve the standardisation of variables, for example by using a thermostatically-controlled water bath
• taking repeat readings (replicates) to assess the reliability of the data
• calculating mean results
• using a different way to measure the dependent variable so the results are more accurate
• using a different piece of apparatus to measure the dependent variable and reduce the percentage error (see above)
You may also have to justify your suggested improvements. When you do this, make sure you explain how they will improve the confi dence you have in the data and therefore in the conclusion.
Paper 4 A Level Structured QuestionsThere are 85 marks for Section A and 15 for Section B.
• Section A consists of structured questions that have a variable number of marks.
• Questions on genetics may have genetic diagrams to complete and chi-squared tests to carry out.
• Section B has two essays from which you must choose one. If you write answers to both essays then the higher mark will be the one that you are given. It is unlikely that you will gain a better mark by writing two essays in a hurry, rather than one which you have planned and written more carefully.
Paper 5 Planning, Analysis and EvaluationRemember that this is not a practical paper like Paper 3, but does require a lot of experience of practical work. The paper tests your skills of planning, analysis and evaluation. Each question is based on a practical investigation. You can expect that these investigations will be unfamiliar to you. The advice is the same as for other papers: read the information carefully, underline key words and phrases, annotate any diagrams, graphs and tables that you are given.
Paper 5 differs signifi cantly from Paper 3 in its approach to data presentation. As Paper 5 is a written paper rather than a practical paper you are not required to construct tables and complete them with observations or numerical results. You will be given data and be expected to carry out an analysis, interpretation and evaluation. This means that it is assumed that you understand how data is presented.
In Paper 5 you will be asked to do such tasks as:
• identify anomalous results
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• process raw data, for example by calculating means, standard deviations, standard errors, ratios and correlations
• identify and describe patterns and trends
• explain raw or processed data.
In most cases the data is more complex than in Paper 3 and often involves making comparisons. Complex tables, where variables are being compared may have a different layout to the one given in Paper 3 and you should look carefully for the dependent variable. In some cases, the table layout means that the dependent variable is a table heading across several columns and the independent variable is given in a row underneath.
You may be asked to plot a graph using fi gures provided although this is less likely than on Paper 3. In addition to the rules given for Paper 3, you should know how to add error bars to line graphs or bar charts using standard deviation or standard error. You should certainly understand why error bars are added to graphs.
In other cases, a graph plotted from the results of an investigation may be given and labels for the axes required. In this case units would be expected which may be in table headings or may have to be deduced from information in the question. In some cases, arbitrary units are acceptable, although you are expected to be familiar with units used to measure common variables, such as light, temperature, time and volume.
Paper 5 may also use scatter graphs or correlation curves to show the effect of one variable on another. You should know how to interpret these forms of presentation.
You should know how to make a sketch graph to predict the results of an investigation. As always, the axes should be orientated with the independent variable as the x-axis and the dependent variable as the y-axis. Axis labels are expected. Units are not required in sketch graphs unless they are specifi ed in the question.
Planning investigations
One of the questions involves writing a plan for an investigation. You will be given some information about the investigation and this will be enough material for you to write your plan.
The skills that you are being tested on are:
1. Identifying key variables.
2. Describing a workable practical procedure.
3. Selecting appropriate methods for measuring the independent variable.
4. Selecting appropriate methods for varying and measuring the dependent variable.
5. Selecting appropriate methods for controlling other variables.
6. Suggesting a suitable control experiment.
7. Suggesting a quantitative, testable, prediction.
8. Selecting equipment of a level of precision appropriate to ensure accuracy.
9. Planning to collect suffi cient results to ensure reliability.
10. Describing how results will be recorded.
11. Suggesting how results will be analysed.
12. Risk assessing the practical procedure.
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• When you read through the information provided on the paper, try to work out three main things:
1. what should be changed – this is the independent variable
2. what is going to be measured – this is the dependent variable
3. what should be kept the same – these are the control variables
• You should organise your plan under several headings and then write as concisely as possible. Suitable headings are:
– hypothesis and/or prediction
– variables
– risk assessment
– method
– collecting results
– analysis of results.
• Some investigations need to have two parts.
– The experimental – which measures the process being studied and contains the living organism, part of an organism (e.g. a leaf) or enzyme being tested.
– The control – which will be exactly the same as the experimental except that the living organism will be missing or replaced by something non-living. The control shows that the results are due to the activity of the living organism and is not due to the apparatus or an environmental factor.
• Make sure you explain carefully how to standardise the control variables; for example, ‘put test-tubes in to a thermostatically-controlled water bath’ is better than ‘keep the test-tubes at the same temperature’.
• All investigations should be repeated to increase the reliability of the results. If the same results are achieved (or the results are very similar) then they are reliable. You can also include the calculation of means and standard deviation in your plan under the heading of analysis of results.
• Always give quantities in appropriate terms – avoid the use of the word ‘amount’ as this does not convey precise meaning to any specifi c quantity. ‘Amount’ could mean volume, mass or concentration. For example, you can give the volume in cm3, mass in grams and concentration in an appropriate unit, such as grams 100 cm–3.
• Suggest appropriate volumes and concentrations in your plan. Include instructions on making up dilutions either by serial dilution or proportional dilution. You should have learnt how to do this when preparing for Paper 3.
• Choose apparatus that will give precise results. For example, if you are measuring using a syringe or measuring cylinder it may be diffi cult to measure to the nearest cm3. You should think about ways in which the precision can be improved before writing your answer.
• Write out your method as a list of numbered steps as if you are writing a set of instructions for someone else to follow. Think of your method as a recipe.
• Carry out a risk assessment on your plan and include a section headed risk assessment or safety precautions.
Analysing data, making conclusions and evaluation
In preparation for Paper 3, you will have learnt how to analyse data, draw graphs, evaluate data and experimental methods, and make conclusions. You will be tested on these skills in Paper 5. In addition, you should know about some statistical methods and apply them to the data provided.
There is always a question that asks you to analyse the data from an investigation. You should know about the following aspects of statistics:
• calculating standard deviation and standard error (formulae will be provided)
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• using statistical tests – the chi-squared test, the t-test, and the Pearson and Spearman tests for correlation (formulae for these tests will be provided)
• making a null hypothesis.
You should know when and how to use these methods. There are several different styles of questions that test your understanding of these statistical methods. The best preparation is to look at the way data is presented in past paper questions and see what sort of questions are asked.
Section 3: What will be tested?
32 Cambridge International AS and A Level Biology 9700
Section 3: What will be tested?
The assessment objectives (AOs) describe the knowledge, skills and abilities that you will be expected to demonstrate at the end of your course.
There are three main objectives:
AO1 Knowledge with understanding – what you remember and how you make use of what you know in both familiar and unfamiliar situations.
AO2 Handling information and solving problems – how you handle information provided in the question and how well you solve the problems posed.
AO3 Experimental skills and investigations
The theory papers test AO1 and AO2. The purpose of the practical papers is to test AO3. Your teacher will be able to give you more information about how each of these is used in the examination papers.
The following tables show you the range of skills you will need to develop:
Skill area You will need to demonstrate this skill in relation to:
AO1 Knowledge with understanding
biological phenomena, facts, laws, defi nitions, concepts and theories
biological vocabulary, terminology, conventions (including symbols, quantities and units)
scientifi c instruments and apparatus used in biology, including techniques of operation and aspects of safety
scientifi c quantities and their determination
biological and technological applications with their social, economic and environmental implications
Questions testing the skills in the table above will usually begin with one of the following words: defi ne, state, name, describe, explain or outline. See Section 6 for an explanation of these words.
Section 3: What will be tested?
33Cambridge International AS and A Level Biology 9700
Skill area You will need to use written, symbolic, graphical and numerical forms of presentation to:
AO2 Handling information and solving problems
locate, select, organise and present information from a variety of sources
translate information from one form to another
manipulate numerical and other data
use information to identify patterns, report trends and draw conclusions
present reasoned explanation for phenomena, patterns and relationships
make predictions and propose hypotheses
apply knowledge, including principles, to novel situations
demonstrate awareness of the limitations of biological theories and models
solve problems
Questions testing the skills in the table above will usually begin with one of the following words: discuss, predict, suggest, calculate or determine. See Section 6 for an explanation of these words.
Look carefully at the skills you need to develop during your course in preparation for Papers 3 and 5.
Skill area You will need to be able to:
AO3 Experimental skills and investigations
plan experiments and investigations
collect, record and present observations, measurements and estimates
analyse and interpret quality of data to reach conclusions
evaluate methods and quality of data and suggest possible improvements
The following table will give you a general idea of the allocation of marks to assessment objectives in the different examination papers – though the balance in each paper may vary slightly.
Assessment objective Weighting (%) Examination papers
AO1 Knowledge with understanding 40 Papers 1, 2 and 4
AO2 Handling information and solving problems 37 Papers 1, 2 and 4
AO3 Experimental skills and investigations 23 Papers 3 and 5
In addition, 15% of the total marks will be awarded for an awareness of the social, economic, environmental and technological implications and applications of biology. These marks will be awarded within the AO1 and AO2 categories.
Section 4: What you need to know
34 Cambridge International AS and A Level Biology 9700
Section 4: What you need to know
This is in the form of a table, which describes what you may be tested on in the examination. It is divided into the syllabuses for AS and A Level.
How to use the tableThe table is divided into a number of columns.
Topic – this is a main subject area within each syllabus. There are a varying number of topics within each syllabus;
Sub-topic – this column subdivides the main topic into a number of different topics.
You should be able to – this column gives you all the detail that you will be expected to know and understand in relation to each topic. It is arranged in bullet points. Each bullet point is a learning outcome taken from the syllabus. You should read these learning outcomes very carefully as examiners set questions on these. If you know the learning outcomes you will be well prepared for the examinations as you will know what topics you are being tested on.
Examiners can set questions on unfamiliar situations and expect you to apply your knowledge to understanding and analysing them. Do not panic if you have a question on an organism you have not been taught about or something else that is new to you. There will be clues in the question to help you identify the topic that is being tested in the question.
You can use the table throughout your course to check the topic areas you have covered.
You can also use it as a revision aid. When you think you have a good knowledge of a topic, you can place a tick in the checklist column.
The column headed Comments can be used:
• to add further information about the details for each bullet point
• to add learning aids
• to highlight areas of diffi culty/things about which you need to ask your teacher.
Section 4: What you need to know
35Cambridge International AS and A Level Biology 9700
AS
Lev
el m
ater
ial
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
1 C
ell s
truc
ture
1.1
Th
e m
icro
sco
pe
in
cell
stu
die
s
A
n un
ders
tand
ing
of t
he p
rinci
ples
of
mic
rosc
opy
show
s w
hy li
ght
and
elec
tron
m
icro
scop
es h
ave
been
ess
entia
l in
impr
ovin
g ou
r kn
owle
dge
of c
ells
.
a)
com
pare
the
str
uctu
re o
f ty
pica
l ani
mal
and
pla
nt c
ells
by
mak
ing
tem
pora
ry p
repa
ratio
ns o
f liv
e m
ater
ial a
nd u
sing
ph
otom
icro
grap
hs
b)
calc
ulat
e th
e lin
ear
mag
nifi c
atio
ns o
f dr
awin
gs,
phot
omic
rogr
aphs
and
ele
ctro
n m
icro
grap
hs
c)
use
an e
yepi
ece
grat
icul
e an
d st
age
mic
rom
eter
sca
le
to m
easu
re c
ells
and
be
fam
iliar
with
uni
ts (m
illim
etre
, m
icro
met
re, n
anom
etre
) use
d in
cel
l stu
dies
d)
expl
ain
and
dist
ingu
ish
betw
een
reso
lutio
n an
d m
agni
fi cat
ion,
with
ref
eren
ce t
o lig
ht m
icro
scop
y an
d el
ectr
on m
icro
scop
y
e)
calc
ulat
e ac
tual
siz
es o
f sp
ecim
ens
from
dra
win
gs,
phot
omic
rogr
aphs
and
ele
ctro
n m
icro
grap
hs
Section 4: What you need to know
36 Cambridge International AS and A Level Biology 9700
AS
Lev
el m
ater
ial
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
1 C
ell s
truc
ture
1.2
Cel
ls a
s th
e b
asic
u
nit
s o
f liv
ing
o
rgan
ism
s
Th
e ce
ll is
the
bas
ic
unit
of a
ll liv
ing
orga
nism
s. T
he
inte
rrel
atio
nshi
ps
betw
een
thes
e ce
ll st
ruct
ures
sh
ow h
ow c
ells
fu
nctio
n to
tra
nsfe
r en
ergy
, pro
duce
bi
olog
ical
mol
ecul
es
incl
udin
g pr
otei
ns
and
exch
ange
su
bsta
nces
with
th
eir
surr
ound
ings
.
P
roka
ryot
ic c
ells
an
d eu
kary
otic
ce
lls s
hare
som
e fe
atur
es, b
ut t
he
diff
eren
ces
betw
een
them
illu
stra
te t
he
divi
de b
etw
een
thes
e tw
o ce
ll ty
pes.
a)
desc
ribe
and
inte
rpre
t el
ectr
on m
icro
grap
hs a
nd
draw
ings
of
typi
cal a
nim
al a
nd p
lant
cel
ls a
s se
en w
ith
the
elec
tron
mic
rosc
ope
b)
reco
gnis
e th
e fo
llow
ing
cell
stru
ctur
es a
nd o
utlin
e th
eir
func
tions
:
• ce
ll su
rfac
e m
embr
ane
• nu
cleu
s, n
ucle
ar e
nvel
ope
and
nucl
eolu
s
• ro
ugh
endo
plas
mic
ret
icul
um
• sm
ooth
end
opla
smic
ret
icul
um
• G
olgi
bod
y (G
olgi
app
arat
us o
r G
olgi
com
plex
)
• m
itoch
ondr
ia (i
nclu
ding
sm
all c
ircul
ar D
NA
)
• rib
osom
es (8
0S in
the
cyt
opla
sm a
nd 7
0S in
ch
loro
plas
ts a
nd m
itoch
ondr
ia)
• ly
soso
mes
• ce
ntrio
les
and
mic
rotu
bule
s
• ch
loro
plas
ts (i
nclu
ding
sm
all c
ircul
ar D
NA
)
• ce
ll w
all
• pl
asm
odes
mat
a
• la
rge
perm
anen
t va
cuol
e an
d to
nopl
ast
of p
lant
cel
ls
c)
stat
e th
at A
TP is
pro
duce
d in
mito
chon
dria
and
ch
loro
plas
ts a
nd o
utlin
e th
e ro
le o
f A
TP in
cel
ls
d)
outli
ne k
ey s
truc
tura
l fea
ture
s of
typ
ical
pro
kary
otic
cel
ls
as s
een
in a
typ
ical
bac
teriu
m (i
nclu
ding
: uni
cellu
lar,
1-
5µm
dia
met
er, p
eptid
ogly
can
cell
wal
ls, l
ack
of
orga
nelle
s su
rrou
nded
by
doub
le m
embr
anes
, nak
ed
circ
ular
DN
A,
70S
rib
osom
es)
e)
com
pare
and
con
tras
t th
e st
ruct
ure
of t
ypic
al p
roka
ryot
ic
cells
with
typ
ical
euk
aryo
tic c
ells
(ref
eren
ce t
o m
esos
omes
sho
uld
not
be in
clud
ed)
f)
outli
ne t
he k
ey f
eatu
res
of v
iruse
s as
non
-cel
lula
r st
ruct
ures
(lim
ited
to p
rote
in c
oat
and
DN
A/R
NA
)
Section 4: What you need to know
37Cambridge International AS and A Level Biology 9700
AS
Lev
el m
ater
ial
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
2 B
iolo
gica
l mol
ecul
es2.
1 T
esti
ng
fo
r b
iolo
gic
al
mo
lecu
les
Te
sts
for
biol
ogic
al
mol
ecul
es c
an b
e us
ed in
a v
arie
ty
of c
onte
xts,
suc
h as
iden
tifyi
ng t
he
cont
ents
of
mix
ture
s of
mol
ecul
es a
nd
follo
win
g th
e ac
tivity
of
dige
stiv
e en
zym
es.
a)
carr
y ou
t te
sts
for
redu
cing
sug
ars
and
non-
redu
cing
su
gars
, the
iodi
ne in
pot
assi
um io
dide
sol
utio
n te
st f
or
star
ch, t
he e
mul
sion
tes
t fo
r lip
ids
and
the
biur
et t
est
for
prot
eins
to
iden
tify
the
cont
ents
of
solu
tions
b)
carr
y ou
t a
sem
i-qua
ntita
tive
Ben
edic
t’s
test
on
a re
duci
ng s
ugar
usi
ng d
ilutio
n, s
tand
ardi
sing
the
tes
t an
d us
ing
the
resu
lts (c
olou
r st
anda
rds
or t
ime
to fi
rst
colo
ur
chan
ge) t
o es
timat
e th
e co
ncen
trat
ion
Section 4: What you need to know
38 Cambridge International AS and A Level Biology 9700
AS
Lev
el m
ater
ial
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
2 B
iolo
gica
l mol
ecul
es2.
2 C
arb
oh
ydra
tes
and
lip
ids
C
arbo
hydr
ates
an
d lip
ids
have
im
port
ant
role
s in
th
e pr
ovis
ion
and
stor
age
of e
nerg
y an
d fo
r a
varie
ty
of o
ther
fun
ctio
ns
such
as
prov
idin
g ba
rrie
rs a
roun
d ce
lls:
the
phos
phol
ipid
bi
laye
r of
all
cell
mem
bran
es a
nd t
he
cellu
lose
cel
l wal
ls
of p
lant
cel
ls.
a)
desc
ribe
the
ring
form
s of
α-g
luco
se a
nd β
-glu
cose
b)
defi n
e th
e te
rms
mon
omer
, pol
ymer
, mac
rom
olec
ule,
m
onos
acch
arid
e, d
isac
char
ide
and
poly
sacc
harid
e
c)
desc
ribe
the
form
atio
n of
a g
lyco
sidi
c bo
nd b
y co
nden
satio
n, w
ith r
efer
ence
bot
h to
pol
ysac
char
ides
an
d to
dis
acch
arid
es, i
nclu
ding
suc
rose
d)
desc
ribe
the
brea
kage
of
glyc
osid
ic b
onds
in
poly
sacc
harid
es a
nd d
isac
char
ides
by
hydr
olys
is, w
ith
refe
renc
e to
the
no
n-re
duci
ng s
ugar
tes
t
e)
desc
ribe
the
mol
ecul
ar s
truc
ture
of
poly
sacc
harid
es
incl
udin
g st
arch
(am
ylos
e an
d am
ylop
ectin
), gl
ycog
en a
nd
cellu
lose
and
rel
ate
thes
e st
ruct
ures
to
thei
r fu
nctio
ns in
liv
ing
orga
nism
s
f)
desc
ribe
the
mol
ecul
ar s
truc
ture
of
a tr
igly
cerid
e w
ith
refe
renc
e to
the
for
mat
ion
of e
ster
bon
ds a
nd r
elat
e th
e st
ruct
ure
of t
rigly
cerid
es t
o th
eir
func
tions
in li
ving
or
gani
sms
g)
desc
ribe
the
stru
ctur
e of
a p
hosp
holip
id a
nd r
elat
e th
e st
ruct
ure
of p
hosp
holip
ids
to t
heir
func
tions
in li
ving
or
gani
sms
Section 4: What you need to know
39Cambridge International AS and A Level Biology 9700
AS
Lev
el m
ater
ial
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
2 B
iolo
gica
l mol
ecul
es2.
3 P
rote
ins
and
wat
er
A
n un
ders
tand
ing
of p
rote
in s
truc
ture
an
d ho
w it
is r
elat
ed
to f
unct
ion
is c
entr
al
to m
any
aspe
cts
of b
iolo
gy, s
uch
as
enzy
mes
, ant
ibod
ies
and
mus
cle
cont
ract
ion.
G
lobu
lar
and
fi bro
us p
rote
ins
play
impo
rtan
t ro
les
in b
iolo
gica
l pr
oces
ses
such
as
the
tra
nspo
rt o
f ga
ses
and
prov
idin
g su
ppor
t fo
r tis
sues
.
W
ater
is a
spe
cial
m
olec
ule
with
ex
trao
rdin
ary
prop
ertie
s th
at m
ake
life
poss
ible
on
this
pl
anet
150
mill
ion
kilo
met
res
from
the
S
un.
a)
desc
ribe
the
stru
ctur
e of
an
amin
o ac
id a
nd t
he f
orm
atio
n an
d br
eaka
ge o
f a
pept
ide
bond
b)
expl
ain
the
mea
ning
of
the
term
s pr
imar
y st
ruct
ure,
se
cond
ary
stru
ctur
e, t
ertia
ry s
truc
ture
and
qua
tern
ary
stru
ctur
e of
pro
tein
s an
d de
scrib
e th
e ty
pes
of b
ondi
ng
(hyd
roge
n, io
nic,
dis
ulfi d
e an
d hy
drop
hobi
c in
tera
ctio
ns)
that
hol
d th
ese
mol
ecul
es in
sha
pe
c)
desc
ribe
the
mol
ecul
ar s
truc
ture
of
haem
oglo
bin
as a
n ex
ampl
e of
a g
lobu
lar
prot
ein,
and
of
colla
gen
as a
n ex
ampl
e of
a fi
brou
s pr
otei
n an
d re
late
the
se
stru
ctur
es t
o th
eir
func
tions
(The
impo
rtan
ce o
f iro
n in
th
e ha
emog
lobi
n m
olec
ule
shou
ld b
e em
phas
ised
. A
haem
oglo
bin
mol
ecul
e is
com
pose
d of
tw
o al
pha
(α)
chai
ns a
nd t
wo
beta
(β) c
hain
s, a
lthou
gh w
hen
desc
ribin
g th
e ch
ains
the
ter
ms α-
glob
in a
nd β
-glo
bin
may
be
used
. The
re s
houl
d be
a d
istin
ctio
n be
twee
n co
llage
n m
olec
ules
and
col
lage
n fi b
res)
d)
expl
ain
how
hyd
roge
n bo
ndin
g oc
curs
bet
wee
n w
ater
m
olec
ules
and
rel
ate
the
prop
ertie
s of
wat
er t
o its
rol
es
in li
ving
org
anis
ms
(lim
ited
to s
olve
nt a
ctio
n, s
peci
fi c
heat
cap
acity
and
late
nt h
eat
of v
apou
risat
ion)
Section 4: What you need to know
40 Cambridge International AS and A Level Biology 9700
AS
Lev
el m
ater
ial
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
3 En
zym
es3.
1 M
od
e o
f ac
tio
n o
f en
zym
es
Th
ere
are
man
y di
ffer
ent
enzy
mes
, ea
ch o
ne s
peci
fi c t
o a
part
icul
ar r
eact
ion.
Th
is s
peci
fi city
is t
he
key
to u
nder
stan
ding
th
e ef
fi cie
nt
func
tioni
ng o
f ce
lls
and
livin
g or
gani
sms.
a)
expl
ain
that
enz
ymes
are
glo
bula
r pr
otei
ns t
hat
cata
lyse
m
etab
olic
rea
ctio
ns
b)
stat
e th
at e
nzym
es f
unct
ion
insi
de c
ells
(int
race
llula
r en
zym
es) a
nd o
utsi
de c
ells
(ext
race
llula
r en
zym
es)
c)
expl
ain
the
mod
e of
act
ion
of e
nzym
es in
ter
ms
of a
n ac
tive
site
, enz
yme/
subs
trat
e co
mpl
ex, l
ower
ing
of
activ
atio
n en
ergy
and
enz
yme
spec
ifi ci
ty (t
he lo
ck a
nd
key
hypo
thes
is a
nd t
he in
duce
d fi t
hyp
othe
sis
shou
ld b
e in
clud
ed)
d)
inve
stig
ate
the
prog
ress
of
an e
nzym
e-ca
taly
sed
reac
tion
by m
easu
ring
rate
s of
for
mat
ion
of p
rodu
cts
(for
ex
ampl
e, u
sing
cat
alas
e) o
r ra
tes
of d
isap
pear
ance
of
subs
trat
e (f
or e
xam
ple,
usi
ng a
myl
ase)
3 En
zym
es3.
2 Fa
cto
rs t
hat
aff
ect
enzy
me
acti
on
In
vest
igat
ing
the
effe
cts
of f
acto
rs
on e
nzym
e ac
tivity
gi
ves
oppo
rtun
ities
fo
r pl
anni
ng
and
carr
ying
out
ex
perim
ents
un
der
cont
rolle
d co
nditi
ons.
a)
inve
stig
ate
and
expl
ain
the
effe
cts
of t
he f
ollo
win
g fa
ctor
s on
the
rat
e of
enz
yme-
cata
lyse
d re
actio
ns:
• te
mpe
ratu
re
• pH
(usi
ng b
uffe
r so
lutio
ns)
• en
zym
e co
ncen
trat
ion
• su
bstr
ate
conc
entr
atio
n
• in
hibi
tor
conc
entr
atio
n
b)
expl
ain
that
the
max
imum
rat
e of
rea
ctio
n (V
max
) is
used
to
der
ive
the
Mic
hael
is-M
ente
n co
nsta
nt (K
m) w
hich
is
used
to
com
pare
the
affi
nity
of
diff
eren
t en
zym
es f
or
thei
r su
bstr
ates
c)
expl
ain
the
effe
cts
of r
ever
sibl
e in
hibi
tors
, bot
h co
mpe
titiv
e an
d no
n-co
mpe
titiv
e, o
n th
e ra
te o
f en
zym
e ac
tivity
d)
inve
stig
ate
and
expl
ain
the
effe
ct o
f im
mob
ilisi
ng a
n en
zym
e in
alg
inat
e on
its
activ
ity a
s co
mpa
red
with
its
activ
ity w
hen
free
in s
olut
ion
Section 4: What you need to know
41Cambridge International AS and A Level Biology 9700
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Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
4 C
ell m
embr
anes
and
tr
ansp
ort
4.1
Flu
id m
osa
ic
mem
bra
nes
Th
e st
ruct
ure
of c
ell
surf
ace
mem
bran
es
allo
ws
mov
emen
t of
sub
stan
ces
betw
een
cells
and
th
eir
surr
ound
ings
an
d al
low
s ce
lls t
o co
mm
unic
ate
with
ea
ch o
ther
by
cell
sign
allin
g.
a)
desc
ribe
and
expl
ain
the
fl uid
mos
aic
mod
el o
f m
embr
ane
stru
ctur
e, in
clud
ing
an o
utlin
e of
the
rol
es
of p
hosp
holip
ids,
cho
lest
erol
, gly
colip
ids,
pro
tein
s an
d gl
ycop
rote
ins
b)
outli
ne t
he r
oles
of
cell
surf
ace
mem
bran
es in
clud
ing
refe
renc
es t
o ca
rrie
r pr
otei
ns, c
hann
el p
rote
ins,
cel
l su
rfac
e re
cept
ors
and
cell
surf
ace
antig
ens
c)
outli
ne t
he p
roce
ss o
f ce
ll si
gnal
ling
invo
lvin
g th
e re
leas
e of
che
mic
als
that
com
bine
with
cel
l sur
face
rec
epto
rs o
n ta
rget
cel
ls, l
eadi
ng t
o sp
ecifi
c re
spon
ses
Section 4: What you need to know
42 Cambridge International AS and A Level Biology 9700
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u s
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om
men
ts
4 C
ell m
embr
anes
and
tr
ansp
ort
4.2
Mo
vem
ent
of
sub
stan
ces
into
an
d o
ut
of
cells
Th
e fl u
id m
osai
c m
odel
allo
ws
an
unde
rsta
ndin
g of
ho
w s
ubst
ance
s en
ter
and
exit
cells
by
a va
riety
of
diff
eren
t m
echa
nism
s.
In
vest
igat
ing
the
effe
ct o
f in
crea
sing
th
e si
ze o
f m
odel
ce
lls a
llow
s an
un
ders
tand
ing
of
the
cons
trai
nts
of
obta
inin
g re
sour
ces
acro
ss t
he c
ell
surf
ace
and
mov
ing
subs
tanc
es o
ut o
f ce
lls.
a)
desc
ribe
and
expl
ain
the
proc
esse
s of
diff
usio
n,
faci
litat
ed d
iffus
ion,
osm
osis
, act
ive
tran
spor
t,
endo
cyto
sis
and
exoc
ytos
is (n
o ca
lcul
atio
ns in
volv
ing
wat
er p
oten
tial w
ill b
e se
t)
b)
inve
stig
ate
sim
ple
diff
usio
n us
ing
plan
t tis
sue
and
non-
livin
g m
ater
ials
, suc
h as
glu
cose
sol
utio
ns, V
iski
ng t
ubin
g an
d ag
ar
c)
calc
ulat
e su
rfac
e ar
eas
and
volu
mes
of
sim
ple
shap
es
(e.g
. cub
es) t
o ill
ustr
ate
the
prin
cipl
e th
at s
urfa
ce a
rea
to
volu
me
ratio
s de
crea
se w
ith in
crea
sing
siz
e
d)
inve
stig
ate
the
effe
ct o
f ch
angi
ng s
urfa
ce a
rea
to v
olum
e ra
tio o
n di
ffus
ion
usin
g ag
ar b
lock
s of
diff
eren
t si
zes
e)
inve
stig
ate
the
effe
cts
of im
mer
sing
pla
nt t
issu
es in
so
lutio
ns o
f di
ffer
ent
wat
er p
oten
tial,
usin
g th
e re
sults
to
estim
ate
the
wat
er p
oten
tial o
f th
e tis
sues
f)
expl
ain
the
mov
emen
t of
wat
er b
etw
een
cells
and
so
lutio
ns w
ith d
iffer
ent
wat
er p
oten
tials
and
exp
lain
the
di
ffer
ent
effe
cts
on p
lant
and
ani
mal
cel
ls
Section 4: What you need to know
43Cambridge International AS and A Level Biology 9700
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ater
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men
ts
5 Th
e m
itotic
cel
l cyc
le5.
1 R
eplic
atio
n a
nd
d
ivis
ion
of
nu
clei
an
d c
ells
D
urin
g th
e m
itotic
ce
ll cy
cle,
DN
A
is r
eplic
ated
and
pa
ssed
to
daug
hter
ce
lls.
S
tem
cel
ls in
bon
e m
arro
w a
nd t
he
skin
con
tinua
lly
divi
de b
y m
itosi
s to
pr
ovid
e a
cont
inuo
us
supp
ly o
f ce
lls t
hat
diff
eren
tiate
into
bl
ood
and
skin
cel
ls.
a)
desc
ribe
the
stru
ctur
e of
a c
hrom
osom
e, li
mite
d to
DN
A,
hist
one
prot
eins
, chr
omat
ids,
cen
trom
ere
and
telo
mer
es
b)
expl
ain
the
impo
rtan
ce o
f m
itosi
s in
the
pro
duct
ion
of
gene
tical
ly id
entic
al c
ells
, gro
wth
, cel
l rep
lace
men
t,
repa
ir of
tis
sues
and
ase
xual
rep
rodu
ctio
n
c)
outli
ne t
he c
ell c
ycle
, inc
ludi
ng in
terp
hase
(gro
wth
and
D
NA
rep
licat
ion)
, mito
sis
and
cyto
kine
sis
d)
outli
ne t
he s
igni
fi can
ce o
f te
lom
eres
in p
erm
ittin
g co
ntin
ued
repl
icat
ion
and
prev
entin
g th
e lo
ss o
f ge
nes
e)
outli
ne t
he s
igni
fi can
ce o
f m
itosi
s in
cel
l rep
lace
men
t an
d tis
sue
repa
ir by
ste
m c
ells
and
sta
te t
hat
unco
ntro
lled
cell
divi
sion
can
res
ult
in t
he f
orm
atio
n of
a t
umou
r
5 Th
e m
itotic
cel
l cyc
le5.
2 C
hro
mo
som
e b
ehav
iou
r in
m
ito
sis
Th
e ev
ents
tha
t oc
cur
durin
g m
itosi
s ca
n be
fol
low
ed
by u
sing
a li
ght
mic
rosc
ope.
a)
desc
ribe,
with
the
aid
of
phot
omic
rogr
aphs
and
dia
gram
s,
the
beha
viou
r of
chr
omos
omes
in p
lant
and
ani
mal
cel
ls
durin
g th
e m
itotic
cel
l cyc
le a
nd t
he a
ssoc
iate
d be
havi
our
of t
he n
ucle
ar e
nvel
ope,
cel
l sur
face
mem
bran
e an
d th
e sp
indl
e (n
ames
of
the
mai
n st
ages
of
mito
sis
are
expe
cted
)
b)
obse
rve
and
draw
the
mito
tic s
tage
s vi
sibl
e in
tem
pora
ry
root
tip
squ
ash
prep
arat
ions
and
in p
repa
red
slid
es o
f ro
ot t
ips
of s
peci
es s
uch
as t
hose
of
Vici
a fa
ba a
nd
Alli
um c
epa
Section 4: What you need to know
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ater
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u s
ho
uld
be
able
to
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hec
klis
tC
om
men
ts
6 N
ucle
ic a
cids
and
pr
otei
n sy
nthe
sis
6.1
Str
uct
ure
an
d
rep
licat
ion
of
DN
A
U
nder
stan
ding
th
e st
ruct
ure
of
nucl
eic
acid
s al
low
s an
und
erst
andi
ng
of t
heir
role
in
the
stor
age
of
gene
tic in
form
atio
n an
d ho
w t
hat
info
rmat
ion
is u
sed
in t
he s
ynth
esis
of
prot
eins
.
a)
desc
ribe
the
stru
ctur
e of
nuc
leot
ides
, inc
ludi
ng t
he
phos
phor
ylat
ed n
ucle
otid
e A
TP (s
truc
tura
l for
mul
ae a
re
not
requ
ired)
b)
desc
ribe
the
stru
ctur
e of
RN
A a
nd D
NA
and
exp
lain
the
im
port
ance
of
base
pai
ring
and
the
diff
eren
t hy
drog
en
bond
ing
betw
een
base
s (in
clud
e re
fere
nce
to a
deni
ne
and
guan
ine
as p
urin
es a
nd t
o cy
tosi
ne, t
hym
ine
and
urac
il as
pyr
imid
ines
. Str
uctu
ral f
orm
ulae
for
bas
es a
re
not
requ
ired
but
the
reco
gniti
on t
hat
purin
es h
ave
a do
uble
rin
g st
ruct
ure
and
pyrim
idin
es h
ave
a si
ngle
rin
g st
ruct
ure
shou
ld b
e in
clud
ed)
c)
desc
ribe
the
sem
i-con
serv
ativ
e re
plic
atio
n of
DN
A d
urin
g in
terp
hase
6 N
ucle
ic a
cids
and
pr
otei
n sy
nthe
sis
6.2
Pro
tein
syn
thes
is
Th
e ge
netic
cod
e sp
ecifi
es t
he a
min
o ac
ids
that
are
as
sem
bled
to
mak
e po
lype
ptid
es. T
he
way
tha
t D
NA
cod
es
for
poly
pept
ides
is
cen
tral
to
our
unde
rsta
ndin
g of
how
cel
ls a
nd
orga
nism
s fu
nctio
n.
a)
stat
e th
at a
pol
ypep
tide
is c
oded
for
by
a ge
ne a
nd t
hat
a ge
ne is
a s
eque
nce
of n
ucle
otid
es t
hat
form
s pa
rt o
f a
DN
A m
olec
ule
b)
stat
e th
at a
gen
e m
utat
ion
is a
cha
nge
in t
he s
eque
nce
of n
ucle
otid
es t
hat
may
res
ult
in a
n al
tere
d po
lype
ptid
e
c)
desc
ribe
the
way
in w
hich
the
nuc
leot
ide
sequ
ence
co
des
for
the
amin
o ac
id s
eque
nce
in a
pol
ypep
tide
with
re
fere
nce
to t
he n
ucle
otid
e se
quen
ce f
or H
bA (n
orm
al)
and
HbS (s
ickl
e ce
ll) a
llele
s of
the
gen
e fo
r th
e β-
glob
in
poly
pept
ide
d)
desc
ribe
how
the
info
rmat
ion
in D
NA
is u
sed
durin
g tr
ansc
riptio
n an
d tr
ansl
atio
n to
con
stru
ct p
olyp
eptid
es,
incl
udin
g th
e ro
le o
f m
esse
nger
RN
A (m
RN
A),
tran
sfer
R
NA
(tR
NA
) and
the
rib
osom
es
Section 4: What you need to know
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men
ts
7 Tr
ansp
ort
in p
lant
s7.
1 S
tru
ctu
re o
f tr
ansp
ort
tis
sues
P
lant
s ha
ve t
wo
tran
spor
t tis
sues
: xy
lem
and
phl
oem
.
a)
draw
and
labe
l fro
m p
repa
red
slid
es p
lan
diag
ram
s of
tra
nsve
rse
sect
ions
of
stem
s, r
oots
and
leav
es o
f he
rbac
eous
dic
otyl
edon
ous
plan
ts u
sing
an
eyep
iece
gr
atic
ule
to s
how
tis
sues
in c
orre
ct p
ropo
rtio
ns (s
ee 1
.1c)
b)
draw
and
labe
l fro
m p
repa
red
slid
es t
he c
ells
in
the
diff
eren
t tis
sues
in r
oots
, ste
ms
and
leav
es o
f he
rbac
eous
dic
otyl
edon
ous
plan
ts u
sing
tra
nsve
rse
and
long
itudi
nal s
ectio
ns
c)
draw
and
labe
l fro
m p
repa
red
slid
es t
he s
truc
ture
of
xyle
m v
esse
l ele
men
ts, p
hloe
m s
ieve
tub
e el
emen
ts a
nd
com
pani
on c
ells
and
be
able
to
reco
gnis
e th
ese
usin
g th
e lig
ht m
icro
scop
e
d)
rela
te t
he s
truc
ture
of
xyle
m v
esse
l ele
men
ts, p
hloe
m
siev
e tu
be e
lem
ents
and
com
pani
on c
ells
to
thei
r fu
nctio
ns
Section 4: What you need to know
46 Cambridge International AS and A Level Biology 9700
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ater
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u s
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uld
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om
men
ts
7 Tr
ansp
ort
in p
lant
s7.
2 T
ran
spo
rt
mec
han
ism
s
M
ovem
ent
of x
ylem
sa
p an
d ph
loem
sap
is
by
mas
s fl o
w.
Mov
emen
t in
the
xy
lem
is p
assi
ve
as it
is d
riven
by
evap
orat
ion
from
th
e le
aves
; pla
nts
use
ener
gy t
o m
ove
subs
tanc
es in
the
ph
loem
.
X
ylem
sap
mov
es in
on
e di
rect
ion
from
th
e ro
ots
to t
he
rest
of
the
plan
t.
The
phlo
em s
ap
in a
phl
oem
sie
ve
tube
mov
es in
one
di
rect
ion
from
the
lo
catio
n w
here
it is
m
ade
to t
he lo
catio
n w
here
it is
use
d or
st
ored
. At
any
one
time
phlo
em s
ap
can
be m
ovin
g in
di
ffer
ent
dire
ctio
ns
in d
iffer
ent
siev
e tu
bes.
a)
expl
ain
the
mov
emen
t of
wat
er b
etw
een
plan
t ce
lls,
and
betw
een
them
and
the
ir en
viro
nmen
t, in
ter
ms
of
wat
er p
oten
tial (
see
4.2.
No
calc
ulat
ions
invo
lvin
g w
ater
po
tent
ial w
ill b
e se
t)
b)
expl
ain
how
hyd
roge
n bo
ndin
g of
wat
er m
olec
ules
is
invo
lved
with
mov
emen
t in
the
xyl
em b
y co
hesi
on-
tens
ion
in t
rans
pira
tion
pull
and
adhe
sion
to
cellu
lose
cel
l w
alls
c)
desc
ribe
the
path
way
s an
d ex
plai
n th
e m
echa
nism
s by
w
hich
wat
er a
nd m
iner
al io
ns a
re t
rans
port
ed f
rom
soi
l to
xyl
em a
nd f
rom
roo
ts t
o le
aves
(inc
lude
ref
eren
ce
to t
he s
ympl
astic
pat
hway
and
apo
plas
tic p
athw
ay a
nd
Cas
paria
n st
rip)
d)
defi n
e th
e te
rm t
rans
pira
tion
and
expl
ain
that
it is
an
inev
itabl
e co
nseq
uenc
e of
gas
exc
hang
e in
pla
nts
e)
inve
stig
ate
expe
rimen
tally
and
exp
lain
the
fac
tors
tha
t af
fect
tra
nspi
ratio
n ra
te u
sing
sim
ple
poto
met
ers,
leaf
im
pres
sion
s, e
pide
rmal
pee
ls, a
nd g
rids
for
dete
rmin
ing
surf
ace
area
f)
mak
e an
nota
ted
draw
ings
, usi
ng p
repa
red
slid
es o
f cr
oss-
sect
ions
, to
show
how
leav
es o
f xe
roph
ytic
pla
nts
are
adap
ted
to r
educ
e w
ater
loss
by
tran
spira
tion
g)
stat
e th
at a
ssim
ilate
s, s
uch
as s
ucro
se a
nd a
min
o ac
ids,
m
ove
betw
een
sour
ces
(e.g
. lea
ves
and
stor
age
orga
ns)
and
sink
s (e
.g. b
uds,
fl ow
ers,
fru
its, r
oots
and
sto
rage
or
gans
) in
phlo
em s
ieve
tub
es
h)
expl
ain
how
suc
rose
is lo
aded
into
phl
oem
sie
ve t
ubes
by
com
pani
on c
ells
usi
ng p
roto
n pu
mpi
ng a
nd t
he c
o-tr
ansp
orte
r m
echa
nism
in t
heir
cell
surf
ace
mem
bran
es
i) ex
plai
n m
ass
fl ow
in p
hloe
m s
ap d
own
a hy
dros
tatic
pr
essu
re g
radi
ent
from
sou
rce
to s
ink
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8 Tr
ansp
ort
in
mam
mal
s8.
1 T
he
circ
ula
tory
sy
stem
Th
e m
amm
alia
n ci
rcul
ator
y sy
stem
co
nsis
ts o
f a
pum
p,
man
y bl
ood
vess
els
and
bloo
d, w
hich
is
a s
uspe
nsio
n of
re
d bl
ood
cells
and
w
hite
blo
od c
ells
in
plas
ma.
a)
stat
e th
at t
he m
amm
alia
n ci
rcul
ator
y sy
stem
is a
clo
sed
doub
le c
ircul
atio
n co
nsis
ting
of a
hea
rt, b
lood
ves
sels
an
d bl
ood
b)
obse
rve
and
mak
e pl
an d
iagr
ams
of t
he s
truc
ture
of
arte
ries,
vei
ns a
nd c
apill
arie
s us
ing
prep
ared
slid
es
and
be a
ble
to r
ecog
nise
the
se v
esse
ls u
sing
the
ligh
t m
icro
scop
e
c)
expl
ain
the
rela
tions
hip
betw
een
the
stru
ctur
e an
d fu
nctio
n of
art
erie
s, v
eins
and
cap
illar
ies
d)
obse
rve
and
draw
the
str
uctu
re o
f re
d bl
ood
cells
, m
onoc
ytes
, neu
trop
hils
and
lym
phoc
ytes
usi
ng p
repa
red
slid
es a
nd p
hoto
mic
rogr
aphs
e)
stat
e an
d ex
plai
n th
e di
ffer
ence
s be
twee
n bl
ood,
tis
sue
fl uid
and
lym
ph
f)
desc
ribe
the
role
of
haem
oglo
bin
in c
arry
ing
oxyg
en a
nd
carb
on d
ioxi
de w
ith r
efer
ence
to
the
role
of
carb
onic
an
hydr
ase,
the
for
mat
ion
of h
aem
oglo
bini
c ac
id a
nd
carb
amin
ohae
mog
lobi
n (d
etai
ls o
f th
e ch
lorid
e sh
ift a
re
not
requ
ired)
g)
desc
ribe
and
expl
ain
the
sign
ifi ca
nce
of t
he o
xyge
n di
ssoc
iatio
n cu
rves
of
adul
t ox
yhae
mog
lobi
n at
diff
eren
t ca
rbon
dio
xide
con
cent
ratio
ns (t
he B
ohr
effe
ct)
h)
desc
ribe
and
expl
ain
the
sign
ifi ca
nce
of t
he in
crea
se in
th
e re
d bl
ood
cell
coun
t of
hum
ans
at h
igh
altit
ude
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8 Tr
ansp
ort
in
mam
mal
s8.
2 T
he
hea
rt
Th
e m
amm
alia
n he
art
is a
dou
ble
pum
p: t
he r
ight
sid
e pu
mps
blo
od a
t lo
w p
ress
ure
to t
he
lung
s an
d th
e le
ft
side
pum
ps b
lood
at
high
pre
ssur
e to
the
re
st o
f th
e bo
dy.
a)
desc
ribe
the
exte
rnal
and
inte
rnal
str
uctu
re o
f th
e m
amm
alia
n he
art
b)
expl
ain
the
diff
eren
ces
in t
he t
hick
ness
of
the
wal
ls o
f th
e di
ffer
ent
cham
bers
in t
erm
s of
the
ir fu
nctio
ns w
ith
refe
renc
e to
res
ista
nce
to fl
ow
c)
desc
ribe
the
card
iac
cycl
e (in
clud
ing
bloo
d pr
essu
re
chan
ges
durin
g sy
stol
e an
d di
asto
le)
d)
expl
ain
how
hea
rt a
ctio
n is
initi
ated
and
con
trol
led
(ref
eren
ce s
houl
d be
mad
e to
the
sin
oatr
ial n
ode,
the
at
riove
ntric
ular
nod
e an
d th
e P
urky
ne t
issu
e, b
ut n
ot t
o ne
rvou
s an
d ho
rmon
al c
ontr
ol)
9 G
as e
xcha
nge
and
smok
ing
9.1
Th
e g
as e
xch
ang
e sy
stem
Th
e ga
s ex
chan
ge
surf
ace
in t
he lu
ngs
is e
xten
sive
, ver
y th
in, w
ell s
uppl
ied
with
blo
od a
nd
wel
l ven
tilat
ed.
The
trac
hea
and
bron
chi p
rovi
de li
ttle
re
sist
ance
to
the
mov
emen
t of
air
to
and
from
the
alv
eoli.
a)
desc
ribe
the
gros
s st
ruct
ure
of t
he h
uman
gas
exc
hang
e sy
stem
b)
obse
rve
and
draw
pla
n di
agra
ms
of t
he s
truc
ture
of
the
wal
ls o
f th
e tr
ache
a, b
ronc
hi, b
ronc
hiol
es a
nd a
lveo
li in
dica
ting
the
dist
ribut
ion
of c
artil
age,
cili
ated
epi
thel
ium
, go
blet
cel
ls, s
moo
th m
uscl
e, s
quam
ous
epith
eliu
m a
nd
bloo
d ve
ssel
s
c)
desc
ribe
the
func
tions
of
cart
ilage
, cili
a, g
oble
t ce
lls,
muc
ous
glan
ds, s
moo
th m
uscl
e an
d el
astic
fi br
es a
nd
reco
gnis
e th
ese
cells
and
tis
sues
in p
repa
red
slid
es,
phot
omic
rogr
aphs
and
ele
ctro
n m
icro
grap
hs o
f th
e ga
s ex
chan
ge s
yste
m
d)
desc
ribe
the
proc
ess
of g
as e
xcha
nge
betw
een
air
in t
he
alve
oli a
nd t
he b
lood
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9 G
as e
xcha
nge
and
smok
ing
9.2
Sm
oki
ng
S
mok
ing
is o
ne o
f th
e m
ajor
avo
idab
le
risk
fact
ors
of
chro
nic,
life
-th
reat
enin
g di
seas
es
of t
he g
as e
xcha
nge
and
circ
ulat
ory
syst
ems.
a)
desc
ribe
the
effe
cts
of t
ar a
nd c
arci
noge
ns in
tob
acco
sm
oke
on t
he g
as e
xcha
nge
syst
em w
ith r
efer
ence
to
lung
can
cer
and
chro
nic
obst
ruct
ive
pulm
onar
y di
seas
e (C
OP
D)
b)
desc
ribe
the
shor
t-te
rm e
ffec
ts o
f ni
cotin
e an
d ca
rbon
m
onox
ide
on t
he c
ardi
ovas
cula
r sy
stem
10 In
fect
ious
dis
ease
10.1
In
fect
iou
s d
isea
ses
W
hile
man
y in
fect
ious
di
seas
es h
ave
been
suc
cess
fully
co
ntro
lled
in s
ome
part
s of
the
wor
ld,
man
y pe
ople
w
orld
wid
e ar
e st
ill
at r
isk
of t
hese
di
seas
es.
a)
defi n
e th
e te
rm d
isea
se a
nd e
xpla
in t
he d
iffer
ence
be
twee
n an
infe
ctio
us d
isea
se a
nd a
non
-infe
ctio
us
dise
ase
(lim
ited
to s
ickl
e ce
ll an
aem
ia a
nd lu
ng c
ance
r)
b)
stat
e th
e na
me
and
type
of
caus
ativ
e or
gani
sm
(pat
hoge
n) o
f ea
ch o
f th
e fo
llow
ing
dise
ases
: cho
lera
, m
alar
ia, t
uber
culo
sis
(TB
), H
IV/A
IDS
, sm
allp
ox a
nd
mea
sles
(det
aile
d kn
owle
dge
of s
truc
ture
is n
ot r
equi
red.
Fo
r sm
allp
ox (V
ario
la) a
nd m
easl
es (M
orbi
llivi
rus)
onl
y th
e na
me
of g
enus
is n
eede
d)
c)
expl
ain
how
cho
lera
, mea
sles
, mal
aria
, TB
and
HIV
/AID
S
are
tran
smitt
ed
d)
disc
uss
the
biol
ogic
al, s
ocia
l and
eco
nom
ic f
acto
rs t
hat
need
to
be c
onsi
dere
d in
the
pre
vent
ion
and
cont
rol o
f ch
oler
a, m
easl
es, m
alar
ia, T
B a
nd H
IV/A
IDS
(a d
etai
led
stud
y of
the
life
cyc
le o
f th
e m
alar
ial p
aras
ite is
not
re
quire
d)
e)
disc
uss
the
fact
ors
that
infl u
ence
the
glo
bal p
atte
rns
of
dist
ribut
ion
of m
alar
ia, T
B a
nd H
IV/A
IDS
and
ass
ess
the
impo
rtan
ce o
f th
ese
dise
ases
wor
ldw
ide
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10 In
fect
ious
dis
ease
10.2
An
tib
ioti
cs
Th
e ‘a
ge o
f an
tibio
tics’
beg
an
in t
he 1
940s
with
th
e av
aila
bilit
y of
pe
nici
llin.
With
an
incr
ease
in a
ntib
iotic
re
sist
ance
is t
his
age
abou
t to
com
e to
an
end?
a)
outli
ne h
ow p
enic
illin
act
s on
bac
teria
and
why
ant
ibio
tics
do n
ot a
ffec
t vi
ruse
s
b)
expl
ain
in o
utlin
e ho
w b
acte
ria b
ecom
e re
sist
ant
to
antib
iotic
s w
ith r
efer
ence
to
mut
atio
n an
d se
lect
ion
c)
disc
uss
the
cons
eque
nces
of
antib
iotic
res
ista
nce
and
the
step
s th
at c
an b
e ta
ken
to r
educ
e its
impa
ct
11 Im
mun
ity11
.1 T
he
imm
un
e sy
stem
Th
e im
mun
e sy
stem
ha
s no
n-sp
ecifi
c an
d sp
ecifi
c re
spon
ses
to p
atho
gens
. A
uto-
imm
une
dise
ases
are
the
re
sult
of f
ailu
res
in t
he s
yste
m t
o di
stin
guis
h be
twee
n se
lf an
d no
n-se
lf.
a)
stat
e th
at p
hago
cyte
s (m
acro
phag
es a
nd n
eutr
ophi
ls)
have
the
ir or
igin
in b
one
mar
row
and
des
crib
e th
eir
mod
e of
act
ion
b)
desc
ribe
the
mod
es o
f ac
tion
of B
-lym
phoc
ytes
and
T-
lym
phoc
ytes
c)
desc
ribe
and
expl
ain
the
sign
ifi ca
nce
of t
he in
crea
se
in w
hite
blo
od c
ell c
ount
in h
uman
s w
ith in
fect
ious
di
seas
es a
nd le
ukae
mia
s
d)
expl
ain
the
mea
ning
of
the
term
imm
une
resp
onse
, m
akin
g re
fere
nce
to t
he t
erm
s an
tigen
, sel
f an
d no
n-se
lf
e)
expl
ain
the
role
of
mem
ory
cells
in lo
ng-t
erm
imm
unity
f)
expl
ain,
with
ref
eren
ce t
o m
yast
heni
a gr
avis
, tha
t th
e im
mun
e sy
stem
som
etim
es f
ails
to
dist
ingu
ish
betw
een
self
and
non-
self
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11 Im
mun
ity11
.2 A
nti
bo
die
s an
d
vacc
inat
ion
A
ctiv
e an
d pa
ssiv
e im
mun
isat
ions
are
ef
fect
ive
way
s to
tr
eat
and
prev
ent
infe
ctio
us d
isea
ses.
S
mal
lpox
has
bee
n er
adic
ated
; oth
er
dise
ases
may
soo
n fo
llow
, but
vac
cine
de
velo
pmen
t ha
s pr
oved
mor
e di
ffi c
ult
for
dise
ases
suc
h as
m
alar
ia.
a)
rela
te t
he m
olec
ular
str
uctu
re o
f an
tibod
ies
to t
heir
func
tions
(see
2.3
b)
b)
outli
ne t
he h
ybrid
oma
met
hod
for
the
prod
uctio
n of
m
onoc
lona
l ant
ibod
ies
c)
outli
ne t
he u
se o
f m
onoc
lona
l ant
ibod
ies
in t
he d
iagn
osis
of
dis
ease
and
in t
he t
reat
men
t of
dis
ease
d)
dist
ingu
ish
betw
een
activ
e an
d pa
ssiv
e, n
atur
al a
nd
artifi
cia
l im
mun
ity a
nd e
xpla
in h
ow v
acci
natio
n ca
n co
ntro
l dis
ease
e)
disc
uss
the
reas
ons
why
vac
cina
tion
prog
ram
mes
hav
e er
adic
ated
sm
allp
ox, b
ut n
ot m
easl
es, t
uber
culo
sis
(TB
), m
alar
ia o
r ch
oler
a
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12 E
nerg
y an
d re
spira
tion
12.1
En
erg
y
A
TP is
the
uni
vers
al
ener
gy c
urre
ncy
as it
pro
vide
s th
e im
med
iate
sou
rce
of e
nerg
y fo
r ce
llula
r pr
oces
ses.
a)
outli
ne t
he n
eed
for
ener
gy in
livi
ng o
rgan
ism
s, a
s ill
ustr
ated
by
anab
olic
rea
ctio
ns, s
uch
as D
NA
rep
licat
ion
and
prot
ein
synt
hesi
s, a
ctiv
e tr
ansp
ort,
mov
emen
t an
d th
e m
aint
enan
ce o
f bo
dy t
empe
ratu
re
b)
desc
ribe
the
feat
ures
of
ATP
tha
t m
ake
it su
itabl
e as
the
un
iver
sal e
nerg
y cu
rren
cy
c)
expl
ain
that
ATP
is s
ynth
esis
ed in
sub
stra
te-li
nked
re
actio
ns in
gly
coly
sis
and
in t
he K
rebs
cyc
le
d)
outli
ne t
he r
oles
of
the
coen
zym
es N
AD
, FA
D a
nd
coen
zym
e A
in r
espi
ratio
n
e)
expl
ain
that
the
syn
thes
is o
f A
TP is
ass
ocia
ted
with
th
e el
ectr
on t
rans
port
cha
in o
n th
e m
embr
anes
of
mito
chon
dria
and
chl
orop
last
s (s
ee 1
2.2g
)
f)
expl
ain
the
rela
tive
ener
gy v
alue
s of
car
bohy
drat
e, li
pid
and
prot
ein
as r
espi
rato
ry s
ubst
rate
s an
d ex
plai
n w
hy
lipid
s ar
e pa
rtic
ular
ly e
nerg
y-ric
h
g)
defi n
e th
e te
rm r
espi
rato
ry q
uotie
nt (R
Q) a
nd d
eter
min
e R
Qs
from
equ
atio
ns f
or r
espi
ratio
n
h)
carr
y ou
t in
vest
igat
ions
, usi
ng s
impl
e re
spiro
met
ers,
to
det
erm
ine
the
RQ
of
germ
inat
ing
seed
s or
sm
all
inve
rteb
rate
s (e
.g. b
low
fl y la
rvae
)
12 E
nerg
y an
d re
spira
tion
12.2
Res
pir
atio
n
R
espi
ratio
n is
the
pr
oces
s w
here
by
ener
gy f
rom
co
mpl
ex o
rgan
ic
mol
ecul
es is
tr
ansf
erre
d to
ATP
.
a)
list
the
four
sta
ges
in a
erob
ic r
espi
ratio
n (g
lyco
lysi
s, li
nk
reac
tion,
Kre
bs c
ycle
and
oxi
dativ
e ph
osph
oryl
atio
n) a
nd
stat
e w
here
eac
h oc
curs
in e
ukar
yotic
cel
ls
b)
outli
ne g
lyco
lysi
s as
pho
spho
ryla
tion
of g
luco
se a
nd t
he
subs
eque
nt s
plitt
ing
of f
ruct
ose
1,6-
bisp
hosp
hate
(6C
) in
to t
wo
trio
se p
hosp
hate
mol
ecul
es, w
hich
are
the
n fu
rthe
r ox
idis
ed t
o py
ruva
te w
ith a
sm
all y
ield
of
ATP
and
re
duce
d N
AD
c)
expl
ain
that
, whe
n ox
ygen
is a
vaila
ble,
pyr
uvat
e is
co
nver
ted
into
ace
tyl (
2C) c
oenz
yme
A in
the
link
rea
ctio
n
Section 4: What you need to know
53Cambridge International AS and A Level Biology 9700
A L
evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
12 E
nerg
y an
d re
spira
tion
Th
is p
roce
ss o
f A
TP
synt
hesi
s us
ing
the
ener
gy in
pro
ton
grad
ient
s is
com
mon
to
bot
h re
spira
tion
and
phot
osyn
thes
is.
d)
outli
ne t
he K
rebs
cyc
le, e
xpla
inin
g th
at o
xalo
acet
ate
(a
4C c
ompo
und)
act
s as
an
acce
ptor
of
the
2C f
ragm
ent
from
ace
tyl c
oenz
yme
A t
o fo
rm c
itrat
e (a
6C
com
poun
d),
whi
ch is
rec
onve
rted
to
oxal
oace
tate
in a
ser
ies
of s
mal
l st
eps
e)
expl
ain
that
rea
ctio
ns in
the
Kre
bs c
ycle
invo
lve
deca
rbox
ylat
ion
and
dehy
drog
enat
ion
and
the
redu
ctio
n of
NA
D a
nd F
AD
f)
outli
ne t
he p
roce
ss o
f ox
idat
ive
phos
phor
ylat
ion
incl
udin
g th
e ro
le o
f ox
ygen
as
the
fi nal
ele
ctro
n ac
cept
or (n
o de
tails
of
the
carr
iers
are
req
uire
d)
g)
expl
ain
that
dur
ing
oxid
ativ
e ph
osph
oryl
atio
n:
• en
erge
tic e
lect
rons
rel
ease
ene
rgy
as t
hey
pass
th
roug
h th
e el
ectr
on t
rans
port
sys
tem
• th
e re
leas
ed e
nerg
y is
use
d to
tra
nsfe
r pr
oton
s ac
ross
the
inne
r m
itoch
ondr
ial m
embr
ane
• pr
oton
s re
turn
to
the
mito
chon
dria
l mat
rix b
y fa
cilit
ated
diff
usio
n th
roug
h A
TP s
ynth
ase
prov
idin
g en
ergy
for
ATP
syn
thes
is (d
etai
ls o
f A
TP s
ynth
ase
are
not
requ
ired)
h)
carr
y ou
t in
vest
igat
ions
to
dete
rmin
e th
e ef
fect
of
fact
ors
such
as
tem
pera
ture
and
sub
stra
te c
once
ntra
tion
on t
he
rate
of
resp
iratio
n of
yea
st u
sing
a r
edox
indi
cato
r (e
.g.
DC
PIP
or
met
hyle
ne b
lue)
i) de
scrib
e th
e re
latio
nshi
p be
twee
n st
ruct
ure
and
func
tion
of t
he m
itoch
ondr
ion
usin
g di
agra
ms
and
elec
tron
m
icro
grap
hs
Section 4: What you need to know
54 Cambridge International AS and A Level Biology 9700
A L
evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
12 E
nerg
y an
d re
spira
tion
S
ome
orga
nism
s an
d so
me
tissu
es
are
able
to
resp
ire
in b
oth
aero
bic
and
anae
robi
c co
nditi
ons.
W
hen
yeas
t an
d pl
ants
res
pire
un
der
anae
robi
c co
nditi
ons,
the
y pr
oduc
e et
hano
l an
d ca
rbon
dio
xide
as
end
-pro
duct
s;
mam
mal
ian
mus
cle
tissu
e pr
oduc
es
lact
ate
whe
n ox
ygen
is
in s
hort
sup
ply.
j) di
stin
guis
h be
twee
n re
spira
tion
in a
erob
ic a
nd a
naer
obic
co
nditi
ons
in m
amm
alia
n tis
sue
and
in y
east
cel
ls,
cont
rast
ing
the
rela
tive
ener
gy r
elea
sed
by e
ach
(a
deta
iled
acco
unt
of t
he t
otal
yie
ld o
f A
TP f
rom
the
ae
robi
c re
spira
tion
of g
luco
se is
not
req
uire
d)
k)
expl
ain
the
prod
uctio
n of
a s
mal
l yie
ld o
f A
TP f
rom
re
spira
tion
in a
naer
obic
con
ditio
ns in
yea
st a
nd in
m
amm
alia
n m
uscl
e tis
sue,
incl
udin
g th
e co
ncep
t of
ox
ygen
deb
t
l) ex
plai
n ho
w r
ice
is a
dapt
ed t
o gr
ow w
ith it
s ro
ots
subm
erge
d in
wat
er in
ter
ms
of t
oler
ance
to
etha
nol
from
res
pira
tion
in a
naer
obic
con
ditio
ns a
nd t
he p
rese
nce
of a
eren
chym
a
m)
carr
y ou
t in
vest
igat
ions
, usi
ng s
impl
e re
spiro
met
ers,
to
mea
sure
the
eff
ect
of t
empe
ratu
re o
n th
e re
spira
tion
rate
of
ger
min
atin
g se
eds
or s
mal
l inv
erte
brat
es
Section 4: What you need to know
55Cambridge International AS and A Level Biology 9700
A L
evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
13 P
hoto
synt
hesi
s13
.1 P
ho
tosy
nth
esis
as
an e
ner
gy
tran
sfer
p
roce
ss
Li
ght
ener
gy
abso
rbed
by
chlo
ropl
ast
pigm
ents
in t
he li
ght
depe
nden
t st
age
of p
hoto
synt
hesi
s is
use
d to
driv
e re
actio
ns o
f th
e lig
ht in
depe
nden
t st
age
that
pro
duce
co
mpl
ex o
rgan
ic
com
poun
ds.
C
hrom
atog
raph
y is
use
d to
iden
tify
chlo
ropl
ast
pigm
ents
an
d w
as a
lso
used
to
iden
tify
the
inte
rmed
iate
s in
the
C
alvi
n cy
cle.
a)
expl
ain
that
ene
rgy
tran
sfer
red
as A
TP a
nd r
educ
ed
NA
DP
fro
m t
he li
ght
depe
nden
t st
age
is u
sed
durin
g th
e lig
ht in
depe
nden
t st
age
(Cal
vin
cycl
e) o
f ph
otos
ynth
esis
to
pro
duce
com
plex
org
anic
mol
ecul
es
b)
stat
e th
e si
tes
of t
he li
ght
depe
nden
t an
d th
e lig
ht
inde
pend
ent
stag
es in
the
chl
orop
last
c)
desc
ribe
the
role
of
chlo
ropl
ast
pigm
ents
(chl
orop
hyll
a, c
hlor
ophy
ll b,
car
oten
e an
d xa
ntho
phyl
l) in
ligh
t ab
sorp
tion
in t
he g
rana
d)
inte
rpre
t ab
sorp
tion
and
actio
n sp
ectr
a of
chl
orop
last
pi
gmen
ts
e)
use
chro
mat
ogra
phy
to s
epar
ate
and
iden
tify
chlo
ropl
ast
pigm
ents
and
car
ry o
ut a
n in
vest
igat
ion
to c
ompa
re t
he
chlo
ropl
ast
pigm
ents
in d
iffer
ent
plan
ts (r
efer
ence
sho
uld
be m
ade
to R
f val
ues
in id
entifi
cat
ion)
f)
desc
ribe
the
light
dep
ende
nt s
tage
as
the
phot
oact
ivat
ion
of c
hlor
ophy
ll re
sulti
ng in
the
pho
toly
sis
of w
ater
and
the
tr
ansf
er o
f en
ergy
to
ATP
and
red
uced
NA
DP
(cyc
lic a
nd
non-
cycl
ic p
hoto
phos
phor
ylat
ion
shou
ld b
e de
scrib
ed in
ou
tline
onl
y)
g)
outli
ne t
he t
hree
mai
n st
ages
of
the
Cal
vin
cycl
e:
• fi x
atio
n of
car
bon
diox
ide
by c
ombi
natio
n w
ith
ribul
ose
bisp
hosp
hate
(RuB
P),
a 5C
com
poun
d, t
o yi
eld
two
mol
ecul
es o
f G
P (P
GA
), a
3C c
ompo
und
• th
e re
duct
ion
of G
P t
o tr
iose
pho
spha
te (T
P) i
nvol
ving
A
TP a
nd r
educ
ed N
AD
P
• th
e re
gene
ratio
n of
rib
ulos
e bi
spho
spha
te (R
uBP
) us
ing
ATP
h)
desc
ribe,
in o
utlin
e, t
he c
onve
rsio
n of
Cal
vin
cycl
e in
term
edia
tes
to c
arbo
hydr
ates
, lip
ids
and
amin
o ac
ids
and
thei
r us
es in
the
pla
nt c
ell
Section 4: What you need to know
56 Cambridge International AS and A Level Biology 9700
A L
evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
13 P
hoto
synt
hesi
s13
.2 I
nve
stig
atio
n o
f lim
itin
g f
acto
rs
E
nviro
nmen
tal
fact
ors
infl u
ence
th
e ra
te o
f ph
otos
ynth
esis
. In
vest
igat
ing
thes
e sh
ows
how
the
y ca
n be
man
aged
in
pro
tect
ed
envi
ronm
ents
use
d in
cro
p pr
oduc
tion.
a)
expl
ain
the
term
lim
iting
fac
tor
in r
elat
ion
to
phot
osyn
thes
is
b)
expl
ain
the
effe
cts
of c
hang
es in
ligh
t in
tens
ity, c
arbo
n di
oxid
e co
ncen
trat
ion
and
tem
pera
ture
on
the
rate
of
phot
osyn
thes
is
c)
expl
ain
how
an
unde
rsta
ndin
g of
lim
iting
fac
tors
is u
sed
to in
crea
se c
rop
yiel
ds in
pro
tect
ed e
nviro
nmen
ts, s
uch
as g
lass
hous
es
d)
carr
y ou
t an
inve
stig
atio
n to
det
erm
ine
the
effe
ct
of li
ght
inte
nsity
or
light
wav
elen
gth
on t
he r
ate
of
phot
osyn
thes
is u
sing
a r
edox
indi
cato
r (e
.g. D
CP
IP) a
nd a
su
spen
sion
of
chlo
ropl
asts
(the
Hill
rea
ctio
n)
e)
carr
y ou
t in
vest
igat
ions
on
the
effe
cts
of li
ght
inte
nsity
, ca
rbon
dio
xide
and
tem
pera
ture
on
the
rate
of
phot
osyn
thes
is u
sing
who
le p
lant
s, e
.g. a
quat
ic p
lant
s su
ch a
s El
odea
and
Cab
omba
13 P
hoto
synt
hesi
s13
.3 A
dap
tati
on
s fo
r p
ho
tosy
nth
esis
A
ll th
e st
ages
of
phot
osyn
thes
is
occu
r in
the
ch
loro
plas
t. S
ome
trop
ical
cro
ps h
ave
C4
met
abol
ism
an
d ad
apta
tions
to
max
imis
e ca
rbon
di
oxid
e fi x
atio
n.
a)
desc
ribe
the
rela
tions
hip
betw
een
stru
ctur
e an
d fu
nctio
n in
the
chl
orop
last
usi
ng d
iagr
ams
and
elec
tron
m
icro
grap
hs
b)
expl
ain
how
the
ana
tom
y an
d ph
ysio
logy
of
the
leav
es
of C
4 pl
ants
, suc
h as
mai
ze o
r so
rghu
m, a
re a
dapt
ed
for
high
rat
es o
f ca
rbon
fi xa
tion
at h
igh
tem
pera
ture
s in
te
rms
of:
• th
e sp
atia
l sep
arat
ion
of in
itial
car
bon
fi xat
ion
from
th
e lig
ht d
epen
dent
sta
ge (b
ioch
emic
al d
etai
ls o
f th
e C
4 pa
thw
ay a
re r
equi
red
in o
utlin
e on
ly)
• th
e hi
gh o
ptim
um t
empe
ratu
res
of t
he e
nzym
es
invo
lved
Section 4: What you need to know
57Cambridge International AS and A Level Biology 9700
A L
evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
14 H
omeo
stas
is14
.1 H
om
eost
asis
in
mam
mal
s
H
omeo
stas
is in
m
amm
als
requ
ires
com
plex
sys
tem
s to
mai
ntai
n in
tern
al
cond
ition
s ne
ar
cons
tant
.
Th
e ki
dney
s re
mov
e w
aste
s fr
om t
he
bloo
d an
d ar
e th
e ef
fect
ors
for
cont
rolli
ng t
he w
ater
po
tent
ial o
f th
e bl
ood.
a)
disc
uss
the
impo
rtan
ce o
f ho
meo
stas
is in
mam
mal
s an
d ex
plai
n th
e pr
inci
ples
of
hom
eost
asis
in t
erm
s of
in
tern
al a
nd e
xter
nal s
timul
i, re
cept
ors,
cen
tral
con
trol
, co
-ord
inat
ion
syst
ems,
eff
ecto
rs (m
uscl
es a
nd g
land
s)
b)
defi n
e th
e te
rm n
egat
ive
feed
back
and
exp
lain
how
it is
in
volv
ed in
hom
eost
atic
mec
hani
sms
c)
outli
ne t
he r
oles
of
the
nerv
ous
syst
em a
nd e
ndoc
rine
syst
em in
co-
ordi
natin
g ho
meo
stat
ic m
echa
nism
s,
incl
udin
g th
erm
oreg
ulat
ion,
osm
oreg
ulat
ion
and
the
cont
rol o
f bl
ood
gluc
ose
conc
entr
atio
n
d)
desc
ribe
the
deam
inat
ion
of a
min
o ac
ids
and
outli
ne t
he
form
atio
n of
ure
a in
the
ure
a cy
cle
(bio
chem
ical
det
ail o
f th
e ur
ea c
ycle
is n
ot r
equi
red)
e)
desc
ribe
the
gros
s st
ruct
ure
of t
he k
idne
y an
d th
e de
taile
d st
ruct
ure
of t
he n
ephr
on w
ith it
s as
soci
ated
bl
ood
vess
els
usin
g ph
otom
icro
grap
hs a
nd e
lect
ron
mic
rogr
aphs
f)
desc
ribe
how
the
pro
cess
es o
f ul
trafi
ltra
tion
and
sele
ctiv
e re
abso
rptio
n ar
e in
volv
ed w
ith t
he f
orm
atio
n of
ur
ine
in t
he n
ephr
on
g)
desc
ribe
the
role
s of
the
hyp
otha
lam
us, p
oste
rior
pitu
itary
, AD
H a
nd c
olle
ctin
g du
cts
in o
smor
egul
atio
n
h)
expl
ain
how
the
blo
od g
luco
se c
once
ntra
tion
is r
egul
ated
by
neg
ativ
e fe
edba
ck c
ontr
ol m
echa
nism
s, w
ith
refe
renc
e to
insu
lin a
nd g
luca
gon
i) ou
tline
the
rol
e of
cyc
lic A
MP
as
a se
cond
mes
seng
er
with
ref
eren
ce t
o th
e st
imul
atio
n of
live
r ce
lls b
y ad
rena
line
and
gluc
agon
Section 4: What you need to know
58 Cambridge International AS and A Level Biology 9700
A L
evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
14 H
omeo
stas
isj)
desc
ribe
the
thre
e m
ain
stag
es o
f ce
ll si
gnal
ling
in t
he
cont
rol o
f bl
ood
gluc
ose
by a
dren
alin
e as
fol
low
s:
• ho
rmon
e-re
cept
or in
tera
ctio
n at
the
cell
surf
ace
(see
4.
1c)
• fo
rmat
ion
of c
yclic
AM
P w
hich
bin
ds t
o ki
nase
pr
otei
ns
• an
enz
yme
casc
ade
invo
lvin
g ac
tivat
ion
of e
nzym
es
by p
hosp
hory
latio
n to
am
plify
the
sig
nal
k)
expl
ain
the
prin
cipl
es o
f op
erat
ion
of d
ip s
ticks
co
ntai
ning
glu
cose
oxi
dase
and
per
oxid
ase
enzy
mes
, an
d bi
osen
sors
tha
t ca
n be
use
d fo
r qu
antit
ativ
e m
easu
rem
ents
of
gluc
ose
in b
lood
and
urin
e
l) ex
plai
n ho
w u
rine
anal
ysis
is u
sed
in d
iagn
osis
with
re
fere
nce
to g
luco
se, p
rote
in a
nd k
eton
es
14 H
omeo
stas
is14
.2 H
om
eost
asis
in
pla
nts
S
tom
atal
ape
rtur
e is
reg
ulat
ed in
re
spon
se t
o th
e re
quire
men
ts
for
upta
ke o
f ca
rbon
dio
xide
for
ph
otos
ynth
esis
and
co
nser
ving
wat
er.
a)
expl
ain
that
sto
mat
a ha
ve d
aily
rhy
thm
s of
ope
ning
and
cl
osin
g an
d al
so r
espo
nd t
o ch
ange
s in
env
ironm
enta
l co
nditi
ons
to a
llow
diff
usio
n of
car
bon
diox
ide
and
regu
late
wat
er lo
ss b
y tr
ansp
iratio
n
b)
desc
ribe
the
stru
ctur
e an
d fu
nctio
n of
gua
rd c
ells
and
ex
plai
n th
e m
echa
nism
by
whi
ch t
hey
open
and
clo
se
stom
ata
c)
desc
ribe
the
role
of
absc
isic
aci
d in
the
clo
sure
of
stom
ata
durin
g tim
es o
f w
ater
str
ess
(the
rol
e of
cal
cium
io
ns a
s a
seco
nd m
esse
nger
sho
uld
be e
mph
asis
ed)
Section 4: What you need to know
59Cambridge International AS and A Level Biology 9700
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evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
15 C
ontr
ol a
nd
co-o
rdin
atio
n15
.1 C
on
tro
l an
d c
o-
ord
inat
ion
in
mam
mal
s
Th
e ne
rvou
s sy
stem
pro
vide
s fa
st c
omm
unic
atio
n be
twee
n re
cept
ors
and
effe
ctor
s.
Tr
ansm
issi
on
betw
een
neur
ones
ta
kes
plac
e at
sy
naps
es.
a)
com
pare
the
ner
vous
and
end
ocrin
e sy
stem
s as
co
mm
unic
atio
n sy
stem
s th
at c
o-or
dina
te r
espo
nses
to
chan
ges
in t
he in
tern
al a
nd e
xter
nal e
nviro
nmen
t (s
ee
14.1
a an
d 14
.1b)
b)
desc
ribe
the
stru
ctur
e of
a s
enso
ry n
euro
ne a
nd a
mot
or
neur
one
c)
outli
ne t
he r
oles
of
sens
ory
rece
ptor
cel
ls in
det
ectin
g st
imul
i and
stim
ulat
ing
the
tran
smis
sion
of
nerv
e im
puls
es in
sen
sory
neu
rone
s (a
sui
tabl
e ex
ampl
e is
the
ch
emor
ecep
tor
cell
foun
d in
hum
an t
aste
bud
s)
d)
desc
ribe
the
func
tions
of
sens
ory,
rel
ay a
nd m
otor
ne
uron
es in
a r
efl e
x ar
c
e)
desc
ribe
and
expl
ain
the
tran
smis
sion
of
an a
ctio
n po
tent
ial i
n a
mye
linat
ed n
euro
ne a
nd it
s in
itiat
ion
from
a r
estin
g po
tent
ial (
the
impo
rtan
ce o
f so
dium
an
d po
tass
ium
ions
in im
puls
e tr
ansm
issi
on s
houl
d be
em
phas
ised
)
f)
expl
ain
the
impo
rtan
ce o
f th
e m
yelin
she
ath
(sal
tato
ry
cond
uctio
n) in
det
erm
inin
g th
e sp
eed
of n
erve
impu
lses
an
d th
e re
frac
tory
per
iod
in d
eter
min
ing
thei
r fr
eque
ncy
g)
desc
ribe
the
stru
ctur
e of
a c
holin
ergi
c sy
naps
e an
d ex
plai
n ho
w it
fun
ctio
ns, i
nclu
ding
the
rol
e of
cal
cium
io
ns
h)
outli
ne t
he r
oles
of
syna
pses
in t
he n
ervo
us s
yste
m in
al
low
ing
tran
smis
sion
in o
ne d
irect
ion
and
in a
llow
ing
conn
ectio
ns b
etw
een
one
neur
one
and
man
y ot
hers
(s
umm
atio
n, f
acili
tatio
n an
d in
hibi
tory
syn
apse
s ar
e no
t re
quire
d)
i) de
scrib
e th
e ro
les
of n
euro
mus
cula
r ju
nctio
ns, t
rans
vers
e sy
stem
tub
ules
and
sar
copl
asm
ic r
etic
ulum
in s
timul
atin
g co
ntra
ctio
n in
str
iate
d m
uscl
e
Section 4: What you need to know
60 Cambridge International AS and A Level Biology 9700
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evel
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eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
15 C
ontr
ol a
nd
co-o
rdin
atio
n
Th
e en
docr
ine
syst
em is
a s
low
er
syst
em t
hat
cont
rols
lo
ng-t
erm
cha
nges
. Fe
rtili
ty m
ay b
e co
ntro
lled
by u
se o
f ho
rmon
es.
j) de
scrib
e th
e ul
tras
truc
ture
of
stria
ted
mus
cle
with
pa
rtic
ular
ref
eren
ce t
o sa
rcom
ere
stru
ctur
e
k)
expl
ain
the
slid
ing
fi lam
ent
mod
el o
f m
uscu
lar
cont
ract
ion
incl
udin
g th
e ro
les
of t
ropo
nin,
tro
pom
yosi
n,
calc
ium
ions
and
ATP
l) ex
plai
n th
e ro
les
of t
he h
orm
ones
FS
H, L
H, o
estr
ogen
an
d pr
oges
tero
ne in
con
trol
ling
chan
ges
in t
he o
vary
and
ut
erus
dur
ing
the
hum
an m
enst
rual
cyc
le
m)
outli
ne t
he b
iolo
gica
l bas
is o
f co
ntra
cept
ive
pills
co
ntai
ning
oes
trog
en a
nd/o
r pr
oges
tero
ne
15 C
ontr
ol a
nd
co-o
rdin
atio
n15
.2 C
on
tro
l an
d c
o-
ord
inat
ion
in p
lan
ts
P
lant
co-
ordi
natio
n sy
stem
s in
volv
e ra
pid
resp
onse
s as
in t
he c
ase
of
the
Ven
us fl
y tr
ap,
but
also
com
plex
in
tera
ctio
ns b
etw
een
plan
t gr
owth
re
gula
tors
, suc
h as
au
xin
and
gibb
erel
lin.
P
lant
s re
spon
d qu
ite d
iffer
ently
to
diff
eren
t co
ncen
trat
ions
of
pla
nt g
row
th
regu
lato
rs.
a)
desc
ribe
the
rapi
d re
spon
se o
f th
e V
enus
fl y
trap
to
stim
ulat
ion
of h
airs
on
the
lobe
s of
mod
ifi ed
leav
es a
nd
expl
ain
how
the
clo
sure
of
the
trap
is a
chie
ved
b)
expl
ain
the
role
of
auxi
n in
elo
ngat
ion
grow
th b
y st
imul
atin
g pr
oton
pum
ping
to
acid
ify c
ell w
alls
c)
desc
ribe
the
role
of
gibb
erel
lin in
the
ger
min
atio
n of
w
heat
or
barle
y
d)
expl
ain
the
role
of
gibb
erel
lin in
ste
m e
long
atio
n in
clud
ing
the
role
of
the
dom
inan
t al
lele
, Le,
tha
t co
des
for
a fu
nctio
ning
enz
yme
in t
he g
ibbe
relli
n sy
nthe
sis
path
way
, an
d th
e re
cess
ive
alle
le, l
e, t
hat
code
s fo
r a
non-
func
tiona
l enz
yme
Section 4: What you need to know
61Cambridge International AS and A Level Biology 9700
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evel
mat
eria
l
Top
icS
ub
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Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
16 In
herit
ed c
hang
e16
.1 P
assa
ge
of
info
rmat
ion
fro
m
par
ent
to o
ffsp
rin
g
D
iplo
id o
rgan
ism
s co
ntai
n pa
irs
of h
omol
ogou
s ch
rom
osom
es.
The
beha
viou
r of
mat
erna
l an
d pa
tern
al
chro
mos
omes
du
ring
mei
osis
ge
nera
tes
muc
h va
riatio
n am
ongs
t in
divi
dual
s of
the
ne
xt g
ener
atio
n.
a)
expl
ain
wha
t is
mea
nt b
y ho
mol
ogou
s pa
irs o
f ch
rom
osom
es
b)
expl
ain
the
mea
ning
s of
the
ter
ms
hapl
oid
and
dipl
oid
and
the
need
for
a r
educ
tion
divi
sion
(mei
osis
) prio
r to
fe
rtili
satio
n in
sex
ual r
epro
duct
ion
c)
outli
ne t
he r
ole
of m
eios
is in
gam
etog
enes
is in
hum
ans
and
in t
he f
orm
atio
n of
pol
len
grai
ns a
nd e
mbr
yo s
acs
in
fl ow
erin
g pl
ants
d)
desc
ribe,
with
the
aid
of
phot
omic
rogr
aphs
and
di
agra
ms,
the
beh
avio
ur o
f ch
rom
osom
es in
pla
nt a
nd
anim
al c
ells
dur
ing
mei
osis
, and
the
ass
ocia
ted
beha
viou
r of
the
nuc
lear
env
elop
e, c
ell s
urfa
ce m
embr
ane
and
the
spin
dle
(nam
es o
f th
e m
ain
stag
es a
re e
xpec
ted,
but
not
th
e su
b-di
visi
ons
of p
roph
ase)
e)
expl
ain
how
cro
ssin
g ov
er a
nd r
ando
m a
ssor
tmen
t of
ho
mol
ogou
s ch
rom
osom
es d
urin
g m
eios
is a
nd r
ando
m
fusi
on o
f ga
met
es a
t fe
rtili
satio
n le
ad t
o ge
netic
var
iatio
n in
clud
ing
the
expr
essi
on o
f ra
re, r
eces
sive
alle
les
Section 4: What you need to know
62 Cambridge International AS and A Level Biology 9700
A L
evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
16 In
herit
ed c
hang
e16
.2 T
he
role
s o
f g
enes
in
det
erm
inin
g t
he
ph
eno
typ
e
P
atte
rns
of
inhe
ritan
ce a
re
expl
aine
d by
usi
ng
gene
tic d
iagr
ams.
Th
e re
sults
of
gene
tic c
ross
es a
re
anal
ysed
sta
tistic
ally
us
ing
the
chi-
squa
red
test
.
S
tudi
es o
f hu
man
ge
netic
con
ditio
ns
have
rev
eale
d th
e lin
ks b
etw
een
gene
s, e
nzym
es a
nd
the
phen
otyp
e.
a)
expl
ain
the
term
s ge
ne, l
ocus
, alle
le, d
omin
ant,
re
cess
ive,
cod
omin
ant,
link
age,
tes
t cr
oss,
F1
and
F2,
phen
otyp
e, g
enot
ype,
hom
ozyg
ous
and
hete
rozy
gous
b)
use
gene
tic d
iagr
ams
to s
olve
pro
blem
s in
volv
ing
mon
ohyb
rid a
nd d
ihyb
rid c
ross
es, i
nclu
ding
tho
se
invo
lvin
g au
toso
mal
link
age,
sex
link
age,
cod
omin
ance
, m
ultip
le a
llele
s an
d ge
ne in
tera
ctio
ns (t
he t
erm
epi
stas
is
does
not
nee
d to
be
used
; kno
wle
dge
of t
he e
xpec
ted
ratio
for
var
ious
typ
es o
f ep
ista
sis
is n
ot r
equi
red.
The
fo
cus
is o
n pr
oble
m s
olvi
ng)
c)
use
gene
tic d
iagr
ams
to s
olve
pro
blem
s in
volv
ing
test
cr
osse
s
d)
use
the
chi-s
quar
ed t
est
to t
est
the
sign
ifi ca
nce
of
diff
eren
ces
betw
een
obse
rved
and
exp
ecte
d re
sults
(the
fo
rmul
a fo
r th
e ch
i-squ
ared
tes
t w
ill b
e pr
ovid
ed) (
see
Mat
hem
atic
al r
equi
rem
ents
)
e)
expl
ain
that
gen
e m
utat
ion
occu
rs b
y su
bstit
utio
n,
dele
tion
and
inse
rtio
n of
bas
e pa
irs in
DN
A a
nd o
utlin
e ho
w s
uch
mut
atio
ns m
ay a
ffec
t th
e ph
enot
ype
f)
outli
ne t
he e
ffec
ts o
f m
utan
t al
lele
s on
the
phe
noty
pe
in t
he f
ollo
win
g hu
man
con
ditio
ns: a
lbin
ism
, sic
kle
cell
anae
mia
, hae
mop
hilia
and
Hun
tingt
on’s
dis
ease
g)
expl
ain
the
rela
tions
hip
betw
een
gene
s, e
nzym
es a
nd
phen
otyp
e w
ith r
espe
ct t
o th
e ge
ne f
or t
yros
inas
e th
at is
in
volv
ed w
ith t
he p
rodu
ctio
n of
mel
anin
Section 4: What you need to know
63Cambridge International AS and A Level Biology 9700
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eria
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icS
ub
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Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
16 In
herit
ed c
hang
e16
.3 G
ene
con
tro
l
S
ome
gene
s ar
e tr
ansc
ribed
all
the
time
to p
rodu
ce
cons
titut
ive
prot
eins
; oth
ers
are
only
‘sw
itche
d on
’ whe
n th
eir
prot
ein
prod
ucts
are
re
quire
d.
a)
dist
ingu
ish
betw
een
stru
ctur
al a
nd r
egul
ator
y ge
nes
and
betw
een
repr
essi
ble
and
indu
cibl
e en
zym
es
b)
expl
ain
gene
tic c
ontr
ol o
f pr
otei
n pr
oduc
tion
in a
pr
okar
yote
usi
ng t
he la
c op
eron
c)
expl
ain
the
func
tion
of t
rans
crip
tion
fact
ors
in g
ene
expr
essi
on in
euk
aryo
tes
d)
expl
ain
how
gib
bere
llin
activ
ates
gen
es b
y ca
usin
g th
e br
eakd
own
of D
ELL
A p
rote
in r
epre
ssor
s, w
hich
nor
mal
ly
inhi
bit
fact
ors
that
pro
mot
e tr
ansc
riptio
n
17 S
elec
tion
and
evol
utio
n17
.1 V
aria
tio
n
Th
e va
riatio
n th
at e
xist
s w
ithin
a
spec
ies
is
cate
goris
ed a
s co
ntin
uous
and
di
scon
tinuo
us.
The
envi
ronm
ent
has
cons
ider
able
in
fl uen
ce o
n th
e ex
pres
sion
of
fea
ture
s th
at
show
con
tinuo
us
(or
quan
titat
ive)
va
riatio
n.
a)
desc
ribe
the
diff
eren
ces
betw
een
cont
inuo
us a
nd
disc
ontin
uous
var
iatio
n an
d ex
plai
n th
e ge
netic
bas
is o
f co
ntin
uous
(man
y, a
dditi
ve g
enes
con
trol
a c
hara
cter
istic
) an
d di
scon
tinuo
us v
aria
tion
(one
or
few
gen
es c
ontr
ol
a ch
arac
teris
tic) (
exam
ples
fro
m 1
6.2f
may
be
used
to
illus
trat
e di
scon
tinuo
us v
aria
tion;
hei
ght
and
mas
s m
ay
be u
sed
as e
xam
ples
of
cont
inuo
us v
aria
tion)
b)
expl
ain,
with
exa
mpl
es, h
ow t
he e
nviro
nmen
t m
ay a
ffec
t th
e ph
enot
ype
of p
lant
s an
d an
imal
s
c)
use
the
t-tes
t to
com
pare
the
var
iatio
n of
tw
o di
ffer
ent
popu
latio
ns (s
ee M
athe
mat
ical
req
uire
men
ts)
d)
expl
ain
why
gen
etic
var
iatio
n is
impo
rtan
t in
sel
ectio
n
Section 4: What you need to know
64 Cambridge International AS and A Level Biology 9700
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evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
17 S
elec
tion
and
evol
utio
n17
.2 N
atu
ral a
nd
ar
tifi
cial
sel
ecti
on
P
opul
atio
ns o
f or
gani
sms
have
the
po
tent
ial t
o pr
oduc
e la
rge
num
bers
of
offs
prin
g, y
et t
heir
num
bers
rem
ain
fairl
y co
nsta
nt y
ear
afte
r ye
ar.
H
uman
s us
e se
lect
ive
bree
ding
(a
rtifi
cial
sel
ectio
n)
to im
prov
e fe
atur
es
in o
rnam
enta
l pl
ants
, cro
p pl
ants
, do
mes
ticat
ed
anim
als
and
lives
tock
.
a)
expl
ain
that
nat
ural
sel
ectio
n oc
curs
as
popu
latio
ns h
ave
the
capa
city
to
prod
uce
man
y of
fspr
ing
that
com
pete
fo
r re
sour
ces;
in t
he ‘s
trug
gle
for
exis
tenc
e’ o
nly
the
indi
vidu
als
that
are
bes
t ad
apte
d su
rviv
e to
bre
ed a
nd
pass
on
thei
r al
lele
s to
the
nex
t ge
nera
tion
b)
expl
ain,
with
exa
mpl
es, h
ow e
nviro
nmen
tal f
acto
rs c
an
act
as s
tabi
lisin
g, d
isru
ptiv
e an
d di
rect
iona
l for
ces
of
natu
ral s
elec
tion
c)
expl
ain
how
sel
ectio
n, t
he f
ound
er e
ffec
t an
d ge
netic
dr
ift m
ay a
ffec
t al
lele
fre
quen
cies
in p
opul
atio
ns
d)
use
the
Har
dy–W
einb
erg
prin
cipl
e to
cal
cula
te a
llele
, ge
noty
pe a
nd p
heno
type
fre
quen
cies
in p
opul
atio
ns a
nd
expl
ain
situ
atio
ns w
hen
this
prin
cipl
e do
es n
ot a
pply
e)
desc
ribe
how
sel
ectiv
e br
eedi
ng (a
rtifi
cial
sel
ectio
n) h
as
been
use
d to
impr
ove
the
milk
yie
ld o
f da
iry c
attle
f)
outli
ne t
he f
ollo
win
g ex
ampl
es o
f cr
op im
prov
emen
t by
se
lect
ive
bree
ding
:
• th
e in
trod
uctio
n of
dis
ease
res
ista
nce
to v
arie
ties
of
whe
at a
nd r
ice
• th
e in
corp
orat
ion
of m
utan
t al
lele
s fo
r gi
bber
ellin
sy
nthe
sis
into
dw
arf
varie
ties
so in
crea
sing
yie
ld b
y ha
ving
a g
reat
er p
ropo
rtio
n of
ene
rgy
put
into
gra
in
• in
bree
ding
and
hyb
ridis
atio
n to
pro
duce
vig
orou
s,
unifo
rm v
arie
ties
of m
aize
Section 4: What you need to know
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ub
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Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
17 S
elec
tion
and
evol
utio
n17
.3 E
volu
tio
n
Is
olat
ing
mec
hani
sms
can
lead
to
the
accu
mul
atio
n of
di
ffer
ent
gene
tic
info
rmat
ion
in
popu
latio
ns,
pote
ntia
lly le
adin
g to
ne
w s
peci
es.
O
ver
prol
onge
d pe
riods
of
time,
so
me
spec
ies
have
re
mai
ned
virt
ually
un
chan
ged,
oth
ers
have
cha
nged
si
gnifi
cant
ly a
nd
man
y ha
ve b
ecom
e ex
tinct
.
a)
stat
e th
e ge
nera
l the
ory
of e
volu
tion
that
org
anis
ms
have
ch
ange
d ov
er t
ime
b)
disc
uss
the
mol
ecul
ar e
vide
nce
that
rev
eals
sim
ilarit
ies
betw
een
clos
ely
rela
ted
orga
nism
s w
ith r
efer
ence
to
mito
chon
dria
l DN
A a
nd p
rote
in s
eque
nce
data
c)
expl
ain
how
spe
ciat
ion
may
occ
ur a
s a
resu
lt of
ge
ogra
phic
al s
epar
atio
n (a
llopa
tric
spe
ciat
ion)
, and
ec
olog
ical
and
beh
avio
ural
sep
arat
ion
(sym
patr
ic
spec
iatio
n)
d)
expl
ain
the
role
of
pre-
zygo
tic a
nd p
ost-
zygo
tic is
olat
ing
mec
hani
sms
in t
he e
volu
tion
of n
ew s
peci
es
e)
expl
ain
why
org
anis
ms
beco
me
extin
ct, w
ith r
efer
ence
to
clim
ate
chan
ge, c
ompe
titio
n, h
abita
t lo
ss a
nd k
illin
g by
hu
man
s
Section 4: What you need to know
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evel
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eria
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ub
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Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
18 B
iodi
vers
ity,
clas
sifi c
atio
n an
d co
nser
vatio
n
18.1
Bio
div
ersi
ty
B
iodi
vers
ity is
muc
h m
ore
than
a li
st o
f al
l the
spe
cies
in a
pa
rtic
ular
are
a.
a)
defi n
e th
e te
rms
spec
ies,
eco
syst
em a
nd n
iche
b)
expl
ain
that
bio
dive
rsity
is c
onsi
dere
d at
thr
ee d
iffer
ent
leve
ls:
• va
riatio
n in
eco
syst
ems
or h
abita
ts
• th
e nu
mbe
r of
spe
cies
and
the
ir re
lativ
e ab
unda
nce
• ge
netic
var
iatio
n w
ithin
eac
h sp
ecie
s
c)
expl
ain
the
impo
rtan
ce o
f ra
ndom
sam
plin
g in
de
term
inin
g th
e bi
odiv
ersi
ty o
f an
are
a
d)
use
suita
ble
met
hods
, suc
h as
fra
me
quad
rats
, lin
e tr
anse
cts,
bel
t tr
anse
cts
and
mar
k-re
leas
e-re
capt
ure,
to
asse
ss t
he d
istr
ibut
ion
and
abun
danc
e of
org
anis
ms
in a
lo
cal a
rea
e)
use
Spe
arm
an’s
ran
k co
rrel
atio
n an
d P
ears
on’s
line
ar
corr
elat
ion
to a
naly
se t
he r
elat
ions
hips
bet
wee
n th
e di
strib
utio
n an
d ab
unda
nce
of s
peci
es a
nd a
biot
ic o
r bi
otic
fac
tors
f)
use
Sim
pson
’s In
dex
of D
iver
sity
(D) t
o ca
lcul
ate
the
biod
iver
sity
of
a ha
bita
t, u
sing
the
for
mul
a
D
= 1
–2
Nn ``
jj
/ a
nd s
tate
the
sig
nifi c
ance
of
diff
eren
t
va
lues
of
D
Section 4: What you need to know
67Cambridge International AS and A Level Biology 9700
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evel
mat
eria
l
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icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
18 B
iodi
vers
ity,
clas
sifi c
atio
n an
d co
nser
vatio
n
18.2
Cla
ssifi
cati
on
O
rgan
ism
s st
udie
d lo
cally
may
be
used
to
show
ho
w h
iera
rchi
cal
clas
sifi c
atio
n sy
stem
s ar
e or
gani
sed.
a)
desc
ribe
the
clas
sifi c
atio
n of
spe
cies
into
the
tax
onom
ic
hier
arch
y of
dom
ain,
kin
gdom
, phy
lum
, cla
ss, o
rder
, fa
mily
, gen
us a
nd s
peci
es
b)
outli
ne t
he c
hara
cter
istic
fea
ture
s of
the
thr
ee d
omai
ns
Arc
haea
, Bac
teria
and
Euk
arya
c)
outli
ne t
he c
hara
cter
istic
fea
ture
s of
the
kin
gdom
s P
roto
ctis
ta, F
ungi
, Pla
ntae
and
Ani
mal
ia
d)
expl
ain
why
viru
ses
are
not
incl
uded
in t
he t
hree
dom
ain
clas
sifi c
atio
n an
d ou
tline
how
the
y ar
e cl
assi
fi ed,
lim
ited
to t
ype
of n
ucle
ic a
cid
(RN
A o
r D
NA
) and
whe
ther
the
se
are
sing
le s
tran
ded
or d
oubl
e st
rand
ed
Section 4: What you need to know
68 Cambridge International AS and A Level Biology 9700
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evel
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eria
l
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icS
ub
-to
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Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
18 B
iodi
vers
ity,
clas
sifi c
atio
n an
d co
nser
vatio
n
18.3
Co
nse
rvat
ion
M
aint
aini
ng
biod
iver
sity
is
impo
rtan
t fo
r m
any
reas
ons.
A
ctio
ns t
o m
aint
ain
biod
iver
sity
mus
t be
tak
en a
t lo
cal,
natio
nal a
nd g
loba
l le
vels
.
It
is im
port
ant
to c
onse
rve
ecos
yste
ms
as w
ell
as in
divi
dual
spe
cies
.
a)
disc
uss
the
thre
ats
to t
he b
iodi
vers
ity o
f aq
uatic
and
te
rres
tria
l eco
syst
ems
(see
18.
1b)
b)
disc
uss
the
reas
ons
for
the
need
to
mai
ntai
n bi
odiv
ersi
ty
c)
disc
uss
met
hods
of
prot
ectin
g en
dang
ered
spe
cies
, in
clud
ing
the
role
s of
zoo
s, b
otan
ic g
arde
ns, c
onse
rved
ar
eas
(nat
iona
l par
ks a
nd m
arin
e pa
rks)
, ‘fr
ozen
zoo
s’ a
nd
seed
ban
ks
d)
disc
uss
met
hods
of
assi
sted
rep
rodu
ctio
n, in
clud
ing
IVF,
em
bryo
tra
nsfe
r an
d su
rrog
acy,
use
d in
the
con
serv
atio
n of
end
ange
red
mam
mal
s
e)
disc
uss
the
use
of c
ullin
g an
d co
ntra
cept
ive
met
hods
to
prev
ent
over
popu
latio
n of
pro
tect
ed a
nd n
on-p
rote
cted
sp
ecie
s
f)
use
exam
ples
to
expl
ain
the
reas
ons
for
cont
rolli
ng a
lien
spec
ies
g)
disc
uss
the
role
s of
non
-gov
ernm
enta
l org
anis
atio
ns,
such
as
the
Wor
ld W
ide
Fund
for
Nat
ure
(WW
F) a
nd t
he
Con
vent
ion
on In
tern
atio
nal T
rade
in E
ndan
gere
d S
peci
es
of W
ild F
auna
and
Flo
ra (C
ITE
S),
in lo
cal a
nd g
loba
l co
nser
vatio
n
h)
outli
ne h
ow d
egra
ded
habi
tats
may
be
rest
ored
with
re
fere
nce
to lo
cal o
r re
gion
al e
xam
ples
Section 4: What you need to know
69Cambridge International AS and A Level Biology 9700
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evel
mat
eria
l
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icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
19 G
enet
ic te
chno
logy
19.1
Pri
nci
ple
s o
f g
enet
ic t
ech
no
log
y
G
enet
ic e
ngin
eerin
g in
volv
es t
he
man
ipul
atio
n of
na
tura
lly o
ccur
ring
proc
esse
s an
d en
zym
es.
G
enom
e se
quen
cing
gi
ves
info
rmat
ion
abou
t th
e lo
catio
n of
ge
nes
and
prov
ides
ev
iden
ce f
or t
he
evol
utio
nary
link
s be
twee
n or
gani
sms.
a)
defi n
e th
e te
rm r
ecom
bina
nt D
NA
b)
expl
ain
that
gen
etic
eng
inee
ring
invo
lves
the
ext
ract
ion
of g
enes
fro
m o
ne o
rgan
ism
, or
the
synt
hesi
s of
gen
es,
in o
rder
to
plac
e th
em in
ano
ther
org
anis
m (o
f th
e sa
me
or a
noth
er s
peci
es) s
uch
that
the
rec
eivi
ng o
rgan
ism
ex
pres
ses
the
gene
pro
duct
c)
desc
ribe
the
prin
cipl
es o
f th
e po
lym
eras
e ch
ain
reac
tion
(PC
R) t
o cl
one
and
ampl
ify D
NA
(the
rol
e of
Taq
po
lym
eras
e sh
ould
be
emph
asis
ed)
d)
desc
ribe
and
expl
ain
how
gel
ele
ctro
phor
esis
is u
sed
to a
naly
se p
rote
ins
and
nucl
eic
acid
s, a
nd t
o di
stin
guis
h be
twee
n th
e al
lele
s of
a g
ene
(lim
ited
to t
he s
epar
atio
n of
pol
ypep
tides
and
the
sep
arat
ion
of D
NA
fra
gmen
ts c
ut
with
res
tric
tion
endo
nucl
ease
s)
e)
desc
ribe
the
prop
ertie
s of
pla
smid
s th
at a
llow
the
m t
o be
us
ed in
gen
e cl
onin
g
f)
expl
ain
why
pro
mot
ers
and
othe
r co
ntro
l seq
uenc
es m
ay
have
to
be t
rans
ferr
ed a
s w
ell a
s th
e de
sire
d ge
ne
g)
expl
ain
the
use
of g
enes
for
fl uo
resc
ent
or e
asily
sta
ined
su
bsta
nces
as
mar
kers
in g
ene
tech
nolo
gy
h)
expl
ain
the
role
s of
res
tric
tion
endo
nucl
ease
s, r
ever
se
tran
scrip
tase
and
liga
ses
in g
enet
ic e
ngin
eerin
g
i) ex
plai
n, in
out
line,
how
mic
roar
rays
are
use
d in
the
an
alys
is o
f ge
nom
es a
nd in
det
ectin
g m
RN
A in
stu
dies
of
gene
exp
ress
ion
Section 4: What you need to know
70 Cambridge International AS and A Level Biology 9700
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evel
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icS
ub
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Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
19 G
enet
ic te
chno
logy
19.2
Gen
etic
tec
hn
olo
gy
app
lied
to
med
icin
ea)
de
fi ne
the
term
bio
info
rmat
ics
b)
outli
ne t
he r
ole
of b
ioin
form
atic
s fo
llow
ing
the
sequ
enci
ng o
f ge
nom
es, s
uch
as t
hose
of
hum
ans
and
para
site
s, e
.g. P
lasm
odiu
m (d
etai
ls o
f m
etho
ds o
f D
NA
se
quen
cing
are
not
req
uire
d)
c)
expl
ain
the
adva
ntag
es o
f pr
oduc
ing
hum
an p
rote
ins
by
reco
mbi
nant
DN
A t
echn
ique
s (r
efer
ence
sho
uld
be m
ade
to s
ome
suita
ble
exam
ples
, suc
h as
insu
lin, f
acto
r V
III f
or
the
trea
tmen
t of
hae
mop
hilia
and
ade
nosi
ne d
eam
inas
e fo
r tr
eatin
g se
vere
com
bine
d im
mun
odefi
cie
ncy
(SC
ID))
d)
outli
ne t
he a
dvan
tage
s of
scr
eeni
ng f
or g
enet
ic
cond
ition
s (r
efer
ence
may
be
mad
e to
tes
ts f
or s
peci
fi c
gene
s su
ch a
s th
ose
for
brea
st c
ance
r, B
RC
A1
and
BR
CA
2, a
nd g
enes
for
hae
mop
hilia
, sic
kle
cell
anae
mia
, H
untin
gton
’s d
isea
se a
nd c
ystic
fi br
osis
)
e)
outli
ne h
ow g
enet
ic d
isea
ses
can
be t
reat
ed w
ith
gene
the
rapy
and
dis
cuss
the
cha
lleng
es in
cho
osin
g ap
prop
riate
vec
tors
, suc
h as
viru
ses,
lipo
som
es a
nd
nake
d D
NA
(ref
eren
ce m
ay b
e m
ade
to S
CID
, inh
erite
d ey
e di
seas
es a
nd c
ystic
fi br
osis
)
f)
disc
uss
the
soci
al a
nd e
thic
al c
onsi
dera
tions
of
usin
g ge
ne t
estin
g an
d ge
ne t
hera
py in
med
icin
e (r
efer
ence
sh
ould
be
mad
e to
gen
etic
con
ditio
ns f
or w
hich
tr
eatm
ents
exi
st a
nd w
here
non
e ex
ist,
als
o to
IVF,
em
bryo
bio
psy
and
pres
elec
tion
and
to t
hera
peut
ic
abor
tions
)
g)
outli
ne t
he u
se o
f P
CR
and
DN
A t
estin
g in
for
ensi
c m
edic
ine
and
crim
inal
inve
stig
atio
ns
Section 4: What you need to know
71Cambridge International AS and A Level Biology 9700
A L
evel
mat
eria
l
Top
icS
ub
-to
pic
Yo
u s
ho
uld
be
able
to
:C
hec
klis
tC
om
men
ts
19 G
enet
ic te
chno
logy
19.3
Gen
etic
ally
m
od
ifi ed
o
rgan
ism
s in
ag
ricu
ltu
re
Th
e ab
ility
to
man
ipul
ate
gene
s ha
s m
any
pote
ntia
l ben
efi t
s in
agr
icul
ture
, but
th
e im
plic
atio
ns o
f re
leas
ing
gene
tical
ly
mod
ifi ed
org
anis
ms
(GM
Os)
into
the
en
viro
nmen
t ar
e su
bjec
t to
muc
h pu
blic
deb
ate
in
som
e co
untr
ies.
a)
expl
ain
the
sign
ifi ca
nce
of g
enet
ic e
ngin
eerin
g in
im
prov
ing
the
qual
ity a
nd y
ield
of
crop
pla
nts
and
lives
tock
in s
olvi
ng t
he d
eman
d fo
r fo
od in
the
wor
ld, e
.g.
Bt
mai
ze, v
itam
in A
enh
ance
d ric
e (G
olde
n ric
eTM) a
nd
GM
sal
mon
b)
outli
ne t
he w
ay in
whi
ch t
he p
rodu
ctio
n of
cro
ps s
uch
as m
aize
, cot
ton,
tob
acco
and
oil
seed
rap
e m
ay b
e in
crea
sed
by u
sing
var
ietie
s th
at a
re g
enet
ical
ly m
odifi
ed
for
herb
icid
e re
sist
ance
and
inse
ct r
esis
tanc
e
c)
disc
uss
the
ethi
cal a
nd s
ocia
l im
plic
atio
ns o
f us
ing
gene
tical
ly m
odifi
ed o
rgan
ism
s (G
MO
s) in
foo
d pr
oduc
tion
Section 5: Useful websites
72 Cambridge International AS and A Level Biology 9700
Section 5: Useful websites
These web pages can be used as useful resources to help you study for your Cambridge International AS and A Level Biology.
www.biozone.co.ukThis is an excellent gateway to many other websites with useful material to support topics in both AS and A Level. Click on Biolinks Database on the home page.
www.s-cool.co.uk Many web pages of structured notes to help you with most of the topics at AS and A Level. There is plenty of useful advice on revision.
users.rcn.com/jkimball.ma.ultranet/BiologyPages/ Kimball’s Biology Pages: an American online textbook. This is very well organised so that you can fi nd information easily.
www.biotopics.co.uk/A private web site run by a teacher in the UK. It has many useful resources and links.
www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.htmlThis is the table of contents for Mike Farabee’s online textbook of biology. Many topics from the AS and A Level syllabus are covered.
www.bozemanscience.com/science-videos/You will fi nd many videos on biological topics on YouTube; this site has video lessons that support Advanced Placement (AP), but are just as suitable for A Level.
www.cellsalive.com An interactive website with lots of good images and animations to help you with cell biology, microscopy, microbiology and the immunity section in AS Level.
www.biology.arizona.edu/default.html The Biology Project from the University of Arizona. This has many excellent animations, tutorials and online tests.
www.dnaftb.org/dnaftb/ DNA from the beginning: online tutorials on the structure of DNA, genetics, and genetic organisation and control. There are 41 different topics including easy-to-follow explanations of key experiments in the history of genetics from Mendel onwards.
www-medlib.med.utah.edu/kw/pharm/hyper_heart1.html An excellent site that shows you what happens during the cardiac cycle. You need Adobe Shockwave to run the animation.
www.who.ch This is the website of the World Health Organization. Use this website to fi nd up-to-date information on infectious and non-infectious diseases.
Section 5: Useful websites
73Cambridge International AS and A Level Biology 9700
www.cdc.gov/This is the website of the Centers for Disease Control in the USA. You can also use this website for up-to-date information about diseases.
www.mbgnet.net/bioplants/main.htmlThe biology of plants – the website of the Missouri Botanic Gardens. A simple introduction to plant science.
images.botany.org/This site has many useful images of plant biology to complement the website above.
www.bu.edu/histology/m/index.htmThe Histology Learning System has many electron micrographs of animal cells (see the section called Ultrastructure of the Cell) and photomicrographs of tissues.
www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMAtlas.htmlThis site has many excellent transmission electron micrographs – all in black and white, not false colour as in many textbooks. Electron micrographs in examination papers are always printed in black and white and you should get used to interpreting them.
www.chemguideforcie.co.uk/index.htmlThis is a site that supports Cambridge International AS and A Level Chemistry. You may fi nd this useful for Section 2 on biological molecules if you are unsure about some basic chemistry.
www.rsc.org/Education/Teachers/Resources/cfb/Chemistry for Biologists from the Royal Society of Chemistry which will also help you with Section B on biological molecules. You can visualise molecules on this website with Jmol the open access molecular visualisation application.
www.johnkyrk.com/This site has animations for a variety of topics in your course, such as DNA replication, transcription, translation, mitosis, meiosis, respiration and photosynthesis.
highered.mcgraw-hill.com/sites/dl/free/0072437316/120060/ravenanimation.htmlThe animations that support the American textbook: Biology by Raven and Johnson are highly recommended.
www.sumanasinc.com/webcontent/animation.htmlThis site has animations for a wide variety of topics in the syllabus.
learn.genetics.utah.edu/This is the website of Learn GeneticsTM, the Genetic Science Learning Center of the University of Utah. This will help you with the ethics of modern genetics as well as much else.
www.yourgenome.org/This is the educational website of the Wellcome Trust’s Sanger Institute in Cambridge, UK. This will bring you up-to-date on many aspects of your course.
www.wellcome.ac.uk/Education-resources/Teaching-and-education/Big-Picture/index.htmOnline resources for post-16 biology courses from the Wellcome Trust in the UK.
www.beep.ac.uk/The Bioethics Education Project based at Bristol in the UK. Many useful resources for the ethical issues discussed in the A Level course.
Section 5: Useful websites
74 Cambridge International AS and A Level Biology 9700
library.med.utah.edu/WebPath/This site has many useful images of human anatomy and histology.
evolution.berkeley.edu/Many resources on evolution from the University of California Museum of Palaeontology.
www.nobelprize.org/The Nobel Prize website has many useful educational resources as well as information about past Nobel Prize winners, such as Francis Watson, James Crick, Melvin Calvin and Hans Krebs, and their discoveries.
www.wellcometreeofl ife.org/The Interactive Tree of Life from the Wellcome Trust. this will help you with biodiversity in the A Level course.
www.iucn.org/The website of the International Union for Conservation of Nature (IUCN). This holds lots of information about biodiversity and conservation. The IUCN has a database of many endangered species showing their conservation status at www.iucnredlist.org/
www.kew.org/science-conservation/index.htmThese are the Science and Conservation pages of the website of the Royal Botanic Gardens at Kew, London.
www.zsl.org/conservation/The conservation pages of the website of ZSL – the Zoological Society of London.
textbookofbacteriology.net/themicrobialworld/homepage.htmlThe New Microbial World. Although designed for university students, you will fi nd useful background material on the microorganisms you study in sections on prokaryote structure, disease, classifi cation and biotechnology.
Section 6: Appendices
75Cambridge International AS and A Level Biology 9700
Section 6: Appendices
Mathematical skillsThis is a checklist of the mathematical skills you need for your biology examination. You should tick each box in the checklist when you know that you have learned the skill.
Ask your teacher to explain any skill you are unsure about. The ‘Comments’ column is for extra notes and examples.
You can use a calculator for all the examination papers. If your calculator is one that can be programmed, you should make sure that any information in it is removed before the examination.
You should be able to: Checklist Comments
At AS Level and A Level
• recognise and use expressions in decimal and standard form
• use a calculator for addition, subtraction, multiplication and division,
fi nding the arithmetical mean and to fi nd and use x, x2, x1 , log10x and
Ïłx
• understand and use the symbols <, >, Δ, ≈, /, ∞, Σ
• understand and use the prefi xes: giga (G), mega (M), kilo (k), milli (m), micro (µ), and nano (n)
• calculate magnifi cations and actual sizes
• take account of accuracy in numerical work and handle calculations so that signifi cant fi gures are neither lost unnecessarily nor carried beyond what is justifi ed
• make estimations of the results of calculations (without using a calculator)
• use a spreadsheet program for collating, analysing and presenting data
• recognise and use ratios
• calculate percentages and percentage changes
• express errors in experimental work as percentage errors
• calculate areas of right-angled and isosceles triangles, circumferences and areas of circles, areas and volumes of cylinders, rectangles and rectangular blocks
• translate information between graphical, numerical, and algebraic forms
• construct and interpret frequency distributions and diagrams, such as pie charts, bar charts and histograms
• understand when information should be presented in the form of a bar chart, histogram or line graph
Section 6: Appendices
76 Cambridge International AS and A Level Biology 9700
You should be able to: Checklist Comments
• select appropriate variables and scales for graph plotting using standard 2 mm square graph paper
• recognise when it is appropriate to join the points on a graph with straight ruled lines and when it is appropriate to use a line (straight or curved) of best fi t
• calculate the rate of change from a line on a graph
• draw and use the slope of a tangent to a curve as a means to obtain the rate of change.
At A Level only
• have suffi cient understanding of probability to understand genetic ratios
• understand the principles of sampling as applied to biological situations and data
• understand the importance of chance when interpreting data
• use the Petersen or Lincoln index to calculate an estimate of population size using mark-release-recapture data and the formula:
N = n1 × n2
m2
N = population estimate
n1 = number of marked individuals released
n2 = number of individuals (both marked and unmarked) captured
m2 = number of marked individuals recaptured
• calculate Simpson’s Index of Diversity (D) using the formula:
D = 1– nNN ON OΣ
2
n = number of individuals of each type present in the sample (types may be species and/or higher taxa such as genera, families, etc.)
N = the total number of all individuals of all types
• calculate standard deviation and standard error
• understand the benefi ts of using standard error and 95% confi dence intervals (95%CI) to make statements about data and to use as error bars on graphs
• understand the difference between correlation and causation; use Spearman’s rank correlation and Pearson’s linear correlation to test for correlation
• use the χ2 test and the t-test
• use a spreadsheet program for analysing and presenting data, making calculations and carrying out statistical tests.
Section 6: Appendices
77Cambridge International AS and A Level Biology 9700
More information about the examinationThe command words used in biology examination papers are given in the sections that follow. It is very important that you know and understand all of them before you take your examination. You should ask your teacher to explain anything that you are unsure about.
NumbersThe decimal point will be placed on the line, e.g. 52.35.
Numbers from 1000 to 9999 will be printed without commas or spaces.
Numbers greater than or equal to 10 000 will be printed without commas. A space will be left between each group of three whole numbers, e.g. 4 256 789.
UnitsThe International System of units or, where appropriate, units approved by the BIPM for use with the SI (e.g. minute) will be used. Units will be indicated in the singular not in the plural, e.g. 28 kg.
(a) SI units commonly used in biology
N.B. Care should be taken in the use of mass and weight. In most biological contexts, the term mass is correct, e.g. dry mass, biomass.
Quantity Name of unit Symbol for unitlength kilometre km metre m centimetre cm millimetre mm micrometer µm
mass tonne (1000 kg) (no symbol) kilogram kg gram g milligram mg microgram µg
time year y day d hour h minute min second samount of substance mole mol
(b) Derived SI units
energy kilojoule kJ joule J (the calorie is obsolete)
Section 6: Appendices
78 Cambridge International AS and A Level Biology 9700
(c) Recommended units for area, volume and density are listed below.
area hectare = 104 m2 ha square metre m2
square decimetre dm2
square centimetre cm2
square millimetre mm2
volume cubic kilometre km3
cubic metre m3
cubic decimetre (preferred to litre) dm3
litre dm3 (not l) cubic centimetre cm3 (not ml) cubic millimetre mm3
density kilogram per cubic metre or kg m–3
gram per cubic centimetre or g cm–3
(d) Use of Solidus
The solidus (/) will not be used for a quotient, e.g. m/s will not be used for metres per second.
Presentation of dataThis section is relevant to Papers 3 and 5. You should follow these conventions when presenting data in tables and graphs.
The solidus (/) is to be used for separating the quantity and the unit in tables, graphs and charts, e.g. time/s for time in seconds.
(a) Tables
(i) Each column of a table will be headed with the physical quantity and the appropriate unit, e.g. time/s There are three acceptable methods of stating units, e.g. metres per sec or m per s or m s–1.
(ii) The column headings of the table can then be directly transferred to the axes of a constructed graph.
(b) Graphs
(i) The independent variable should be plotted on the x-axis (horizontal axis) and the dependent variable plotted on the y-axis (vertical axis).
(ii) Each axis will be labelled with the physical quantity and the appropriate unit, e.g. time/s.
(iii) The graph is the whole diagrammatic presentation. It may have one or several curves plotted on it.
(iv) Curves and lines joining points on the graph should be referred to as ‘curves’.
(v) Points on the curve should be clearly marked as crosses (x) or by dots within circles. If a further curve is included, vertical crosses (+) may be used to mark the points.
(c) Pie charts
These should be drawn with the sectors in rank order, largest fi rst, beginning at ‘noon’ and proceeding clockwise. Pie Charts should preferably contain no more than six sectors.
(d) Bar charts
These are drawn when one of the variables is not numerical, e.g. percentage of vitamin C in different fruits. They should be made up of narrow blocks of equal width that do not touch.
Section 6: Appendices
79Cambridge International AS and A Level Biology 9700
(e) Column graphs
These are drawn when plotting frequency graphs from discrete data, e.g. frequency of occurrence of leaves with different numbers of prickles or pods with different numbers of seeds. They should be made up of narrow blocks of equal width that do not touch.
(f) Histograms
These are drawn when plotting frequency graphs with continuous data, e.g., frequency of occurrence of leaves of different lengths. The blocks should be drawn in order of increasing or decreasing magnitude and they should be touching.
Cambridge International Examinations 1 Hills Road, Cambridge, CB1 2EU, United Kingdom tel: +44 1223 553554 fax: +44 1223 553558 email: info@cie.org.uk www.cie.org.uk
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