Mathematical skills that they can ask you to use in questions:
 Use an appropriate number of significant figures;
 Find arithmetic means
 Construct and interpret frequency tables and diagrams, bar charts and histograms
 Have sufficient understanding of probability to understand how genetic ratios arise
 Use ratios, fractions and percentages
 Understand the principles of sampling as applied to biological data
 Understand the importance of chance when interpreting data
 Understand the terms mean, median and mode
 Use a scatter diagram to identify a correlation between two variables

Use a simple statistical test (you will only get examination questions on the 2 test)
NB You should be familiar with the use of the Chisquared test, understand when it might be validly applied and be able to interpret results obtained. You will not be expected to recall the formula in written papers.
Synoptic skills and understanding relating to practical work
Practical work has the following key areas:
 Overview
 Defining the question
 Planning
 Implementation
 Data analysis
You can be asked questions which test your understanding of these areas. The back of this booklet contains example past paper questions
Overview
One of the aims of the specification is that you should develop an understanding of scientific method. You should know the following:
 Hypothesis – a suggested explanation of an observation that can be tested by experiment
 Theory – a well established hypothesis that is supported by a substantial body of evidence.
 ‘Proof’ and experiment can either support or disprove a hypothesis, but it cannot prove that it is certainly true
 Variable are things which can be changed e.g. light intensity, pH, etc
The independent variable is the thing that you change in experiments (it always goes on the x axis on graphs). In an experiment you change one independent variable and keep all the others constant. The effect is shown on the dependant variable e.g. exercise intensity can be an independent variable heart rate would be a dependent variable. In this practical external temperature would be one of the other independent variables you would keep constant. The dependent variable is always plotted on the y axis on graphs
You should be able to:
 Formulate a hypothesis/suggested explanation
 Examine data/results/observations, then suggest one plausible biological hypothesis consistent with the information given.
 Analyse whether a suggested explanation is consistent with the data.
Planning Investigations
You should be able to:
 Describe how one independent variable would be varied
 Describe experimental controls keeping all conditions constant except independent variable
 describe how dependant variable would be measured
 Explain how reliable data could be obtained/dealing with variability in living organisms.
Implementation
You should be familiar with the following methods of measurement:
 Methods of measurement
 Biochemical tests
 Chromatography and Rf
 Isotonic solutions
 Indicators
 Controlling temperature
 Colorimetry
 Dilutions
 Safety measures
 Replication
 Centrifugation
Data Analysis
Chisquared is the only statistical test you need to know so it will probably be examined in module 5.
This is a very typical chi squared type exam question
Table 1. Data from a survey
Table 2 shows part of chisquared table
Question
Are there any significant differences between the population sizes in areas X,Y and Z between 1976 and 1983? Explain your answer.
Large numbers of student asked this did not understand degrees of freedom. Because there were three areas X,Y and Z, they opted for (31)=2. The trouble is the table shows 3 individual chi squared tests each with 1 degree of freedom. So the correct answer was one.
Many student gained one mark for ‘There are significant differences in areas Y and Z,’ but did not explain why, nor note that there is a significant increase in Y and a significant decrease in Z.
General Points
You need to understand the concept of null hypothesis and understand X2 value in relation to table values at probability of 0.05
Standard Deviation
This is another reasonably advanced mathematical concept – it is the average distance individual results are from the mean. So spread out data have a high standard deviation and closely grouped data have a small standard deviation.
The table below shows the typical type of question you could get
Question
What is the range of the concentration of zinc
1 within 1 standard deviation at 4km
2 within 2 standard deviations at 22 km
Answers
1 at 4km; 0.72.5 mg dm3
2 at 22 km; 0.0320.48 mg dm3
3. Essay
The Essay
The essay question will be part of the module 8 exam. You will have to choose one of two titles. It is vital to choose the one, which is easier to answer bringing in information from lots of the course
Important points about writing the essay:
 In the answer to this question you should bring together relevant principles and concepts for as many different areas of biology as possible.
 Your essay will be marked not only for its scientific accuracy, but also for the selection of relevant material.

The essay should be written in continuous prose not bullet points.
 Unless diagrams are clearly annotated they are a waste of time.
Essays the titles from summer 2002
 The different ways in which organisms use ATP
 How the structure of cells is related to their function
The ways in which organisms use ATP
the role of ATP could have been described in:
 Active transport
 Maintaining resting potential
 Resynthesis of acetylcholine and rhodopsin
 Glycolysis of respiration
 Light independent reactions of photosynthesis
 Synthesis (anabolism)
 Kidney function
 Translocation
 Nitrogen fixation
At least 50% of candidates went into great detail about ATP production and consequently lost 1 relevance mark.
Some candidates stated that what they were about to write was not a use, but continued nevertheless.
The bombproof approach to writing your essay is to write 8 paragraphs, each on a relevant scientific concept. If you wrote 4 paragraphs per page your essay would be approximately two sides long. This is a good length. Aim to stay under three sides if you go any longer you could be wasting time that you should be spending on the other exam questions
How the structure of cells is related to their function
Many candidates were not clear what a cell is, confusing cells with:
 Organelles such as mitochondria and chloroplasts
 Tissues
 Organs
 Villi
Some students did not relate structure to function eg ‘red blood cells carry oxygen’
Common mistakes included the following
 Nerve cells – but did not relate length to function

Blood cells – did not relate shape to function also must say red blood cells if you mean that
 Sperm – has a tail so it can swim is far too simplistic
 Ova – but no structural detail (should have said large reserve of nutrients for developing embryo)
 Epithelial cells –‘ have villi to increase the surface area for digestion’ – it should have been microvilli
 ‘Leaf cells’ – have a large SA for light absorption – should be palisade mesophyll cells shape for light absorption.
 Xylem – confusion between tissue and cell
 Phloem – same structure as xylem’
 Stomata – confused with guard cells
Students should have known 2 cells well from AS:
Intestinal epithelial
 Microvilli – increase S?A and uptake of products of digestion
 Site of enzymic breakdown of disaccharides
 Many mitochondria to release energy for active transport in the form of ATP
 Large extensive golgi bodies for mucus/enzyme secretion
Palisade mesophyll
 Cell wall – support/resistance to turgor

Shape – uptake of light, CO2
 Chloroplasts – arrangement of grana
 Vacuole – turgor, economical deployment of cytoplasm
Marking Essays
Essays are marked on the following sections:
 Scientific Content /16
 Breadth /3
 Relevance /3
 QWC /3
Which makes the total marks available 25.
Based on the cells essay for 3 breadth marks candidates should refer to at least 6 different cell types including at least one plant
Tips for scoring breadth mark:
 Aim to use information from at least 23 different modules.
 Make sure you include plant information if appropriate.
Students who write a paragraph about an irrelevant topic (such as detailed biochemistry of respiration for the ATP question) will lose one relevance mark.
QWC
The essay should be structured in a reasonable logical way appropriate and relevant to the title. Ideas and concepts should be explained sufficiently clearly to be readily understood. Continuous prose should be used and sentences should generally be complete and constructed grammatically. However, minor errors of punctuation or style should not get penalized.
Appropriate A level terminology should be used. You should not use such phrases as ‘fighting disease’ ‘messages passing along nerves’ enzymes being killed etc but a single lapse would not necessarily disqualify.