1. Exam technique and PAGs
AS Biology
Exam technique and PAGs

2. Key words – Exam papers
Define This requires a formal statement, mainly just easy recall. E.g. Define the term active transport This is the movement of molecules from where they are in lower concentration to where they are in higher concentration. The process requires energy. Explain This requires a reason. The amount of detail needed is shown by the number of marks allocated. E.g. Explain the difference between resolution and magnification Resolution is the ability to be able to distinguish between two points, whereas magnification is the number of times an image is bigger than an object itself. State This requires a brief answer without any reason. E.g. State one role of blood plasma in a mammal Transport of hormones to their target organ. List This requires a sequence of points with no explanation. E.g. List the abiotic factors which can affect the rate of photosynthesis in pond weed CO2 concentration, light intensity, temperature, pH of the water
All key words for exam papers – in hand book

3. Describe This requires a piece of prose that gives key points
Describe This requires a piece of prose that gives key points. Diagrams can be included. If you are describing a graph make sure you include some values from key parts of the graph. E.g. Describe the nervous control of heart rate The medulla oblongata √ of the brain connects to the sino-atrial node in the right atrium wall √ via the vagus nerve and the sympathetic nerve. √ The sympathetic nerve speeds up the rate √ the vagus nerve slows it down. Suggest This means that there is no single correct answer. Often you are given an unfamiliar situation to analyse. The examiners hope for logical deductions from the data given and that, usually, you apply your knowledge of biological concepts and principles. E.g. The graph shows that the population of lynx decreased in Suggest reasons for this. Weather conditions may have prevented plant growth √ so the snowshoe hares could not get enough food and their population remained low √ so the lynx did not have enough hares (prey) to predate upon. √ The lynx could have had a disease which reduced numbers. √ Calculate This requires that you work out a numerical answer. Remember to give the units and to show your working, marks are usually available for a partially correct answer. If you work everything out in stages, write down the sequence. Otherwise if you merely give the answer and it is wrong, then you will score 0 marks. E.g. Calculate the Rf value of spot X (X is 25mm from the start and solvent front is 100mm) Rf = distance moved by the spot Distance moved by the solvent front

4. Practice exam questions
from-2015//
After each topic, download and practice exam questions. When answering a question , reread the question at least twice and then highlight key phrases, always take note of the number of marks available.
Complete questions at the end of each chapter in the book to assess understanding
Put all questions in a separate area in your folder for review.
Practice an exam question

5. Module 1—Development of practical skills in Biology (PAG)
PAG books available from the prep room
PAG books should be separated into sections
(1-3, 4-6, 7-9 and )
All PAG’s should be written up in your PAG books
Stick in the PAG sheet or write out the method – you may need to refer to these in the exam
Tick off which PAG is completed on your PAG assessment tracker with the date completed
Certain areas will be focused on in each PAG; tables, graphs drawings, dilutions, calculations, ICT, Research
Extension questions are extremely important in prep for the exam; focus on understanding, conclusions (qualitative and quantitative), evaluation, health an safety
Students to refer to PAG assessment tracker, each PAG will be completed with in certain blocks throughout the year (very important where possible not to miss these – if you do you must catch up).
There are lso the front section of the text book, it is expected that you refer to this throughout the course to help with you understanding.

6. Other key words Mean Median Mode Range
A. The difference between the lowest and highest values. To calculate: e.g. In {4, 6, 9, 3, 7} the lowest value is 3, and the highest is 9, so it is 9 − 3 = 6.
Mean
Median
Mode
Range
B. The average of the numbers: a calculated "central" value of a set of numbers.
To calculate: Just add up all the numbers, then divide by how many numbers there are
C. The middle number (in a sorted list of numbers).  To calculate: place the numbers you are given in value order and find the middle number.
Mean B, median C, Mode D, Range A
D. The number which appears most often in a set of numbers. 

7. Presenting your data
Time taken for indicator to become yellow (secs)
Temperature 1 2 3
454
476
468
10oC
287
295
305
15oC
210 62
212
20oC
121
123
126
25oC
105
110
109
30oC 68
63.5
65.5
35oC
Temperature is the independent variable (IV) and so should be the first column;
the units for temperature shouldbe shown in the column heading and not in the table rows;
the unit for time should be written as (s);
At 20oC repeat 2 anomalous result shpuld be removed and then there should be a column for mean values;
there should also be a column showing mean rate of reaction; RATE = 1/TIME TAKEN (1000/TIME – MORE USER FRIENDLY IN THIS CASE) RATE =
the numbers in each column should be to the same number of decimal places, so many figures need a trailing zero.
In pairs state 6 ways in which this table can be improved

8. Tables
 The following guidelines should be followed when presenting results in tables.
All raw data in a single table with ruled lines and border.
Independent variable (IV) in the first column; dependent variable (DV) in columns to the right
(for quantitative observations) OR descriptive comments in columns to the right (for qualitative observations).
Processed data (e.g. means, rates, standard deviations) in columns to the far right.
No calculations in the table, only calculated values.

9. Tables
Each column headed with informative description (for qualitative data) or physical quantity and correct SI units (for quantitative data); units separated from physical quantity using either brackets or a solidus (slash).
No units in the body of the table, only in the column headings.
Raw data recorded to a number of decimal places and significant figures appropriate to the least accurate piece of equipment used to measure it.
All raw data recorded to the same number of decimal places and significant figures.
Processed data recorded to up to one decimal place more than the raw data.

10. Which Graph? When should you use each graph?
Line –
Bar -
Scattergram -
A. IV is discontinuous and DV continuously variable
B. between two continuous variables, a causal link cannot be assumed (usually as it is one variable out of many)
C. Between two continuous variables, a likely causal link between the IV and DV.
Line C, Bar A, Scatter B

11. Presenting your graph
Join with a curve if the trend is very clear and you can predict the values in between the points
Join with straight lines when the trend is not clear and the values in between the points cannot be assumed/predicted
Bar charts – bars must be separated from each other. If the bars touch it is a histogram!

12. Graph rules
Graphs
The following general guidelines should be followed when presenting data in graphs.
• The type of graph used (e.g. bar chart, histogram, line graph, pie chart or scattergram)
should be appropriate to the data collected.
• The graph should be of an appropriate size to make good use of the paper.
• There should be an informative title, and axes should be fully labelled with units.

13. Bar charts and histograms
These are used when the dependent variable on the y-axis is discrete, i.e. whole numbers,
fractions are impossible and the data under consideration deal with frequencies.
Bar charts
Bar charts are used when the independent variable is non-numerical, e.g. the number of different insect species found on trees. These data are discontinuous.
They can be made up of lines, or blocks of equal width, which do not touch.
The lines or blocks can be arranged in any order, but it can aid comparison if they are arranged in descending order of size.

14. The Experiment – Validity (or did it measure what you wanted it to?)
Limitations
Uncontrolled variables
Results
Effects of errors (systematic and random)
Reliability
Repeatability/reproducibility
Accuracy
Precision

15. Evaluation
Keywords
Accuracy - results that are close to the true answer
Precise – The closeness of the agreement between measured values obtained by repeat/ those taken with sensitive instruments that measure small increments eg. Mm rather than cm / to 1 dp
Reliability - results can be consistently reproduced in independent experiments
Addressing limitations
What is the science behind the practical?
What variables did you control? Why?
Think about the steps to the practical, why was each one important?

16. Limitations Limitation How limitation affects method or results
Example of how to overcome limitation
Insufficient intermediate readings taken e.g. every 60 sec.
Could miss changes occurring between intervals measured.
Take readings at smaller intervals eg 30 sec instead of 60 sec.
Insufficient range of independent variable; e.g OC.
Lack of results beyond range – makes determining trend difficult.
Extend the range, eg 10-80OC.
Insufficient number of values for independent variable.
Makes determining trend difficult.
Include more intermediate values.
One measurement or only two replicates.
Unable to detect anomalous results, decreases reliability.
Perform at least three replicates.
Difficulty in judging colours or changes when using ‘by eye’ methods.
Lack of consistency in judgement causing less reliable, precise and accurate results.
Use colour standards, colorimeter, movement of ball bearing for coagulation or a standard method for comparing change.
Inconsistent stirring of solutions.
Inconsistent rate of product formation or separation /non-mixing of components of solution.
Standardise method and time of stirring.
Samples from different sources.
Different age/state may introduce random errors
Use same source for samples
Method of timing.
Used to a greater/lesser level of precision than sensible (e.g 0.01s)
Record times to nearest second, 10 seconds or whatever is appropriate.
Impossible to start all reactions at same time.
Some reactions occurred for longer or shorter times.
Use a staggered start, e.g.at 1 minute intervals
pH not controlled.
pH affects enzyme activity.
Use a buffer solution to control pH.

17. Systematic Errors
Errors that are the same throughout the investigation.
e.g. A measuring device that is ‘out’ by a certain value, one of the controlled variables is always incorrect by the same quantity.
Results may still be precise, but not accurate.

18. Random Errors
Occur when procedure not carried out in the same way each time it is performed.
e.g. Reading the apparatus differently every time, using any of the equipment a different way each time or due to variations in biological material used in experiment.
Some results will be affected, but not all. May cause one or more anomalous results.