# 68 AS Experimental skills and investigations

Almost one quarter of the total marks for your AS examination are for experimental skills and investigations. These are assessed on Paper 3, which is a practical examination.









There is a total of 40 marks available on this Paper. Although the questions are different on each paper 3, the number of marks assigned to each skill is always the same. This is shown in the table below.

The syllabus explains each of these skills in detail, and it is important that you read the appropriate pages in the syllabus so that you know what each skill is, and what you will be tested on.

The next few pages explain what you can do to make sure you get as many marks as possible for each of these skills. They give you guidance in how you can build up your skills as you do practical work during your course, and also how to do well in the examination itself. They are not arranged In the same order as in the syllabus, or in the table above. Instead, they have been arranged by the kind of task you will be asked to do, either in practical work during your biology course or in the examination.

There is a great deal of information for you to take in, and skills for you to develop. The only way to do this really successfully is to do lots of practical work, and gradually build up your skills bit by bit. Don't worry if you don't get everything right first time. Just take note of what you can do to improve next time - you will steadily get better and better.

The examination questions

There are usually two questions on Paper 3. The examiners will take care to set questions that are not exactly the same as any you have done before. It is possible that there could be three shorter questions instead of two longer ones, so do not be surprised if that happens.

It is very important that you do exactly what the question asks you to do. Candidates often lose marks by doing something they have already practised, rather than doing what the question actually requires.

Question I

This is likely to be what is sometimes called a 'wet practical'. For example, it could be:
• an investigation into the activity of an enzyme
• an osmosis experiment
• tests for biological molecules

This question will often ask you to investigate the effect of one factor on another for example, the effect of enzyme concentration on rate of reaction, or the effect of leaf area on the rate of  transpiration.

Question 2

This question is likely to involve making drawings from a specimen. This could be a real specimen, or it could be a photograph. You may be asked to use a microscope, a stage micrometer and eyepiece graticule, or images of them, to work out the magnification or size of the specimen.

The two questions are designed to take up approximately equal amounts of your time. You should therefore aim to spend about 1 hour on each question.

Tips 

During your course:
• Every time you do a practical during your AS course, time yourself. Are you making quickly enough? You will probably find that you are very slow to begin with, but as the course progresses try to work a little faster as your confidence improves.

ln the exam:
• Do exactly what the question asks you to do. This is unlikely to be exactly the same as anything you have done before.
• leave yourself enough time to do each question, spending an appropriate number of minutes on each one.