Biology

What is it? Supposedly the easiest of the three sciences. At AS- level you start with cells and molecules, how a cell is built and what's in it - carbohydrate, protein, fats. You follow on into animals and plants, looking at reproduction (yes, the birds and the bees) and ecology, or at least you do if you're studying with the Edexcel exam board. At A-level, you take a few of the topics in greater depth, eg respiration and photosynthesis. You also study more sophisticated genetics as well as evolutionary biodiversity.

Why do it? Because you have always loved collecting insects, like the great American entomologist E O Wilson, and/or because you think it will be useful careerwise. You may fancy a job as a research worker in the new industries associated with the genome and gene therapy, or working for an environmental agency. Or you could teach.

What skills do you need? The ability to soak up facts like a sponge, and sort and synthesise a lot of information as well as explain things fully and accurately.

How much practical work is there? A fair amount. A requirement for AS- and A-level is that you are assessed on a practical project, eg an experiment looking at enzymes in washing powder. That carries 15 per cent of the marks. Plus you undertake a series of named experiments linking with the subject material.

Ratio of coursework to exams: 15:85 (see above)

Is it hard? Thought to be easier than chemistry or physics, partly because it's less mathematical. But, according to Ed Lees, an examiner with Edexcel, that's not the case because you have to describe complicated things pretty technically. And there is some maths, using percentages and ratios, and making sense of statistics.

Is it enjoyable? Of course. You will be a walking expert on the human genome, GM food and global warming, and you will be able to separate myth from fact.

Who takes it? More students than take physics or chemistry - and more girls than boys.

How cool is it? Pretty cool if you're into environmental protection and healthy eating. It certainly beats physics in the cool stakes.

Added value: You can go on some interesting, if maybe damp, field trips to the British coast, inspecting sand dunes and rocks, or other trips to woodland areas.

What subjects go with it? Chemistry.

What degrees does it lead to? Biological sciences, a big umbrella area, and health sciences. Also medicine.

Will it set you up for a brilliant career? Yes. You could, if you have the talent, end up as a writer on science like Richard Dawkins, or as an academic investigating the brain like Susan Greenfield, also at Oxford. Or you could become a research biochemist studying DNA. The fallout from mapping the human genome has thrown out numerous opportunities for research into, for example, cures for Alzheimer's.

What do students say? "I'm doing biology because I want to study medicine. I find the subject interesting, but there is a lot to learn. For that reason I find it harder than chemistry." Hannah Travers, 17, Ridgeway School, Wroughton, near Swindon.

Which awarding bodies offer it? All of them do.

How widely available is it? Very. Virtually all schools and colleges do it.