Biology 14/11/2017

Biology: Command words in context


State, describe, explain, compare, evaluate and suggest are the most important command words in Biology GCSE.  Learn to recognise command words when they come up in exam questions, follow our advice on how to answer them and you’ll pick up precious marks.




It’s very important to recognise command words in the exam and then to tailor your answers to the instructions given to you by these command words.



Take, for example, the picture of the girl. You could state that this is a girl. In the context of an exam question you may need to state the part of the body that produces bile. (Answer: the liver).


Then to describe the girl you could simply say that she has brown hair and brown eyes. Simply say what you see.

Sometimes you may need to describe a process or pathway. For example when you inhale, oxygen travels down the trachea, then into the bronchi, the bronchioles and finally into the alveoli, before diffusing into the blood. In this situation, a describe question is testing your knowledge and testing your factual recall.

It can sometimes be difficult to distinguish between describing a biological structure and describing the function of that structure. The structure is something that you can label on a diagram, like a nucleus in a diagram of a cell. The function is the job or role of that structure (the nucleus contains the DNA that codes for the proteins that control the cell).

Finally, when describing graphs, you need to take a slightly different approach. We’ll cover this in a later blog: ‘Describing, explaining and comparing graphs’.



When asked to explain, you need to give a scientific reason why or how. Here, you need to use the word ‘because’. The girl has brown hair and brown eyes because she has inherited the alleles/genes for these characteristics from her parents. If the exam question is worth several marks you may need to support your answer with a genetic diagram or a Punnet square to really show off your amazing understanding of inheritance!

Application questions ask you to explain why or how something happens but in an unfamiliar context. You may have learnt how famers have selectively bred cows to yield large volumes of milk. But an exam question may ask you to explain how a farmer can selectively breed tomatoes to produce large tasty tomatoes. Here you simply show off your understanding of the process of selective breeding but change ‘cow’ to ‘plant’ and ‘milk yield’ to ‘size and taste’.



When asked to compare, you need to comment on both the similarities and the differences. It’s important to take each similarity and difference in turn as often the mark schemes offer only 1 mark per comparison, rather than a mark for each individual set of similarities and differences. It’s important to use comparative terms such as longer, fewer, faster or one has something while the other lacks something.

For example, if asked to compare mitosis and meiosis, you could write the following: “Mitosis and meiosis are similar because they are both forms of cell division that produce daughter cells. However, there are clear differences. Mitosis produces 2 identical daughter cells, while meiosis produces 4 unique daughter cells. Mitosis involves 1 division, while meiosis involves 2”.

If asked to compare aerobic and anaerobic respiration you could say: “They both transfer energy from glucose. But aerobic respiration releases more ATP molecules than anaerobic respiration and aerobic respiration releases carbon dioxide and water while anaerobic releases lactic acid as a product”.

Common compare questions in Biology are: sexual/asexual reproduction; the role of the menstrual cycle hormones; plant/animal cells; eukaryotic/prokaryotic cells, light/electron microscopes, osmosis/diffusion/active transport; biotic/abiotic factors; communicable/non-communicable diseases; arteries/veins/capillaries; translocation/transpiration; xylem/phloem. These are all worth practicing.



In the exam, if you are asked to evaluate, you have to put forward advantages and disadvantages but you don’t need to give your overall opinion. A good way to revise these questions is to create a table of ‘pros’ and ‘cons’ and use this evaluate the common topics that come up in the exams.

Common evaluate questions in Biology are: Different forms of contraceptives; IVF; genetic engineering; intensive farming; light or electron microscopes; stem cells; treatments for cardiovascular disease. Once again, get practicing!



Finally, in suggest questions, which are often worth only 1 mark, you would not necessarily have been taught the answer and you need to make an educated guess. Here, the examiner is trying to work out how good you are at applying what you have learnt to novel or unfamiliar contexts.



Note for teachers:

AQA provides a long list of other command words including some recently introduced for the new 9-1 GCSEs. Fortunately, for the majority of words the meanings are fairly evident:




Katie Ross

Download PDF