This is one topic that comes up year after year. It can come up in Section A, Section B or Section C, or even in all three sections. So you should make sure you are able to answer all questions that have been asked in previous years by using the marking schemes.
One of the best things about ecology is that there are often a large number of correct answers to many of the questions. You have a chance to display your knowledge gleaned from outside the classroom. However, one word of warning, there are no extra marks for giving an exotic answer. In fact there is a danger that the marker may not recognise it as a correct answer and thus not award the marks you deserve. I always recommend that you give the simplest, most obvious answer; just to be safe.
The questions vary in form depending on which section they are in.
In section A the answers are very short as can be seen in section A of these sample answers.
In the example given each question is worth 20 marks. Note that the first two correct answers got (7) marks each and the next six got (1) mark each. Two correct answers in this question would have got you 14 marks i.e. 70% of the marks for the question. It is very important that you put an answer down for each part of every question in section A. You will be given the marks for the 5 questions you did best, and within each question your best combination of answers will be taken.
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Be aware that if you give any extra answers, to any part of a question in this section, and they are wrong, they will cancel out a correct answer in that part of the question. This is called cancelling and it only happens in Section A and for some one word answers in other Sections. So if you are asked to name a producer do not give two examples because if one is correct and one is wrong then the extra wrong answer will cancel the correct answer and you will get no marks.
In section B the answers are worth 30 marks each and the answers tend to be short as can be seen in section B of these sample answers.
The first (6) marks are got from part (a) and are usually definitions of key words from the topic. The remaining (24) marks come from part (b) which consists of questions dealing with one of the three mandatory practical activities on the syllabus i.e. using sampling techniques, estimating the population of a sedentary (usually a plant) species using a quadrat or an animal species using mark and recapture.
In section C the question comes in two basic forms:-
1. You are given a passage to read and are asked to extract information from it
or you can be asked to interpret or describe a graph. This can be seen in section C of these sample answers.
2. A standard exam question testing your knowledge of ecology. This can be seen in section C of thesesample answers.
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The standard question will nearly always ask for some definitions. If you are asked to explain the word predator you should say “an animal that catches and kills another animal for food” you are not asked for an example so saying “fox” will get you no marks unless you have been asked to give an example.
You may be asked for examples of food chains or webs from a named habitat and you can also asked about any of the mandatory practical activities. If you are asked to draw a food chain or a food web; be sure to draw arrows between each member and make sure they are pointing in the right direction i.e. in the direction the energy flows – from producer to consumer.
In recent years there has been a trend to ask open-ended questions which are designed to test your ability to think, and your understanding of the topic rather than just knowing the information. This can be seen in section C of these sample answers.
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The carbon and nitrogen cycles can be asked here. You don’t need huge detail and a diagram will normally be more than enough to get full marks.
The following description of the nitrogen cycle would get full marks twice over.
Atmospheric nitrogen is fixed by lightning and by nitrifying bacteria and plants use the nitrates formed to make proteins which are then eaten by animals. Excretion, death and decompositionof both plants and animals produce ammonia which is turned to nitrites and nitrates and denitrifying bacteria turn these back to atmospheric nitrogen.
Finally, it is most unlikely that you will be asked to construct a key to help identify plants or animals but you could be asked to use one.