One to four mark questions
One to four mark questions will start with command words such as 'describe' or 'explain'. Some command words are easy to understand such as:
- 'calculate' or 'determine' for maths questions
- 'complete' to fill in a gap in a table or graph
- 'define' to give the meaning of an important word
- 'suggest' where you use your knowledge in an unfamiliar situation
- 'compare' where you describe the similarities and/or differences between things
The command words 'describe' and 'explain' can be confusing. If you are asked to describe a graph, you will be expected to write about its overall shape, whether it is linear or curved, the slope of gradients etc. If you are asked to explain why a pattern or trend is seen in a graph, you will be expected to use your science knowledge, not just say what you see (which is a description), eg the graph shows a steep linear increase for the first three hours because鈥
Explain how and why questions often have the word 'because' in their answer. Describe questions don't.
The number of marks per question part is given in this form '[2 marks]'. It is essential that you give two different answers if a question is worth two marks. Sometimes you can gain a second mark by giving the units in a calculation or stating specific data points, eg during the first two years the number of lions deceased by seven.
You will be expected to write in more depth for three and four mark questions. They might ask you about a process such as the carbon cycle or the method you would use in an experiment.
Edexcel questions courtesy of Pearson Education Ltd.
Sample question 1 - Foundation
Question
A student wanted to estimate the number of earthworms in a field using a quadrat.
The student placed the quadrats at random on the surface of the area being sampled and then watered the area with a very dilute solution of mustard.
This causes the earthworms to come to the surface to be counted.
Give a reason why the quadrats were placed at random. [1 mark]
To obtain a representative sample of the field (1 mark)
Sample question 2 - Foundation
Question
Give two abiotic factors that could affect the distribution and size of daisies growing in this field. [2 marks]
Marks will be given by using any of the following:
- temperature (1 mark)
- pH (1 mark)
- pollutants (1 mark)
- water (1 mark)
- light (1 mark)
- carbon dioxide concentration (1 mark)
Sample question 3 - Foundation
Question
A quadrat sample was taken in an area where there were many overhanging trees. Explain how these trees may have affected the distribution of daisy plants growing in this area. [2 marks]
Full marks will be awarded for including the following points:
- less daisy plants are likely to be growing in this area (1 mark)
- because the trees would cause lower light levels for photosynthesis/lower mineral levels for growth/less water available for photosynthesis (1 mark)
Sample question 4 - Higher
Question
Tropical fish excrete ammonia, which is an alkali.
The pH level of water in a tropical fish tank needs to be maintained between 6.6 and 7.4 for the fish to survive. This is the optimum pH range for the bacteria that are responsible for the conversion of ammonia into nitrates.
Explain why bacteria are needed in tropical fish tanks. [2 marks]
Full marks will be awarded for including the following points:
- the bacteria convert the ammonia into nitrites then nitrates maintain the pH (1 mark)
- (this prevents an increase in pH) which would cause enzymes to denature and kill the fish (1 mark)
Sample question 5 - Higher
Question
Water pollution can be caused by an increase in nitrates and phosphates. Explain the problems associated with an increase of nitrates and phosphates levels in a lake. [3 marks]
An explanation linking three of the following:
- eutrophication (1 mark)
- causes an algal bloom - accept 'increased growth of algae' (1 mark)
- plants (at the bottom of the lake/underneath the algae) cannot get light to photosynthesise (1 mark)
- plants at the bottom of the lake die and microorganisms/decomposers break them down (1 mark)
- microorganisms respire removing oxygen from the water (1 mark)
- reduction in biodiversity (1 mark)
Sample question 6 - Higher
Question
The nitrogen-fixing bacteria provide nitrates for the plants and release any excess into the soil.
Explain how leguminous plants such as clover could be used to reduce the amount of artificial fertilisers. [4 marks]
An explanation linking three of the following:
- clover/leguminous plants could be used in crop rotation (1 mark)
- where at intervals (2-3 years) a field is planted with clover/leguminous plants and left fallow (1 mark)
- the clover/leguminous plants will have colonies of nitrogen fixing bacteria which will produce nitrates (1 mark)
- the nitrates will increase the fertility of the soil and reduce the need for artificial fertilisers (1 mark)