6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Fertiliser containing nitrates is spread on a field next to a pond. After heavy rain, some fertiliser washes into the pond. Over the following weeks the water turns green, then many fish are found dead. This process is called eutrophication.
Explain how fertiliser running into the pond leads to the death of the fish. (6 marks)
In a core practical, a student estimated the number of daisies in a school field using a quadrat of area 0.25 m². They placed the quadrat at random 10 times and counted the daisies each time. The results are shown below.
| Quadrat | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Number of daisies | 6 | 4 | 8 | 5 | 7 | 3 | 6 | 5 | 9 | 7 |
The total area of the field is 2000 m².
(a) Calculate the mean number of daisies per quadrat. (1 mark)
(b) Use your answer to (a) to estimate the total number of daisies in the whole field. Show your working. (3 marks)
Carbon is recycled through ecosystems in the carbon cycle.
(a) Name the process by which carbon dioxide is removed from the air by green plants. (1 mark)
(b) Name two processes that return carbon dioxide to the air. (2 marks)
In a community, a population of rabbits is eaten by a population of foxes. Over many years, the two populations rise and fall in a repeating predator–prey pattern.
(a) Explain why an increase in the number of rabbits is usually followed, a short time later, by an increase in the number of foxes. (2 marks)
(b) State one abiotic factor that could also affect the size of the rabbit population. (1 mark)
Decomposers play an important role in the nitrogen cycle and in recycling materials in an ecosystem.
Explain why decomposers (such as bacteria and fungi) are important for the growth of plants in an ecosystem. (2 marks)
An ecosystem contains many different species living together.
Define the term biodiversity. (1 mark)