AQA GCSE Biology: Ecology

Large areas of tropical rainforest are being cleared by deforestation for timber and to create land for farming. Scientists are concerned that this is reducing biodiversity and contributing to global warming.

Explain how deforestation can reduce biodiversity and contribute to global warming. (6 marks)

Ecologists used quadrats to estimate the population of a plant, buttercup, in a field. They placed a 0.25 m² quadrat at 10 random positions and counted the buttercups in each.

Quadrat	1	2	3	4	5	6	7	8	9	10
Buttercups	6	4	8	5	7	3	6	9	4	8

The total area of the field is 2000 m².

(a) Calculate the mean number of buttercups per quadrat. (2 marks)

(b) Use your mean to estimate the total number of buttercups in the whole field. Show your working. (2 marks)

In a grassland ecosystem, rabbits eat grass and are themselves eaten by foxes. The grass, rabbits and foxes form a simple food chain.

(a) Name the trophic level occupied by the grass in this food chain. (1 mark)

(b) Foxes and another predator, stoats, both hunt the rabbits in this grassland. Explain why the foxes and stoats are said to be in competition. (2 marks)

The carbon cycle returns carbon dioxide to the atmosphere so that it can be used again by plants.

(a) Name the process carried out by plants that removes carbon dioxide from the atmosphere. (1 mark)

(b) Describe two processes that return carbon dioxide to the atmosphere. (2 marks)

A camel is well adapted to survive in a hot, dry desert. One of its adaptations is that it can go for long periods without drinking and loses very little water.

Describe two ways in which a camel is adapted to survive in a hot, dry desert, and explain how each adaptation helps it to survive. (2 marks)

When ecologists carry out sampling in a field, they place quadrats at random positions rather than choosing where to put them.

Give one reason why the quadrats should be placed at random positions. (1 mark)