A small, isolated island has a large population of rabbits that feed on the grass growing there. Because the number of rabbits has been rising quickly, a fe...
Question 1 Report
A small, isolated island has a large population of rabbits that feed on the grass growing there. Because the number of rabbits has been rising quickly, a few foxes are deliberately introduced to the island to bring the population under control. The foxes hunt the rabbits as their prey. Part of the food web for the island community is shown in the diagram below.
(a) Define the term predator. [2]
(b) State what is meant by the term prey. [1]
(c) Describe what is likely to happen to the number of rabbits in the months after the foxes are introduced. [2]
(d) Explain what may happen to the size of the fox population once the number of rabbits has fallen. [3]
(e) Suggest three effects on the rest of the island community if all the foxes were later removed from the island. [3]
(f) State the role played by decomposers in this island ecosystem. [2]
(g) State the term used to describe the grass growing on the island. [1]
Answer Details
This question tests feeding relationships in a food web and the effects of adding or removing a predator.
(a) Define predator. [2] An organism that hunts, catches and kills [1] and eats another organism (its prey) [1].
(b) Meaning of prey. [1] An organism that is hunted, killed and eaten by another organism [1].
(c) Rabbits after foxes are introduced. [2] The number of rabbits decreases [1] because they are eaten/killed by the foxes [1].
(d) Fox population once rabbits fall. [3] With fewer rabbits there is less food available for the foxes [1]; so the foxes compete, some starve, die or move away [1]; and the fox population then falls [1]. This predator-prey link keeps both numbers cycling.
(e) Three effects of removing all foxes. [3] Any three: rabbit numbers rise again; grass/producers are overgrazed and decrease; other prey species increase; the balance of the community is disturbed [3, 1 each].
(f) Role of decomposers. [2] They break down dead organisms and waste material [1], releasing nutrients/mineral ions back into the soil [1] for the grass to reuse.
(g) Term for the grass. [1] Producer [1], because it makes its own food by photosynthesis. Exam tip: describe changes as increases or decreases with a reason, not just "the numbers change".
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