Population size and competitionAQA A-Level Biology: Mind map

Exam questions on Population size and competition

1. A conservation team monitors a population of red deer on an island with no natural predators. Over 40 years the population rose, then levelled off and now fluctuates around 1200 animals. The island's vegetation provides a limited food supply and little shelter in winter.
   Explain why the deer population does not continue to increase above about 1200.2 marks
2. Two species of barnacle, X and Y, live on a rocky shore. Both attach to rock and feed by filtering plankton from the water. Species Y grows faster and smothers species X in the lower zone of the shore, but Y cannot survive long exposure to air in the upper zone.
   Suggest why species X is found only in the upper zone when species Y is present.2 marks
3. Records of a population of snowshoe hares and of the lynx that feed on them were collected over many decades in a boreal forest. Both populations rise and fall in regular cycles with peaks about 10 years apart. Each lynx peak occurs one to two years after the hare peak. Hares feed on vegetation, and lynx feed mainly on hares.
   Explain why each peak in the lynx population occurs after the peak in the hare population.3 marks