The effect of biotic and abiotic factors on populations：练习题

In an ecological context, which of the following best defines a community?

During primary succession, pioneer species such as lichens and mosses colonize bare rock. Which statement best explains how these species facilitate the subsequent growth of larger plants?

A graph of the population size of a prey species and its predator shows cyclical fluctuations. The prey population peak is consistently followed by a predator population peak with a distinct time lag. Which of the following best explains why the predator population does not peak at the exact same time as the prey?

In an ecosystem, which of the following provides the most accurate definition of a community?

A population of a specific plant species in a valley was observed to decline rapidly following a period of exceptionally low rainfall and high temperatures. Which category of factor is responsible for this variation in population size?

Distinguish between interspecific competition and intraspecific competition, providing one example of a resource that could be the subject of such competition.

Explain why species adapted to extreme abiotic conditions, such as high salinity or extreme pH, are often restricted to those specific habitats despite the high metabolic cost of their physiological adaptations.

A study of two competing species of desert rodents found that their population sizes were both significantly lower when they shared a habitat compared to when they were isolated.

Suggest how interspecific competition and the concept of the ecological niche explain why neither species is able to reach its carrying capacity in the shared habitat.

In an ecological context, the terms population and community have specific meanings.
(a) Define the term community. (1 mark)
(b) Explain how the niche of a species is determined by its adaptations to both biotic and abiotic conditions. (2 marks)

A large area of forest was cleared for timber, leaving behind bare soil. Over the following decades, ecologists recorded the return of various species.

(a) Name the type of ecological succession occurring in this forest after the timber was cleared. (1 mark)
(b) Describe how pioneer species change the environment during the early stages of this process to allow other species to survive. (2 marks)
(c) Explain why the biodiversity of the area typically increases as the community progresses towards a climax community. (2 marks)