AP Environmental Science : Ecological Succession

Study concepts, example questions & explanations for AP Environmental Science

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Example Questions

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Example Question #101 : Ecosystems And Biology

Which of the following is an accurate example of primary ecological succession?

Possible Answers:

Boreal forests throughout Alaska and Canada are undergoing a transition where short-lived conifer stands are slowly replaced by deciduous hardwood stands, which are characteristic of a more mature forest.

A wildfire burns through the underbrush of a hardwood forest, freeing up available sunlight for new understory brush.

A woodland ecosystem has been overbrowsed by moose that quite enjoy low-lying willow branches and seedlings, resulting in a depletion of young willow trees. Deer soon replace moose in the woodland to graze on the abundant grasses and sedges.

A windstorm displaces nutrient-rich topsoil that has been heavily tilled, resulting in diminished fertility and inability for plant communities to establish themselves.

River sediments are deposited along a waterfront consisting of barren rock, resulting in the establishment of moss and grass communities.

Correct answer:

River sediments are deposited along a waterfront consisting of barren rock, resulting in the establishment of moss and grass communities.

Explanation:

Primary succession is, by definition, the establishment of living communities in areas where life had not previously existed. A waterfront that is barren rock does not initially have the potential to support life until mineral and soil deposits allow new plant communities to establish themselves. The other answers are not correct because plant communities already exist in these examples, which is not characteristic of primary succession. 

Example Question #11 : Ecological Succession

Which of the following organisms would be most likely to be found in an ecosystem undergoing primary succession?

Possible Answers:

Atlantic Cedar

Lichen

Blueberry

Black Oak

White Pine

Correct answer:

Lichen

Explanation:

Lichens are able to survive on bare rocks, with very few nutrients available. As a result, they are one of the first organisms to colonize an area of primary succession, where they usually break down rocks over time to form the base of soil in the new habitat.

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