GRE Subject Test: Biology : Understanding Environmental Impacts

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #2 : Ecological Succession

Which of the following provides the most accurate example of primary succession? 

Possible Answers:

Native grass communities forming after a wildfire burned through a meadow/woodland ecosystem

Lichens re-establish themselves on rocks and shallow soil beds following a tundra fire

Lichen and grass communities establishing themselves on a recently-formed island, resulting from an uplift in the ocean bedrock

Seedlings establishing themselves in a heavily logged area where the seed-tree cutting method was employed

Coral reef and aquatic wildlife communities that have re-established themselves in regions of the South Pacific that were evacuated following the nuclear tests conducted by the U.S. military

Correct answer:

Lichen and grass communities establishing themselves on a recently-formed island, resulting from an uplift in the ocean bedrock

Explanation:

Primary succession is characterized by plants establishing themselves in areas that were initially devoid of soil (usually bedrock). Grasses establishing themselves on a newly-formed island that is mostly bedrock is the best fit for this definition.

Example Question #4 : Ecological Succession

Which of the following would NOT contribute significantly to primary succession?

Possible Answers:

Wind-carried soil particles and nutrients

Soil nutrients deposited by a nearby river

The time-consuming process of weathering the bedrock into smaller particles

Feces from wildlife populations that occupy the region

Pre-existing nitrogen-fixing plant communities

Correct answer:

Pre-existing nitrogen-fixing plant communities

Explanation:

Primary succession is characterized by pioneer species establishing themselves in areas that are predominantly bedrock and devoid of organic material. The formation of organic material in these areas typically occurs with the accumulation of wind-carried soil erosion, nutrients deposited by flowing bodies of water, and erosion of bedrock. Wildlife populations are also a significant contributor of soil nutrients, with feces being rich in both nitrogen and phosphorus. In contrast, pre-existing nitrogen-fixing plants (or any pre-existing plant communities) are uncommon to nonexistent in an area with no established soil system.

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