Biology Test Biology Ecology & Environmental Interactions 2

Question 1

Which of the following best describes a keystone species?

Accepted Answer

A species whose removal causes dramatic ecosystem change disproportionate to its abundance

Answer

Keystone species have outsized ecological roles; their removal triggers cascading changes far beyond what their population size would suggest.

Question 2

In a food web, secondary consumers are organisms that

Accepted Answer

Eat primary consumers

Answer

Secondary consumers occupy the third trophic level, feeding on primary consumers (herbivores).

Question 3

The nitrogen cycle is critical to ecosystems primarily because nitrogen is

Accepted Answer

An essential component of amino acids and nucleic acids

Answer

Nitrogen is a core element of proteins and DNA, making its cycling through ecosystems vital for all living organisms.

Question 4

Which term describes the gradual process by which a bare rock surface develops into a mature forest community?

Accepted Answer

Primary succession

Answer

Primary succession begins on lifeless substrates like bare rock where no soil exists, starting with pioneer species like lichens.

Question 5

An organism that benefits from a relationship while its host is neither helped nor harmed is engaged in

Accepted Answer

Commensalism

Answer

Commensalism is a +/0 relationship where one species benefits and the other experiences no significant effect.

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