WCAS - Washington Comprehensive Assessment of Science Ecosystems: Interactions and Dynamics Questions and Answers

Question 1

In a forest ecosystem, the removal of wolves, a top predator, leads to a dramatic increase in the deer population.
This, in turn, causes overgrazing of aspen trees, significantly reducing their numbers.
This entire chain of events is an example of:

Accepted Answer

A trophic cascade

Answer

Competitive exclusion

Answer

Primary succession

Answer

Biomagnification

Question 2

A small island ecosystem can support a maximum population of 500 seabirds due to limited nesting sites and food resources. If the seabird population grows to 600 individuals, which of the following is the MOST likely outcome?

Accepted Answer

The population will experience a decline due to density-dependent limiting factors.

Answer

The island's carrying capacity will permanently increase to 600.

Answer

The birds will evolve to require fewer resources.

Answer

Other species will immigrate to the island to support the larger population.

Question 3

The relationship between a clownfish and a sea anemone is a classic example of mutualism. The clownfish is protected from predators by the anemone's stinging tentacles, to which it is immune. In return, the clownfish cleans the anemone and provides nutrients through its waste. Which of the following best describes this type of interaction?

Accepted Answer

A symbiotic relationship where both species benefit.

Answer

Parasitism, where one organism benefits and the other is harmed.

Answer

Commensalism, where one organism benefits and the other is unaffected.

Answer

A predator-prey relationship where the clownfish is the prey.

Question 4

A certain pesticide is sprayed on crops to control insects. This pesticide is persistent and accumulates in the fatty tissues of organisms. Which organism in the following food chain would be expected to have the highest concentration of this pesticide: Grass -> Grasshopper -> Shrew -> Owl?

Accepted Answer

Owl

Answer

Grasshopper

Answer

Shrew

Answer

Grass

Question 5

Sea otters are a crucial component of the kelp forest ecosystem. They prey on sea urchins, which in turn feed on kelp. Without sea otters, sea urchin populations explode, leading to the destruction of the kelp forests that provide habitat for numerous other species. Because of their disproportionately large effect on the ecosystem relative to their abundance, sea otters are considered a(n):

Accepted Answer

Keystone species

Answer

Invasive species

Answer

Producer

Answer

Decomposer

Question 6

Which of the following describes a density-independent limiting factor that could affect a population of deer in a forest?

Accepted Answer

A sudden, severe forest fire that burns a large area.

Answer

An outbreak of a contagious disease that spreads quickly among the deer.

Answer

Increased competition for a limited supply of acorns during the winter.

Answer

A rise in the population of wolves, the primary predator of the deer.