Q58. Harbor seal populations along the coast of British Columbia have recovered

Question

Q58. Harbor seal populations along the coast of British Columbia have recovered since hunting stopped in 1968. As you can see in the graph to the right, changes in population size over time resemble logistic growth somewhat, although the seal population size continues to fluctuate after its nominal carrying capacity is reached.

If the variation in seal population size from 1995 to 2010 is a result of year-to-year variation in sea temperature, then this would be an example of:

A. Environmental stochasticity

B. Demographic stochasticity

C. Delayed density dependence

D. Chaos

Q59. Which of the following is an example of an Allee effect?

A. A highly virulent and fast-spreading fungal disease causes the collapse of a population of cave-dwelling bats.

B. Mountain lions cause the decline of a bighorn sheep population that is too small to effectively watch for predators.

C. A butterfly population declines when its host plant (on which it lays eggs) is displaced by non-native (introduced) plants.

D. A frog population’s reproductive success drops drastically when the water in its habitat is contaminated with toxins.

Explanation / Answer

58. C. Delayed density dependence

This is an example of delayed density dependence as the variation in population is observed over a time period and is dependent upon temperature.

59. A. A highly virulent and fast-spreading fungal disease causes the collapse of a population of cave-dwelling bats.

This is an example of allee effect because the fungus is virulent and fast spreading which increases its fitness or invasion level and leaves a negative impact on the population of bats.

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