Problem 8 - Biology: The Dynamic Science

Question

Which example might reflect density-dependent regulation of population size? a. An exterminator uses a pesticide to eliminate carpenter ants from a home. b. Mosquitoes disappear from an area after the first frost. C. The lawn dies after a month-long drought. d. Storms blow over and kill all willow trees along a lake. e. The size of a clam population declines as the number of predatory herring gulls explodes.

Step-by-Step Solution

Answer

Option e reflects density-dependent regulation of population size. The explosion in the number of predatory herring gulls leads to a decline in the clam population. This shows that some factor associated with population density (here, predation) is inhibiting further population growth.

Step 1: Analyze Option a

In this case, the exterminator uses a pesticide to eliminate carpenter ants from a home. This action does not depend on the density of the ant-population, but on an external factor. Hence, it does not reflect density-dependent regulation.

Step 2: Analyze Option b

In this situation, mosquitoes disappear from an area after the first frost. Again, this is not due to the mosquito population density, but an environmental change (frost). It's not a case of density-dependent regulation.

Step 3: Analyze Option c

Here, the lawn dies after a month-long drought. This is also a consequence of an environmental change, not by the density of the population, hence this doesn't reflect density-dependent regulation.

Step 4: Analyze Option d

Storms blow over and kill all willow trees along a lake. Once again the population decrease resulted from an environmental change (storm), not the density of their population. This is not density-dependent regulation.

Step 5: Analyze Option e

The size of a clam population declines as the number of predatory herring gulls explodes. This is an example of Predator-Prey interaction, which can regulate population size based on the density of both predator and prey. This is an example of density-dependent regulation.