Questions: Which statement explains how a stable ecosystem can exist even while the populations in it vary over time? A. If individuals in a population cannot find shelter, they will use new abiotic factors for shelter so the population can continue to grow. B. If a prey population grows, it will decrease the size of the predator population because the predators will have less competition for food. C. Less rain one year will cause populations to decrease due to a lack of food, and populations will stay at this reduced size even when rain returns. D. If a disease spreads through a population that has a lot of genetic variation, resistant individuals will survive and the population will recover.

The answer is D: If a disease spreads through a population that has a lot of genetic variation, resistant individuals will survive and the population will recover.

Explanation for each option:

A. If individuals in a population cannot find shelter, they will use new abiotic factors for shelter so the population can continue to grow.

• This statement is incorrect because it oversimplifies the adaptability of organisms. While some species can adapt to new abiotic factors, it is not guaranteed that all individuals will find suitable alternatives, and this does not directly explain how a stable ecosystem can exist.

B. If a prey population grows, it will decrease the size of the predator population because the predators will have less competition for food.

• This statement is incorrect. An increase in prey population typically leads to an increase in predator population, as more food is available. The statement does not accurately describe predator-prey dynamics.

C. Less rain one year will cause populations to decrease due to a lack of food, and populations will stay at this reduced size even when rain returns.

• This statement is incorrect because it suggests that populations do not recover after environmental conditions improve, which is not typically the case. Populations often rebound when favorable conditions return.

D. If a disease spreads through a population that has a lot of genetic variation, resistant individuals will survive and the population will recover.

• This statement is correct. Genetic variation within a population allows for some individuals to have resistance to diseases, enabling the population to recover over time. This resilience contributes to the stability of the ecosystem despite fluctuations in population sizes.

In summary, option D correctly explains how genetic variation can contribute to the resilience and stability of an ecosystem, allowing it to persist even as populations fluctuate.