Question

with shorter wingspans and bodies in the population increased.

which of the following identifies a selection pressure and describes its effect on the fitness of birds in the population?

a automobiles exerted selection against a longer wingspan and body; over time the fitness of individuals with a shorter wingspan and body increased.

b automobiles exerted selection for a longer wingspan and body; over time the fitness of birds that chose to have a shorter wingspan increased.

c a longer wingspan and body exerted selection against living under bridges; over time birds with longer wingspans and bodies moved to forested areas to increase their fitness.

d a shorter wingspan and body exerted selection for mates; over time female birds chose mates with shorter wingspans and bodies to increase their fitness.

Explanation:

To solve this, we analyze each option:

• Option A: Automobiles (a human - made factor) can be a selection pressure. If longer wingspanned/bodied birds are more likely to be harmed by automobiles, selection is against them. Then, shorter - wingspanned/bodied birds would have higher fitness over time as their population increases, which matches the context (shorter wingspans and bodies in the population increased).
• Option B: Says automobiles exert selection for longer wingspan, which contradicts the population change (shorter ones increased). Also, birds don't "choose" their wingspan (it's heritable, not a choice).
• Option C: The selection pressure is misidentified. The wingspan/body size is a trait, not the selector. Living under bridges is not the main selection pressure here, and moving to forested areas is not related to the given population change.
• Option D: Mating choice is not the main selection pressure here. The population change is due to environmental (automobile - related) pressure, not mate choice based on wingspan/body size.

Answer:

A. Automobiles exerted selection against a longer wingspan and body; over time the fitness of individuals with a shorter wingspan and body increased.