Question

Males of the Indian robin in two populations sing songs of different lengths. Which one or more of the options given is/are an ultimate (not proximate) explanation(s) of the difference in song length between the two populations?

• A. Females prefer to mate with males that sing longer songs in one population but not in the other.
• B. The two populations have different forms of the gene that determines song duration.
• C. The two populations differ in hormone levels that activate the start and end of singing behaviour.
• D. Differences between populations in food availability during development affect neural circuitry that is involved in song production.

Hint:

Understanding the role of sexual selection in evolution helps explain why certain traits, like song length in birds, may vary significantly between populations, reflecting differences in mating strategies and female preferences.

Answer 1

The Correct Option is A

Step 1: Evaluate the ultimate nature of Option (A). Option (A) proposes that differences in female mating preferences across populations have led to variations in male song length. This is considered an ultimate explanation because it addresses the evolutionary reasons—specifically, sexual selection—that could lead to genetic differentiation and behavioral adaptations in song length among populations. Step 2: Implications of sexual selection. Sexual selection is a form of natural selection where certain traits become preferred by one sex, in this case, females. These preferences can drive significant evolutionary changes in populations, leading to traits that are advantageous in specific mating contexts but may vary geographically depending on local preferences.