[Campbell Biology P.1189] According to Figure 51.2 and the accompanying text, what is the "si... | Practice Question

According to Figure 51.2 and the accompanying text, what is the "sign stimulus" that triggers the aggressive territorial response in male three-spined sticklebacks?

  • A: The overall shape and species identity of an invading fish.
  • B: The red coloration on the underside of an invading male.
  • C: The size and movement patterns of an intruder.
  • D: The presence of any fish within their nesting territory.

Explanation

The text explicitly states, "Researchers concluded that the red belly of the intruding male is a sign stimulus that releases the aggressive behavior." Figure 51.2 b also clearly shows that models with red undersides elicit a territorial response, while those without do not, regardless of other realistic features.