AP BIOLOGY

Detailed explanation-1: -Answer and Explanation: The correct answer is e. instinct.

Detailed explanation-2: -From an evolutionary standpoint, there’s some reason for the salmon to die after making it upriver; they use all their energy on reaching this spot and mating, and their decomposing bodies will provide nutrients for the stream (and for insects, which will become prey in the future for their offspring).

Detailed explanation-3: -Scientists believe that salmon navigate by using the earth’s magnetic field like a compass. When they find the river they came from, they start using smell to find their way back to their home stream. They build their ‘smell memory-bank’ when they start migrating to the ocean as young fish.

Detailed explanation-4: -Adult salmon fishes lay eggs in rivers and incubate their eggs there. Thus the life cycle of a salmon fish springs from the incubation stage in a river. After emerging from eggs, the infant salmon spend their next stage in freshwater and this phase is called emergence. Then they stay in freshwater to grow further.