A population of ducks lives in an area that floods many times each year. Some of the ducks are better at finding food on dry land, while other ducks are better at finding food in wet, muddy areas. Eventually, the land around the lake permanently changes from dry soil to wet, marshy mud. How will this change to the land most likely affect the duck population?

The population will remain stable because the ducks will not be affected by this kind of change.
The population will eventually balance out so that there are equal numbers of both types of ducks.
The population will evolve so that most ducks survive no matter how they find food.
The population will evolve so that most ducks are better at finding food in wet, muddy areas.

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.

Patient has just received an organ transplant which treatment would be most effective in preventing the patient’s body from

Which feature would you expect to find in a population in which sexual selection depends on male competition?