Question

In the winter, some Horned Larks from the arctic tundra migrate to southern Indiana, where they coexist with our local Horned Larks. In the summer, the arctic larks migrate back to the tundra to breed, and our local larks stay in southern Indiana to breed. Based on this description:

		The local Horned Larks and the arctic Horned Larks are separate populations, because populations must occupy the same area year round.
		The local Horned Larks and the arctic Horned Larks are a single population, because they occupy the same area for at least part of the year.
		The local Horned Larks and the arctic Horned Larks are a single population, because they are the same species.
		The local Horned Larks and the arctic Horned Larks are separate populations, because they do not interbreed.

Answer 1

Population defines a group of organisms of the same species, living in same environment, using same food resouces and exposed to similar environmental factors. Here it is clear that the two groups of Horned larks mentioned, being exposed to entirely different ecological factors at least in one entire season. Moreover they are using different resources as exposed to different habitat during winter. Above all they are not interbreeding.

Population means same species in same area occuring at same time.

Examining each sentance

1. Considerin a specific population,it can move from one area to other ie population can migrate as a single unit. It is not necessary that population should exsist in a particular palce round the year.

2.Individual in a population has to expose with same environmental forces/conditions throughout their life. Hence the 2 groups mentioned here are not same population.

3. They are not same species because it is clearly mentioned that they move at different sites during mating time.

The correct answer is the last sentance ie The local Horned Larks and the arctic Horned Larks are separate populations, because they do not interbreed.