Jacob is studying a population of wrens in Michigan. Over several years, he notices that the population always stabilizes at around 45 individuals. Forty-five individuals is a density-independent factor. a density-dependent factor. the carrying capacity. the growth rate. the density.

the carrying capacity

Explanation:

The forty-five individuals is a figure that represents the carrying capacity of Michigan for wrens.

The carrying capacity of an environment or habitat is the maximum number of individuals of a particular species that the environment/habitat can support at a time based on the resources that the environment/habitat has.

The species whose population is below the environment's carrying capacity still has the potential to experience growth in their population while those whose population is already at the carrying capacity can no longer experience significant population growth.

The population is kept oscillating around the carrying capacity by environmental factors such as competition, diseases, predation, etc.

b. heterotroph

explanation: