Final answer:
Competitive exclusion happens when one species outcompetes another for the same resources, leading to the extinction of the less adapted species. The growth of forests in New England after settlers' arrival was due to the decline of Native American populations from introduced diseases. so, option c and d are correct.
Step-by-step explanation:
Competitive exclusion happens when c) one species outcompetes another for the same resources, leading to the extinction or exclusion of the other species. This is based on the competitive exclusion principle, which posits that two different species cannot occupy the same niche in the same place for long. One species will out-compete the other for resources, and the less adapted species may face extinction.
The forests in New England grew back after settlers arrived because d) the Native American population declined due to introduced diseases. This decline in the human population allowed the forests to reestablish themselves over areas that were previously cleared for agriculture or settlements.
The competitive exclusion principle states that two species cannot occupy the exact same niche in a habitat. In other words, different species cannot coexist in a community if they are competing for all the same resources. This principle works because if there is competition between two species for the same resources, then natural selection will favor traits that lessen reliance on the shared resource, thus reducing competition. If either species is unable to evolve to reduce competition, then the species that most efficiently exploits the resource will drive the other species to extinction.