Biology  5/e   Raven/Johnson
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Natural selection: Evolutionary change occurs in populations because of natural selection. Individuals that have traits that make them better adapted to their environment will be selected for. These more fit individuals will be more likely to survive and produce more offspring than the less fit members of the population. Over time, the advantageous traits become more and more common in the population as a result of the differential survival and reproduction of individuals. The end result is populations that are highly adapted to their environments, both the abiotic factors and the other populations with which they must interact.

Adaptation: Adaptations increase the likelihood of survival and reproduction of an individual in its environment. We see populations with remarkable adaptations, because over time natural selection has favored the better adapted individuals and selected against the poorly adapted members of the population. As a result, adaptations become more and more common in the population.

Demography: Demography is the statistical study of populations. It includes the study of such population characteristics as size, growth rate, mortality, and age distribution. To understand why a population has the demographic characteristics that it does, you must also understand the factors that influence the population; factors such as the climate, availability of resources, intra- and interspecific competition, predator-prey interactions, parasitism, and other symbiotic relationships.

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