Extinction may be defined as the disappearance of a species. Throughout history, there have been minor and major extinctions, with minor extinctions composing the majority of all extinctions. The process of extinction is not well understood due to our reliance on the fossil record and complicated roles of competition and evolution.

Adaptation can be defined as the gradual outcome of evolution that makes an organism or group of organisms better suited to live in a given habitat. Adaptation is a result of natural selection and increases the chance of survival and reproduction. This outcome can result from either a loss of an ancestral feature or the development of a new trait.

Evolution impacts the allele frequencies within a population through mutation, genetic drift, gene flow, and natural selection. These mechanisms of evolution result in adaptation, cooperation, speciation, extinction, and co-evolution.

Cooperation is an outcome of evolution that features beneficial interactions between species, leading to the species evolving together. Cooperation is thought to have evolved from kin selection—where organisms work together to raise another’s kin for the benefit of the population.

The Founder Effect is due to a sampling error. By taking a small sample of an existing population and creating a new population, there is zero probability that the new population will have all of the same alleles as the old population. Therefore, the alleles of the new population are likely to differ from the original population. 

The three key requirements for natural selection are variation, differential reproduction, and heredity. That is, there must be variation in the population, and that variation must affect the mating success of some individuals (differential reproduction). Organisms who successfully mate must be able to pass on their genes to their offspring (heredity).

Gene flow refers to movement of alleles between populations, and is not necessary for natural selection to occur.

Because the males croak loudly when females approach, this behavior is suggestive of sexual selection. It is likely the males are demonstrating for the females in an effort to attract a mate. Sexual selection occurs when one sex (usually females) choose a mate based on a trait that does not directly affect survival (here, the frog's croak). There is not enough information to determine if the selection is stabilizing, directional, or neither. Territorial selection is not one of the types of a natural selection.

It is incorrect to think of natural selection as a response to a "need." Natural selection will select among variants in a population, resulting in evolution. Individuals and populations cannot influence the course of natural selection based on wants or needs.

Convergent evolution is the development of characteristics in unrelated species, resulting from adaptations to similar environmental conditions whereas the other choices identify other variations of evolution. Divergent evolution is the loss of similar structures in related species due to different environmental conditions. Speciation is the process by which new species evolve as a result of environmental conditions. Genetic drift is the change in allele frequencies within a population due to the imperfections of random sampling techniques. Coevolution is the phenomenon characterized by the evolution of two organisms simultaneously as a result of their interaction with each other. 

A type of natural selection in which genetic diversity decreases as the population stabilizes with respect to a particular trait value is stabilizing selection. In this mode of natural selection, the "average" phenotype is selected for and its proportion in the population increases over time. Directional selection is a type of natural selection in which a polarized phenotype is selected for over the other phenotypes, causing a shift toward the extremes with respect to proportion of individuals with that phenotype. Diversifying selection is another type of natural selection in which both extremes of a phenotype are selected for, causing an increase in the proportion of those alleles in the population. Nonspontaneous selection is not a type of natural selection.