A bat's wing and a bird's wing are analogous structures, as the development of these structures does not share an evolutionary history. The common ancestor of bats and birds did not have wings, therefore these traits arose independently. Therefore, they are not homologous, but represent convergent evolution, as similar traits arose from different lineages due to environmental pressures.

Mutation, migration, natural selection, and genetic drift all change the presence and proportion of alleles in a given population, contributing to evolution. An unchanging environment would not contribute to changes in alleles and, therefore, does not contribute to evolution.

We see natural selection because those chickens that are entirely immune to the disease produce more offspring than those chickens who were infected but survive. The gene(s) that offers protection against contracting the disease is retained at a greater rate than the gene(s) that protects the chicken from dying of the disease. If the genetic diversity of the population is reduced generations later, this suggests that the chickens experienced a population bottleneck when the population number dropped to half of its original number.

The founder effect is when genetic variability is lost due to a small number of individuals from a larger population forming a new population. The smaller population only breeds with each other and is not genetically representative of the larger group from which it was founded. Thus, the humans on a deserted island are an example of this. The hurricane might be an example of a population bottle neck and the breeder might be causing a population bottleneck by only breeding certain dogs, but the humans are a better example of the deliberate formation of a new breeding population.

In order for animals to belong to the same species, they must, by definition, be able to mate with one another to produce viable offspring. The question stem says that these two animals cannot mate to produce viable offspring; therefore, they cannot belong to the same species. Since they cannot belong to the same species, they cannot "represent closely related variants of the same species," either. Although they are not the same species, the information about their similar anatomy and diet suggests that they likely evolved from a common ancestor, making the answer choice "The two animals are adapted to live in completely different environments" also incorrect.

An organism's evolutionary fitness is defined by the number of offspring that it produces. Mutations that increase the number of offspring that an organism can have will, by definition, increase its evolutionary fitness. Evolutionary fitness is not defined by strength, size, or habitat. While it is theoretically possible that each of the wrong answers might increase the fitness of an organism in the right circumstances, none of the wrong answers are guaranteed to increase the number of offspring produced by the organism.