The only absolutely correct answer is the one that states that an animal can successfully mate with another animal and produce viable offspring that are capable of successfully reproducing. The key to defining a species is that the offspring are both viable and fertile. The correct answer encompasses both of those tenets.

"One animal mates with another animal and produces viable offspring that are not capable of reproducing successfully." This choice is incorrect because it states that the offspring are not fertile.

"One animal lives in a closed environment with 250 to 500 other animals that look similar to one another and support each others' basic needs (food, shelter, protection)." This example may describe a species, but there is not enough information to definitively conclude that. It does not explicitly state that the animals successfully mate with one another, or that their offspring (if they do mate with each other) are fertile. 

"One animal lives in a closed environment with greater than 500 other animals that look similar to one another and support each others' basic needs (food, shelter, protection)." This example may describe a species, but there is not enough information to definitively conclude that. It does not explicitly state that the animals successfully mate with one another, or that their offspring (if they do mate with each other) are fertile.

The Urey-Miller experiment was used to determine if the early atmospheric conditions were favorable for the creation of organic materials. Their experiments determined that basic organic molecules, such as urea and amino acids, were able to form in early atmospheric conditions.

The Mehselson-Stahl experiment revealed the semi-conservative nature of DNA replication.

A physiological condition making two speciated animals unable to mate is a mechanical difference.

Directional selection is when a population undergoes a change biased in a certain direction away from the original average of the population. Since the fish are getting bigger in once sense and smaller in another, this is directional selection.

Allopatric speciation occurs when a physical barrier, or in some cases emigration of subpopulations of a species, prevents interspecies mingling that eventually leads to the inability to interbreed. Sympatric speciation describes a process by which new species form while in the same geographic location. Parapatric and peripatric speciation are subcategories of sympatric speciation.

The situation described is a classic example of the evolutionary principle of "bottlenecking," making this the best answer choice. Bottlenecking describes the phenomenon in which the genetic diversity of a population changes suddenly, often due to a natural disaster, which then results in future generations appearing more genetically and phenotypically similar to one another than in the pre-disaster generations. In this instance, pink flmaginos were initially more common than white flamingos, but both were fairly prevalent. They then encounter a hurricane that kills all but a few flamingos, which were almost entirely white-feathered, which led to all ensuing generations being predominantly white-feathered. 

This does not represent "selective mating," "spontaneous mutation," or "genetic engineering," as white-feathered flamingos became most prevalent due to a natural disaster, not white flamingos selectively seeking to mate with other white flamingos, not due to a single mutation, and not due to scientists artificially manipulating the genes within the flamingos. 

This does not represent "genetic drift," because the changes in phentype prevalence were not due to random chance fluctuations, they were due to an explainable event, a natural disaster that resulted in an initially low number of white flamingos remaining and becoming most predominant.

Inbreeding increases the expression of recessive traits due to more heterozygous carriers mating with each other. As the same individuals mate, the chance of a homozygous recessive child increases. This is the same as estimating the likelihood of a single healthy child from two carrier parents (0.75) versus eight healthy children from two carrier parents (0.10).

Inbreeding decreases genetic diversity, rather than increasing it. The rate of spontaneous mutation is not impacted by this type of breeding. There is no reason to infer increased levels of aggression.

For the Hardy-Weinberg equation to be true, the population in question must be very large. This ensures that coincidental occurrences do not drastically alter allelic frequencies.

The two equations pertaining to Hardy-Weinberg equilibrium are:

In this second equation, each term refers to the frequency of a given genotype.  is the homozygous dominant frequency,  is the heterozygous frequency, and  is the homozygous recessive frequency.

From the question, we know that:

We now know the dominant allele frequency. Using the other Hardy-Weinberg equation, we can find the recessive allele frequency:

Returning to our genotype frequency terms, we can use this recessive allele frequency to find the homozygous recessive frequency: