The founder effect describes the phenomenon when a smaller group that originally came from a part of a larger population forms their own population. This new population will likely have a biased gene pool that will not be identical to the parent population. For example, if a certain species of bird gains a mutation such that some members are capable of flying farther, these birds may eventually separate to a different location and form their own unique population with a higher predominance of the "sustained flight" mutation than the original population.

The founder effect, after a long time, can lead to speciation, but this is not an essential part of the founder effect. Introducing a new species to native populations may influence the balance of the ecosystem and change genetic frequencies, but is not linked to the founder effect. A decrease in genetic variety due to fluctuation of certain traits would more aptly describe the bottleneck effect.

The founder effect describes a scenario in which a new population is started by a small group from a larger population. This smaller population is most likely not representative of the larger group and displays certain genetic bias. The high rate of Huntington's disease is most likely a result of the fact that the small group of European colonists had a high rate of the gene that produces the disease.

Natural selection and sympatric speciation do not apply in this situation. The bottleneck effect occurs when a large population is thinned, and a non-representative group of the original population is all that remains; this does not describe the situation presented above. 

A smaller group being separated permanently from a larger population is a classic example of the founder effect. These 500 members likely have far less genetic diversity than the larger population, so the subsequent population that develops will only contain alleles found in these 500 members.

The founder effect is a particular example of the bottleneck effect, wherein the number of individuals in a population is reduced very quickly from a non-selective pressure, such as a natural disaster or geographic barrier. Though the rest of the larger population is presumably still alive, these 500 people have gone from living in a large population to living in a relatively small one. The result is a decrease in genetic diversity when the smaller portion of the population is compared to the previously-existing larger group.

In the immediate future, this group could experience genetic drift wherein the relative frequencies of their alleles shift due to random chance. Genetic drift is more prominent in smaller groups, and would therefore help to understand what could happen in the population's immediate future. Since the group is relatively small, we could expect to see the results of genetic drift as early as fifty years after the separation event.

Natural selection occurs over many generations and longer time periods. It would not help us to understand the immediate future of this new population.

Genetic drift is a change in allele frequencies in a population through random chance. It occurs over time and isn't a result of more fit organisms passing on their genes. In all but one of the answer choices there is some selective pressure that causes a change in the population that is not related to random chance. Thus, the example with the exact same selective pressures is the only scenario that could result in genetic drift. Predation can cause one allele to die out and another to prosper if one allele causes the organism to be better camouflaged. If individuals in a population have a preference for one type of allele then that allele will prosper. Sources of food can also cause an organism to change. For instance, if on one side of the lake the dominant food source is algae and on the other side smaller, quicker fish are the source of food, then over time the fish on either side of the hypothetical lake could diverge. One gaining a better ability to scoop algae and the other becoming very agile.

The bottleneck effect occurs when a random and catastrophic event reduces the population of an organism by a large number. The remaining individuals repopulate the area after the event, but the genetic diversity of the population is greatly reduced. The founder effect occurs when a group of individuals are separated from the main population and subsequently establish a new population. This new population's genetic diversity is also greatly reduced.  In both cases a small number of individual establish a population and this small "pool" of genes is how genetic diversity is reduced. The wolves are separated from their pack by being released in a new area and then established a new population; this is an example of the founder effect. The pea plants were killed by a random event, but the survivors did not survive by random chance. Instead they had a gene that gave them higher fitness compared to the other members. This is a better example of natural selection. The fish in the flash flood were separated from the main population and subsequently established a new population in the nearby lake. This is an example of the founder effect. The drought lake is the best example of the Bottleneck effect because the event was random and the survivors lived due to random chance. A small number of the fish reestablished their population in the lake, their genetic diversity was also reduced.

Genetic drift is a change in allele frequency between generations due to sampling error. Since genetic drift makes certain allele variations disappear, it decreases genetic variation. Additionally, genetic drift has a smaller effect in larger populations and a large effect in small populations.

Gene flow is a mechanism of evolution in which genes are transferred between populations. Two examples of gene flow are migration and horizontal gene transfer. In the case of migration, the movement of individuals into or out of a population also results in a transfer of alleles. Horizontal gene transfer (common in bacteria) is the transfer of genes through means other than reproduction (i.e. plasmid exchange).

Genetic drift is due to the production of a finite number of zygotes within a population. This causes allele frequencies to change from one generation to the next. Genetic drift can result in the reduction of the fitness of individuals within a population if the alleles passed on are deleterious.

When a population is reduced for a short period of time, only the rarest alleles are usually lost, as is seen in bottlenecking. In order for a significant change in allelic frequency to be seen, the population must become significantly small, and it must stay small for a significant amount of time. The latter is referred to as the Founder Effect.

This is an example of gene flow, because a small number of individuals from one population are passing some genes on to those in another population. Genetic drift occurs within a single population, so it does not apply here. This is not an example of speciation. There can't be a prezygotic barrier present if the geese are able to successfully mate.