Small populations tend to have less genetic variation to begin with. Introducing a bottleneck effect further reduces variation and population size, amplifying the effect of genetic drift. This leaves them susceptible to changes in the environment that they may not be capable of adapting to due to limited differences among individuals.

A bottleneck effect is the term used to describe the loss of genetic variation that occurs after outside forces destroy most of a population. The few individuals left to reproduce pass their traits on to all of their offspring, which then may thrive without the competition of a large population. Eventually, there may be a large, very genetically similar population based on the traits of the few original survivors.

The founder effect describes the low genetic variation of a population derived from a small group of individuals in a new geographic location. Genetic drift is the random change of allele frequency in a population.

The bottleneck effect describes the phenomenon when a population has a sudden reduction in the gene pool due to natural environmental events, natural disasters, disease, or human involvement. This reduction in the gene pool will likely cause a bias that did not exist in the original population. For example, suppose a population of birds has a small number with a mutation making them unable to fly. If a disease reaches this population that kills all birds when they reach an altitude above 50m, then the gene pool of the population will suddenly shift to favor the flightless birds.

The bottleneck effect, after a long time, could potentially lead to speciation, but this is not a defining factor of the effect. Introducing a new species can increase the pressures of natural selection, but does not directly relate to the bottleneck effect. A decrease in genetic variety due to a small number of individuals from a larger population establishing a new population more aptly describes the founder effect.

The bottleneck effect describes the sudden, sharp decrease in the size of a population. After a bottleneck event, a population could either recover or go extinct depending on the fitness of the individuals remaining in the population.

Depending on the type of event that created the bottleneck, it is possible that the surviving members are the most fit, but this is not always the case. The new smaller population likely has less genetic diversity, which typically makes successful adaption more difficult and less likely, but if the surviving members of the population are highly fit, their ability to adapt may not be hindered.

While man-made events certainly are a source of bottleneck effects in the world today, there are still natural bottleneck events and no concrete evidence to say that man-made bottleneck events are more frequent or have more of an effect on genetic drift than natural events.

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.