When a sexual reproduction takes place, the genes of two parents are mixed to produce different gene combinations. This event creates different traits in a population. On the other hand, asexual reproduction does not involve the exchange and combination of genetic information between organisms. Instead, it produces the same genetic information from a single parent. Therefore, sexual reproduction increases the genetic variation in a particular gene pool.

The reason for this event is due to the evolution of drug-resistant bacteria. Antibiotic resistance is a major consequence of evolution that occurs due to natural selection. The effect of the antibiotic is like an environmental pressure. If the bacteria are exposed to the same kind of antibiotic, it will become fully resistant to it. To address this problem, scientists created a more powerful antibiotic that is only used for the most serious infections. In this way, it would have an effect on the bacteria that is resistant to the weaker antibiotics.

Hypothesis A indicates that the same type of fish, which exists in both lakes, is the possible ancestor of the brown and gold fishes.

Hypothesis B claims that each lake contained a separate ancestor. The brown fishes dominated lake 1 and there gold fishes in lake 2. Since both lakes occasionally experience flooding, some brown fishes from lake 1 were brought into the other lake, while some of the gold fishes from lake 2 were brought into the other lake. This resulted in a change in the genetic pool of both lakes.

The main difference between the two hypotheses is that hypothesis A shows an evolution via natural selection, while hypothesis B shows an evolution due to genetic drift.

Hypothesis A shows how a common ancestor has evolved into the modern species. It indicates that over the years, nature has favored the fishes in brown and gold colors.

Hypothesis B shows how genetic drift occurred between the two small populations of the fishes. A random change in the allele frequency was caused when some species moved into a new habitat due to flooding.

When two fish species have closely related genetic structure or makeup, this means that they both share the same recent ancestor. In this case, hypothesis A best supports the evidence shown in the DNA analysis.

According to the table, the frequency of allele B has decreased from 1990 to 1970. On the other hand, the frequency of allele b has increased from 1910 to 1970.

This event shows a natural selection on a single-gene trait. The increase in the frequency of allele b indicates that nature has favored this trait over the other one. Species with this trait were able to adapt, survive, and reproduce; hence, allele b becomes more common in this population. On the other hand, since the frequency of allele B has decreased, this means that the species with this trait are not able to adapt to the current environment or condition. Therefore, allele B becomes less common in the population.

The term reproductive isolation is a mechanism that involves two populations that are no longer mating and producing offspring. When the finches arrived in the different islands of Galápagos, they were isolated and they do not share the common gene pool anymore because they rarely flew over open water. Even when some flew across from one island to another, their differences in mating rituals, ecological competition, and other behavioral patterns have made interbreeding and coexisting in one habitat difficult. Because of this, the gene pools of the two populations remained isolated. As a result, populations of finches in the different islands evolved separately and eventually, they have become separate species.

The small population of finches did not evolve into the 13 species right away. The evolution of the finches in the different islands of Galápagos occurred due to an interplay of several factors including the founding of new population, reproductive isolation, geographic isolation, changes in the new population’s gene pool, and ecological competition.

When the finches arrived in the different islands of Galápagos, they were isolated and they do not share the common gene pool anymore because they rarely flew over open water. Even when some flew across from one island to another, their differences in mating rituals, ecological competition, and other behavioral patterns have made interbreeding and coexisting in one habitat difficult. Because of this, their gene pools remained isolated and the populations of finches in the different islands have evolved separately. Eventually, this event led to speciation.

The small population of finches did not evolve into the 13 species right away. The evolution of the finches in the different islands of Galápagos occurred due to an interplay of several factors including the founding of new population, reproductive isolation, geographic isolation, changes in the new population’s gene pool, and ecological competition.

Evolution via genetic drift usually occurs in a small population due to some random events, such as natural disasters or migration. These events may alter the allele frequency in a gene pool. This process is usually the result of the founder effect or the bottleneck effect.

The founder effect occurs when a small subgroup of a population is forced to move into a new habitat or they decide to migrate from one place to another. As a result, there are changes in their allele frequencies that are different from the original species.

On the other hand, the bottleneck effect occurs when a natural disaster wipes out almost an entire population. As a result, the surviving species might have a different set of traits that vary from the lost population.