DNA evidence indicates that two species of land snails are closely related and may only recently have become distinct species. What would a biologist infer has happened to the original population of land snails? A. The original snall population became extinct because of environmental changes. B. The original snal population had a group of snalls that became reproductively isolated. C. The original snall population interbred with a different species of snall to form an entirely new specles. D. The original snall population became too large for the ecosystem so the species adapted by forming a new specles.

## Step 1<br />The problem is about the concept of speciation, which is the process by which populations evolve to become distinct species. The question provides evidence that two species of land snails are closely related, suggesting that they may have recently become distinct species.<br /><br />## Step 2<br />The biologist would infer that the original population of land snails had a group of snails that became reproductively isolated. This is because reproductive isolation is a key factor in speciation. <br /><br />## Step 3<br />Reproductive isolation means that a group within a population is unable to interbreed with other groups. This can lead to the development of new species over time, as the isolated group evolves independently from the rest of the population.<br /><br />## Step 4<br />The other options (A, C, and D) do not directly address the concept of speciation through reproductive isolation. They either suggest extinction, interbreeding with a different species, or adaptation due to population size, none of which are directly related to the formation of new species through reproductive isolation.