Speciation is defined as allopatric or sympatric based on whether which of the following occurs?

• A. Species evolve due to genetic drift alone.
• B. Geographic isolation leads to the formation of new species.
• C. New species arise without geographic separation.
• D. Speciation occurs only in response to environmental changes.

Answer: (B)

Verified step by step guidance

1. Begin by understanding the concept of speciation, which is the process by which new species arise. Speciation can occur through different mechanisms, primarily allopatric and sympatric speciation.
2. Allopatric speciation occurs when a population is geographically isolated, leading to the formation of new species. This isolation prevents gene flow between separated groups, allowing them to evolve independently.
3. Sympatric speciation, on the other hand, occurs without geographic separation. It can happen due to factors like genetic mutations, polyploidy, or behavioral changes that lead to reproductive isolation within the same area.
4. Consider the options given in the problem: 'Geographic isolation leads to the formation of new species' aligns with allopatric speciation, while 'New species arise without geographic separation' aligns with sympatric speciation.
5. Evaluate the other options: 'Species evolve due to genetic drift alone' and 'Speciation occurs only in response to environmental changes' are not directly related to the definitions of allopatric or sympatric speciation. Focus on the geographic aspect to determine the type of speciation.