Question

Why is geographic isolation necessary for most cases of speciation?

a) To prevent gene flow
b) To promote gene flow
c) To increase genetic diversity
d) None of the above

Answer 1

Geographic isolation is vital for speciation as it prevents gene flow between populations. The correct option is a.

Step-by-step explanation:

Geographic isolation is necessary for most cases of speciation because it prevents gene flow between isolated populations. This lack of gene flow is essential for new species to evolve, as it prevents the mixing of genetic information among these populations.

Over time, isolated groups accumulate genetic differences due to mutation, natural selection, and genetic drift, leading to the emergence of new species.

For instance, if a new river branch forms and divides a population of rodents, they are unlikely to cross over it, resulting in two separate populations that may eventually diverge into distinct species. This process is known as allopatric speciation.

However, if populations with the potential for high dispersal, like flying insects, become separated by a geographical barrier, they might still maintain gene flow if they are capable of flying back and forth across the barrier.

Therefore, the nature of the geographic separation necessary to successfully lead to speciation largely depends on the organism’s biology and dispersal capabilities.

Other mechanisms that may lead to speciation include prezygotic and postzygotic barriers which inhibit the formation of viable offspring between different species, thereby reinforcing speciation. The correct option is a.