Question

B. Consider the following scenario. A large population of lizards occupies an extensive range that is rela-tively uniform ecologically (i.e., in terms of climate and co-occurring species). At a certain point in time, the ancestral population becomes divided down the middle into two similar-sized portions by a barrier that completely prevents the movement of lizards between the descendent populations. Around the same time, a major flood occurs, and a small number of individuals are swept away from the mainland on floating debris and arrive alive on a small offshore island that has no lizards of this species. The habitat on the island is similar to their homeland, but not identical (the climate is slightly different, many mainland species of plants and animals are absent, and a few island species of plants and animals are different from any present on the mainland. Thus, there are now three separate populations. Compare and contrast the expected evolu-tionary consequences for these populations in the future.

Answer 1

Isolation is the prevention of mating amongst interbreeding groups due to physical( geographical, ecological) and biotic (eg physiological, behavioral) barriers.

In this case, there is Geographical isolation which leads to Reproductive isolation.

It stops the flow of genes between two groups of organisms and over the course of generations, two isolated populations of the same species will become well adapted to their environments and different from each other because they are adapting to different environments.

In the absence of gene flow, there is no way for genes that appear in separated lizard population will get same gene and will lead to morphologic differences . If enough of those differences accumulate in the two separate gene pools, they can eventually make interfertility impossible, even if the two populations meet. At that point, you have separate species, both of which descend from a shared ancestor.