Final answer:
Sympatric speciation occurs when new species evolve from a single ancestral species within the same geographic region. Genetic isolation in sympatric speciation is achieved through mechanisms like different mating behaviors or polyploidy, rather than through geographic barriers.
Step-by-step explanation:
Sympatric speciation refers to the process by which new species evolve from a single ancestral species while inhabiting the same geographic region. In sympatric speciation, genetic isolation occurs not through physical barriers, like in allopatric speciation, but through mechanisms that cause reproductive isolation within the shared habitat. This may include different mating seasons, changes in mating behaviors, or polyploidy (the presence of extra sets of chromosomes).
Polyploidy can result from errors during meiosis, leading to gametes that, when they fuse, form organisms with more than two sets of chromosomes, a condition known as autopolyploidy within the same species, or allopolyploidy between closely related species. These polyploid individuals are genetically isolated from the original population because they cannot produce fertile offspring with the diploid members of their species. As a result, these polyploid organisms might represent the start of a new sympatric species. Other mechanisms of sympatric speciation may include behavioral changes that affect mating patterns, such as shifts in mating calls or other courtship rituals.