Which term describes the evolution of species that occurs without physical barriers?

The term that accurately describes the evolution of species that occurs without physical barriers is sympatric speciation. This process involves the emergence of new species from a single ancestral species while remaining in the same geographical area. In sympatric speciation, reproductive isolation occurs due to factors such as behavioral differences, ecological preferences, or genetic mutations that segregate populations even when they coexist in the same environment.

This form of speciation contrasts with allopatric speciation, which occurs when populations are separated by physical barriers, leading to the divergence of species as they adapt to different environments. Parapatric speciation involves populations that are partially separated and experience differing selection pressures along a gradient, while peripatric speciation is a similar concept but involves a smaller population becoming isolated at the edge of the range. Understanding these distinctions helps clarify how species evolve in various contexts, especially in relation to their environments and interactions.