Final answer:
In biology, 'subspecies' refers to distinct genetic populations within a species, often geographically isolated, leading to reproductive isolation. The use of 'race' is historical and less favored. Speciation, including sympatric speciation and adaptive radiation, contributes to biodiversity and the subspecies concept.
Step-by-step explanation:
The terms subspecies and "race" in a biological context often describe populations of organisms within a species that are distinct genetically and may have morphological or behavioral differences. However, the term "race" is rarely used in modern biological sciences due to its ambiguity and historical misuse, particularly in relation to human populations. Instead, biologists prefer the term subspecies for populations of a species that exhibit distinct characteristics and could interbreed but are typically geographically separated leading to reproductive isolation. Aside from geographic isolation, other mechanisms of speciation include sympatric speciation, where species evolve from a common ancestor in the same geographic location often through mate selection or ecological niches; and adaptive radiation, where a single species rapidly evolves into multiple new species to fill different ecological niches, as seen in the example of East African cichlid fish.
Speciation that leads to the designation of subspecies may also reflect biodiversity, such as variations in coloration within the same species that do not necessarily prevent interbreeding but do signify genetic divergence. Overall, subspecies designation is an important aspect of biodiversity that reflects the subtle nuances of evolution within species.