What defines a species?

A species is defined as a group of organisms that can interbreed and produce fertile offspring. This definition emphasizes the biological aspect of species, focusing on reproductive compatibility and the ability to maintain genetic continuity. When members of a species mate, they produce offspring that can, under normal circumstances, reproduce themselves, allowing the species to persist over generations. This concept is fundamental in understanding biodiversity and the evolutionary relationships among different organisms.

The emphasis on reproductive isolation is crucial because it distinguishes one species from another; if two groups can mate and produce fertile offspring, they belong to the same species. This definition also accounts for the concept of speciation, where two populations diverge to the point where they can no longer produce viable, fertile offspring, eventually leading to the formation of new species.

In contrast, other options do not capture the essence of what defines a species. Some options address community structures or physical traits but fail to incorporate the critical element of reproductive compatibility that distinguishes species in biological terms.