How did Ernst Mayr define a species?

Ernst Mayr defined a species as groups of interbreeding populations that are reproductively isolated from one another. This definition emphasizes the importance of reproductive isolation as a key factor in the formation and maintenance of species. It highlights that members of a species can mate and produce fertile offspring, while different species are unable to do so under natural conditions. This concept not only focuses on the ability to interbreed but also underscores the importance of barriers to reproduction, which can be behavioral, temporal, mechanical, or geographical. This reproductive aspect is fundamental in defining a species, as it allows for the delineation of one species from another based on their reproductive capabilities and isolation from gene flow with other groups.