Which of the following is not true for a species?

Gene flow is the "transfer" of genes from one population to another. This does happen between populations of a species, and tends to reduce the differences between populations. Gene flow occurs between populations of a species by gene migration i.e., emigration and immigration. This is because gene flow ensures that all the populations of a particular species share a common gene pool. Variations too, exist between members of a particular species. Related Theory In biology, species is the most basic unit of classification, as well as a taxonomic rank. The next taxonomic rank on the hierarchy of biological classification is a genus. Species is the lowest taxon in the taxonomical hierarchy. The members of a particular species can interbreed, but are reproductively isolated from members of other species.