What does the biological species concept define?

The biological species concept defines species as groups of organisms that can interbreed and produce fertile offspring. This concept emphasizes reproductive isolation as the primary criterion for delineating species. Essentially, if members of a group are capable of interbreeding in nature and their offspring are also fertile, they are considered to belong to the same species. This definition is particularly useful for understanding species in the context of sexual reproduction and it takes into account the dynamics of natural populations.

In contrast, the other concepts focus on different criteria for defining species. Morphological similarities rely on physical characteristics, which can sometimes misrepresent the true relationships among organisms. The concept of distinct evolutionary lineages emphasizes genetic divergence and evolutionary history, often utilizing phylogenetic trees rather than direct reproductive capabilities. Lastly, defining species by their ecological niches looks at the role or function of a species within its ecosystem rather than the genetic or reproductive connections between organisms. Each of these other concepts provides useful insights but does not specifically address the reproductive aspect that is central to the biological species concept.