How is a species defined?

A species is defined as a group of organisms that can interbreed and produce fertile offspring. This concept, known as the biological species concept, emphasizes the reproductive capabilities of a group and the ability to share genetic material within that group, leading to offspring that are viable and capable of further reproduction. This definition allows for the classification of organisms based on their reproductive isolation from other groups, meaning that members of one species do not breed successfully with members of another species, even if they coexist in the same environment.

This understanding underscores the importance of genetic compatibility and the contributions of reproductive barriers in maintaining distinct species. By focusing on the ability to produce fertile offspring, the definition captures the continuity of genetic traits and adaptations, which are critical for natural selection and evolutionary processes. Consequently, species are recognized not just as random collections of organisms, but as groups that share a lineage and ecological niche, playing specific roles in ecosystems.