How do reproductive barriers relate to the biological species concept?

Evolution and adaptation postulates that over time a group from one species can adapt so much they become a different species; in an attempt to classify groups you could say that a species A of felines and species B of felines must be totally different because although they came from a common ancestor, they can't mate. This is different from other methods of defining species, like RNA differences. Species change from adaptation, and this is especially true when an adaptation is favored.

Reproductive barriers can arise from habitat differences; birds living in different parts of the forest may reduce mating competition, but the two groups may still be physically compatible; therefore, the theory is not a complete explanation. Alternatively, reproductive barriers can be physiological, such as species A evolving to be taller so mating isn't physically possible.

The biological species concept defines a species as a group of organisms capable of interbreeding and producing fertile offspring, while reproductively isolated from other groups. Therefore, reproductive barriers are essential for maintaining the integrity of species according to the biological species concept, as they prevent gene flow between different species, which leads to the divergence of populations and ultimately the formation of new species. Reproductive barriers are mechanisms that prevent members of different species from producing viable offspring when they attempt to interbreed.