What defines a species in biological terms?

A species is defined biologically as a group of organisms capable of interbreeding and producing fertile offspring. This concept emphasizes the importance of reproductive isolation, which plays a critical role in maintaining the integrity of a species. When members of a species can mate and produce viable offspring, it indicates a shared gene pool and genetic cohesion that defines their identity as a distinct group.

The ability to produce fertile offspring ensures that the genetic traits of the species are passed on to subsequent generations, thereby maintaining the lineage over time. This reproductive criterion also helps differentiate one species from another, especially in cases where physical characteristics might overlap or vary considerably.

In contrast, options focused solely on reproduction in captivity, ecological habitats, or physical characteristics do not encapsulate the full biological definition of a species. Reproductive capabilities and the potential for offspring viability are essential for understanding speciation, diversification, and the relationships between different organisms in an evolutionary context.