Which of the following best defines a species?

The concept of a species is best defined as groups of organisms that can interbreed to produce fertile offspring. This definition emphasizes the biological aspect of species, which focuses on the ability of members of the same species to mate and produce viable offspring that can also reproduce. This reproductive isolation is key to identifying distinct species in nature, as it encompasses genetic compatibility and the continuity of heredity within a population.

Understanding this definition helps clarify the importance of reproductive barriers that prevent interbreeding between different species, thereby maintaining distinct genetic lineages. While other options mention aspects related to species, such as habitat, common ancestry, or physical characteristics, they do not encapsulate the essential biological criterion that defines a species in terms of reproductive capability and potential.