What is a Species?

• A. A population of organisms that share the same habitat
• B. The basic unit of classification that can breed
• C. A group of similar organisms that can breed and produce fertile offspring
• D. A set of organisms that occupy different niches

Answer: (C)

A species is a group of organisms that can mate with each other and produce offspring that are capable of reproducing themselves. This reproductive compatibility defines boundaries between species, because when two populations can interbreed and their offspring survive and reproduce, they belong to the same species; when they cannot, they form separate species. The idea here is about reproductive isolation as the key criterion for grouping.

This is why the description that emphasizes a group of organisms that can breed and produce fertile offspring is the most precise. It directly captures the defining feature used to distinguish one species from another. The other descriptions don’t pin down that boundary: simply sharing a habitat doesn’t guarantee interbreeding, and the notion of an ecological niche focuses on how organisms live rather than whether they can interbreed. Likewise, naming a “basic unit of classification” hints at taxonomy but doesn’t specify the essential reproductive criterion.