The document discusses different species concepts: 1. The typological species concept defines a species as having an idealized, invariant pattern shared by all members. It considers variation as trivial. 2. The nominalistic species concept believes that only individuals exist in nature, not species, which are human constructs. 3. The biological species concept defines a species as a group of interbreeding natural populations reproductively isolated from other such groups. It is widely accepted but has limitations for asexual groups, cryptic species, and evolutionary intermediates. 4. The evolutionary species concept defines a species as a lineage evolving separately from other lineages with its own ecological niche. It aims to address limitations of the biological concept.