Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving … See more

It is difficult to define a species in a way that applies to all organisms. The debate about species concepts is called the species problem. The problem was recognised even in 1859, when Darwin wrote in On the Origin of S… See more

The commonly used names for kinds of organisms are often ambiguous: "cat" could mean the domestic cat, Felis catus, or the cat family, Felidae. Another problem with common names is that they often vary from place to pla… See more

Species are subject to change, whether by evolving into new species, exchanging genes with other species, merging with other species or by becoming extinct.
The evolutionary process by which biological population… See more

Biologists and conservationists need to categorise and identify organisms in the course of their work. Difficulty assigning organisms reliably to a species constitutes a threat to the validity of research results, for example m… See more

In his biology, Aristotle used the term γένος (génos) to mean a kind, such as a bird or fish, and εἶδος (eidos) to mean a specific form within a kind, such as (within the birds) the crane, eagle, crow, or sparrow. These terms were transl… See more

• Cline
• Encyclopedia of Life
• Endangered species
• Global biodiversity
• Lists of animal species… See more