The term morphology in biology refers to the outward appearance (shape, structure, colour, pattern) of an organism or taxon and its component parts. This article or section does not cite its references or sources. ... This article or section does not cite its references or sources. ... A taxon (plural taxa), or taxonomic unit, is a grouping of organisms (named or unnamed). ...

Also in use is the term "gross morphology", which refers to the prominent or principal aspects of an organism or taxon's morphology. A description of an organism's gross morphology would include, for example, its overall shape, overall colour, main markings etc. but not finer details.

Most taxa differ morphologically from other taxa. Typically closely related taxa differ much less than more distantly related ones, but there are exceptions to this. Cryptic species are species which look very similar, or perhaps even outwardly identical, but are reproductively isolated. Conversely, sometimes unrelated taxa acquire similar appearance through convergent evolution. In biology, a cryptic species complex is a group of species that satisfy the scientific definition of species — that is, they are reproductively isolated from each other — but which are anatomically indistinguishable. ... In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. ...

See also

Comparative morphology is comparing the physical aspects of organisms.

• Comparative anatomy