Species

A collection of organisms that have alike physiological properties and that are capable of interbreeding and passing on their genes to the next generation [1]. 

Species Concepts and Their Definitions

There are numerous concepts that can be used to define a species:

i. Biological species concept

A biological species is a group of organisms that are capable of interbreeding and producing fertile offspring, and are isolated from other such groups to avoid reproduction [2].

ii. Ecological species concept

An ecological species is a group of organisms that share the same ecological niche.

iii. Morphological species concept

A morphological species is a group of organisms that share a unique set of structural features.

iv. Phylogenetic species concept

A phylogenetic species is a group of organisms that are bound by a unique ancestry and share one or more derived characters, which is also known as synapomorphy. 

References

Catherine Soanes, Angus Stevenson (2008). Concise Oxford English Dictionary . 11th ed. Oxford University press Inc : Oxford Univeristy . 1385.

Brooker, R. J. (2005). Genetics: Analysis & Principles (Second Edition). McGraw-Hill.

Mayr, E. (2000). The Biological Species Concept. Q. Wheeler; R. Meier, Species Concepts and Phylogenetic Theory: A Debate (p. 17). New York: Columbia University Press.