1. Common Descent: All members of a species naturally descend from a common ancestor. Dr. Siddique Publications
2. Specific and Smallest Group of Organisms: Species is the smallest and specific group of organisms in the light of morphological and chromosomal characteristics.
3. Mode of Reproduction: Species are capable of producing fertile offspring by sexual intercourse among themselves. Dr. Siddique Publications
4. Ecological niche: Each species has a specific ecological niche.
5. Genetic unit: A species is the darkness of a gene pool.