Is population a group of closely related organisms that can mate to produce fertile offspring

A Species is a group of organisms that can interbreed (reproduce with one another) to produce offspring that are fertile (able to reproduce). But sometimes two closely related species can breed and produce Hybrids. Hybrids aren't one species nor the other which show characteristics from both parents.

Species are the organism that can mate with each other to produce a fertile offspring.

Explanation:

Specie is the smallest component of classification. In species, organisms are very close to each other in appearance and in many characteristics. Species produce fertile offspring i. e. new organism when the male organism mate with female organism. In this mating, the sperm cells of male fused with egg cells of female produce a zygote which turns into a new organism.