Q.What is meant by the 'concept of species'? How is one species distinguished from a closely related species?

[!TLDR] A species is a group of interbreeding organisms distinguishable from other such groups. [!ANSWER] The species concept defines a species as a group of individuals sharing fundamental similarities and capable of interbreeding to produce fertil …

The concept of species holds that a species is the basic, natural unit of classification: a group of individual organisms that share fundamental structural and genetic similarities, are capable of interbreeding with one another under natural conditions to produce fertile offspring, and remain reproductively isolated from other, related groups. One species is distinguished from a closely related one primarily through consistent, heritable differences — traditionally morphological (structural) features observable and measurable by a taxonomist, though modern taxonomy also draws on genetic, biochemical and behavioural evidence. For example, the lion (Panthera leo) and tiger (Panthera tigris) belong to the same genus and resemble each other closely, yet are recognised as dis …

First state the defining criteria of a species (similarity + interbreeding + reproductive isolation), then explain the practical basis (differences) …

Students sometimes define a species using only 'looks similar' without mentioning the interbreeding/reproductive-isolation criterion, which is …