What is the definition of a species

A group of living organisms consisting of similar individuals capable of exchanging genes

A population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring but do not produce viable, fertile offspring with members of other such groups

Explanation:

I used my bio textbook for this but basically only organisms in a group is a population and they can't produce offspring that survive or reproduce unless they are in the same population or populations. Think of like how a liger is a cross of a tiger and a lion and can't reproduce because its not fertile and its from two different species but a lion and a lion can produce a living offspring that can reproduce.