"What is human nature?" is the key question psycology seeks to answer
I think it is the Epidermis
The system of classification relates to the diversity of species because the system of classification is how we organize the diversity of species. With out it we would have a hard time trying to determine which animals belong with which group. There would be no order, just chaos of trying to determine animal likeness of one another.
To cut this answer short, it helps them organize organisms.
Exo means outside
So planets outside our solar system
Cause it can kill if you use un-subscribed meds