I will give you BRAINLIEST what happens if you don't sleep good at night

You will lose weight and your immune system going be weak under your eyes going be black and your going have pale skin high blood pressure,  heart attack, stroke.  

And heres why we dream

help you store important memories and things you've learned, get rid of unimportant memories, and sort through complicated thoughts and feelings.

genetics is the study of how dna works, the methodologies defining the new recent technologies allow scientist to have a panoramic view of the entire dna landscape, especially how genomes interact with their environment, including off course, factors outside their organisms.

thus is very possible the existence of both scenarios, where populations of isolated individuals have different genetic traits, and share traits related to genetic mutation, due rats can easily travel overseas using human transport channels. so scientists could get a vast number of data, including human interaction, evolution of rodents, health development, spread of infections, development of new organisms, how genomes evolve in different environments and so on.