Answer:
Animals engage in characteristic behaviors that increase the odds of reproduction. Animals and plants develop characteristic structures and behaviors to help them survive in their environment and pass on genetic information to their offspring. It is important that the offspring be cared for and protected so they can grow to adulthood and reproduce.
Nucleus for what?
Atom? Animal Cell? Plant Cell? Each have different structures.
White Blood cells Because they are produced in your body and they are constantly used more than they are replaced
Artificial active immunity. I'm a bio major, hope I helped :)