It means to take certain types o the organism that have favorable traits and breed them to keep producing such favorable traits, such as continually breeding fatter chickens or cows, or certain breeds or pure-bred dogs.
Parasites are organisms that survive by harming anouther organism (feeding off of it, ex. tick, flea)
A :-) Sickle cell disease occurs more often among people from parts of the world where malaria is or was common. It is believed that people who carry the sickle cell trait are less likely to have severe forms of malaria.
The body would start to shut down, reactions would become weaker and slower, you would begin to get tireder and you's slowly be dying. If no fod is onsued within 2-3 weeks, then the brain will have no nutrients and will die
The Mother and Father each give half of the chromosomes to the offspring, which will decide traits and inheritance.
Hope this helps!
