What are some examples of the survival of the fittest?
People with Sickle cell anemia and blind fish of Death Valley
People with Sickle cell anemia are the most fit to survive in an environment where malaria is very common.
People with no damaged genes for making red blood cells are vulnerable to malaria. The protozoa that causes malaria hides inside of the red blood cells where the immune system can not attack it.
People with one damaged gene for sickle cell anemia have damaged red blood cells that can open up allowing the immune system access to attack the malaria protozoa. These people will survive a malaria infection so they are more fit than people with undamaged genes.
The blind fish of Death Valley are the most fit to survive in an environment of total darkness found in the underground rivers and lakes of Death Valley
the blind fish have lost genes needed to make eye tissues. Not having a vulnerable outer eye is an advantage. Normal fish would run into rocks causing bleeding in the damaged eye and possible death. The blind fish can run into rocks without damage to the eye tissue because the outer vulnerable eye tissue is no longer there.
The blind fish are most fit to live in the environment of total darkness
These are just two examples of survival of the fittest.