Convergence, Natural Selection, 'Survival of the Fittest'

 Convergent evolution occurs when two distinct species that have a very distant relationship develop the same characteristic as each other through means independent of one another.

My example is the octopus and human eyeballs. Our last common ancestor was a flatworm about 750 mya, which is a long time to evolve apart from each other. Despite the fact that we are terrestrial beings, and octopuses are subterrainian beings, we both evolved the same type of eyeball: a camera eye with a lens, photreceptors, an iris, a retina, a cornea, and vitreous body. 

Both of our reasonings for developing camera eyes was to have a motion-based vision that takes in light easily, as both species are predators or hunters that must capture our food (as far as meat goes), but the evolutionary distance between is is so grand that our hunting needs vary in other aspects of our characteristics. Octopuses must be able to swim very quickly to catch up to their fishy prey, while our prey is mainly on land, so our legs are better made for running and jumping.

Please enjoy my lovely illustration I made on PicsArt.