Commensalism is the biological association between two organisms whereby one benefits and the other is neither harmed nor benefitted.
A good example is Remora fish and sharks. The remora fish attaches itself to the shark bodies and feed on crumbs of leftovers food eaten by the shark, also get protection from the shark, while the shark is absolutely unaffected.
Never still, the earth and its environment are constantly changing. ... Surviving in a changing world is difficult if an organism cannot change along with it. ... Slowly, the population of fish will become more fully adapted to its new environment. ... Sometimes the changes cannot take place fast enough and a whole population
