Natural selection is the process by which organisms with variations most sutied to their local environment survive and leave offsprings. There are some conditions to natural selection, they are the struggle for existence, variations and adaptations, and survival of the fittest.
Darwin named is mechanism for evolution natural selection. Natural selection occurs in any situation in which more individuals are born than can survive, there is natural heritable variation and there is variable fitness among individuals. Well adapted individuals survive and reproduce. When a change in the environment happens natural selection steps in and helps animals adapt to the new changes by altering their traits. An example is a human, that has been on the earts for several million years, has evolved from a monkey to a walking human.
If more individuals reproduce more than the environment could handle, then struggle for existence would happen. In order for a population of animals to survive they will need a steady supply for food, water, living space, and other limited necessities of life. An organism example of the struggle for existence is when a species overpopulates an area and everyone is trying to get the things that they need to survive. They animal that would most likely survive is the predator.
Darwin hypothesized that that some species are better suited for life in there environment than others. Darwin knew that individuals have natural variations among their heritable traits. An example of this is a predator have sharper claws or teeth than others.