Natural Selection is a mechanism for change in populations that occurs when organisms with favorable variations for a particular environment survive, reproduce, and pass these variations on to the next generation.

Natural Selection:
-Individuals within the same species are not identical.
-The environment presents many different challenges to an individual's ability to survive and reproduce.
-Organisms tend to produce more offspring than their environment can support; thus, individuals of a species often compete with one another to survive.
-Individuals within a population that are better able to cope with the challenges of their environment tend to leave more offspring than those less suited to the environment.
-The traits of the fittest individuals those best suited to a particular environment tend to increase.

  • For example, a species of fish will lay thousands, sometimes millions, of eggs. In this population of eggs, individuals will exhibit slight variations. Fishes may differ slightly in color, fin and tail size, and speed. An egg that grows to be a fast fish with a skin color that allows it to blend in better with its surroundings is more likely to survive to reproductive age than a slow fish with more obvious coloring. These adaptations carried over several generations will produce a change in the species. This would be evident in fossils, DNA sequencing of the fishes, anatomical and physiological changes, and embryology.

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Fish Eggs
  • For example, in a herd of animals such as elephants the weaker individuals will be picked off and killed while the stronger individuals will survive longer to produce more young.