The driving force behind evolution, by which the environment "selects" the fittest organism.

Quite Simply...

  • Traits represented in the population are based off of the "survival of the fittest."
  • Individuals well adapted to their environment are more likely to reproduce than individuals who are not well adapted. This means that the genes and traits of well adapted individuals are more likely to be passed down to the next generation, making their genes more prevalent in the population.

Examples of Natural Selection

  • If there is a pack of gazelles being chased by cheetahs, the slowest gazelles get caught by the fastest cheetahs; the fastest gazelles are the ones left to reproduce. As a result, the slower and more vulnerable gazelles are slowly eliminated. Also, the slow cheetahs that can't catch gazelles starve to death; speedy cheetahs are the ones left to reproduce and eventually the cheetahs get faster.
  • In a snowy region, white rabbits will blend in better with the snow and be less vulnerable to their predators. Therefore, they have an increased chance of survival, will reproduce, and will eventually outnumber brown rabbits.
  • Anteaters developed longer tongues over time. This started out as a mutation, but when the anteaters developed longer tongues, the ants burrowed deeper into the ground. The anteaters with long tongues survived, and the anteaters with shorter tongues died off because they could not get to the food source. This led to the anteater population possessing the trait of long tongues.
  • If two lizards live in the desert, the lighter-toned lizard would tend to survive longer then the dark lizard because it wouldn't stand out to the predators.
  • Darwin observed on the Galapagos Islands that each island had a different type of finch that lived on the island. Each finch species had different-shaped beaks in order for them to reach the unique food supply on each island. The birds who were unable to adapt died off and the birds who could access the food source on each island survived and continued to reproduce, passing the best trait down to their children and causing the evolution of their beak shape.
  • In humanity, great height is a desirable trait. So, when it came to mating, people tend to choose taller mates, raising the average height of mankind year by year.

See Also