Natural selection is based on _____

Natural selection is based on several key principles: variation, inheritance, selection, and time.

1. Variation: There must be variations in the traits of individuals within a population. These variations can be in physical characteristics, behavior, or physiological functions.

2. Inheritance: The traits that cause the variations amongst individuals must be heritable, meaning that they can be passed down from parents to offspring.

3. Selection: Certain traits give individuals an advantage in surviving and reproducing in their particular environment. These individuals are more likely to pass on their traits to the next generation. This selective process is what leads to evolution.

4. Time: Natural selection operates over many generations; it is a gradual process that can lead to significant changes in a species over long periods.

The phrase often used to summarize natural selection is "survival of the fittest," although "fittest" refers not just to physical fitness but overall reproductive success.