1. Variation: Individuals within a population exhibit variation in their traits. This variation can be in physical characteristics, behavior, or even at the molecular level.
2. Inheritance: These variations are heritable, meaning they can be passed down from parents to offspring.
3. Differential Survival and Reproduction: Individuals with certain traits are more likely to survive and reproduce in a given environment. This is because those traits give them an advantage in obtaining resources, avoiding predators, or coping with environmental challenges.
4. Adaptation: Over time, the traits that increase survival and reproduction become more common in the population. This is because individuals with those traits leave more offspring, who inherit those traits. This leads to the population becoming better adapted to its environment.
It's important to note:
* Natural selection is not a goal-oriented process. It doesn't have a "plan" or a "direction." It simply favors traits that increase survival and reproduction in a particular environment at a particular time.
* Natural selection is constantly happening. It's not something that only happened in the past, but is happening all the time in all living populations.
* Natural selection can lead to speciation. If a population is isolated and undergoes enough changes through natural selection, it can become a new species.
Therefore, instead of "phases," we can think of natural selection as a continuous process that involves these four key components working together to shape the diversity of life on Earth.
