1. Variation: Individuals within a population exhibit variation in their traits. This variation can be due to genetic differences or environmental factors.
2. Heritability: Some of these variations are heritable, meaning they can be passed down from parents to offspring.
3. Overproduction: Organisms produce more offspring than the environment can support. This leads to competition for resources.
4. Differential Survival and Reproduction: Individuals with traits that make them better adapted to their environment are more likely to survive and reproduce, passing on their advantageous traits to their offspring.
5. Gradual Change: Over generations, the frequency of advantageous traits increases in the population, leading to gradual changes in the species.
Here's a simple explanation of how these tenants work together:
* Imagine a population of rabbits living in a forest. Some rabbits have brown fur, while others have white fur.
* Variation: There's variation in fur color within the rabbit population.
* Heritability: This fur color is a heritable trait.
* Overproduction: The rabbits produce many offspring, but not all of them will survive.
* Differential Survival and Reproduction: In a forest with lots of predators, the brown rabbits are better camouflaged and less likely to be eaten. They survive longer and produce more offspring, passing on their brown fur genes. The white rabbits are more likely to be eaten and leave fewer offspring.
* Gradual Change: Over time, the proportion of brown rabbits in the population will increase, while the proportion of white rabbits will decrease. This change in the population is due to natural selection favoring the brown fur trait.
Key Points:
* Natural selection is a process, not a force. It acts on existing variation within a population.
* It does not create new traits, but rather selects for existing ones that are advantageous in a given environment.
* Evolution by natural selection is a slow and gradual process that happens over many generations.
By understanding these tenants, we can gain a deeper understanding of how life on Earth has evolved and continues to evolve.
