1. Variation: Individuals within a population exhibit variation in their traits. These variations can be in physical characteristics, behaviors, or even genetic makeup.

2. Inheritance: Some of these variations are heritable, meaning they can be passed down from parents to offspring. This is key for natural selection to act upon, as traits need to be able to persist across generations.

3. Overproduction: Organisms produce more offspring than can survive. This leads to competition for resources, such as food, water, and shelter.

4. Differential Survival and Reproduction: Individuals with traits that make them better adapted to their environment are more likely to survive and reproduce, passing those advantageous traits onto their offspring. This results in a gradual shift in the population towards the more beneficial traits over time.

These principles work together to drive the process of natural selection, leading to the evolution of species over many generations.