1. Variation exists in populations: Individuals within a species are not identical. They have variations in traits, such as beak shape, fur color, or height.
2. Traits are heritable: These variations are passed on from parents to offspring. This means that offspring tend to resemble their parents in their characteristics.
3. Individuals struggle to survive and reproduce: Organisms produce more offspring than can survive. This leads to competition for resources like food, shelter, and mates.
4. Survival and reproduction are not random: Individuals with traits better suited to their environment are more likely to survive and reproduce. This means they pass on their advantageous traits to their offspring, who are then also more likely to survive and reproduce.
These four ideas together explain how natural selection drives evolution. Over many generations, populations can change significantly as advantageous traits become more common due to the higher reproductive success of individuals possessing them.
