1. Variation exists: Individuals within a species are not identical. They have small variations in their traits, like beak size in finches or fur color in rabbits.
2. Inheritance: These variations are passed down from parents to offspring.
3. Competition for resources: Organisms compete for resources like food, shelter, and mates. This competition can be intense, leading to some individuals surviving and reproducing more successfully than others.
4. Natural selection: Individuals with traits better suited to their environment are more likely to survive, reproduce, and pass on those favorable traits to their offspring. This process is called natural selection.
5. Gradual change over time: Over many generations, the accumulation of these small changes in a population leads to significant evolutionary change. This can result in the development of new species, adaptations to different environments, and the extinction of poorly adapted species.
Key points:
* It's not about "survival of the fittest," but about "survival of the fit enough". Even the "weakest" organism can survive if it happens to have traits that are advantageous in a given environment.
* Evolution is not a ladder. It's not about organisms becoming "better" over time. It's about organisms becoming better adapted to their environment.
* Evolution is a continuous process. Evolution is not a single event, but an ongoing process that is constantly shaping life on Earth.
Darwin's theory was revolutionary because it explained the diversity of life on Earth without invoking divine intervention. It provided a scientific framework for understanding how species change over time, and it continues to be a cornerstone of modern biology.
