What does the theory of evolution by natural selection suggest?

The theory of evolution by natural selection suggests that organisms that are better adapted to their environment are more likely to survive and reproduce than those that are not. This process leads to a gradual change in the traits of populations over generations, as advantageous traits become more common in the population.

Natural selection operates on the variation present within a population. It allows individuals with favorable traits—those that enhance survival and reproductive success—to pass those traits to the next generation. Over time, this can lead to adaptations that are suited to specific environmental conditions. For instance, a species of birds may develop stronger beaks if they primarily feed on hard seeds, allowing them to access a food source that other birds cannot.

This concept does not imply that all species will become extinct or that species evolve at a constant rate. Instead, the rate of evolution and its pathways can vary widely depending on numerous factors, including environmental changes and genetic diversity. Additionally, adaptations typically take multiple generations to develop and are not seen as occurring within a single generation. This gradual process is what makes the theory of evolution by natural selection a cornerstone of biological sciences.