describe how a population is thought to evolve through natural selection. Provide an example (specifically, the peppered moth)

The process of evolution through natural selection involves the gradual change in a population's traits over time due to the differential survival and reproduction of individuals with certain advantageous traits. Here's a step-by-step explanation of how a population is thought to evolve through natural selection:

1. Variation: Within a population, there exists natural variation in traits. This variation is due to differences in DNA, resulting in individuals having slightly different physical and genetic characteristics.

2. Environmental Pressures: The environment exerts pressures on the population, such as predation, competition for resources, or changes in habitat. These pressures create selective forces that favor individuals with certain traits.

3. Favorable Traits: Some individuals exhibit traits that provide a survival or reproductive advantage in the given environment. These traits can be physical (e.g., coloration, body shape) or behavioral (e.g., hunting strategies, mating displays).

4. Differential Survival and Reproduction: Individuals with advantageous traits tend to survive and reproduce more successfully than those without these traits. This leads to a higher frequency of the advantageous traits in subsequent generations.

5. Heredity: The successful individuals pass on their advantageous traits to their offspring through genetics. This process ensures that the next generation inherits the traits that confer a fitness advantage.

6. Generational Change: With each successive generation, individuals with advantageous traits become more prevalent, while individuals lacking these traits become rarer. Over time, this results in a population that is better adapted to its environment.

An example of evolution through natural selection is the case of the peppered moth (Biston betularia) during the Industrial Revolution in England. Prior to industrialization, the moth population consisted mostly of light-colored (typica) individuals, which camouflaged well against lichen-covered tree trunks. However, as industrial pollution darkened the tree trunks with soot, a dark-colored form (carbonaria) of the moth became more advantageous as it blended better with the new environment.

The darker moths had higher survival rates due to reduced predation, while the lighter moths became more visible and prone to predation. Consequently, the frequency of the dark form increased while the light form declined over time. This change in the moth population's coloration is an example of evolution through natural selection driven by changes in the environment and the differential survival of certain traits.