1. Variation within a Population:
* Genetic Diversity: Individuals within a population possess variations in their genetic makeup, leading to differences in traits. These variations arise from mutations, gene flow, and sexual reproduction.
* Phenotypic Diversity: Variations in genetic makeup translate into differences in observable characteristics (phenotypes), such as size, color, behavior, and disease resistance.
2. Environmental Pressures:
* Competition for Resources: Organisms compete for limited resources like food, water, shelter, and mates.
* Predation: Predators select prey based on their vulnerability, favoring traits that enhance survival.
* Disease: Individuals with greater resistance to diseases are more likely to survive and reproduce.
* Climate Change: Shifts in temperature, rainfall, and other environmental factors can create selective pressures.
3. Differential Survival and Reproduction:
* Fitness: Individuals with traits that are advantageous in a given environment are more likely to survive, reproduce, and pass those traits to their offspring. This is known as "fitness".
* Selection: The environment "selects" for individuals with favorable traits, leading to a gradual increase in their frequency within the population over generations.
* Adaptation: As a result of natural selection, populations become better adapted to their environment, increasing their chances of survival and reproduction.
In summary, natural selection is a process where individuals with traits that enhance their survival and reproduction in a particular environment are more likely to pass those traits on to their offspring. This leads to a gradual change in the genetic makeup of a population over time, known as evolution.
