Selection is a fundamental mechanism of evolution, as it determines which individuals survive, reproduce, and pass on their traits to the next generation. It plays a major role in shaping the genetic structure of populations over time. There are two main types of selection:
1. Natural Selection:
Proposed by Charles Darwin, natural selection explains how organisms with advantageous traits survive and reproduce more successfully than those without them.
This process leads to the gradual adaptation of populations to their environment.
Example: In a population of moths, darker-colored moths became more common during the Industrial Revolution because they were better camouflaged against soot-darkened trees, while lighter moths were more easily spotted by predators.
2. Artificial Selection:
Unlike natural selection, artificial selection is controlled by humans to enhance desirable traits in organisms.
Example: Selective breeding in livestock and crops has resulted in improved milk production in cows, disease-resistant wheat, and different dog breeds.
3. Sexual Selection:
A form of natural selection where traits that improve mating success become more common.
Example: Peacocks with larger, more colorful tails are more likely to attract mates, even if their tails make them more visible to predators.
4. Genetic Drift:
In small populations, chance events can cause certain traits to become more common or disappear entirely, leading to evolution without natural selection.
Example: If a few individuals of a species survive a natural disaster, the traits they carry may dominate future generations.
Selection leads to evolutionary changes over time by favoring traits that enhance survival and reproduction. However, other factors such as genetic drift, mutations, and migration also contribute to evolution.