Overview of the Theory
The theory of evolution by natural selection, proposed by Charles Darwin in 1859, explains how species change over time through a process where organisms better adapted to their environment tend to survive and reproduce more successfully. This leads to the gradual accumulation of favorable traits in populations. The theory posits that all life on Earth shares a common ancestor and has diversified through descent with modification, driven by natural selection acting on heritable variations.
Key Principles
Natural selection operates on four main principles: variation, where individuals in a population differ in traits; inheritance, where these traits are passed to offspring; overproduction, where more offspring are produced than can survive; and differential survival and reproduction, where those with advantageous traits are more likely to survive and pass on their genes. This results in adaptations becoming more common over generations, without requiring purposeful design.
Practical Examples
A classic example is the peppered moth in industrial England, where dark-colored moths became predominant in polluted areas due to better camouflage against soot-covered trees, while light moths were more visible to predators. Another is the Galápagos finches observed by Darwin, where beak shapes varied by island, adapting to available food sources like seeds or insects, demonstrating how environmental pressures select for specific traits.
Importance and Applications
This theory forms the foundation of modern biology, explaining biodiversity and informing fields like medicine, where antibiotic resistance in bacteria evolves through natural selection, urging careful use of drugs. It also guides conservation efforts by highlighting how human activities can disrupt natural selection, leading to species endangerment.