Definition of the Theory
The theory of evolution by natural selection, proposed by Charles Darwin in 1859, explains how species change over time. It posits that organisms with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits to offspring. Over generations, this process leads to adaptations and the formation of new species.
Key Principles
The theory rests 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, where natural selection favors those with beneficial traits, leading to gradual evolutionary change.
A Practical Example
A classic example is Darwin's observation of finches on the Galápagos Islands. Finches with beaks suited to available food sources, such as seeds or insects, survived better and reproduced more during environmental changes. Over time, this resulted in diverse finch species, each adapted to specific niches, illustrating natural selection in action.
Importance and Applications
This theory is fundamental to modern biology, underpinning fields like genetics, ecology, and medicine. It explains biodiversity, antibiotic resistance in bacteria, and human evolution. Understanding it aids in conservation efforts, predicting disease outbreaks, and addressing challenges like climate change impacts on ecosystems.