Definition of the Theory of Evolution
The theory of evolution in biology posits that all species of organisms on Earth have descended from common ancestors and have changed over time through processes such as natural selection, genetic drift, and mutation. Proposed primarily by Charles Darwin in his 1859 book 'On the Origin of Species,' it explains the diversity of life as a result of gradual adaptations to environmental pressures.
Key Principles of Evolution
Central principles include descent with modification, where species evolve from preexisting forms; natural selection, the mechanism by which advantageous traits become more common in populations; and genetic variation, driven by mutations, gene flow, and sexual reproduction. These components are supported by evidence from fossils, comparative anatomy, embryology, and molecular biology.
Practical Example: Antibiotic Resistance in Bacteria
A clear illustration is the evolution of antibiotic resistance in bacteria. When exposed to antibiotics, bacteria with random mutations conferring resistance survive and reproduce, passing the trait to offspring. Over generations, resistant strains dominate, demonstrating natural selection in action and highlighting challenges in modern medicine.
Importance and Applications in Biology
The theory of evolution is foundational to biology, informing fields like medicine, agriculture, and conservation. It explains phenomena such as disease emergence, crop breeding, and biodiversity preservation, enabling scientists to predict and address ecological changes while unifying diverse biological observations under a single explanatory framework.