Evolution and Natural Selection

Evolution

Natural Selection

• Process by which individuals with favorable traits are more likely to survive and reproduce
• Leads to accumulation of adaptations over time
• Three components:
  1. Variation: existence of different traits in a population
  2. Heritability: traits are passed down from parents to offspring
  3. Differential reproduction: individuals with favorable traits produce more offspring

Adaptation

• Trait that increases an individual's fitness (ability to survive and reproduce)
• Can be:
  • Structural: physical characteristics (e.g. wings, armor)
  • Behavioral: learned or innate behaviors (e.g. migration, camouflage)
  • Physiological: internal functions (e.g. temperature regulation, venom production)

Darwin's Theory

• Proposed by Charles Darwin in 1859
• States that all species share a common ancestor and evolve over time through natural selection
• Key components:
  • Descent with modification: species change over time
  • Common ancestry: all species share a common ancestor
  • Gradualism: evolution occurs gradually, over long periods of time

Species Change

• Process by which a new species emerges from an existing one
• Can occur through:
  • Allopatric speciation: geographic isolation of a population
  • Sympatric speciation: reproductive isolation within a population
  • Hybrid speciation: formation of a new species through hybridization of two existing species
• Results in the formation of a new species with distinct characteristics and reproductive barriers