Lesson 6 of 8
Lesson 6: Evolution and Natural Selection
Evolution is the change in the inherited traits of a population over many generations. Charles Darwin explained how it happens through natural selection.
How Natural Selection Works
- 1Variation: individuals in a population are slightly different
- 2Some traits help an individual survive and reproduce in its environment
- 3Those individuals pass their helpful traits to more offspring
- 4Over time, the helpful traits become more common in the population
KEY TERM
Survival of the fittest does not mean the strongest or biggest. Fitness means how well an organism survives and reproduces in its environment. The best-fit traits get passed on.
Evidence for Evolution
- ●Fossils that show how species changed over time
- ●Similar body structures in related species (homologous structures)
- ●Shared DNA and proteins between species
- ●Observed changes today, like bacteria becoming resistant to antibiotics
REMEMBER
Natural selection acts on whole populations over time, not on a single individual changing during its own life.