Evidence for Evolution

Key Points

• Evolution is supported by various lines of evidence from different fields of biology:
  • Anatomy: Homologous structures suggest common ancestry.
  • Molecular Biology: DNA similarities indicate shared ancestry.
  • Biogeography: Distribution of species reflects evolutionary history and geological changes.
  • Fossils: Document extinct species related to current species.
  • Direct Observation: Evolution observed in organisms with short lifecycles.

Introduction to Evolution

• Evolution is a unifying principle in biology.
• Defined as change in genetic makeup over time.
• Two scales:
  • Macroevolution: Large-scale changes over long periods, like new species.
  • Microevolution: Small-scale changes in populations over shorter periods.

Types of Evolutionary Evidence

Anatomy and Embryology

• Evolution as "descent with modification" (Darwin).
• Species traced back to a common ancestor.

Homologous Features

• Shared physical features due to common ancestry.
• Example: Forelimbs of whales, humans, birds, and dogs.

Analogous Features

• Similar features due to convergent evolution, not common ancestry.
• Example: Arctic fox and ptarmigan both change color seasonally.

Molecular Biology

• Shared genetic material among all organisms suggests a common ancestor.
• Comparison of homologous genes to determine relatedness.

Biogeography

• Geographic distribution aligns with evolutionary history and tectonic movement.
• Example: Unique species in isolated regions like Australia.

Fossil Record

• Fossils provide insight into evolution over time.
• Fossil stratification helps date species evolution.

Direct Observation

• Observable microevolution in populations, like pesticide-resistant insects.

Mechanisms of Natural Selection

• Natural Selection: Traits that improve survival become more common.
• Example: DDT resistance in mosquitoes developed through selection.

Summary

• Multiple evidences support evolution:
  • Homologous structures for common ancestry.
  • DNA sequences for species relatedness.
  • Biogeography for species distribution.
  • Fossils for historical species data.
  • Direct observation of rapid evolution in certain populations.