Evidence for Evolution

Categories of Evidence

1. Fossil Evidence

   • Fossils: Traces/remains of organisms from the past.
   • Found primarily in sedimentary rock (mud, sand, silt).
   • Fossilization process:
     • Organism dies, buried quickly to avoid decomposition.
     • Minerals replace tissue, creating molds/casts.
   • Law of Superposition: Older layers are beneath younger layers in rock.
     • Used for relative dating.
     • Example: Letter Z in a lower rock layer is older than letter X in a higher layer.
   • Absolute Dating
     • Methods: Radiometric, luminescence, dendrochronology, amino acid dating.
     • Also known as chronometric/calendar dating due to uncertainty in precision.
     • Example: Dendrochronology counts tree rings to estimate age.
   • Transitional species: Intermediate evolutionary forms.
     • Example: Archaeopteryx links birds to reptiles.

2. Anatomical Evidence

   • Homologous Structures
     • Shared anatomical structures indicating a common ancestor.
     • Example: Similar bone structures in pterodactyls, bats, birds.
     • Different usage for flight.
   • Analogous Structures
     • Similar functions without a common ancestor.
   • Vestigial Structures
     • Seemingly functionless structures resembling functional ones in other organisms.
     • Example: Human appendix, initially thought to be a remnant of the cecum.
     • Recently found to house mutualistic bacteria aiding digestion.

3. Embryological Evidence

   • Study of embryo development.
   • Closely related species exhibit similar early developmental stages.
   • Early work: Ernst Haeckel's exaggerated drawings.
   • Modern studies focus on accurate embryonic stages.

4. Biochemical Evidence

   • Molecular Clock
     • Uses DNA and amino acids to trace evolutionary ancestry.
     • Steady mutation rate indicates species relations.
     • More mutations = more distant relationship.
     • Example: Fewer amino acid differences between humans and gorillas than with lampreys, indicating closeness.

Summary

• Each category provides unique insights and evidence supporting evolutionary theory.
• Fossil, anatomical, embryological, and biochemical evidence collectively reinforce our understanding of evolutionary processes.

Note: This summary is based on the video content from Teacher's Pet. Follow @sciencepet for more educational content.