Evolution - Lecture Notes

Jul 21, 2024

Evolution - Lecture Notes

Overview

  • Chapter: Evolution (Paper 2)
  • Marks: ~66

Key Topics

  1. Definition of Biological Evolution
  2. Hypothesis vs. Theory
  3. Theory of Evolution
  4. Evidence for Evolution
  5. Causes of Variation

1. Definition of Biological Evolution

  • Biological Evolution: Changes in life forms over time through genetic changes inherited in populations.
  • Microevolution: Changes in the genotype.
  • Macroevolution: Formation of new species.

2. Hypothesis vs. Theory

  • Hypothesis: Informed assumption, limited evidence, starting point needing further investigation.
  • Theory: Well-substantiated explanation, repeatedly verified through experiments.
  • Theory of Evolution: Regarded as scientific theory, hypotheses tested and verified over time.

3. Theory of Evolution

  • Based on multiple hypotheses tested and verified.
  • Forms a scientific theory through accumulated evidence.

4. Evidence for Evolution

  • Fossil Record: Not complete, shows organism remains, footprints, imprints. Example: Coral fossil in Kansas shows ancient ocean.
  • Biogeography: Geographical distribution of species, common ancestors, geographical barriers leading to new species.
  • Modification by Descent: Homologous structures, similar anatomy with different functions (e.g., human forearm, cat paw, whale flipper, bat wing).
  • Genetics: DNA similarities indicate close relationships, gene pools change.

Fossil Record Details

  • Incomplete Record: Not all organisms fossilize, especially soft-bodied ones.
  • Processes: High pressure, low oxygen, rapid burial.
  • Dating Fossils: Older fossils deeper in sediment, younger ones shallower. Can map out periods/eras/eons.
  • Other Preservations: Amber, tar pits example with the premise for Jurassic Park.

Biogeography Examples

  • Geographical Barriers: Oceans, mountains, deserts separate species leading to new species.
  • Large Birds: Ostrich, emu, moa, rhea share common ancestor but evolved differently due to separation.

Modification by Descent

  • Homologous Structures: Similar anatomical parts adapted for different functions (e.g., humerus, radius, ulna).
  • Species Changes: Example of elephants (Asian, African, woolly mammoth) and horses.

Genetics

  • DNA Similarities: Closer DNA, closer relationship.
  • Gene Pools: Changes in gene pools lead to new species.

5. Causes of Variation

  • Biological Species Definition: Similar characteristics, interbreed to produce fertile offspring.
  • Population Definition: Same species, defined area, given time, able to interbreed.

Variation Factors

  1. Crossing Over: Prophase I of meiosis, exchange of genetic material, leads to unique chromosomes.
  2. Random Arrangement: Metaphase of meiosis, new genetic combinations.
  3. Random Fertilization: Fusion of different egg and sperm cells.
  4. Random Mating: Different mates lead to unique offspring genetics.
  5. Mutation: Changes in gene/chromosome structure.

Types of Variation

  • Continuous Variation: No distinct categories, e.g., height, weight. Shown in line graphs.
  • Discontinuous Variation: Distinct categories, e.g., tongue rolling, fingerprints, eye color, blood groups. Shown in bar graphs or histograms.

End of the first part of evolution.