Evolutionary Biology

• Definition: Study of history of life forms on Earth.
• Context: To understand evolution, knowledge of the universe, earth, and stars' origins is essential.
• Story: Origin and evolution of life, biodiversity, and universe.

6.1 Origin of Life

• Observation of Stars: Peering into the past due to light years.
• Age of Universe: Approximately 20 billion years old.
• Big Bang Theory: Universe originated from a huge explosion; formation of galaxies from hydrogen and helium.
• Formation of Earth: Approximately 4.5 billion years ago.
• Initial Earth Conditions: Lacking atmosphere; UV rays led to formation of water and ozone.
• Life's Origin: Appeared 500 million years post Earth’s formation.
• Theories:
  • Panspermia: Life came from space.
  • Spontaneous Generation: Disproved by Pasteur, life arises from pre-existing life.
  • Oparin-Haldane Hypothesis: Life arose from non-living organic molecules via chemical evolution.
  • S.L. Miller's Experiment: Amino acids formed under simulated early Earth conditions.

6.2 Evolution of Life Forms: A Theory

• Theory of Special Creation: Challenged by Darwin’s observations.
• Darwin’s Observations: Life forms share similarities and have evolved; extinctions and new life forms have occurred.
• Natural Selection: Mechanism of evolution; survival and reproductive fitness.
• Common Ancestors: Existing life forms share common ancestors; Earth’s age is billions of years.

6.3 Evidences for Evolution

• Fossils: Indicators of life forms in Earth's history.
• Embryological Evidence: Early development features common to vertebrates.
• Comparative Anatomy: Homologous structures imply common ancestry; analogous structures show convergent evolution.
• Biochemical Similarities: Indicate common ancestry.
• Artificial Selection: Breeding by humans demonstrates potential for natural evolution.

6.4 Adaptive Radiation

• Darwin’s Finches: Different beak types evolved for varied diets.
• Australian Marsupials: Show adaptive radiation.
• Convergent Evolution: Similar adaptations in isolated areas (e.g., placental mammals in Australia).

6.5 Biological Evolution

• Evolution Initiation: Began with cellular life forms.
• Darwin’s Theory: Natural selection is central; fitness linked to life cycle.
• Genetic Basis: Inherited traits provide adaptive ability; fitness leads to selection.

6.6 Mechanism of Evolution

• Variation Origin: Mutations and genetic recombination.
• Hardy-Weinberg Principle: Allele frequencies remain constant without evolutionary forces.
• Factors Affecting Equilibrium: Gene flow, genetic drift, mutation, recombination, and selection.
• Natural Selection Effects: Can lead to stabilization, directional change, or disruption.

6.7 A Brief Account of Evolution

• Timeline:
  • Cellular life: 2000 mya.
  • Multicellular life: 500 mya.
  • Amphibians, reptiles, mammals evolved over millions of years.
  • Mass extinctions and diversifications (e.g., dinosaurs).
  • Mammalian dominance post-reptiles.

6.8 Origin and Evolution of Man

• Hominid Evolution:
  • Dryopithecus & Ramapithecus: Primitive primates.
  • Australopithecines: Early man-like primates.
  • Homo habilis: First human-like being.
  • Homo erectus & Neanderthals: Subsequent evolutions with larger brains.
  • Homo sapiens: Modern humans evolving through migration and cultural development.

Exercises

1. Explain Darwinian selection theory with antibiotic resistance.
2. Discover new fossil finds or evolutionary controversies.
3. Define species.
4. Trace human evolution components.
5. Investigate self-consciousness in animals.
6. Link modern animals to ancient fossils using internet.
7. Draw animals and plants.
8. Describe an example of adaptive radiation.
9. Discuss human evolution as adaptive radiation.
10. Trace horse evolutionary stages.

Summary

• Understanding life’s origin requires a background of Earth and universe’s origin.
• Chemical evolution likely preceded cellular life.
• Darwinian evolution explains biodiversity changes via natural selection.
• Evolution of modern man parallels brain and language development.