Biology Unit 4: History of Earth and Human Society Summary

Important Announcements

  • Section BB notifications
  • Upcoming deadlines:
    • Survey checkpoint 2 (Individual) due before next Monday's class.
    • Writing assignment 2 (Group) due Nov 21st at midnight.
    • Exam 4 on Dec 3.
    • Final exam on Dec 10, 6-8 PM.
  • Other information related to team activities and Thanksgiving break.

Unit 4 Learning Objectives

  • Compare mass extinction events with current biodiversity loss.
  • Identify major threats to biodiversity caused by humans.
  • Describe trends in climate over geological history.
  • Explain how environmental changes influence biota.
  • Define the Anthropocene and assess human evolution context.
  • Evaluate human impacts on carbon, nitrogen, and phosphorus cycles.
  • Discuss species loss and its ecological, evolutionary, and societal consequences.
  • Compare strategies in conservation biology and approaches to climate change.
  • Examine sustainable living practices.

Earth's Geologic Timeline

  • Earth is approximately 4.6 billion years old, divided into eons:
    • Hadean
    • Archean
    • Proterozoic
    • Phanerozoic
  • Key events:
    • 4.6 BYA: Earth forms.
    • 3.8-3.5 BYA: First life (anaerobic prokaryotes).
    • 2.4 BYA: Great Oxygenation Event, ozone layer forms.
    • 1.8 BYA: Eukaryotes arise via endosymbiosis.
    • 575 MYA: Cambrian Explosion diversifies multicellular life.
    • 65 MYA: Dinosaur extinction triggers mammal evolution.
    • 200-300 KYA: Homo sapiens evolve.

The Great Oxygenation Event

  • Cyanobacteria's oxygen production changed Earth's atmosphere.
  • This event caused mass extinction of anaerobic bacteria.
  • Led to the development of aerobic respiration.

Endosymbiotic Events in Eukaryotic Evolution

  • Eukaryotic cells formed through engulfment of prokaryotic cells.
    • First event: Aerobic bacteria became mitochondria.
    • Second event: Photosynthetic bacteria became chloroplasts.

Cambrian Explosion and Animal Diversification

  • Rapid diversification of life forms began around 541 MYA.
  • Key innovations included:
    • Development of hard parts, complex eyes, and increased nervous system coordination.
  • Predation led to evolutionary arms races among species.

Mass Extinctions and their Impact

  • "Big Five" mass extinctions shaped current biodiversity.
    • End-Permian: Largest, caused by volcanic eruptions and climate change.
    • Cretaceous: Asteroid impact and volcanic activity led to dinosaur extinction.
  • Mass extinctions promote subsequent adaptive radiations among surviving species.