Extinction Notes

Extinction

  • Process where a species ceases to exist.
  • Occurs when death rate exceeds birth rate.
  • Once extinct, an organism is lost forever.

Famous Extinctions

  • Permian-Triassic Extinction:
    • Largest extinction event, ~250 mya.
    • "The Great Dying" - 90% of organisms died.
    • Possibly caused by a meteor (12km radius) or massive volcanic eruption.
  • Triassic-Jurassic Extinction:
    • ~200 mya, killed mostly reptiles and amphibians.
    • Caused by massive lava flows due to the breaking apart of Pangea.
  • Cretaceous-Tertiary Extinction:
    • ~65 mya.
    • Caused by a massive asteroid impact (Yucatan, Mexico) and/or massive volcanic eruptions.
    • Resulted in climate cooling.

Causes of Extinction

  • Natural vs. Anthropogenic (human-induced) causes.

Natural Causes

  • Massive Volcanic Eruptions:
    • Release toxic gases, ash, and lava, causing habitat destruction and climate shifts.
    • Example: Siberian Traps eruptions contributed to the Permian-Triassic Extinction.
  • Climate Heating and Cooling:
    • Extreme temperature changes disrupt ecosystems.
    • Example: Ice Age led to the extinction of large mammals.
  • Changes in Sea Conditions:
    • Ocean acidification, rising temperatures, and oxygen loss harm marine life.
    • Example: End-Triassic Extinction involved massive CO_2 emissions and ocean acidification.
  • Asteroid or Comet Impact:
    • Causes massive destruction and atmospheric debris disrupting photosynthesis.
    • Example: Chicxulub asteroid impact caused the Cretaceous-Paleogene Extinction.

Anthropogenic Causes

  • Overexploitation:
    • Uncontrolled hunting, fishing, or resource extraction.
  • Pollution:
    • Toxic chemicals, plastic waste, and air pollution damage ecosystems.
  • Habitat Destruction:
    • Deforestation, urbanization, and agriculture eliminate ecosystems.
  • Introduction of New Species:
    • Invasive species compete with native species.