1. Definition

  • Extinction Event: A rapid and widespread decrease in the biodiversity on Earth, marked by the loss of a significant proportion of species in a relatively short geological period.

2. Historical Overview

  • Prehistoric Extinctions:

    • Ordovician-Silurian (c. 443 million years ago): ~85% of marine species lost due to climate cooling and glaciation.
    • Late Devonian (c. 372 million years ago): ~75% species lost; causes include ocean anoxia and asteroid impact.
    • Permian-Triassic (c. 252 million years ago): “The Great Dying” – up to 96% of marine and 70% of terrestrial species lost; triggers include volcanic eruptions (Siberian Traps), methane release.
    • Triassic-Jurassic (c. 201 million years ago): ~80% species lost; volcanic activity, climate change.
    • Cretaceous-Paleogene (K-Pg, c. 66 million years ago): ~76% species lost, including non-avian dinosaurs; asteroid impact (Chicxulub crater), volcanic activity (Deccan Traps).

  • Quaternary Extinctions (Recent):

    • Late Pleistocene (c. 50,000–10,000 years ago): Extinction of megafauna (mammoths, saber-toothed cats); debated causes include human hunting, climate change.

3. Key Experiments & Discoveries

  • Iridium Layer Discovery (1980):

    • Luis Alvarez et al. found a global layer of iridium at the K-Pg boundary, supporting the asteroid impact hypothesis.

  • Siberian Traps Volcanism Studies:

    • Geochemical analysis of ancient lava flows linked massive volcanic eruptions to the Permian-Triassic extinction.

  • Ancient DNA Analysis:

    • Sequencing of extinct species (e.g., woolly mammoth) provides insights into population decline and genetic bottlenecks.

  • CRISPR Technology in De-Extinction:

    • Modern gene editing (CRISPR-Cas9) enables targeted genetic modifications, raising possibilities for “reviving” extinct species (e.g., passenger pigeon, mammoth).

4. Modern Applications

  • Biodiversity Conservation:

    • Data from extinction events guide conservation strategies for endangered species.
    • Identification of “extinction risk factors” (habitat loss, climate change, invasive species).

  • De-Extinction Research:

    • CRISPR used to edit genomes of living relatives (e.g., Asian elephant for mammoth traits).
    • Ethical debates on ecological impacts, resource allocation, and genetic diversity.

  • Climate Change Mitigation:

    • Lessons from past extinctions inform models predicting species vulnerability to current global warming.

  • Education & Outreach:

    • Museums, documentaries, and interactive simulations use extinction event data to raise awareness.

5. Case Studies

A. The Mammoth Revival Project

  • Objective:
    • Use CRISPR to insert mammoth genes into Asian elephant embryos.
  • Progress:
    • Successfully edited genes for cold resistance and hair growth (Church et al., 2021).
  • Challenges:
    • Ethical concerns, gestational viability, ecological impact.

B. Amphibian Declines

  • Event:
    • Ongoing global amphibian extinction due to chytrid fungus (Batrachochytrium dendrobatidis).
  • Experiment:
    • Field trials of probiotic treatments to boost resistance.

C. Coral Bleaching

  • Event:
    • Mass coral die-offs linked to rising sea temperatures.
  • Research:
    • CRISPR-based gene editing to enhance thermal tolerance in coral larvae (Cleves et al., 2020).

6. Data Table – Major Extinction Events

Event Time (MYA) % Species Lost Main Cause(s) Notable Species Lost
Ordovician-Silurian 443 ~85% Glaciation, sea level Early marine invertebrates
Late Devonian 372 ~75% Anoxia, impact Jawless fish, corals
Permian-Triassic 252 ~96% (marine) Volcanism, methane Trilobites, amphibians
Triassic-Jurassic 201 ~80% Volcanism, climate Large amphibians
Cretaceous-Paleogene (K-Pg) 66 ~76% Asteroid impact Dinosaurs, ammonites

7. Teaching in Schools

  • Curriculum Placement:

    • Taught in biology, earth science, and environmental science modules.

  • Methods:

    • Interactive timelines, fossil analysis, simulation games (e.g., extinction modeling).
    • Group debates on conservation and de-extinction ethics.
    • Integration with genetics (CRISPR), climate science, and ecology.

  • Assessment:

    • Lab practicals (fossil identification), research projects, presentations.
    • Use of recent case studies and news articles for critical analysis.

8. Recent Research

  • Citation:

    • Cleves, P.A., et al. (2020). “CRISPR/Cas9-mediated genome editing in coral to study gene function and stress response.” Proceedings of the National Academy of Sciences, 117(52), 32962–32968.
    • Highlights: Demonstrated gene editing in coral, paving the way for enhancing resilience against climate-induced extinction.

  • News Article:

    • “CRISPR gene editing brings extinct species back into the conversation,” Nature News, March 2022.
      • Discusses advances in de-extinction research, ethical debates, and ecological considerations.

9. Summary

  • Extinction events have shaped Earth’s biodiversity through dramatic losses driven by natural and anthropogenic factors.
  • Key experiments (iridium layer, ancient DNA, CRISPR) have deepened understanding and opened new avenues for conservation and de-extinction.
  • Modern applications focus on preventing current extinctions and exploring ethical use of gene editing.
  • Case studies such as mammoth revival and coral resilience illustrate both promise and complexity.
  • Schools teach extinction events through active learning, integrating genetics, climate science, and ethics.
  • Recent research (2020+) demonstrates the role of CRISPR in understanding and potentially mitigating extinction risks.