Mass extinctions 2024-25 (MOODLE)

Five Mass Extinctions

Overview

  • The concept of extinctions is relatively new; its acceptance faced resistance from religious and political beliefs.

  • Five major mass extinctions have significantly influenced the life we observe today.

  • Recoveries from these events often lead to new evolutionary directions, shaping modern biodiversity.

  • There are ongoing concerns about the potential for a sixth mass extinction due to human impact.


Themes of the Presentation

  1. Radiation & Extinctions

    • Importance of studying the origins of animals and the evolutionary processes that led to diverse body plans.

    • Speciation and adaptive radiations, particularly among fish, mammals, and birds, along with amphibians colonizing land.

  2. Major Extinctions

    • Explanation of the five main mass extinction events and their underlying causes.

    • Exploration of the responses of various ecosystems to these extinctions.

  3. Geological Toolbox

    • Tools for tracing back geological and climatic events, such as fossil series, isotopes, and plate tectonics.


Major Mass Extinctions

The "Big Five"

  1. End-Ordovician Extinction (445-443 mya)

    • First known major extinction event.

    • Estimated loss: 85% of all marine species.

  2. Late Devonian Extinction (372-359 mya)

    • Multiple extinction pulses, less defined than others.

  3. End-Permian Extinction (251 mya)

    • Known as "The Great Dying"

    • Most significant extinction event, marked by massive biodiversity loss across both terrestrial and marine organisms.

  4. End-Triassic Extinction (201 mya)

    • Transition marked by the rise of dinosaurs.

  5. Cretaceous-Paleogene Extinction (66 mya)

    • Famous for the extinction of non-avian dinosaurs, likely caused by a meteor impact (Chicxulub crater) and volcanic activity.


Factors Causing Extinctions

  • Global temperature changes, marine habitat shifts, and geological events are common factors in extinction events.

  • Hypotheses for different extinction mechanisms: hypoxic conditions, marine eutrophication, climate changes, and bolide impacts.


Recovery and Response

  • Different responses:

    • Extinct ecological groups leave empty niches, allowing surviving organisms to diversify and adapt.

    • Recovery phases can last millions of years, impacting biodiversity significantly.


Current Epoch - Anthropocene Extinction

  • Discusses the ongoing Anthropocene extinction due to human activities that adversely affect megafauna and biodiversity.

  • Monitor global temperature increases related to extinction risks, suggesting we may be approaching significant biodiversity loss comparable to historical mass extinctions.

robot