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.