Major Mass Extinction Events

Mass extinction events have dramatically shaped life on Earth, influencing ecosystems and biodiversity. Understanding these events, like the End-Permian and Cretaceous-Paleogene extinctions, reveals how past changes inform current ecological dynamics and the evolution of species.

1. End-Ordovician extinction

   • Occurred approximately 445 million years ago, marking the second-largest mass extinction event.
   • Resulted in the loss of about 85% of marine species, particularly affecting brachiopods and trilobites.
   • Likely caused by a combination of glaciation and a drop in sea levels, leading to habitat loss.
   • The event significantly altered marine ecosystems and paved the way for new species to emerge in subsequent periods.

2. Late Devonian extinction

   • Spanning from about 375 to 360 million years ago, this extinction event unfolded over several million years.
   • Estimated to have eliminated around 75% of species, particularly impacting reef-building organisms and fish.
   • Potential causes include global cooling, anoxic events in oceans, and changes in sea level.
   • The extinction reshaped marine biodiversity and led to the rise of new fish groups and terrestrial plants.

3. End-Permian extinction (Great Dying)

   • Occurred around 252 million years ago, it is the most severe extinction event, with about 96% of marine species and 70% of terrestrial vertebrates lost.
   • Likely triggered by massive volcanic eruptions in the Siberian Traps, leading to climate change and ocean acidification.
   • Resulted in the collapse of ecosystems and a prolonged recovery period for biodiversity.
   • This event set the stage for the rise of dinosaurs and the dominance of reptiles in the Mesozoic era.

4. End-Triassic extinction

   • Happened approximately 201 million years ago, leading to the extinction of about 80% of species, including many reptiles and amphibians.
   • The primary causes are believed to be volcanic activity, climate change, and possibly asteroid impacts.
   • This extinction event allowed dinosaurs to become the dominant terrestrial vertebrates in the Jurassic period.
   • It marked a significant turnover in both marine and terrestrial ecosystems.

5. Cretaceous-Paleogene extinction (K-Pg extinction)

   • Occurred around 66 million years ago, famously known for the extinction of the non-avian dinosaurs, with about 75% of species lost.
   • The leading cause is widely accepted to be a massive asteroid impact, along with volcanic activity in the Deccan Traps.
   • This event drastically changed terrestrial and marine ecosystems, allowing mammals and birds to diversify and thrive.
   • The K-Pg extinction is a pivotal moment in Earth's history, marking the end of the Mesozoic era and the beginning of the Cenozoic era.