End-Ordovician Mass Extinction

Definition

The End-Ordovician mass extinction was a significant global event that occurred around 445 million years ago, marking the second largest extinction event in Earth's history. This event led to the extinction of approximately 85% of marine species, largely impacting life in the oceans during the Ordovician period. It is characterized by two distinct pulses of extinction, which were likely driven by dramatic environmental changes.

5 Must Know Facts For Your Next Test

1. The End-Ordovician mass extinction is believed to have occurred in two main phases, with the first pulse related to rapid climate cooling and the second linked to glaciation and changes in sea levels.
2. It resulted in the loss of around 85% of marine species, including many types of trilobites, brachiopods, and coral-like organisms.
3. The event is associated with a significant drop in atmospheric carbon dioxide levels, which contributed to global cooling.
4. Evidence suggests that the extinction was influenced by both extraterrestrial impacts and volcanic activity that released large amounts of gases into the atmosphere.
5. The recovery from this extinction event led to the rise of new groups of organisms, including jawed fish and land plants, setting the stage for future biodiversity.

Review Questions

• What were the main environmental factors contributing to the End-Ordovician mass extinction?
  • The End-Ordovician mass extinction was primarily driven by dramatic climate changes, including global cooling and glaciation. The onset of ice ages led to a significant drop in sea levels, which adversely affected marine habitats. Additionally, changes in atmospheric carbon dioxide levels and volcanic activity played crucial roles in altering environmental conditions, pushing many species beyond their survival limits.
• Compare the two phases of extinction observed during the End-Ordovician mass extinction event.
  • The two phases of the End-Ordovician mass extinction involved distinct processes. The first phase was characterized by rapid climate cooling, leading to habitat loss for many marine species. In contrast, the second phase involved extensive glaciation that further impacted sea levels and marine ecosystems. Together, these two pulses created an unstable environment that resulted in widespread extinctions.
• Evaluate the long-term impacts of the End-Ordovician mass extinction on marine biodiversity and ecosystem development.
  • The End-Ordovician mass extinction had profound long-term effects on marine biodiversity and ecosystem structure. Following this event, there was a notable shift in dominance among marine organisms, with new groups such as jawed fish emerging. This transition paved the way for increased complexity in marine ecosystems and eventually influenced terrestrial life as well. The recovery phase after this mass extinction allowed for diversification that would shape future biological innovations and adaptations.

Related terms

Ordovician Period: A geological period that lasted from about 485 to 444 million years ago, marked by a diversification of marine life and the appearance of early land plants.

Climate Change: Long-term alterations in temperature and weather patterns that can lead to significant ecological shifts, often influencing mass extinction events.

Glaciation: The process of ice sheets expanding over the Earth's surface, which can lead to sea-level changes and drastically alter habitats.