End-Ordovician extinction

Definition

The End-Ordovician extinction refers to one of the largest mass extinctions in Earth's history, occurring approximately 444 million years ago, marking the end of the Ordovician period. This event resulted in the loss of about 85% of marine species, dramatically reshaping marine biodiversity and ecosystems. Factors contributing to this extinction include significant climate changes, including glaciation and ocean anoxia, which altered habitats and disrupted the food chain.

5 Must Know Facts For Your Next Test

1. The End-Ordovician extinction was primarily caused by a series of environmental changes, including a major ice age that led to falling sea levels.
2. This extinction event was particularly devastating for marine life, especially brachiopods, trilobites, and graptolites, with many species unable to adapt to the rapidly changing conditions.
3. The event is divided into two distinct pulses, with the first pulse occurring due to glacial expansion and the second pulse linked to oceanic anoxia.
4. After the End-Ordovician extinction, life slowly recovered, leading to the diversification of fish and other marine organisms in subsequent periods.
5. This extinction event provides critical insights into how current climate change could potentially impact biodiversity today.

Review Questions

• What were the primary environmental changes that led to the End-Ordovician extinction?
  • The End-Ordovician extinction was driven by significant environmental changes, notably a major glaciation that resulted in lowered sea levels and cooler global temperatures. These changes led to habitat loss for many marine organisms. Additionally, ocean anoxia created inhospitable conditions for aerobic life forms. Together, these factors caused widespread disruption in marine ecosystems, leading to one of the largest mass extinctions in Earth's history.
• Discuss the two pulses of extinction that characterized the End-Ordovician extinction event and their respective causes.
  • The End-Ordovician extinction is marked by two distinct pulses. The first pulse was largely caused by glacial expansion during a cooling period that lowered sea levels and altered marine habitats. The second pulse followed as oceanic anoxia set in due to stratification of water layers, further decreasing oxygen availability for marine life. This two-phased event highlights how different environmental pressures can cumulatively lead to mass extinctions.
• Evaluate the long-term impacts of the End-Ordovician extinction on marine biodiversity and ecosystems.
  • The End-Ordovician extinction had profound long-term impacts on marine biodiversity and ecosystems. It eliminated approximately 85% of marine species at the time, drastically reshaping ecological dynamics. In its aftermath, there was a slow recovery and diversification of life forms, particularly among fish and other marine organisms. This event also set the stage for future evolutionary trends in marine life. Understanding these impacts provides essential context for evaluating how contemporary environmental changes could similarly affect today's biodiversity.

Related terms

Mass Extinction: A widespread and rapid decrease in the biodiversity on Earth, often characterized by the loss of a significant percentage of species in a relatively short geological time frame.

Glaciation: The process during which large parts of the Earth's surface are covered by ice sheets and glaciers, significantly affecting global climate and sea levels.

Anoxia: A condition characterized by a deficiency of oxygen in the environment, which can lead to the death of aerobic organisms and significantly impact marine ecosystems.