End-Ordovician extinction

Definition

The end-Ordovician extinction was a major mass extinction event that occurred approximately 445 million years ago, marking the second-largest extinction event in Earth's history. It led to the loss of about 85% of marine species and dramatically reshaped marine biodiversity, particularly affecting trilobites, brachiopods, and graptolites. This extinction is significant as it highlights the impact of environmental changes on biodiversity and ecosystems.

5 Must Know Facts For Your Next Test

1. The end-Ordovician extinction is believed to have been caused by a combination of rapid climate changes, including glaciation and sea level fluctuations.
2. Two primary pulses of extinction are noted during this event: one associated with cooling temperatures and the other linked to a subsequent warming period.
3. Trilobites were among the most affected groups, with many species going extinct, which significantly altered marine ecosystems.
4. The event resulted in the extinction of approximately 60% of marine families and nearly 85% of all marine species at the time.
5. The end-Ordovician extinction set the stage for new evolutionary opportunities in the Silurian Period, leading to the rise of different marine life forms.

Review Questions

• What were the primary causes of the end-Ordovician extinction, and how did they affect marine biodiversity?
  • The end-Ordovician extinction was primarily driven by rapid climate changes, including glaciation that lowered sea levels and caused cooler temperatures. These environmental shifts led to habitat loss and altered oceanic conditions, severely impacting marine biodiversity. The drastic loss of species, particularly among trilobites and brachiopods, illustrates how sensitive ecosystems can be to abrupt changes in their environment.
• Discuss the significance of the end-Ordovician extinction in relation to the patterns observed in other mass extinctions throughout Earth's history.
  • The end-Ordovician extinction serves as a critical example of how environmental factors can trigger mass extinctions, a pattern that is observed in other significant events like the Permian-Triassic extinction. By understanding this event, scientists can draw parallels to how similar stressors, such as climate change or volcanic activity, have repeatedly led to large-scale biodiversity loss throughout geological time. This understanding enhances our knowledge of resilience and recovery in ecosystems following catastrophic events.
• Evaluate the long-term effects of the end-Ordovician extinction on subsequent evolutionary trends during the Paleozoic Era.
  • The end-Ordovician extinction had profound long-term effects on evolutionary trends during the Paleozoic Era, paving the way for significant diversification in marine life during the Silurian Period. The decline of dominant groups like trilobites allowed for new taxa to emerge and fill ecological niches left vacant. As ecosystems recovered from this extinction event, new forms of life adapted to changing conditions, illustrating how mass extinctions can act as catalysts for evolutionary innovation and shifts in biodiversity dynamics.

Related terms

Mass Extinction: A widespread and rapid decrease in the biodiversity on Earth, typically characterized by the loss of a large number of species in a relatively short period.

Ordovician Period: A geologic period that lasted from about 485 to 443 million years ago, known for a diverse marine life and significant geological developments.

Paleozoic Era: A major era in Earth's history that lasted from about 541 to 252 million years ago, characterized by the emergence and diversification of early life forms in oceans and on land.