End-Ordovician Extinction

Definition

The End-Ordovician extinction was one of the five major mass extinctions in Earth's history, occurring approximately 445 million years ago. This event is characterized by the loss of about 85% of marine species, primarily affecting life in the oceans, and is believed to have been triggered by significant global cooling and a drop in sea levels. The event highlights the dynamic interplay between climate change and biogeography, influencing the distribution and evolution of species over time.

5 Must Know Facts For Your Next Test

1. The End-Ordovician extinction occurred in two main pulses, with the first pulse resulting from a rapid cooling phase that led to glaciation and a second pulse driven by changes in ocean chemistry.
2. This extinction event primarily affected marine life, with bryozoans, trilobites, and graptolites being among the hardest hit groups.
3. The end-Ordovician extinction had profound effects on marine ecosystems, leading to the disappearance of many species and opening niches for new life forms to evolve.
4. Research suggests that increased volcanic activity during this period may have contributed to environmental stress, exacerbating the extinction's impact.
5. Following this mass extinction, life on Earth rebounded with significant diversification during the Silurian period, setting the stage for new evolutionary pathways.

Review Questions

• What were the main causes and effects of the End-Ordovician extinction event?
  • The End-Ordovician extinction was primarily caused by significant global cooling that led to glaciation and subsequent drops in sea levels. This drastic change in climate resulted in habitat loss for many marine species. The extinction event severely impacted marine biodiversity, resulting in the loss of approximately 85% of all marine life at that time, particularly affecting groups like trilobites and graptolites.
• How did the End-Ordovician extinction influence subsequent evolutionary trends in marine life?
  • The End-Ordovician extinction created a massive shift in marine ecosystems, paving the way for new groups of organisms to thrive. After this event, there was a significant diversification during the Silurian period. The ecological niches left vacant by extinct species allowed for innovations such as new predator-prey dynamics and adaptations in surviving lineages that would shape future evolutionary trajectories.
• Evaluate how the End-Ordovician extinction can be connected to broader patterns of climate change and mass extinctions throughout Earth's history.
  • The End-Ordovician extinction serves as a critical example of how climate change can trigger mass extinctions. Similar patterns are observed in other major extinction events, where shifts in climate led to habitat loss and disruptions in ecosystems. By studying this event alongside others like the Permian-Triassic extinction, scientists can gain insights into how current climate challenges may influence biodiversity and ecosystem stability today.

Related terms

Mass Extinction: A widespread and rapid decrease in the biodiversity on Earth, usually characterized by the extinction of a large number of species in a relatively short geological time frame.

Glaciation: A period of time when large parts of the Earth's surface were covered by ice sheets, significantly affecting global climates and sea levels.

Biodiversity: The variety of life forms within a given ecosystem, biome, or on the entire planet, encompassing the differences in species, genetic variation, and ecosystems.