Ordovician-Silurian extinction

Definition

The Ordovician-Silurian extinction was a global event that occurred around 443 million years ago, marking the end of the Ordovician period. It is considered one of the five major mass extinctions in Earth's history, significantly impacting marine biodiversity.

5 Must Know Facts For Your Next Test

1. It resulted in the loss of approximately 85% of marine species.
2. The extinction event is divided into two distinct pulses separated by about 1 million years.
3. Primary causes include severe global cooling and glaciation, leading to habitat loss and changes in sea levels.
4. The extinction primarily affected marine organisms such as brachiopods, trilobites, and graptolites.
5. This event led to significant evolutionary changes, paving the way for new species to dominate in the Silurian period.

Review Questions

• What percentage of marine species were lost during the Ordovician-Silurian extinction?
• What were primary causes attributed to this extinction event?
• Which types of organisms were most severely affected by this extinction?

Related terms

Silurian Period: The geological period that followed the Ordovician and is known for significant evolutionary developments among marine life.

Mass Extinction: A rapid and widespread decrease in biodiversity on Earth, often characterized by a sharp decline in the number of species.

Brachiopods: Marine organisms with hard shells on their upper and lower surfaces, heavily impacted by the Ordovician-Silurian extinction.