End-Ordovician

Definition

The end-Ordovician refers to a significant geological time marker that denotes the end of the Ordovician Period, approximately 445 million years ago, characterized by one of the largest mass extinction events in Earth's history. This event led to the loss of around 85% of marine species, reshaping marine biodiversity and ecosystems dramatically. It is often associated with rapid climatic changes, including glaciation, which impacted sea levels and habitats.

5 Must Know Facts For Your Next Test

1. The end-Ordovician mass extinction is considered the second-largest extinction event, significantly impacting marine life.
2. This extinction event is believed to have been triggered by a short but intense ice age that lowered sea levels.
3. The majority of the affected species were marine organisms, particularly trilobites and brachiopods.
4. After the end-Ordovician, marine ecosystems underwent major shifts, leading to the dominance of new groups of organisms in the Silurian Period.
5. The end-Ordovician serves as an important marker for paleontologists to study evolutionary patterns and responses to environmental changes.

Review Questions

• What were the primary causes and effects of the end-Ordovician mass extinction?
  • The end-Ordovician mass extinction was primarily caused by significant climatic changes, including a short ice age that led to glaciation. This resulted in dramatic drops in sea levels, altering marine habitats and causing widespread habitat loss. The effects were profound, with approximately 85% of marine species going extinct, fundamentally changing the composition of marine ecosystems and paving the way for new groups to emerge in later periods.
• How does the end-Ordovician extinction compare to other mass extinctions in terms of biodiversity loss?
  • The end-Ordovician extinction is one of the five major mass extinction events in Earth's history, second only to the end-Permian extinction in terms of biodiversity loss. Unlike some other extinctions that affected terrestrial organisms significantly, this event primarily impacted marine species due to its oceanic context. The loss of diverse taxa during this time emphasizes its critical role in shaping future marine biodiversity and evolutionary trajectories.
• Evaluate the long-term impacts of the end-Ordovician event on subsequent geological periods and evolutionary trends.
  • The long-term impacts of the end-Ordovician mass extinction set the stage for evolutionary changes during the Silurian Period. With a substantial loss of dominant marine species, new organisms like jawless fish began to thrive in the altered ecosystems. This shift not only influenced marine biodiversity but also initiated ecological dynamics that would lead to increased complexity in life forms, laying down foundational structures for future evolutionary trends in both aquatic and terrestrial environments.

Related terms

Ordovician Period: A geological time period that lasted from about 485 to 444 million years ago, known for diverse marine life and significant geological developments.

Mass Extinction: A widespread and rapid decrease in biodiversity on Earth, typically recognized by a significant loss of species in a relatively short period.

Glaciation:

The process during which large areas of the Earth are covered by ice sheets and glaciers, influencing global climate and sea levels.