Ordovician

Definition

The Ordovician was a geological period that lasted from about 485 to 444 million years ago, following the Cambrian and preceding the Silurian. It is marked by significant developments in marine life, including the proliferation of diverse reef ecosystems and the first major appearance of corals, which laid the groundwork for modern coral reefs. The Ordovician saw a flourishing of life forms, both in terms of diversity and complexity, in the world's oceans.

5 Must Know Facts For Your Next Test

1. The Ordovician is known for its great diversification of life, often referred to as the 'Ordovician Radiation,' which included an explosion of marine species.
2. During this period, the first true coral reefs began to form, which were critical for creating habitats for other marine organisms.
3. The climate during the Ordovician was generally warm and tropical, which favored the development of diverse marine environments.
4. The Ordovician ended with a major mass extinction event, which wiped out about 85% of marine species, drastically altering the course of life on Earth.
5. The presence of graptolites in rock layers is a key tool for geologists to identify and date Ordovician deposits.

Review Questions

• How did the Ordovician period contribute to the evolution of reef ecosystems?
  • The Ordovician period marked a significant evolutionary step for reef ecosystems due to the emergence and diversification of corals. These corals formed complex structures that provided habitats for various marine species, contributing to increased biodiversity in oceanic environments. The development of these early reefs set the foundation for modern coral ecosystems that we see today.
• What impact did the climate during the Ordovician have on marine biodiversity?
  • The warm and tropical climate of the Ordovician created favorable conditions for marine life to thrive, leading to what is known as the 'Ordovician Radiation.' This period saw a remarkable increase in species diversity as various organisms adapted to different ecological niches within the ocean. The rich habitats established during this time contributed significantly to the complexity and variety of marine ecosystems.
• Evaluate the significance of mass extinction events in shaping the evolution of life during and after the Ordovician period.
  • The mass extinction event at the end of the Ordovician was one of the most significant in Earth's history, leading to the loss of approximately 85% of marine species. This drastic reduction reshaped ecosystems and allowed for new groups of organisms to emerge and diversify in subsequent periods. Understanding these extinction events helps reveal patterns in evolutionary biology and highlights how environmental changes can drastically influence life on Earth.

Related terms

Stromatolites: Layered sedimentary formations created by the activities of microbial mats, primarily cyanobacteria, that were abundant in early marine ecosystems.

Graptolites: Fossilized colonial organisms that were widespread during the Ordovician, serving as important index fossils for dating rocks of this period.

Biodiversity: The variety of life forms within a particular habitat or ecosystem, which significantly increased during the Ordovician, particularly in marine environments.