Devonian

Definition

The Devonian is a geologic period and system that spans from approximately 419 to 359 million years ago, known for significant developments in Earth's history, particularly the evolution of early land plants and the diversification of fish. This period is often referred to as the 'Age of Fishes' due to the vast variety of fish species that thrived in the oceans, while also marking the transition of some organisms from water to land.

5 Must Know Facts For Your Next Test

1. The Devonian period is part of the Paleozoic Era and follows the Silurian period, marking significant biological transitions.
2. The first forests appeared during the Devonian, as early vascular plants like Archaeopteris began to dominate terrestrial landscapes.
3. The diversification of jawed fish occurred in the Devonian, leading to the emergence of many modern fish lineages.
4. Fossil evidence from this period reveals a wide range of marine life, including reef-building corals and ammonites.
5. The end of the Devonian is marked by a mass extinction event that greatly affected marine life, paving the way for ecological changes in subsequent periods.

Review Questions

• How did the environment of the Devonian period contribute to the evolution of early land plants?
  • The Devonian period offered diverse environments, including river deltas and floodplains, which allowed early land plants to adapt and thrive. The presence of shallow seas facilitated nutrient-rich sediments that promoted plant growth. As plants evolved vascular systems for transporting water and nutrients, they began to colonize land more effectively, leading to the development of larger forms such as Archaeopteris, which contributed to the first forests.
• Discuss the role of lobefin fish during the Devonian period and their significance in vertebrate evolution.
  • Lobefin fish played a crucial role during the Devonian as they are considered direct ancestors of all tetrapods. Their fleshy lobed fins provided structural support that facilitated movement onto land. This transition marks an important evolutionary step as these fish adapted to new environments and gave rise to amphibians and ultimately reptiles, making them significant players in vertebrate evolution.
• Evaluate the impact of the Devonian mass extinction on marine ecosystems and subsequent evolutionary trends.
  • The mass extinction event at the end of the Devonian significantly altered marine ecosystems by wiping out a large portion of marine life, including many species of fish and reef-building organisms. This drastic reduction led to shifts in dominant groups within marine communities and paved the way for new ecological niches. As a result, subsequent periods saw the rise of different life forms, including increased diversity in reptiles and better adaptation strategies among surviving species.

Related terms

Echinoderms: A group of marine animals that includes starfish, sea urchins, and sea cucumbers, which were abundant during the Devonian period.

Lobefin Fish: A type of fish characterized by fleshy, lobed fins that are thought to be ancestral to the first land vertebrates, significant during the Devonian.

Silurian: The geologic period preceding the Devonian, known for early fish evolution and the first terrestrial plants, setting the stage for further developments in the Devonian.