Devonian

Definition

The Devonian is a period in the geologic time scale that lasted from about 419 to 359 million years ago, often referred to as the 'Age of Fishes' due to the significant diversification and dominance of fish species during this time. This period also saw the emergence of early amphibians, which evolved from lobe-finned fish, marking a crucial step in the transition from water to land.

5 Must Know Facts For Your Next Test

1. The Devonian period is known for a dramatic increase in fish diversity, including the emergence of both jawless and jawed fish species.
2. Amphibians first appeared during the Devonian, evolving from lobe-finned fish and adapting to life on land while still needing aquatic environments for reproduction.
3. The period also saw the development of early terrestrial ecosystems, with the colonization of land by plants and fungi, setting the stage for future terrestrial life.
4. The end of the Devonian is marked by a series of extinction events that significantly affected marine life, possibly due to changes in sea levels and climate.
5. Corals and other marine invertebrates thrived during this time, leading to the formation of extensive reef systems that contributed to biodiversity in shallow seas.

Review Questions

• How did the evolution of lobe-finned fish contribute to the development of early amphibians during the Devonian?
  • Lobe-finned fish played a critical role in the evolution of early amphibians during the Devonian because they possessed fleshy, robust fins that allowed them to venture onto land. These adaptations provided an evolutionary pathway for these fish to develop limbs and lungs over time. As a result, lobe-finned fish gave rise to tetrapods, enabling vertebrates to transition from aquatic environments to terrestrial habitats.
• Discuss the significance of the Devonian period in shaping modern ecosystems and biodiversity.
  • The Devonian period was crucial for shaping modern ecosystems because it marked significant evolutionary advancements such as the emergence of amphibians and the colonization of land by plants. The establishment of terrestrial ecosystems during this time laid the groundwork for future biodiversity, influencing the development of complex interactions between plants, animals, and their environments. This diversification ultimately set up ecosystems that would evolve into those we recognize today.
• Evaluate the factors that led to the extinction events at the end of the Devonian and their implications for marine life.
  • The extinction events at the end of the Devonian were likely caused by a combination of factors including climatic changes, fluctuations in sea levels, and possibly anoxic conditions in oceans. These changes resulted in a loss of habitat and disrupted marine ecosystems, significantly impacting various species such as corals and certain fish groups. The implications were profound; not only did it lead to a reduction in biodiversity, but it also paved the way for new evolutionary opportunities for surviving species in subsequent periods.

Related terms

Lobe-finned Fish: A group of fish characterized by their fleshy, lobed fins, which are more robust than those of ray-finned fish, and are ancestors to early tetrapods.

Tetrapod: A vertebrate animal having four limbs; early tetrapods evolved from lobe-finned fish and gave rise to amphibians, reptiles, birds, and mammals.

Fossil Record: The history of life on Earth as documented by fossils, providing insights into the evolution of species and environmental changes over time.