Devonian Period

Definition

The Devonian Period, often referred to as the 'Age of Fishes,' lasted from about 419 to 359 million years ago. It is notable for significant evolutionary developments, particularly in fish and the emergence of early amphibians from their aquatic ancestors. Additionally, it marked the diversification of seedless vascular plants, which colonized land, contributing to major shifts in terrestrial ecosystems.

5 Must Know Facts For Your Next Test

1. The Devonian Period saw the rise of jawed fish, which diversified into various forms including placoderms and cartilaginous fish.
2. Amphibians are believed to have evolved from lobe-finned fish during this period, adapting to life both in water and on land.
3. Seedless vascular plants like ferns became more prominent on land, contributing to the formation of lush forests and changing terrestrial ecosystems.
4. The climate during the Devonian was generally warm, with higher sea levels and widespread shallow seas that provided rich habitats for marine life.
5. The end of the Devonian was marked by a mass extinction event, potentially caused by global cooling and changes in sea level, significantly impacting marine and terrestrial life.

Review Questions

• How did the Devonian Period contribute to the evolution of vertebrates, particularly in relation to the transition from aquatic to terrestrial environments?
  • The Devonian Period was crucial for vertebrate evolution as it witnessed the emergence of lobe-finned fish, which had adaptations that allowed them to venture onto land. These fish are considered precursors to early amphibians. The changes in environment and the development of limbs suitable for locomotion on land facilitated this transition, marking a significant evolutionary milestone that set the stage for the colonization of terrestrial ecosystems.
• Discuss the significance of seedless vascular plants during the Devonian Period and their impact on Earth's ecosystems.
  • Seedless vascular plants played a vital role in shaping terrestrial ecosystems during the Devonian. Their ability to grow taller and form dense forests altered soil composition and increased organic matter, which helped retain moisture and stabilize soils. This transformation created new habitats for various organisms and allowed for greater biodiversity on land. As these plants photosynthesized, they also contributed significantly to oxygen levels in the atmosphere.
• Evaluate the factors leading to the mass extinction at the end of the Devonian Period and its implications for subsequent evolutionary trends.
  • The mass extinction at the end of the Devonian was likely driven by a combination of global cooling, changes in sea level, and possibly asteroid impacts or volcanic activity. This event significantly reduced marine biodiversity, particularly affecting reef ecosystems and leading to the decline of many species. The loss of these organisms paved the way for new evolutionary pathways in both marine and terrestrial environments, setting a foundation for later developments in the Carboniferous Period and beyond.

Related terms

Lobe-finned Fish: A group of fish characterized by fleshy, lobed fins that are thought to be the ancestors of tetrapods, playing a crucial role in the transition to land-dwelling vertebrates.

Eurypterids: Also known as sea scorpions, these were large predatory arthropods that thrived in marine environments during the Devonian Period, showcasing the diversity of life during this time.

Stromatolites: Layered structures created by the activity of microorganisms, particularly cyanobacteria, which were prevalent in marine environments during the Devonian and contributed to oxygen production.