Question

In what way did terrestrial environments of the Late Devonian Period look different from those of Early Devonian time?

Short answer

The terrestrial environments of the Late Devonian Period looked different from those of the Early Devonian Period due to several factors. Vegetation saw a change from small, simple plants to larger, more complex ones like Archaeopteris, forming early forests. Animal life evolved from arthropods to early tetrapods, such as Ichthyostega and Acanthostega, beginning to inhabit terrestrial environments. The Late Devonian Period experienced significant climatic fluctuations, with cooling and warming events, unlike the warm and stable climate of the Early Devonian Period. Finally, geographical changes included the formation of the supercontinent Pangaea, the development of large coastal swamps, and the spread of plants, which affected global climate and carbon cycles.

Step-by-step solution

Understand the timeframes and characteristics of Early and Late Devonian Periods

The Devonian Period is a part of the Paleozoic Era and is divided into the Early, Middle, and Late Devonian Periods. The Early Devonian Period lasted from around 419 million years ago (Mya) to 393 Mya, while the Late Devonian Period lasted from 383 Mya to 359 Mya. The terrestrial environments during these periods underwent significant changes, especially in terms of plant life, animals, climate, and geography.

Examine the changes in vegetation between the Early and Late Devonian Periods

During the Early Devonian Period, the first land plants started to colonize the Earth. These early plants were mostly small, simple, and lacked roots or leaves, such as the Cooksonia and Rhynia. By the Late Devonian Period, the terrestrial environments were populated by larger and more complex plants, including tree-sized plants like Archaeopteris, which possessed leaves and roots, contributing to the formation of early forests.

Explore the differences in animal life between the Early and Late Devonian Periods

The Early Devonian Period saw the emergence of arthropods, such as spiders and scorpions, on land. However, the Late Devonian Period was marked by the appearance of early tetrapods, which were vertebrate animals with four limbs. These animals, like Ichthyostega and Acanthostega, started to inhabit the terrestrial environments and diversify, although their full transition to land happened later during the Carboniferous Period.

Discuss the changes in climate between the Early and Late Devonian Periods

The Early Devonian Period had a generally warm climate with high sea levels. However, the Late Devonian Period experienced climatic fluctuations, and there were several cooling and warming events. During the Frasnian-Famennian boundary (around 372 Mya), an extinction event occurred, which was characterized by rapid global cooling and led to marine ecosystem disturbances. This period saw a drop in sea levels and considerable climatic fluctuations.

Address the geographical changes from the Early to the Late Devonian Periods

During the Early Devonian Period, the continental landmasses were assembled into larger continents, such as Euramerica, Gondwana, and Siberia. The Late Devonian Period saw the continents moving closer together, leading to the formation of the supercontinent Pangaea. The terrestrial environment changed as large swamps developed along the coastlines, creating new ecological niches for the plants and animals inhabiting the land. The formation of early forests and the spread of plants affected the global climate and the carbon cycle, contributing to the Late Devonian Period's climatic fluctuations.

Key concepts

Terrestrial Environments

The Devonian Period is often called the "Age of Fishes," but significant changes also occurred on land. During the Early Devonian, terrestrial environments were mostly barren landscapes with little life, as plants were just starting to emerge from aquatic habitats. These early landscapes featured rocky surfaces with small, simple plants like the Cooksonia and Rhynia.
By the Late Devonian, however, the terrestrial environment had transformed dramatically. Larger and more complex plants, including significant tree-like species such as Archaeopteris, began to populate the Earth. These developments led to the creation of the planet's earliest forests.

• Forests had complex structures, providing habitats for many land organisms.
• Forests initiated soil formation and changed rainfall patterns.

The expansion of forests profoundly impacted the atmosphere and soil structure, making the environments more hospitable to animal life.

Plant Evolution

Plants underwent remarkable evolutionary changes during the Devonian Period, paving the way for modern terrestrial ecosystems. The earliest Devonian flora were simple and non-vascular, lacking true roots or leaves. Over millions of years, plants like the lycophytes and ferns evolved to become more structurally complex.
By the Late Devonian, the evolution of plants had facilitated the formation of extensive forests, largely due to the emergence of plants such as Archaeopteris. Archaeopteris is considered one of the first "true trees," boasting both leaves and a more extensive root system.

• The development of woody tissues in plants allowed them to grow taller and compete for sunlight more effectively.
• Root systems played a crucial role in stabilizing soil, enabling the retention of nutrients and moisture.

These evolutionary changes in plants were critical in transforming global ecosystems and atmospheric conditions.

Animal Life

The Devonian saw critical advances in animal life, both in the sea and on land. Initially, terrestrial animal life was dominated by arthropods, including ancient species of spiders and scorpions. However, the Late Devonian marked the beginning of a significant evolutionary event: the rise of tetrapods.
These early four-limbed vertebrates, like Ichthyostega and Acanthostega, are considered the precursors to modern land vertebrates. While still largely aquatic, these animals began to venture onto land, exploring and exploiting new ecological niches.

• The evolution of limbs was a crucial adaptation for movement on land.
• Later Devonian species showed more developed lungs for breathing on land.

These evolutionary steps were significant in the eventual dominance of vertebrates on terrestrial environments.

Climatic Changes

The Devonian Period was a time of significant climatic shifts, influencing both marine and terrestrial life. Initially, climate conditions were generally warm with high sea levels, fostering diverse marine life.
As the Late Devonian unfolded, climatic fluctuations became more pronounced. These changes included a rapid global cooling and a series of extinction events around the Frasnian-Famennian boundary, approximately 372 million years ago.

• The cooling events were partly due to increased plant growth, which reduced atmospheric carbon dioxide.
• Fluctuations had severe impacts on marine ecosystems, initiating widespread extinctions.

Such climatic changes not only affected sea levels but also influenced the evolution of life on land, encouraging the spread of forests and new animal adaptations.