Cambrian

Definition

The Cambrian is a geological period that lasted from approximately 541 to 485 million years ago, marking the first period of the Paleozoic Era. This time is significant due to the rapid diversification of life forms, often referred to as the 'Cambrian Explosion,' where most major groups of animals first appeared in the fossil record.

5 Must Know Facts For Your Next Test

1. The Cambrian period is notable for the emergence of a wide variety of organisms, including early arthropods, mollusks, and the first vertebrates.
2. During the Cambrian, there was a dramatic increase in the complexity of life forms, leading to many body plans that still exist today.
3. The Cambrian marked significant geological changes, including the breakup of supercontinents and rising sea levels that created extensive shallow marine environments.
4. The period's rock layers are rich in trilobite fossils, which are key index fossils used for dating and correlating rock strata.
5. The end of the Cambrian was marked by a series of extinctions that paved the way for new life forms in subsequent geological periods.

Review Questions

• How did the Cambrian period contribute to our understanding of evolutionary biology?
  • The Cambrian period is crucial for understanding evolutionary biology because it showcases a significant event known as the 'Cambrian Explosion,' where a vast number of diverse life forms rapidly emerged. This period highlights how quickly new body plans and ecological niches can evolve under changing environmental conditions. The diversity seen during this time provides insights into how complex organisms developed and adapted, serving as a key reference point for studying evolution.
• Evaluate the role of the Cambrian in shaping the fossil record and its implications for stratigraphy.
  • The Cambrian plays a vital role in shaping the fossil record due to its abundance of fossils, particularly trilobites, which serve as index fossils for stratigraphic correlation. These fossils help geologists and paleontologists date rock layers accurately and understand the relative timing of evolutionary events. The presence of diverse organisms in this period allows for better stratigraphic resolution and correlation across different geographical regions.
• Analyze how environmental factors during the Cambrian contributed to biological diversity and extinction events.
  • During the Cambrian, environmental factors such as rising sea levels and increased oxygen levels facilitated the development of diverse marine ecosystems. These changes provided numerous ecological niches that allowed different organisms to thrive and evolve unique adaptations. However, at the end of this period, significant extinction events occurred due to fluctuating environmental conditions, leading to a loss of some species while creating opportunities for others to evolve in subsequent periods. This duality of diversification and extinction illustrates how dynamic Earth’s ecosystems can be.

Related terms

Paleozoic Era: The Paleozoic Era is the geological era that follows the Precambrian and precedes the Mesozoic Era, encompassing a significant portion of Earth's history and characterized by major developments in marine and terrestrial life.

Fossil Record: The fossil record is the collection of all known fossils and their placement in the Earth's strata, which provides important information about past life forms and their evolution over time.

Ordovician: The Ordovician is the geological period that follows the Cambrian, lasting from about 485 to 444 million years ago, known for further diversification of marine life and significant geological changes.