Paleozoic Era Notes

Geologic Time Scale & Paleozoic Introduction

  • Orientation on the Geologic Time Scale.

  • Phanerozoic Diversity Overview.

  • Introduction to the Paleozoic Era.

Geologic Time Scale

  • Eons are the largest divisions, followed by Eras, Periods, and Epochs.

  • Precambrian Supereon: Includes Hadean, Archean, and Proterozoic Eons.

    • This supereon represents the vast majority of Earth's history, preceding the diversification of complex life.

  • Phanerozoic Eon: Contains Paleozoic, Mesozoic, and Cenozoic Eras.

    • The Phanerozoic is marked by the proliferation of complex life forms and is divided into three major eras, each representing significant changes in life on Earth.

Phanerozoic Marine Family Biodiversity

  • Radiations: Periods of rapid increase in diversity.

    • These events often follow major extinctions, as new ecological niches open up.

  • Extinctions: Periods of rapid decrease in diversity.

    • Mass extinctions can be caused by various factors, including volcanic activity, climate change, and asteroid impacts.

  • Diversity Plateaus: Periods of relative stability in diversity.

    • Plateaus may indicate that ecological niches are filled or that environmental conditions are relatively stable.

  • Overall Increase: General trend of increasing diversity through the Phanerozoic.

    • There is a general trend of increasing biodiversity throughout the Phanerozoic, although this trend is punctuated by periods of extinction.

Evolutionary Faunas

  • Cambrian: Trilobites & Archaeocyaths.

    • Trilobites were a dominant group of arthropods during the Cambrian, while Archaeocyaths were early reef-building organisms.

  • Paleozoic: Brachiopods & Echinoderms.

    • Brachiopods and Echinoderms diversified significantly during the Paleozoic, occupying various marine habitats.

  • Modern: Decapods & Bivalves.

    • Decapods (crabs, shrimp) and Bivalves (clams, oysters) are dominant marine groups in modern oceans.

Paleozoic Era

  • Characterized by significant events:

    • Cambrian Radiation.

    • The Cambrian Radiation was an explosion of biodiversity, with the appearance of many major animal phyla.

    • Ordovician Radiation.

    • The Ordovician Radiation saw further diversification of marine life, including the evolution of early fish.

    • End Ordovician mass extinction.

    • The End-Ordovician extinction was likely caused by glaciation and sea-level changes.

    • End Devonian mass extinction.

    • The Late Devonian extinction event was a series of pulses that devastated marine ecosystems.

    • Advent of life on land.

    • The colonization of land by plants and animals was a major evolutionary transition during the Paleozoic.

    • Origin of vertebrates.

    • The first vertebrates evolved during the Paleozoic, including jawless fish and early tetrapods.

    • Late Permian mass extinction (end of era).

    • The Late Permian extinction, also known as the "Great Dying," was the largest mass extinction in Earth's history, wiping out the majority of marine and terrestrial species.

Cambrian Radiation

  • Appearance of all major animal phyla in existence today.

    • Often considered the most important evolutionary event in the history of life.

  • Also known as the Cambrian Explosion.