Paleozoic

The Paleozoic is a geologic era from about 541 to 252 million years ago. It saw major diversification of marine life and the development of terrestrial ecosystems.

Cambrian Period: The first period of the Paleozoic, spanning roughly 541 to 485 million years ago. The Cambrian diversification transformed marine ecosystems near the era’s beginning.
Great Ordovician Biodiversification Event: A major increase in marine biodiversity during the Ordovician Period. This event extended the diversification of marine life beyond the Cambrian.
Geologic time scale: A system for organizing Earth’s history into eons, eras, periods, and smaller units. It places the Paleozoic within the larger chronology of Earth history.
Land plant evolution: The evolutionary history of plants as they adapted to life on land. The spread of land plants transformed soils, habitats, and atmospheric conditions.
Precambrian: The informal span of Earth history before the Cambrian Period, encompassing most of the planet’s existence. It contrasts with the Paleozoic’s abundant record of complex animal life.
Ordovician Period: A Paleozoic period from roughly 485 to 444 million years ago, marked by major marine diversification. Its expanding marine biodiversity preceded the era’s first mass extinction.
Devonian fish diversification: The expansion and diversification of fish groups during the Devonian Period. It illustrates the rapid evolution of vertebrate diversity within the era.
Paleozoic fossil record: Fossil evidence documenting Paleozoic organisms and their changes through time. These fossils reveal the era’s transitions from marine to terrestrial ecosystems.
Tetrapod: A vertebrate with four limbs or descended from four-limbed ancestors. Early tetrapods emerged from aquatic vertebrates during the Devonian.
Cenozoic: The current geologic era, beginning about 66 million years ago. It provides a later comparison for the Paleozoic’s ancient ecosystems and fauna.

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