Comment: 10:00 - 10:50 (00:50)
Source: Annenberg/CPB Resources - Earth Revealed - 11. Evolution Through Time
Keywords: "James Sadd", Cambrian, Paleozoic, evolution, life, fossil, vertebrate, environment, invertebrate, animal, brachiopod, trilobite, coral, fish, plant
Our transcription: The Cambrian Period marks the beginning of what is known as the Paleozoic Era of geologic time.
Conditions on Earth during the Paleozoic were ideal for the evolution of life.
Within the first 50 million years, all of the major groups of organisms which still survive today had evolved, including the first vertebrates, our most ancient ancestors.
During the Paleozoic, continents were drifting toward the Equator transforming cold glaciated terrain into warm, shallow seas.
Organisms thrived and diversified in this environment.
The bottoms of these shallow seas were literally carpeted with invertebrate animals, including brachiopods, trilobites and primitive corals. Above these swam the first fishes.
By middle Paleozoic time, plants and animals had made their way out of the oceans and began to populate the land.
Geology School Keywords