Copyright Pearson Prentice Hall Biology Biology Copyright Pearson Prentice Hall

17-3 Evolution of Multicellular Life Photo credit: ©D.W. Miller Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Geologic Time Scale Clock Model of Earth’s History First humans Radiation of mammals First land plants First prokaryotes First multicellular organisms Cenozoic Era Mesozoic Era Paleozoic Era Precambrian Time Earth’s history is often compared to a familiar measurement, such as the twelve hours between noon and midnight. In such a comparison, notice that Precambrian Time lasts from noon until after 10:30 pm. First eukaryotes Accumulation of atmospheric oxygen Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Precambrian Time Precambrian Time Few fossils exist from Precambrian time because the animals were all soft-bodied. Life existed only in the sea. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Paleozoic Era Paleozoic Era Rich fossil evidence shows that early in the Paleozoic Era, there was a diversity of marine life. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Trilobites Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Crinoid Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Paleozoic Era The Paleozoic Era is divided into the following periods: Cambrian Ordovician Silurian Devonian Carboniferous Permian Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Paleozoic Era Cambrian Period  The diversification of life at this time is called the “Cambrian Explosion.” The first known representatives of most animal phyla evolved. These included: invertebrates brachiopods trilobites Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Paleozoic Era Carboniferous and Permian Periods  Reptiles evolved from certain amphibians. Winged insects evolved into many forms. Giant ferns and other plants formed vast swampy forests. Remains of ancient plants formed thick deposits of sediment that changed into coal over millions of years. Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall Paleozoic Era At the end of the Permian Period, there was a mass extinction in which many living things became extinct at the same time. The mass extinction at the end of the Paleozoic affected both plants and animals on land and in the seas. As much as 95% of the complex life in the oceans disappeared. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mesozoic Era Mesozoic Era During the Mesozoic Era, dinosaurs became dominant. The Mesozoic is also marked by the appearance of flowering plants. The Mesozoic Era is often called the Age of Reptiles. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mesozoic Era Jurassic Period  Dinosaurs became the dominant animals on land. One of the first birds, Archaeopteryx, appeared. Many paleontologists think that birds are close relatives of dinosaurs. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Archaeopteryx Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall Mesozoic Era The Cretaceous Period ended with a mass extinction. More than half of all plant and animal groups were wiped out, including all of the dinosaurs. Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall Cenozoic Era Cenozoic Era During the Cenozoic, mammals evolved adaptations that allowed them to live in various environments—on land, in water, and even in the air. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cenozoic Era The Cenozoic often is called the Age of Mammals. The Cenozoic is divided into the two periods: Tertiary Period Quaternary Period Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-3 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-3 The first vertebrates to appear were the jawless fishes. eurypterids. brachiopods. reptiles. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-3 Coal was formed over millions of years from sediments deposited during the Ordovician Period. Carboniferous Period. Cambrian Period. Permian Period. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-3 The late Triassic Period saw the appearance of the first reptiles. giant ferns. mammals. fish. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-3 The term Cambrian Explosion refers to the impact of a giant meteor that extinguished much of life on Earth. the end of the Cambrian Period when many species were replaced by other species. the first appearance of a great diversity of life representing most animal phyla. a volcanic eruption that buried many of the fossils of Cambrian age. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 17-3 The fossil record indicates that mammals were large meat-eaters that caused the extinction of the dinosaurs. appeared in the Triassic Period but did not flourish until the dinosaurs became extinct. successfully competed with the dinosaurs because they protected their young. are the ancestors of modern birds. Copyright Pearson Prentice Hall

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