1. End Show Slide 1 of 30 Copyright Pearson Prentice Hall Biology

2. End Show Slide 2 of 30 Copyright Pearson Prentice Hall 17-3 Evolution of Multicellular Life

3. End Show 17-3 Evolution of Multicellular Life Slide 3 of 30 Copyright Pearson Prentice Hall Precambrian Time Few fossils exist from Precambrian time because the animals were all soft-bodied. Life existed only in the sea.

4. End Show 17-3 Evolution of Multicellular Life Slide 4 of 30 Copyright Pearson Prentice Hall Paleozoic Era What were the characteristic forms of life in the Paleozoic era?

5. End Show 17-3 Evolution of Multicellular Life Slide 5 of 30 Copyright Pearson Prentice Hall Rich fossil evidence shows that early in the Paleozoic Era, there was a diversity of marine life. Paleozoic Era

6. End Show 17-3 Evolution of Multicellular Life Slide 6 of 30 Copyright Pearson Prentice Hall Paleozoic Era The Paleozoic Era is divided into the following periods: Cambrian Ordovician Silurian Devonian Carboniferous Permian

7. End Show 17-3 Evolution of Multicellular Life Slide 7 of 30 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

8. End Show 17-3 Evolution of Multicellular Life Slide 8 of 30 Copyright Pearson Prentice Hall Paleozoic Era Ordovician and Silurian Periods Some arthropods became the first land animals. The first vertebrates appeared. The first land plants evolved from aquatic ancestors.

9. End Show 17-3 Evolution of Multicellular Life Slide 9 of 30 Copyright Pearson Prentice Hall Devonian Period Some plants adapted to drier areas and invaded more habitats. Insects appeared on land. The Devonian is often called the Age of Fishes because many groups of fishes were present in the oceans. Most fishes had jaws, bony skeletons, and scales. Paleozoic Era

10. End Show 17-3 Evolution of Multicellular Life Slide 10 of 30 Copyright Pearson Prentice Hall During the Devonian, vertebrates began to invade the land. Some of these early four-legged vertebrates evolved into the first amphibians. Paleozoic Era

11. End Show 17-3 Evolution of Multicellular Life Slide 11 of 30 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.

12. End Show 17-3 Evolution of Multicellular Life Slide 12 of 30 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.

13. End Show 17-3 Evolution of Multicellular Life Slide 13 of 30 Copyright Pearson Prentice Hall Mesozoic Era What were the characteristic forms of life in the Mesozoic era?

14. End Show 17-3 Evolution of Multicellular Life Slide 14 of 30 Copyright Pearson Prentice Hall 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.

15. End Show 17-3 Evolution of Multicellular Life Slide 15 of 30 Copyright Pearson Prentice Hall Mesozoic Era Triassic Period Organisms that survived the Permian mass extinction became the main life forms early in the Triassic. These organisms included fishes, insects, reptiles, and cone-bearing plants.

16. End Show 17-3 Evolution of Multicellular Life Slide 16 of 30 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.

17. End Show 17-3 Evolution of Multicellular Life Slide 17 of 30 Copyright Pearson Prentice Hall Mesozoic Era Cretaceous Period Dominant animals during this period included: reptiles, birds, turtles, crocodiles, fishes, and marine invertebrates. New forms of plant life included leafy trees, shrubs, and small flowering plants.

18. End Show 17-3 Evolution of Multicellular Life Slide 18 of 30 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.

19. End Show 17-3 Evolution of Multicellular Life Slide 19 of 30 Copyright Pearson Prentice Hall Cenozoic Era What were the characteristic forms of life in the Cenozoic era?

20. End Show 17-3 Evolution of Multicellular Life Slide 20 of 30 Copyright Pearson Prentice Hall During the Cenozoic, mammals evolved adaptations that allowed them to live in various environments—on land, in water, and even in the air. Cenozoic Era

21. End Show 17-3 Evolution of Multicellular Life Slide 21 of 30 Copyright Pearson Prentice Hall The Cenozoic often is called the Age of Mammals. The Cenozoic is divided into the Tertiary Period and the Quaternary Period. Cenozoic Era

22. End Show 17-3 Evolution of Multicellular Life Slide 22 of 30 Copyright Pearson Prentice Hall Cenozoic Era Tertiary Period The climate was generally warm and mild. Marine mammals such as whales and dolphins evolved. Grasses evolved, providing food for grazing mammals. Some mammals became very large, as did some birds.

23. End Show 17-3 Evolution of Multicellular Life Slide 23 of 30 Copyright Pearson Prentice Hall Cenozoic Era Quaternary Period Earth’s climate cooled, causing a series of ice ages. About 20,000 years ago, Earth’s climate began to warm and sea levels began to rise. In the oceans, algae, coral, mollusks, fishes, and mammals thrived. Insects, birds, and land mammals were common.

24. End Show 17-3 Evolution of Multicellular Life Slide 24 of 30 Copyright Pearson Prentice Hall Cenozoic Era The fossil record suggests that the early ancestors of our species appeared about 4.5 million years ago. The first fossils of Homo sapiens may have appeared as early as 200,000 years ago in Africa. According to one hypothesis, members of our species migrated from Africa and ultimately colonized the world.

25. End Show - or - Continue to: Click to Launch: Slide 25 of 30 Copyright Pearson Prentice Hall 17-3

26. End Show Slide 26 of 30 Copyright Pearson Prentice Hall 17-3 The first vertebrates to appear were the a.jawless fishes. b.eurypterids. c.brachiopods. d.reptiles.

27. End Show Slide 27 of 30 Copyright Pearson Prentice Hall 17-3 Coal was formed over millions of years from sediments deposited during the a.Ordovician Period. b.Carboniferous Period. c.Cambrian Period. d.Permian Period.

28. End Show Slide 28 of 30 Copyright Pearson Prentice Hall 17-3 The late Triassic Period saw the appearance of the first a.reptiles. b.giant ferns. c.mammals. d.fish.

29. End Show Slide 29 of 30 Copyright Pearson Prentice Hall 17-3 The term Cambrian Explosion refers to a.the impact of a giant meteor that extinguished much of life on Earth. b.the end of the Cambrian Period when many species were replaced by other species. c.the first appearance of a great diversity of life representing most animal phyla. d.a volcanic eruption that buried many of the fossils of Cambrian age.

30. End Show Slide 30 of 30 Copyright Pearson Prentice Hall 17-3 The fossil record indicates that mammals a.were large meat-eaters that caused the extinction of the dinosaurs. b.appeared in the Triassic Period but did not flourish until the dinosaurs became extinct. c.successfully competed with the dinosaurs because they protected their young. d.are the ancestors of modern birds.

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