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Chapter 14 - Introduction A Evolutionary biologists can...

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Chapter 15 Lecture Outline Introduction Are Birds Really Dinosaurs with Feathers? A. Evolutionary biologists can learn much about the history of life on Earth from fossil records. John Ostrum raised the controversial question about the origin of birds and the relationship with dinosaurs as their predecessor. B. Through careful analysis of fossil records, Ostrum presented a convincing argument supporting the theory that birds are descendents of dinosaurs ( Archaeopteryx, left page in text). C. More evidence was presented in support of Ostrum’s theory with the new method of evaluating evolutionary relationships called cladistic analysis. D. The current hypothesis of the origin of birds from dinosaurs is now widely accepted. E. Now the debate by the evolutionary biologist is, “How did dinosaurs learn to fly?” There are two common scenarios. 1. Feathered dinosaurs used their feathers to assist when capturing prey or escaping predators. 2. They used them to glide to the ground from trees. F. The second scenario has gained favor, particularly in light of the most recent discovery of a fossil ( Microraptor, right page in text) that dates back to 120 million years. This fossil is a feathered, four-winged gliding dinosaur. I. Macroevolution and Earth’s History Module 15.1 The fossil record chronicles macroevolution. Review: The fossil record (Module 13.2). A. Macroevolution, the main events in the evolutionary history of life on Earth, is determined by comparing the fossil records in strata representing various ages, from various parts of Earth’s surface. B. Using the information gleaned from fossil sequences, a geologic record has been established by geologists. The geologic time scale is a standardized, hierarchical system of age categories (Table 15.1). Earth’s history is divided into three eons: Archaean, Proterozoic, and Phanerozoic. Archaean and Proterozoic are grouped together into the Precambrian, which lasted approximately 4 billion years. The Phanerozoic covers approximately the past 550 million years. C. The oldest fossils are of microorganisms from 3.5 billion years ago (bya) during the early Precambrian era. The oldest eukaryote fossils are from 2.2 bya and multicellular organism fossils are from 1.2 bya. D. Late Precambrian fossils show that animal life had diversified by 600 million years ago (mya). E. Early Paleozoic (542 mya) rocks bear fossils that gave rise to modern organisms, as well as fossils of extinct lineages. F. By 400 mya, during the middle Paleozoic (“ancient animal”) era, life had moved out of water and onto dry land.
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G. The Mesozoic (“middle animal”) era is the age of reptiles and cone-bearing plants. During this era, the first mammals, birds, and angiosperms appeared. H. The Cenozoic (“recent animal”) era began 65 mya and is the age of mammals and flowering plants.
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