Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint® Lectures Lectures by April Lynch The Mammals that Conquered the Seas Current Issues in Biology, Volume 2 Scientific American

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review The Mammals that Conquered the Seas Fossil evidence indicates that vertebrates originated in aquatic environments and later adapted to land. Mammals originated on land. But some mammals, such as whales, later adapted to marine environments, reversing the trend.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review The Mammals that Conquered the Seas Whales may live in water, but they are not fish. They are clearly warm-blooded mammals, breathing air and nursing their young. Along with dolphins and porpoises, they belong to an order of mammals called cetacea. The whales’ return to water was poorly understood until fossil discoveries over the last two decades helped trace their transition.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review The Mammals that Conquered the Seas This shift occurred during the Eocene era, about 55 to 34 million years ago. Archaic whales, or archaeocetes, may have been drawn back to aquatic life by ancient seas teeming with food.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review The Mammals that Conquered the Seas Whales’ transitional ancestors had characteristics of both land and sea creatures – legs and hooves for walking, tails for swimming.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review The Mammals that Conquered the Seas But later fossil and molecular studies suggest closer ties to artiodactyls, even-toed hoofed mammals such as camels and pigs. The hippopotamus may be an especially close whale relative. Scientists once thought whales might be descended from extinct wolf-like hoofed mammals called mesonychids.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension The Mammals that Conquered the Seas Distant ancestors of whales had what characteristics? a) fur b) milk-producing glands c) legs and feet d) all of the above

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension The Mammals that Conquered the Seas Distant ancestors of whales had what characteristics? d) all of the above

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension The Mammals that Conquered the Seas Whales are most closely related to which terrestrial mammals? a) artiodactyls such as camels, pigs, and cows b) carnivores such as bears, raccoons, and otters c) perissodactyls such as horses, donkeys, and zebras d) all of the above

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension The Mammals that Conquered the Seas Whales are most closely related to which terrestrial mammals? a) artiodactyls such as camels, pigs, and cows

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension The Mammals that Conquered the Seas Which of the following do not help explain how modern whales fit into the mammalian family tree? a) DNA analysis b) the fossil record c) modern whale anatomy d) antibody-antigen physiology

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension The Mammals that Conquered the Seas Which of the following do not help explain how modern whales fit into the mammalian family tree? c) modern whale anatomy

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension The Mammals that Conquered the Seas Which of these is not thought to be an ancestor of modern whales? a) Basilosaurus b) Ambulocetus c) Orca d) Dorudon

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension The Mammals that Conquered the Seas Which of these is not thought to be an ancestor of modern whales? c) Orca

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Biology and Society The Mammals that Conquered the Seas Selective pressures in the Eocene environment caused whales to adapt and return to water. Environmental pressures are also driving natural selection in the present-day world. Strongly Agree Strongly Disagree A. E. C. B. D.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Biology and Society The Mammals that Conquered the Seas During the Eocene era, ancient oceans covered much of what is now the Indian subcontinent, including Pakistan. Important whale ancestor fossils have been found there, but such work has also been interrupted by modern-day conflict. Scientists should receive special protection to conduct research globally, despite political or social problems. Strongly Agree Strongly Disagree A. E. C. B. D.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Thinking About Science The Mammals that Conquered the Seas Most mammals cannot live without fresh water. But cetaceans obtain their water, in part, from sips of the salty ocean. To investigate when the ancestors of whales became able to ingest seawater, scientists applied a technique to measure the ratio of certain oxygen isotopes in fossilized teeth. The ratio of these isotopes is different in fresh and salt water. Describe how this difference helped shape the hypothesis of the scientists conducting the research.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Interpreting Data and Graphs The Mammals that Conquered the Seas These drawings illustrate how various hypotheses of whale ancestry have changed as new findings come to light. According to each of the four drawings, which category of creature is the whale’s closest relative?