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Dna comparisons show that some populations of brown

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DNA comparisons showthat some populations ofbrown bears are moreclosely related to polarbears than they are toother brown bears. Whatdo you think this meansfor the classifi cation ofpolar bears?FIGURE 18–12Classification ofPandasBiologists used to classify thered panda and the giant panda together.However, cladistic analysis using DNAsuggests that the giant panda shares a morerecent common ancestor with bears than witheither red pandas or raccoons.XYZLesson 18.2Self-TestLesson AssessmentOften, scientists use DNA evidence when anatomical traitsalone can’t provide clear answers. Giant pandas and red pandas,for example, have given taxonomists a lot of trouble. These twospecies share anatomical similarities with both bears and rac-coons, and both of them have peculiar wrist bones that work like ahuman thumb. DNA analysis revealed that the giant panda sharesa more recent common ancestor with bears than with raccoons.DNA places red pandas, however, outside the bear clade. So pandashave been reclassified, placed with other bears in the clade Ursidae,as shown inFigure 18–12.What happened to the red panda? Itis now placed in a different clade that also includes raccoons andother organisms such as seals and weasels.522Chapter 18 • Lesson 2
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Changing Ideas About KingdomsWhat are the six kingdoms of life as they are now identified?During Linnaeus’s time, the only known differences among livingthings were the fundamental characteristics that separated animalsfrom plants. Animals were organisms that moved from place to placeand used food for energy. Plants were green organisms that generallydid not move and got their energy from the sun.As biologists learned more about the natural world, they realizedthat Linnaeus’s two kingdoms—Animalia and Plantae—did not reflectthe full diversity of life. Classification systems have changed dramati-cally since Linnaeus’s time, as shown inFigure 18–13.And hypothesesabout relationships among organisms are still changing today as newdata are gathered.Building the Tree of LifeKey QuestionsWhat are the six kingdomsof life as they are now identified?What does the tree of lifeshow?VocabularydomainBacteriaArchaeaEukaryaTaking NotesConcept MapAs you read, con-struct a concept map describingthe characteristics of the threedomains.PlantaeAnimaliaProtistaMoneraPlantaePlantaeArchaebacteriaEubacteriaProtistaFungiPlantaeAnimaliaAnimaliaAnimaliaFungiProtistaNames of KingdomsFirst Introduced1700sLate 1800s1950s1990sKingdoms of Life, 1700s–1990sFIGURE 18–13From Two to Six KingdomsThisdiagram shows some of the ways in which organismshave been classified into kingdoms since the 1700s.523Lesson 18.3Lesson OverviewLesson NotesTHINK ABOUT ITThe process of identifying and naming all knownorganisms, living and extinct, is a huge first step toward the goal ofsystematics. Yet naming organisms is only part of the work. The realchallenge is to group everything, from bacteria to dinosaurs to bluewhales, in a way that reflects their evolutionary relationships. Overthe years, new information and ways of studying organisms haveproduced major changes in Linnaeus’s original scheme for organizingliving things.

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Term
Spring
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mitlitski
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Biology: The Dynamic Science
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Chapter 22 / Exercise 1
Biology: The Dynamic Science
Hertz/Russell
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