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9 0 / 2 1 / 5 115/12/09 15:57:35 Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 6 8

6 8 i . 7 8 4 2 Embryology is the study of the development of embryos from fertilization to birth. All species of vertebrates have pharyngeal during their pouches at some stage development. The similarities in location and function of the pharyngeal pouches is a sign that the vertebrate species share a common ancestor. structure. The wings of flies and birds are examples. structure. The wings of flies and indicates that the species are not closely The existence of analogous structures related. structures is that the species that have vestigial The best explanation for vestigial species that still use the structures for a specific structures are related to ancestral purpose. which is a vestigial structure for walking on land. Whales have a tiny pelvic bone, Body parts of organisms that are similar in position but different in function are but different in function that are similar in position Body parts of organisms The forelimbs of different mammals are examples. called homologous structures. this suggests that the species are related. If species have homologous structures, the more likely it is that the are to each other, The more similar two structures common ancestor. species have evolved from a recent parts that perform a similar function but differ in Analogous structures are body Living species that are closely related share a common ancestor. are closely related share a Living species that they diverged, or split, from two species are depends when How closely related ancestor. their common 9 8 _ t u c. a. b. b. Studying the development of embryos can also provide scientists with evidence that certain species are related. Body parts that have lost their original function through evolution are called original function through evolution are called Body parts that have lost their of flightless birds are an example. vestigial structures. The wings a. d. e. a. b. c. a. b. is called structures of living species and differences among The study of similarities comparative anatomy. Evolution does not occur in a straight line with one species replacing another in a another in a species replacing line with one in a straight does not occur Evolution steps. series of orderly O s n A _ F Evidence for Evolution for Evolution Evidence R The and Environment Change Over Time C _ 4. 3. 2. 1. 7 T6 Lesson 3: Biological Evidence of Evolution Evidence 3: Biological Lesson A. Lesson Outline for Teaching Outline for Lesson 8 0 _ 2 8 0 _ 4 1 2 CC214_082_087_CRF_AnsOut_892487.i86 86 CC214_082_087_CRF_AnsOut_892487.i87 87 2 1 4 _ 0 8 2 _ 0 8 7 _ C R

F Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. _ A n s O u t The Environment and Change Over Time Time Over Change Environmentand The dinosaur speciesorwhichmodernaremostcloselyrelatedtothatspecies. dinosaurs ingeneral;itmightgivecluesaboutwhichspecies,ifany, arosedirectlyfromthat It mightgivecluesabouttheancestorofthatspeciesdinosauror biological evolution? How couldstudyingthegeneticsequenceofadinosaur’s DNAprovidefurtherevidenceof Discussion Question B. Lesson continued Outline _ 8 5. 4. 3. 2. 1. 5. 9 2 4 The StudyofEvolutionToday 8 7 . i 8 7

provided evidenceofrelatednessamonglivingandextinctspecies. Scientific studiesoffossils,anatomy, embryology, andmolecularbiologyhave extended hiswork. Since thepublicationofDarwin’s theory, scientistshaveconfirmed,refined,and d. c. b. a. The studyofgenestructureandfunctioniscalledmolecularbiology. more than150years. of Darwin’s ofevolutionbynaturalselectionhaveremainedunchangedfor theory Though scientistsnowstudyevolutionatthemolecularlevel,basicprinciples cause dramaticchangesinorganisms. Scientists todayarestudyinghowgenescanbereorganizedinsimplewaysthat before andafterthemisstrongevidenceofevolutionspecies. ofnewfossilsthathavefeaturesspecieslived The continuousdiscovery 8 7 species divergedfromcommonancestors. Scientists usethismolecularclocktoestimatethetimeinpastwhenliving kind ofmolecularclock. common tomanyspecieschangethroughtimeatsteady, predictable rateslikea Studies inmolecularbiologyhaveshownthatsomestretchesofDNAare proteins are. The morecloselyrelatedtwospeciesare,thesimilartheirgenesand shown tobethesource ofvariationuponwhichnaturalselectionacts. The existenceofgenesprovidesevidenceevolutionbecausetheyhavebeen 115/12/09 15:57:35 T7 5 / 1 2 / 0 9

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