EVIDENCE FOR THE THEORY OF EVOLUTION 3. homologous structures and common ancestry Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Homologous Body Structures Structures that have different mature forms but develop from the same embryonic tissues are called homologous structures. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Evidence of Evolution Homologous Structures Turtle Alligator Bird Mammal The limbs of these four modern vertebrates are homologous structures. They provide evidence of a common ancestor whose bones may have resembled those of the ancient fish shown here. Notice that the same colors are used to show related structures. Homologous structures are one type of evidence for the evolution of living things. Homologous structures are one type of evidence for the evolution of living things. Ancient, lobe- finned fish Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Evidence of Evolution Not all homologous structures serve important functions. The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. These organs are called vestigial organs. Copyright Pearson Prentice Hall

EVIDENCE FOR THE THEORY OF EVOLUTION 4. Similarities in early development, or embryology Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Similarities in Embryology The early stages, or embryos, of many animals with backbones are very similar. The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates. Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Evolutionary Theory Evolutionary Theory Scientific advances in many fields of biology, geology, and physics have confirmed and expanded most of Darwin’s hypotheses. Evolutionary theory continues to change as new data are gathered and new ways of thinking arise. Copyright Pearson Prentice Hall