Evidence of Evolution Part 2

Biology Chapter 12 Section 1b Objectives: Recognize that various lines of evidence for evolution exist Apply knowledge of evolution to organisms (both modern and extinct)

Evidence of Evolution In addition to fossils, other evidence supports the theory of evolution Comparative anatomy: study of the structures of different organisms Remember, a theory in science means: The idea has been tested repeatedly and so far not disproven

Homologous Structures Homologous structures: body parts similar in origin and structure Homologous: from the ancient Greek meaning “to agree” Homologous structures developed from the same body part in a common ancestor Homologous structures are the result of divergent evolution

Homologous Structures From http://itc.gsw.edu/faculty/bcarter/histgeol/paleo2/homol1.htm and Monroe and Wicander, The Changing Earth, 3rd Edition

Homologous Structures Not necessarily similar in function Homologous structures indicate organisms are related (have a common ancestor) The greater the number of homologous structures, the more closely related

Homologous Structures Homologous structures the result of having the same structural genes Structural genes control the presence of a particular part

Homologous Structures Regulatory genes control the shape and form of the structures made by structural genes When the structure begins growth Rate of growth When the structure stops growing

Homologous Structures From http://itc.gsw.edu/faculty/bcarter/histgeol/paleo2/homol1b.htm

Vestigial Structures Suppose a structure becomes unnecessary— the genes making it don’t just disappear Vestigial structures: structures an organism has that are like those another organism has, but which are not used Vestigial structures indicate similarities and common ancestors in organisms because they are created by similar structural genes

Vestigial Structures Examples of vestigial structures: Flightless birds have wings

Vestigial Structures

Vestigial Structures Examples of vestigial structures: Hind leg bones in whales Human tail bone (coccyx) Human appendix Pig toes (the little ones)

Vestigial Structures

Vestigial Structures

Vestigial Structures

Vestigial Structures http://www.hsu.edu/content.aspx?id=5290

Vestigial Structures