8 15 Lecture summary Adaptation Adaptation unique features of an organism which are specialization for their environments of life How do they adapt Argument of design William Paley all traits have purpose predetermined perfect design Problems with the Argument of Design 1 How do you explain imperfections in organisms 2 Organisms aren t perfect eg Throat suffocaition 3 How to explain vestigial organs 4 How to explain ontonogy recapitulating phylogeny 5 Philosophical arhument if it s a miracle you can never understand it 6 Theological argument If its a miracle then you can explain it later shows erosion of gods power 7 Political Legal argument intelligent design requires a god 8 Scientific argument no way to test intelligent design THERE IS A DESIGNER NATURAL SELECTION have to have a designer to have design Argument by natural selection 1 No foresight 2 No predestined direction or design 3 No specific purpose Genetic variability Compromise in natural selection Certain adaptations preclude others How do new characteristics originate Divergent Evolution Pops becoming progressively distant longer they have been in separate gene pools Adaptation Radiation many species w a common ancestor specializing for different life styles finches Convergent Evolution Distantly related species independently evolve similar structures Adaptation is limited by 1 De Novo genetic novelties suddenly form mutations evolve 2 Pre adaptation modification of a pre existing structure for new uses all new steps must have a selective advantage over previous steps How are structures lost Once a structure is no longer used then it becomes more variable selective pressure to remove increases Not all specializations are adaptations for a given environment Some due to 1 Genetic drift 2 Sexual selection 3 Vestigial organs may exist Phyletic Graduation Species change over time in a slow gradual process Punctuated equilibrium rapid changes interrupted by long periods of little change