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lecture20 - ADAPTATION ADAPTATION Galapagos Finches...

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Unformatted text preview: ADAPTATION ADAPTATION Galapagos Finches ADAPTATION= ADAPTATION= • Adaptations = the unique features of an organism which are specializations for their environment & their way of life. How Do Organisms Adapt? Adapt? A) Argument by Design William Paley—1802 “What we observe in nature is attributed to What the existence of a Deity.” the Any given trait is designed for a purpose. Any The purpose is predetermined. The The design is perfect. The Watch Argument The • If you find a watch and have never seen one but examined it closely, you could not help but believe it was designed and had a designer. • Similarly, when you look at the intricacies of an organism you know it must be designed and that there was a designer. Should the argument of Intelligent Design be taught as an alternative to evolution in the science classroom? the 1) NO 2) YES 0 % 1 0 % 2 30 “Intelligent Design?” • Difficulties with the argument: 1) Organisms aren’t perfect: e.g. consider your eyes “Intelligent Design?” • Difficulties with the argument: 1) Organisms aren’t perfect: e.g. consider your throat “Intelligent Design?” • Difficulties with the argument: 1) Organisms aren’t perfect: e.g. consider your prostate “Intelligent Design?” • Difficulties with the argument: 1) Organisms aren’t perfect: Most organisms that ever lived are extinct ! “Intelligent Design?” • Difficulties with the argument: 2) Vestigial organs e.g. Blind cave animals with functionless eyes Vestigial Organs Cont.’ Vestigial e.g. Snakes with one functionless lung e.g. Birds with one functionless ovary “Intelligent Design?” Difficulties with the argument: 3) Embryological problems a) e.g. Aortic arches b) e.g. Whale blowholes c) e.g. Human tails “Intelligent Design?” Difficulties with the argument: 4) The philosophical difficulties that you will ascribe anything that you don’t understand into the category of a miracle understand —You give up trying to understand. “Intelligent Design?” The bacteria flagellum “Intelligent Design?” The Blood Clotting Mechanism The www.millerandlevine.com/.../clot/Clotting.html “Intelligent Design?” 5) The theological argument: If you don’t understand something and call it If a miracle by God & then later come to understand it, there will be a slow erosion of God’s powers. of “Intelligent Design?” 6) Political/Legal argument: “Intelligent Design” requires a designer who is Intelligent God. One cannot impose religion in schools. Those schools who insist on teaching “intelligent design” are in violation of the United States Constitution. “Intelligent Design?” 7) More Scientific Arguments: a) There is no way to really test the There argument. It makes no predictions. argument. Hence, it isn’t science! b) There is an alternative explanation that is b) testable and has passed thousands of tests. We call it evolution. We B) Argument by Natural Selection B) • Darwin & Wallace --Adaptations are characters which are the product of selection within a particular environment. • Natural selection has: – No foresight – No predestined design – No specific purpose DIVERGENT EVOLUTION DIVERGENT = Populations becoming progressively distinct the longer they are have been in separate gene pools. B A C B A A C B A A C DIVERGENT EVOLUTION DIVERGENT ADAPTIVE RADIATION = many species with a common ancestor specializing for different life styles. e.g. Limbs of mammals Moles---------digging Wolves-------running Tigers---------prey capture Bats-----------flying Seals---------swimming Humans------grasping DIVERGENT EVOLUTION DIVERGENT HOMOLOGOUS STRUCTURES result from adaptive radiation. --Common basic design-but function may differ --Common embryological pattern --Common ancestor which had the original design CONVERGENT EVOLUTION CONVERGENT = distantly related species independently evolve similar structures. e.g. bird & insect wings Analogous structures --Common function --Different basic design --Different embryology --”Design” is not from a common ancestor CONVERGENT EVOLUTION CONVERGENT e.g. Shape of swimming vertebrates Reptile Mammal Fish CONVERGENT EVOLUTION CONVERGENT e.g. Placental & Marsupial Mammals show a general convergence in shape & feeding behavior Adaptation is limited by Adaptation • Genetic variability • Compromises in natural selection • Certain adaptations preclude others We use the term “convergent evolution” when we are dealing with when 1) Sympatric speciation 2) Adaptive radiation 3) Allopatric speciation 4) Analogous structures 5) Homologous structures 0% 1 0% 2 0% 3 45 0% 4 0% 5 What is the best term for this pattern? What 1) Convergent evolution 2) Pleiotropy 3) Analogous structures 4) Genetic drift 5) Adaptive radiation 45 0 % 1 0 % 2 0 % 3 0 % 4 0 % 5 How Do New Characteristics (Adaptations) Originate? (Adaptations) 1) De novo (from “scratch”) New adaptations evolve in continuous stages from pre-existing organs, behavior, cells, or molecules How Do New Characteristics (Adaptations) Originate? (Adaptations) 2) Pre-adaptation = modification of a preexisting structure for new uses. e.g. Fish Tetrapod Bat fins legs wings All steps must have a selective advantage over previous steps How Are Structures Lost? How • Once a structure is no longer used, then the structure becomes more variable (the selective pressure to maintain it is removed or lessened). • Then if the structure is potentially deleterious (it uses energy, it can get infected, it gets in the way) there will be a selective pressure to loose it. • e.g. eyes of cave animals Not All Specializations Are Adaptations for a Given Environment Environment • • • • • Alternative solutions can exist Genetic drift can occur Pleiotropy can occur Sexual selection can occur Vestigial organs may exist. Remember: Some adaptations do more than one job TWO VIEWS OF EVOLUTION TWO • Phyletic Gradualism = species change over time in a slow gradual process. No Evolution Evolution Phyletic Gradualism TWO VIEWS OF EVOLUTION TWO • Punctuated Equilibrium = rapid changes interrupted by long periods of little change Punctuated Equilibrium Next time: Lamarck vs. Darwin Next in SmackDown Don’t play d i rt y , Chuck It’s survival of the fittest, Buddy ...
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