Final Exam Essays - 1. Use examples from lecture or text to...

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1. Use examples from lecture or text to help explain (a) the concepts and (b) the processes of adaptation. (c) Explain at least three reasons why adaptations are not ‘perfect.’ Adaptation: an anatomical structure, physiological process or behavioral trait of an organism that has evolved over a period of time by the process of natural selection such that it increases the expected long-term reproductive success of the organism. Something works better than its alternatives, and so is maintained in offspring An adaptation evolved in response to past selection, it is not based on current situation of organism Example: giraffe has evolved a longer neck through natural selection, not by stretching its neck longer and longer (this is not passed on to offspring). Process of adaption: evolution through natural selection Natural selection: a population can change over generations if individuals that possess certain heritable traits leave more offspring than other individuals. Example: Finch beaks on Galapagos Islands – their beaks and behaviors are adapted to the specific foods available in their habitats because through mutations some birds had beaks that worked better in their environment, so they could out compete the other birds and produce more viable offspring. Example: Deer mouse: change in fur coloration depending on where they live because darker fur could blend with darker surroundings and vice versa, thereby increasing survival rate, etc. 3 reasons adaptations are not perfect: You can’t get there from here There is a transition necessary between current and better state that may be less fit Coevolution keeps an organism from being perfectly adapted for its environment You didn’t really want to anyway Tradeoffs select for compromises (reproduction vs. survival in swallow birds) You can but it will take time and luck Chance: it takes time and luck to get that one mutation that will improve an organism; selection only occurs once you get that mutation. Time lags: environment may change faster than an organism can evolve Gene flow disrupts local adaptation Ex. Experimental manipulation with tail length of bird—if you shorten the tail length it takes longer to mate but has higher survival. If you lengthen the tail, it takes shorter to mate but lower survival rate. Fitness depends on survival and reproduction. Tail length creates a fitness tradeoff- stabilizing selection. Ex. Plieotropic genetic effect: Strong selection for early reproduction, tradeoff later survival costs. The cricket experiment: Males commenced calling sooner, reached peak calling effort sooner, and called more per night (called more overall) despite living half as long.
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1. (Answer from another group) (a) ~ Dictionary Def: ~any alteration in the structure or function of an organism or any of its parts that results from natural selection and by which the organism becomes better fitted to survive and multiply in its environment. ~ Darwin focused on adaptation when he traveled to the Galapagos Islands On his voyage he
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This note was uploaded on 03/18/2008 for the course BS 148H taught by Professor Getty during the Fall '07 term at Michigan State University.

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Final Exam Essays - 1. Use examples from lecture or text to...

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