08-ch13-evolution1 - Chapter 13 How Populations Evolve...

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Unformatted text preview: Chapter 13 How Populations Evolve Populations Evolve Great moments in evolution Then Then & now: Darwin’s theory of “descent with modification” **2 hour movie bonus assignment** http://video.pbs.org/video/1372073556/ 1831 voyage of the H.M.S. Beagle: five years at sea changed biology forever Charles Robert Darwin (1809-1882) http://www.amnh.org/exhibitions/darwin/ • endemic island species • different island habitats • corresponding adaptations e.g., galapagos tortoise galapagos tortoise 14 subspecies of two types dome vs. saddle shell Darwin’s diverse Galapagos finches are much more probing bill closely related for insects than they appear tooltool-user fills woodpecker niche grasping bill for insects crushing bill bill for cactus seeds If the habitat changes (or if individuals move tree finches ground warbler-like finches finches mainland ancestor to a new habitat) natural selection may result in new adaptations new adaptations and and ultimately new new species Biological Biological evolution operates on two time scales (1) macroevolution; all changes that have transformed life on earth from its beginnings to its current diversity, resulting from... to its current diversity, resulting from... (2) microevolution; any change in the genetic makeup of population across generations makeup of a population across generations species – a group (of organisms) whose members possess similar anatomical characteristics and have the ability to interbreed successfully over generations interbreed successfully over generations population – members of a species living in the same place at the same time with high potential for interbreeding the same time, with high potential for interbreeding consider the potential for variation within and among populations... variation among rassenkreis – “circle of races” Ensatina escholtzii salamanders one example of a “ring species” http://video.pbs.org/video/1300397304/ Patterns of geographic variation among “subspecies” can blur the line between one species and another http://www.pbs.org/wgbh/evolution/sex/guppy/low_bandwidth.html#discovery Sex & the Single Guppy natural selection – differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment with their environment Check me out! I'm a hot Brazilian male. Did someone say guppies for dinner? Poecilia reticulata is just one species, but we come in many shapes & colors (evolutionary) adaptation (evolutionary) adaptation – accumulation of inherited of inherited characteristics that enhance an organism's ability to survive and reproduce Let’s dissect the logic behind natural selection (Ernst Mayr, after Darwin) Observation #1 #1 For any species, population sizes would increase exponentially if all individuals increase exponentially if all individuals that are born reproduced successfully. Observation #2 #2 Nonetheless, populations tend to remain stable in size stable in size... Observation #3 Resources are limited. Inference #1 Production of more individuals than the env environment can support leads leads to a struggle for existence... with only a fraction of offspring surviving each offspring surviving each generation. generation. “Of course, long before you mature, most of you will be eaten.” Observation #4 Members of a population vary extensively in their characteristics; no two are alike. Observation #5 #5 Much of this variation is heritable. Inference Inference #2 Survival depends in part on inherited traits. Individuals with higher fitness are likely to leave fitness are likely to leave more more offspring. Inference #3 This unequal ability of indi individuals to survive and to and reproduce reproduce leads to a gradual change... with favorable features accumulating in the accumulating in the population population over generations. TURBO “Forget these guys.” http://www.pbs.org/wgbh/evolution/library/10/4/l_104_10.html http://www.pbs.org/wgbh/evolution/library/01/1/l_011_20.html Evolution observed in real time: viruses like HIV a drug does not create resistant pathogens; drug does not create pathogens; it selects for existing resistant individuals selects Evidence Evidence for macroevolution: remnants of once useful structures snake spurs spu vestigial eyes appendix vestigial structures – serve little if any purpose; what remains of ancestral adaptations lost over generations human “tail bone” (coccyx) human “wisdom teeth” http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html s / l 4 5 artificial selection – breeding for particular characteristics process of domestication; results in new species http://www.time.com/time/health/article/0,8599,1961918,00.html c a 8 To read the whole article, please click on the link! ...
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This note was uploaded on 12/12/2011 for the course BIO 2 taught by Professor Poenie during the Fall '08 term at University of Texas.

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