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Concordia University
BIOL 226

Chapter 22 Descent with modificationA Darwinian view of life06Sep10biology is distinguished by genetics and evolution theoryThe 3 key points of the chapter221 The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species p452455222 Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life p455460223 Evolution is supported by an overwhelming amount of scientific evidence p460466Definition of Taxonomy a scientific discipline concerned with naming and classifying the diverse forms of lifeLinnaeus developed the twopart or binomial system of naming species eg Homos sapiens for humans that is still used today He adopted a nested classification system grouping similar species into increasingly general categories ie similar species are grouped in the same genus similar genera plural of genus are grouped in the same family and so onLamarcks principles p4541 use and disuse the idea that parts of the body that are used extensively become larger and stronger while those that are not used deteriorateeg giraffes needed long necks to reach taller trees2 inheritance of acquired characterisitics stated that an organism could pass these modifications to its offspring eg it took several generations of giraffes with long necks genes Today there is no evidence that acquired characteristics can be passed down the way Lamarck proposedDefinition of Natural Selection a process in which individuals with certain inherited traits leave more offspring than individuals with other traitsThe differential reproductive success of individuals within a population based on how well those individuals are adapted to their environment 7th edSome summarizing points on Natural Selectiona process during which individuals with certain heritable traits survive and reproduce at a higher rate than other individuals over time natural selection can increase the match between organisms and their environments if an environment alters or if an individual moves to a new environment natural selection may result in adaptation to these new conditions something giving rise to new species in the process individuals do not evolve populations do natural selection can amplify or diminish only heritable traitsenvironmental factors vary from place to place and over timewhen a lion takes over a new area it gets rid of the baby cubs in order to stop the mothers from lactating thus they will begin to ovulate more and will then conceive the cubs of the lion The lion behaves this way in order to get rid of potential competition and also in order to make sure that HIS genes are passed down survival of the fittestdifference between a small fish and a whale fishs tale propels sideways while the whales tail propels upwards and downwards WHY Because whales used to walk on land the vertical column moves better up and down The fish propels differently because it didnt walk on land Independant evolution caused them to evolve differently Natural selection only edits whats already therehow are bat wings and bird wings both homologous and have evolved through convergent evolution As wings independent mammal and bird as forelimbs common acestor reptile ancestorsTHE ORIGIN OF SPECIED 1859 Darwin this book has had more effect on humans than relativity or quantum mechanicsDarwin didnt want a bad reaction from people so he avoided using the term evolution Instead he only used the word evolvedWhat is EVOLUTION Change in the genetic composition of a population over timeDarwins Fame His great contributionHe first came up with a mechanism and then made it pausible with proof Natural SelectionDarwins two major points that descent with modification explains lifes unity and diversity and that natural selection brings about the match between organisms and their environment1 Species were not created in their present forms but evolved from ancestral species descent with modification2 A mechanism for evolution natural selection In 1858 Wallace wrote a short manuscript similar to his unpublished book Dissection of Darwins theoryO animals vary in phenotypeO some variation is heritableO populations have the capacity to overly reproduceO some survive to reproduce some dieI those with higher reproductive success leave more offspring hypothesis needed here and copies of their genesI genetic change within the populationApply to cheetahs speed Cheetahs vary in running speed variation in some trait some of this variation is heritable genes cheetahs who run faster chatch more prey survive better and leave more offspring hypothesis within the pop of cheetahs the genes for faster running accumulate in the pop genetic change in the pop come up with theories in which theres some sort of diminishing factor DONT MAKE IT LAMARCKIANApply to blind save fish Assumptionthere isnt sufficient light for sight in caves O fish in caves vary in their eye development O some of this variation in eye development is heritable hypothesis fish with less developed eyes save energy which can be used for growth and reproduction I fish with less developed eyes have higher survival and reproduction I genes for less developed eyes spread in the populationPreDarwinian ViewsAristotle 384322 BC Scala naturae the ladder of life Species can be arranged on a scale of increasing complexity AND species do not changehave a fixed place on this ladder exactly the opposite of the Darwinian viewAKA the great chain of beingIs this ranking of life correct No no part of the theory of evolution what is this ranking really about You cant measure complexity To some extent this is kind of like taxonom there is a biology to it ie we dont eat chimps since they are related to usNatural TheologyAdaptations evidence of the Creators design intelligent design
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