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Chapter 24

Evolution Ch. 24.docx

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University of British Columbia
BIOL 121
Martin Adamson

EvolutionChapter 24 Evolution by Natural SelectionKey ConceptsPopulations and species evolve meaning that their heritable characteristics change though time More precisely evolution is defined as changes in allele frequencies over time Natural selection occurs when individuals with certain alleles produce the most surviving offspring in a population An adaption is a genetically based trait that increases an individuals ability to produce offspring in a particular environment Evolution by natural selection is not progressive and it does not change the characteristics of the individuals that are selectedit changes only the characteristics of the population Animals do not do things for the good of the species and not all traits are adaptive All adaptations are constrained by tradeoffs and genetic and historical factors The reproductive process in biology inevitably changes evolutionary processes Mutations will occur pmutations0 To the extent that populations are separated from one another divergence will occur ie some amount of evolution is an inevitable result of thermodynamics associated with reproduction Evidence of evolution Change through time ofossils extinction transitions environmental change ocomparative studies vestigial traits oCurrent studies drug resistance etc Species are not related to one another oBiogeography oHomology structural developmental molecular genetic Fossils First detailed study of fossils Comparative anatomy Correlation of parts Extinction Fossil dating Generic dating PpresPorigagehalflife Isochronic dating is better in that it avoids assumption that there was no daughter isotope at t0 and will signal if new material was added to the site at a late date Radioactive decay and absolute ageEarth 46 billion years old Life arose about 38 billion years ago First eukaryote fossils about 15 billion years ago Humans diverge from other apes about 5 billion years ago Homo sapiens about 05 billion years ago Extinction The Irish elk actually an extinct deer Wildly disturbed in Pleistocene Gurvier 1812 described fossil remains Evidence of extinction Many example are now known of extinct creatures preserved as fossils from all eras
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