EXAM 3 STUDY GUIDECHAPTER 22Evolution Descent with modification-a change in genetic composition of a population from generation to generation Predarwinian ideas on creation of speciesAristotle: No evolution; each organism on ladder of nature is perfect but there isspontaneous generation of lowest organismsJudeo-Christian culture: special creation by a godGeorges Cuvier: catastrophism and paleontologyLinnaeus: created a classification system but still had belief of god creationJames Hutton GradualismGeological change is the result of a slow continuous processCharles Lyell Uniformitarianism- mechanisms of change are constant over time Catastrophic discontinuities in the geological record are the exception. Geological changes are shaped by the same forces that are at work today. No need to invoke supernatural forces to explain geology of fossil record.-the earth is very old-Jean-Baptiste de Lamarck Inheritance of Acquired Characteristics Proposes that organisms not created perfect but evolve toward greater and greater complexity (perfection). Microorganisms created by spontaneous generation and evolve towards greater complexity, moving up the ladder of life. Sees an elaborate branching tree of life. Mechanism for evolutionorganisms acquire newcharacteristics as they strive to adapt to their environment.These acquired characteristics are passed on to theiroffspring Thomas Malthus “The fate of the poor is inescapable because their reproductive powers will always exceed their means of sustenance.”Makes Darwin see the conflict between resources and reproductionIndividuals better able to use limited resources will have more progeny.Characteristics of the population will change from one generation to the next. -- Natural Selection (Darwin and Alfred Wallace’s idea)Elements of Darwin’s theory of natural selection1. Within a population more offspring are produced than can survive. Leads to competition for limited resources2. Variability exists in all organisms, and much of this variability is heritable. 3. Some of this variability affects survival rates. Those that are better adapted have a better chance of survival. (“Survival of the Fittest”)4. Individuals that are more fit will leave more offspring. (“Natural Selection”)5. Survival of the fittest will lead to changes in the population with favorable characteristics accumulating with time.EXAM 3 STUDY GUIDEEvolution and natural selection are blind processesPopulations evolve, not individualsNatural selection can amplify only heritable variationsDarwin’s theory has 2partsEvolution - modern species evolved from ancestral formsNatural Selection - the mechanism for evolutionNatural selection Process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits-If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species -individuals do not evolve, populations evolve over time Influence over Darwin into thinking that populations inevitably grow fasterthan their food supply:Thomas MalthusBiogeography study of the geographic distributions of organisms-evidence for evolutionInfluenced by many factors including continental drift- the slow movement of Earth’s continent over time Endemic Species that are found nowhere else in the world-ties in with biogeography -ex. islands tend to have many species of plants/animals that are endemic Artificial selection Process of selecting and breeding individuals that possess a desired trait Evidence for evolutionGalapagos Finchesrepresent an “adaptive radiation”• 14 species. • Some islands have only one.• Each species is adapted to a local food supply by differences in their beaks• Closest relative is a finch living in costal South AmericaAustralian marsupials compared with placental mammals“Convergent Evolution”Unrelated species adapt similar formswhen living insimilar environmentsThe fossil record demonstrates progression from ancestral forms to modern ones. Fossil record shows close relationships between extinctspecies and living ones from the same geographical area-evidence of evolutionEvolution- straight path?Evolution does not follow a straight path, species respond to changingConditionsEXAM 3 STUDY GUIDEComparative anatomysupports the idea of descent withmodification from a common ancestor - – related species share many common structuresHomology similar structures resulting from common ancestry -evidence for evolutionHomologous structuresRepresent variations on a structural theme that was present in their common ancestor Ex. –arrangement of forelimbs in a human arm and bat wingVestigial structures structures with little or no function that are remnants of ancestral structures with important functionsEx. hip bone in a whale; appendix in humansMolecular biology comparison of DNA or protein sequences provides a measure of relatedness of organisms and confirms family trees based on morphology/anatomyPhylogeny The evolutionary history of a speciesArtificial selection can produce new forms of plants and animals including new speciesImplication Great genetic variability exists within species and new forms can be selected forEvolutionary tree A diagram that reflects evolutionary relationships among groups of organisms Convergent evolution The independent evolution of similar features in different lineagesEx. marsupials vs. mammalsAnalogous Species that share features because of convergence- the resemblance is said to be analogous instead of homologous The “Modern Synthesis” merging Darwinian evolution with genetics1. mutation constantly creates new alleles and genes - therefore individuals in populations are genetically variable for nearly all traits2. Individuals pass their alleles on to their offspring intact3. In most generations more offspring are produced than can survive.4. Individuals that survive and reproduce – or reproduce the most – are those with alleles that best adapt them to their environment As a result alleles associated with higher “fitness” increase in frequency from one generation to the next.Key ideas for natural selection:Natural selection acts on individuals but populations
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