BIL 160 Ch 22
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This 10 page Class Notes was uploaded by Rachael Phillips on Saturday January 9, 2016. The Class Notes belongs to BIL 160 at University of Miami taught by Adrienne DuBois in Spring 2016. Since its upload, it has received 128 views.
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Date Created: 01/09/16
Ch. 22: Decent with Modification Class Notes: Evolution Evolution: decent with modification (how Darwin described), living species = decedents of ancient species; change in allele frequency over time/change in genetic composition of a population over time Darwin came up with evolution o Origin of Species: Decent with modification Species today come from decent from ancient species. Captures life’s unity/diversity. Species today share common characteristics/ancestors. Birds: flamingo, penguin, songbird; all different, but have common ancestor (different shape beak but similar looking, same DNA sequences, same morphology for most part) Natural selection How Darwin proposed we get from an ancestral species to modern species Long history of evolutionary though prior to Darwin o Economics/geology influenced Darwin Natural selection DOES NOT EQUAL evolution o Evolution: process of species change over time o Natural selection: one mechanism of evolution Biodiversity ~10100 million species of organisms Taxonomy: grouping different organisms Prokaryote: before nut (no nucleus) Eukaryote: true nut (with nucleus) All organisms share basic characteristics of life (but differ in how they satisfy requirements for life): o Reproduction o Energy metabolism/respiration o Grow/develop o Homeostasis o Responds to stimuli/environment o Cellular organization Ecology: study of how organisms interact with each other and their environment Population: members of the same species in the same area that are capable of interbreeding to form fertile offspring Community: all species that are living in a given area that interact, but do not interbreed, with each other (without abiotic factors) Ecosystem: all the species in a given area and how they interact with their abiotic environment Biosphere: all ecosystems on earth Scientific studies happen by previous scientific investigation “Darwinian revolution” (1859) challenged traditional ideas of young earth inhavited by unchanging species o Scala Naturae (Aristotle) Classify organism in “ladder” Lowest rung: bacteria, highest: humans (no change/evolution) o Biblical creationism God No evolution Organisms fit into broad groups, not neatly to Aristotle’s characterization o Hard to rank ants against each other Linnaeus: classification of species (founder of taxonomy) [1700s] o Organismal adaptation: creators specific purpose o Nested classification—not a scale o Recognizes hierarchical classification to glorify creation by God Not to do with evolution back then Extinction: why would creator create an organisms just to go extinct o Extinction by humans, not God o Still around just not “here” o Fossils “placed by Satan” Paleontology: by Georges Cuvier Fossils = old Earth Cuvier: catastrophism o Periodic catastrophes > mass extinction Boundaries between strata = catastrophes New species? o Louis Agassiz: multiple creation events Problem: organisms begin to evolve o Fish anatomy like primitive amphibian, doubts arose about permanence of species Lamarck (1800): species evolve through use/disuse o Inheritance of acquired change Baby giraffes eat trees, far from ground, have long neck, (evolve— use/disuse) o Species change, but do not split to 2 species Have x number of species, they change/evolve, still have x number of species even though they changed o Evolutionary ideas began to gain dominance Lamarck mechanism of change does not work o August Weismann: demonstrated traits acquired by parents not passed on as Lamarck said Gametes/genes/sperm/etc. = how traits passed on (DNA) Darwin: graduated from Cambridge > went on HMS Beagle as naturalist and captain’s companion (18311836) o Galapagos Volcanic islands off Ecuador Organisms arrived from mainland Evolved to be different from mainland Became many difference species Returned finches to England to ornithologist o Darwin thought finches were all different, were actually all same o 13/14 species today, all evolved by 1 mainland species Influences on Darwin: o Geology Gradualism/uniformitarianism: big change through slow process over long time Changes in earth surface result from slow/continuous actions still operating today Hutton/Lyell o Thomas Malthus: Populations grow faster than resources (space/food/water) Disease/famine/war Resources limited, limiting population growth, not all offspring survive/reproduce Competition for resources (elephant ~ slowest reproducing animal, 6 offspring, survive > 100 years, after 175 years = 600000 elephants, today there would be elephants everywhere (hypothetically)) 1844: 200 page essay about natural selection/evolution (Darwin) o Didn’t publish (social pressures) 1858: Darwin gets letter (“battle of the beards”) o Alfred Russell Wallace o Worked in Indonesia o Same conclusions o Wanted Darwin’s opinion because Darwin = esteemed scientist Papers presented together Darwin’s idea: book was controversial o Adaptation/origin of new species = closely related Actually true Main ideas: o Decent with modification Evolution explains life’s unity/diversity Argument for extinction of evolution o Natural selection Argument for mechanism of adaptive evolution o Darwin saw the two closely related Tree of life o no label = extinct Darwin bred pigeons, noted if selected for particular plumage trait, could find plumage that varies wildly By selecting variation in different parts of plant, breeders have obtained divergent traits o Wild mustard > kale, Brussel sprouts, cabbage, broccoli, kohlrabi o Artificial selection can cause crops/livestock/pets to bear little resemblance to wild relatives Similar process to artificial selection in nature: o Observation1: Populations over-reproduce (from Malthus) o Observation2: Resources are limited (have finite amount of resources in given place for given population) o Conclusion1: populations grow until limited by resources at which time there will be a “struggle for existence” and most offspring produced will die o Observation3: individual in population vary, some of variation is heritable o Conclusion2: those variants best suited to environment will be more likely to survive/reproduce; “differential reproduction success” o Conclusion3: over time, adaptive traits will accumulate and characteristics of population will change (lineage (linear?) evolution) Heritable variation > differential survival/reproduction > evolution by natural selection Even if advantages of variations are slight, over time they will change the population and the frequency of the variations in a population o Population as a whole will become better fit to environment Corollary (speciation?): sub-population separated in different environments would be selected for different traits and may subsequently lose capacity to interbreed (spacial radial) > different species o Finches radiate: beaks change in response to new feeding techniques, which changes how they sing, which doesn’t allow the different finches to recognize each other/mate Remember: o Individuals don’t evolve, populations evolve o Natural selection can only act on (enhance/diminish) traits if they show variation in population o Environmental factors vary from place to place/over time Traits favorable in one area may be useless/detrimental in another Survival of fittest ≠ survival of strongest Evidence for evolution o Direct observations of evolutionary change Natural selection in response to introduced species (soapberry bug, MRSA) What factors drive the rapid rate of evolution in soapberry bug/MRSA populations? Rapid generation time (MRSA) Less genetically complex Horizontal gene transfer Strong selective pressure (if don’t have shorter beak, can’t eat; if don’t have methicillin resistant genes, will die) o Comparative anatomy Homology: similarity resulting from common ancestry Have different functions for anatomically similar structures (arms in humans/cats/whales/bats) Development All vertebrates have post anal tail/pharyngeal arches, develop into different structures later in life/development Vestigial structures Molecular homologies All living organisms use same genetic code Genes shared across species Convergent evolution: independent evolution of similar features in different mammals Eutherian mammals and marsupial mammal have adapted to similar environments in similar ways Analogous features: share similar function but not common ancestry o Fossil record Evolution predicts that transitional forms should exist , and also that we should find these fossils in the correct strata Hypothesis of common ancestry predicts there will be fossils of transition ancestors Darwin suggest fossil record was incomplete o Biogeography Scientific study of geographic distribution of species Endemic species: found only in one place, nowhere else is world Islands tend to have unique flora/fauna; most closely related to nearest mainland/neighboring island; dominated by “dispersive fauna” Textbook Notes: Key observances about life (3): o Striking ways in which organisms are suited for life in their environments o Many shared characteristic (unity) of life o Rick diversity of life Evolution: decent with modification o Darwin: species = descendants of ancestral species that were different from present day species o OR change in genetic composition of population from generation to generation Pattern of evolutionary change: revealed from data from many scientific disciplines (chem/bio/phys/etc.) o Data = facts; observation about natural world Process of evolution: consists of mechanism that produce observed pattern of change o Represents natural causes of natural phenomena we observe Aristotle: Scala Naturae o Viewed species as unchanging o Recognized certain “affinities” among organism o Concluded life forms could be arranged on ladder of increasing complexity o Each form of life, perfect and permanent, had allotted rung on ladder 1700s: scientists interpreted remarkable match of organisms to environment as evidence that creator (God) designed each species for particular purpose Carolus Linnaeus: sough to classify life’s diversity “for greater glory of God” o Developed two-part format for naming species o Adopted nested classification system Grouping similar species into increasingly general categories Georges Cuvier: developed paleontology o Older stratum, more dissimilar fossils were to current life forms o From one layer to next, some new species appeared while other disappeared o Inferred extinction must have been common occurrence Boundary between strata represented sudden catastrophic even that destroyed many species living in area o Opposed idea of evolution Other scientists: suggested profound change could take place through cumulative effect of slow, continuous processes James Hutton: earth’s geologic features explained by gradual mechanisms (valley formed by rivers) Charles Lyell: same geological processes operating today as in past, and at same rate Jean-Baptiste Lamarck: proposed mechanism for how life change over time o Use and disuse: parts of body used extensively become larger/stronger, those not used deteriorate Giraffe stretching neck to reach leaves on high branches o Inheritance of acquired characteristics: organism could pass modification to offspring o Evolution happens because organisms have innate drive to become more complex Darwin rejected this idea o Recognized match of organisms to environments can be explained by gradual evolutionary change Charles Darwin: father sent him to med school in Edinburgh ; quit, enrolled at Cambridge university, intention: clergyman o Became botany professor prodigy Recommended him to HMS Beagle captain Conversation partner to caption o On beagle voyage actually spent most time on shore observing/collecting thousands plants/animals Described features of organism that made them well suited to their environment Fossils he found, through different than living species, resembles libe organism of south America o Read Lyell’s “principles of geology” Found fossils of marine organisms in Andes Must have been raised there by earth quakes Physical evidence doesn’t support traditional view that earth only couple thousand years old Although mammals in Galapagos resembled species on south American mainland, most Galapagos species not known anywhere else in world o Darwin hypothesized Galapagos colonized by organism that strayed south America, diversified; gave rise to new species Darwin perceived adaptation to environment and origin of species as closely related processes New species arise form ancestral form by gradual accumulation of adaptation to different environment Adaptation: inherited characteristics of organism that enhance their survival/reproduction in specific environments Natural selection: process in which individuals that have certain inherited traits tend to survive/reproduce at higher rates than other individuals because of those traits o Darwin explanation for how adaptations arise centered around this Darwin’s book convinced scientist that life’s diversity is product of evolution o Succeeded because he presents plausible scientific mechanisms with immaculate knowledge, avalanche of evidence Darwin’s book said unity of life, diversity, match between organism/environments resulted from decent with modification by means of natural selection Attributed unity of life > decent of all organisms from ancestor that lived in remote past o As descendants of ancestral organism lived in various habitats, gradually accumulated diverse modification that fit them to specific way of life Branching process (“tree of life”), along with past extinction events, could explain large morphological gaps that sometimes exist between related groups organisms Artificial selection: modification of other species over many generation by selecting/breeding individuals that possess desired traits Thomas Malthus: much of human suffering resulted from human population’s potential to increase faster than food supplies/other resources Darwin realized capacity to overproduce = characteristic of all species o Of all young born, only tiny fraction complete development, leave offspring When advantages increase number of offspring that survive/reproduce, traits favored will likely appear at greater frequency in next generation o Over time natural selection resulting from factors such as predators/lack of food/adverse physical conditions lead to increase in proportion of favorable traits in population Main ideas natural selection: o Natural selection is process in which individuals that have certain heritable traits survive/reproduce at higher rate than other individuals because of those traits o Overtime natural selection can increase match between organisms and their environment o If environment changes or individuals move to new environment, natural selection may result in adaptation to new conditions, sometimes giving rise to new species Individuals do not evolve, population evolves over time Natural selection can amplify/diminish only heritable traits that differ among individuals in population Environmental factors vary place to place o Natural selection always operating, but which traits favored depends on context in which species lives/mates Four types data document pattern evolution/illuminate how occurs o Direct observations o Homology o Fossil record o Biography Multidrug resistant strains of MRSA today may have emerged over time as MRSA strains that were resistant to different antibiotics exchanged genes Key points about natural selection: o Natural selection: process of editing, not creative mechanism Drug doesn’t create pathogens, selects for resistant individuals already in population o Natural selection depends on time/place Favors characteristics in genetically variable population that provide advantage in current/local environment Homology: similarity resulting from common ancestry o Understanding of homology used to make testable predictions/explain observations that are otherwise puzzling Homologous structure: represent variation on structural theme that was present in common ancestor Vestigial structure: remnants of features that saved function in organism’s ancestors All forms life use essentially same genetic code, suggesting all species descended from common ancestors that used this code Like vestigial structures, inactive “pseudogenes” may be present because common ancestor had them Homologous characteristics (evolved more recently) are shared only within smaller groups of organism Homologous characteristics form pattern o All life shares deepest layer; each successive small group adds own homologies to those it shares with larger groups Evolutionary tree accurately reflects evolutionary history o Supported by anatomical and DNA sequence data Convergent evolution: independent evolution of similar features in different lineages Analogous features: share similar function, not common ancestor Homologous features: common ancestry, not (necessarily) similar function Fossil record: documents patter on evolution; shows: o Past organisms differed from present day organisms o Many species have become extinct o Evolutionary changes that have occurred in groups of organisms o Origins of new groups of organisms o Over time, decent with modification produced increasingly large differences among related groups organisms, ultimately resulting in diversity of life we see today Biogeography: scientific study of geographic distributions of species Geographic distribution of organisms influenced by many factors, including continental drift (slow movement of earth continents over time) Can use understanding of evolution/continental drift to predict where fossils of different groups organisms might be found Endemic: found nowhere else in world Can use understanding of evolution to explain biogeographic data o Two islands with similar environments in distant parts of world tend to be populate not by species closely related to each other, but by species related to those of nearest mainland, where environment is different (Darwin)
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