BIL 160: Class Notes Exam 2
BIL 160: Class Notes Exam 2 BIL 160
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Date Created: 09/29/15
BIL Lect 7 02142013 Classical Model 0 Mutation only way to get genetic variation 0 Reverse mutation mutations that can change back to wild type from one generation to the next 0 There are cases where a single mutation can cause reproductive isolation The Balance Model 0 read about balancing selection Frequencydependent selection occurs when the tness of a genotype depends on its frequency 0 Mimicry coral snake and coral snake when organism mimics another organism 2 basic kinds n Bastian harmless species looks like harmful one u malarian Missed Class on 219 Abiogenesis life originated in 4 major phases 0 Generation of small organic molecules from abiotic precursors Joining these smaller subunits into macromolecules Pack these macromolecules into protocells 0 Now still working on origin of selfreplicating molecules that made inheritance possible Early Research in abiogenesis Abiogenesis is the origin of life from inorganic precursors Oparin wrote paper quotThe Origin of Lifequot 0 Suggested that chemical reactions in primitive oceasn could have created life Haldane published similar ideas Reducing atmosphere has a condition where is has very little oxygen Focus has turned to other places on earth as origin of life 0 Deep sea thermal vents 0 Outer space The First Biological Molecules Miller and Urey with their apparatus yielded building blocks of life Organic moecue have back bone of nd out Oro did similar experiment and yielded aso components of DNARNA Colloid substances dispersed throughout a liquid that keeps them in suspensions shaking salad dressing part bw oil and spices Oxidizing Atmosphere Oxygen catastrophe 226 Endosymbiosis TEST 2 will be on ect 710 HardyWeinbery Equilibrium principle stating that the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors Zygotes fertilized egg cell Gametes sperm and ova Genetic drift In each generation some individuals may just by chance leave behind a few more descendents and genes of course than other individuals The genes of the next generation will be the genes of the lucky individuals not necessarily the healthier or better individuals Genotype the set of genes that an organism has AA Aa or aa 0 Gene a unit of heredity A or a Phenotype tallshort greenblue eyes 0 Tall allele 0 Green allele Transmission distortion exaptation Departure from HardyWeinbery Equilibrium when populations evolve How species originate thru reproductive isolation can no longer breed and produce fertile offspring Reproductive Isolating Mechanisms mechanisms that restrict gene ow bw species ie determines whether they can reproduce used to determine different species 0 Prezygotic isolating mechanisms prevent formation of viable zygotes fertilized egg cell 0 Environmentalspatial isolation same geographic region but microhabitatbreeding conditions differ 0 Temporal isolation differing periods of sexual activity 0 Behavioral isolation courtship rituals used to attract those who will produce fertile offspring 0 Mechanical isolation morphological structure differences prevent matingpollination o Gametic isolation sperm and ova not chemically compatible Postzygotic Isolating mechanism prevent hybrids from passing on their genes 0 Hybrid inviability zygote forms but dies parent DNA insufficient 0 Hybrid sterility viable hybrid produced but is fertile mule 0 Hybrid breakdown successive generations become more sterile and die out o 3 possible scenarios 0 species reinforcement hybrids have low tness reproductive isolation maintained bc lack of survival 0 species fusion if have weak reproductive isolation barriers could eventually share common gene pool 0 species stabilityhybrid equilibrium hybrids continually produced hybrids produced wo much survival hybrids may be superior and breed with each other hybrid speciation Reproductive isolating mechanisms can evolve as result of 5 factors or combo that change relative allele frequencies 0 Mutation 0 Small population size 0 Nonrandom mating 0 Migration 0 Natural selection No Mutation When mutant allele inherited new allele added 0 Whether mutant allele remains depends on genetic drift and natural selection o Mutation is raw material of evolution How new mutations might take up residence in a population 0 The Classical Model 0 Holds that one allele functions better than other and natural selection will increase proportion of better allele 0 Wild type phenotype phenotype most common in wild population Any other allele is mutant Forward mutation mutation of wild type allele to mutant form Reverse mutation when mutations change back to wild type Larger population more mutations o Mutations may result in phenotypic traits that are Adaptive maladaptive or neutral 0 The Balance Model 0 Phenomenon in which an allele that is maladaptive can be maintained because it is bene cial in some circumstances 0 Balanced polymorphism maintenance of stable frequencies of 2 phenotypic forms in single population 0 Mechanisms by which balancing selection works Heterozygote advantage heterozygous conditions confer a selective advantage n Ex sickle cell anemia kills but if it is recessive protects from malaria so still around Frequencydependent selection selective pressure against a particular aee changes with that aee39s relative frequency in the population a Positive frequency tness of genotype increasing prefers phenotype when more common a Negative frequency decreasing prefers phenotype when more rare 0 The Neutral Mutation Model genetic drift First proposed by Kimura Neutral mutation just went along for the ride No connection to natural selection 0 Neutral mutations central to idea of genetic drift In nitely Large Population Size 0 In nite population means in nite number of gametes but in nite population impossible Genetic drift changes in relative allele frequency due only to random sampling error 0 So even large populations have genetic shift due to random sampling error 0 Smaller population great chance of genetic drift 0 Can happen in 2 ways Founder effect small sample of breeding individuals from a large population in new area Bottleneck effect most members of large population removed leaving only few survivors Random Mating Means that alleles at a given gene locus combine with the frequency predicted by their frequency in the population 0 Probability of individuals of 2 genotypes mating is the product of the frequencies of those genotypes in the population 0 A 60 of the alleles o a 40 of the alleles o HW equilibriums 6 X 6 36 for AA 26 X 4 48 for Aa 4 X 4 16 for aa 000 0 so product rule for likelihood of AA mating with Aa is 36 X 48 17 o if big deviation from this prediction nonrandom mating can occur possibly changing relative genotype frequencies assortative mating can work in 2 ways 0 positive assortative mating individuals with similar genotype mate more often than the predicted frequencies Results in disproportionate number of homozygotes 0 negative assortive mating opposite Results in disproportionate number of heterozygotes o nonrandom mating inbreeding vs outbreeding o inbreeding occurs when closely related individuals breed more frequently than predicted prefer to breed with relatives 0 outbreeding prefer to breed with nonrelatives 0 small populations and inbreeding can increase the rate of evolution at any given gene locus No Migration Lossaddition of alleles from immigrationemigration will change allele frequency in population 0 Gene ow movement of genes bw populations or demes o Spreads good alleles that have arisen thru mutation 0 Has homogenizing effect is recipient population is small 0 Increase effective size of population 0 Lack of gene ow eventually leads to speciation Cohesive species species whose demes tend not to become reproductively isolated o Hybrids Evolution in ux 0 Hybrid zone area of contact where there may be limited hybridization bw 2 closely related species 0 lntrogression introduction of alleles from one species gene pool into another closely related species No Natural Selection Mutation can be 0 Bene cial adaptive o Deleterious maladaptive 0 Neutral In natural selection organism compete against each other 0 Winner are those that leave the most offspring Natural selection is not random it is directed change Tenets of evolution by natural selection 0 Overproduction organisms capable of producing large 5 of offspring o Hereditable variability 0 Competition must compete for resources 0 Differential reproduction ones with phenotypes that best exploit resources will leave most genes Darwin evolutionary tness measure of proportion of genes contributed to next generations Quantifying Relative Evolutionary Fitness 0 Fitness coefficient W expression of adaptive value of a genotype relative to other genotypes o Genotype that provides most offspring give tness value of 1 0 Selection coef cient measure of selective pressure against a genotype relative to other genotypes 0 Calculated as 1W Components of Fitness Selection at Different Levels 0 Natural selection can operate at different stage s of organism s life cycle individual gamete gene 0 Transmission distortion departure from expected 50 likelihood that any allele will be inherited Caused by 0 Meiotic drive gemeticgenic selection over representation of certain alleles in gametes Is a form of intragenic selection competition bw genes for a spot in individuals reproductive output 0 Postzygotic viability genetically based difference in ability of zygote to survive Other categories of selection 0 Zygotic selection differential mortality of an organism at any stage in its life cycle beyond gamete o Fecundity selection when one genotype is more fertile than another 0 Compatibility selection when combos of eggs and sperm of a particular genotype are more likely to produce viable offspring Sexual Selection based on ability to attract mate 0 Sexual dimorphism when individuals exhibit character that make them more attractive to mates have advantage 0 Can operate in 2 ways Members of one sex compete against each other for mates Members of one sex prefer a trait in members of opposite sex The Effects of Natural Selection 0 look at pic 0 stabilizing selection favor the average state of a trait directional selection one extreme is favored disruptive selection 2 extremes favored while average not 0 results in character displacement production of distinct phenotypes in population due to selective pressure Sum up 0 Organic evolution is change in genetic composition of a population via genetic drift nonrandom mating mutation natural selection Microevolution genetic change in species over time wo speciation Macroevolution genesis of 2 reproductively isolated taxa from single ancestral taxon Macroevolution The Genesis of Reproductively lsolated Populations from an Ancestral Population The Species Concept What makes a species a species Biological species concept based on reproductive isolation lf 2 individuals can produce fertile offspring they are same species Morphological species concept if they look the same they are the same Ecological species concept includes ecological niche of a species Phylogenetic species concept smallest group of individuals descended from a common ancestor Recognition species concept matingcourtship specializations taken into account Cohesion species concept even if share genes 2 species is have distinct phenotypes The Rate of Speciation how fast species separate Depends based on generation time stability of species genetic makeup Biological species concept based on reproduction isolation most useful Modes of Speciation Allopatric single population divided into 2 by geographic barrier Peripatric new species arises at edge range of original population Parapatric gradient of genetic difference develops across a species s range Sympatric speciation occurs without physical separation within range of ancestral population The Pace of Evolution Phyletic gradualism large changes occur due to gradual accumulation of many genetic changes Punctuated equilibrium major changes occur relatively suddenly Speciation Incipient species species on verge of becoming separated Means by which species change into different species 0 Anagenesis phyletic evolution change of entire population to a new form so different that the previous species is considered new species 0 Cladogenesis diversifying evolution divergence of 2 new species from a single ancestral species Adaptive Radiation When ancestral species creates new ones through cadogenesis and descendent species radiate into new ecological niches Sociobiology Edward 0 Wilson 0 Main tenet social behavior is at least partly under genetic control 0 Verno Copner WynneEdwards 0 Suggested that animals regulated their own population density via altruism risking loss of ones own fitness to improve tness of another 0 quotgroup selectionquot Idea that sometimes behave for the good of the group Stopped producing if population too high 0 Thought unlikely but explained by this 0 WD Hamilton 0 Maybe natural selection would prefer an allele that promoted altruism amongst relatives bc if relatives survive genes sti passed on Inclusive Fitness Individual Fitness and Kin Selection 0 individual tness the production of offspring by an individual 0 kin selection assisting relatives in rearing their offspring which may share some of the assisting organism39s genes 0 inclusive tness individual tness PLUS tness gained via kin selection activity 0 Depends on if species is solitary or social Kin selection is not altruism bc staying with group ensures better chance for survival 0 Certain insects are haplodiploid sexdetermination system in which males develop from unfertilized eggs haploid and females develop from fertilized eggs diploid 0 Supports assumptions Behaviors that foster genetic events are heritable Worker bees all have same drone father 0 So promoting one s own genes survival much more logical explanation of altruistic behavior than WynneEdward s idea of group selection Exaptation adaptive trait that started as neutral and became maladaptive or adaptive based on environment Why Natural Selection Doesn39t Produce Perfect Species 0 Selection can act only on existing variation in a population 0 Populations do not evolve traits bc they need them 0 Evolution is considered by the history of evolving organisms 0 Evolution builds on what is already present 0 New structures do not arise fully formed 0 Adaptive traits are often compromises 0 Nat sel Doesn t favors organisms that are versatile 0 Structure may need to perform several things but may not be ideally suited to each function 0 Genetic drift and environmental change may thwart natural selection o Founding populations separated from original may not be best suited to new environment 0 Environmental changed make different traits desirable from year to year The History of Life on Earth microevolution evolutionary change below the species level without reproductive isolation macroevolution evolutionary change at or above the species level The Origin of Life Originated via 4 major phases 0 The generation of small organic molecules from abiotic precursors Joining of smaller subunits into macromolecules proteins nucleic acids carbohydrate lipids Packing of macromolecules into protocells consisting of membrane internal space with uid 0 Origin of selfreplicating molecules that made inheritance possible Early Research in Abiogenesis o Abiogenesis origin of life from inorganic precursors Aleksandr Oparin 0 Suggested that chemical reactions in primitive oceans could gave eventually created life 0 John Burdon Sanderson Haldane 0 Published same idea but in english 0 But sparked race to discover how life had come to exist What was Primordial Earth like 0 Early atmosphere coZ h20 vapor h n ammonia hydrogen sul de co methane MillerUrey experiments suggests that primordial atmosphere had very little oxygen reducing atmosphere Cleaves 0 Suggested that atmosphere was at best only weakly reducing or even neutral 0 Other research suggests was richer in coZ and h2 l so more conducive to form complex organic molecules 0 Focus turned to deep sea thermal vents outer space The First Biological Molecules o MillerUrey made apparatus that simulated conditions of primordial oceans 0 Reaction solution yielded amino acids formic acid acetic acid urea 0 Gas portion yielded hydrogen cyanide formaldehyde other organic volatiles 0 Different proportions gave similar results as long as there was lack of oxygen 0 Joan Oro made similar apparatus that yielded 0 Sugars lipids components of RNADNA o Oparin working on another aspect of origin of life 0 Substances can be agitated to form colloids salad dressing 0 Mixed protein and polysaccharide mimicking early seas 0 Results tiny stable globular structures he call coacervates 0 Adding more substances yielded different results Lipids created membranelike sheet Enzymes and substrates functioned inside 0 Coacervate with working enzyme systems inside protobiont o Protobiont had some but not all properties of life 0 Properties of life Anatomy organized structure Metabolism Homeostasis Reaction to stimuli Growth and development Adaptability Ability to reproduce The Earliest Genetic Material RNA o Is simpler to construct Has enzymatic properties can modify its own structure and self replicate Can be reverse transcribed into DNA 0 John Sutherland 0 Demonstrated that making RNA from inorganic precursors simple as long as you know ingredients and order The Primordial Ooze Earth formed 455 billion years ago 0 As earth cooled pockets of water could persist making oceans 0 Still little to no oxygen Earliest life bw 354 billion years ago 0 First organisms were obligate anaerobes whose only metabolic pathway was fermentation Stromatolites oldest known fossils sedimentary rock with extant cyanobacteria The Origin of the Oxidizing Atmosphere Chlorophyll a o Earth s atmosphere had no oxygen until photosynthetic organisms appeared 0 Earth suffered oxygen catastrophe where cyanobacteria produced so must oxygen it cause an ice age 0 Chlorophyll a most primitive chlorophyll early ancestors of cyanobacteria First eukaryotic autotrophs appeared 1 billion years ago early forms of green algae Took 12 billion years of photosynthetic oxygen production to oxide iron in water and 02 began to go into atmosphere 0 6 billion years ago produced enough oxygen to cause 2 major changes 0 fermentation gave way to cellular respiration as major metabolic pathway 0 generation of ozone to protect from UV Allowed upper levels of ocean to be colonized 4 billion years ago land plants established Origin of Eukaryotes 2 process contributed autogeny inpocketing of external membrane formed internal network of membranes endosymbiosis proposed by Margulis o proposes that small energytransducing prokaryotes were either O ingested as prey internal symbionts inside larger prokaryotes primary endosymbiosis gave rise to heterotrophs must eat secondary endosymbiosis gave rise to photoautotrophic eukaryotes can make on food 0 O evidence in pic how plastids and mitochondria could have migrated to eukaryotes Bigger Things Geology and the Fossil Record How to tell age of fossils Relative dating recent strata layers on top 0 O O O Strata at different locations can be matched by presence of similar organisms know as index fossils Animals with hard body parts make best fossils shells bones Does not allow fossils to be dated in year but only relative to compared fossils Geological time scale made by studying fossils in various strata at different locations 0 Absolute Radiometric Dating 0 O O 0 Molecule exists in a stable form But sometimes molecule may exist as an isotope Radioactive isotope unstable nucleus to become stable emits radiation Carbon has relatively short halflife l so used to date Isotopes with longer halflives used to date older fossils o Halflife the time needed for half the nuclei to decay to stable form Measure proportion of isotope and its decay to determine how much time has elapsed since sample was formed Greater proportion of decay older the sample Carbondating used for young fossils 0 Methods for Absolute Dating Carbon Dating Uraniumlead dating old Amino acid racemization n Affected by climate so only use where temperatures have not changed Tracing Evolutionary Lineages o Transitional fossils show the progression of many different lineages of plants and animals Biogeography 0 Continental drift Pangaea single l Laurasia north and south I Gondwanaland further fragmentation o Subduction zone where one plate forced under another deep tranches o Sea oor spreading zone where volcanic activity causes ocean oor to splits ocean ridges Continental drift have major consequences for life 0 Habitats on and around changed Oceans became deeper Sea level thus lowered Costal areas more habitable bc moisture Inland areas cold and arid o Climates changed Canada and Antarctica were once in tropics Organisms forced to adapt migrate or die 0 Caused allopatric speciation Fossils of same thing found on different continents Mass Extinctions 5 major global extinctions o Permian Mass Extinction 96 of all marine life dies terrestrial animals suffered too 0 Close to time of huge series of volcano eruptions o Affects of lava and ash 0 Excess coZ rose global temp 0 Temp reduced ocean water cycling reducing oxygen content 0 Anaerobic bacteria overgrowth in ocean made toxic Cretaceous Mass Extinction more than half of marine life died and big number of terrestrial species dinosaurs 0 Possibly caused by Chixulub Comet Natural Selection vs Neutral Evolution Neutral Mutations Silentsynonymous mutation doesn t change the amino acid sequence encoded by particular gene 0 Neutral mutation can be any mutation that either 0 Has little to no phenotypic effect 0 Has no effect on Darwinian tness of the individual Kimura also proposed that 0 DNA should mutate at constant rate 0 Neutral mutations should become xed in populations at constant rate 0 that rate is the time it took for new mutations to arise and then spread randomly thru populations via genetic drift pseudogenes non functioning genes vs proteincoding genes 0 protein coding genes of the genome make up proteome 0 but genome entirety of organism s heredity info also contains genes that code for RNA noncoding functional DNA noncoding pseudogens genes that no longer appear to have any function 0 if true assume that more mutations in pseudogens than in proteome bc doesn t matter Molecular Clock 0 Neutral mutations accumulate at regular rate But 0 Neutral evolution is different in different organism lineages 0 Different genes evolve at different rates 0 Rate of neutral evolution can speed upslow over evolutionary time for any given gene 0 So study of neutral evolution can by examined using time frame We are the Results of Ancient Selection 0 By comparing ratio of nonsilent to silent mutations in particular genes can determine whether that gene has been under selective pressure Purifying selection codes from protein so vital that small change lethal therefore puri ed the gene by removing deleterious variations 0 Ratio 0 bc NSS and NS0 0 Neutral genetic drift 0 Not in uenced by natural selection silent and nonsilent mutations accumulate at equal rate 0 Ratio 1 0 Positive selection o If mutations tolerated resulting in new alleles some non silent mutations may result in alleles that function better and will be naturally selected Ratio is greater than 1 0 Positive Selection in Primate Genome FOXP2 protein necessary for language Gene Duplication and Gene Recruitment Step One 0 New genes come form preexisting genes 0 Mistakes can be made 0 during DNA replication mitosis 0 or during crossing over at meiosis Possible results Base pair substitutions Duplications Deletions These mutations can be deleterious bene cial or neutral Pseudogenes inactive genes in the genome 0 Gene duplication provide extra genes that become raw material for new functions that arise via mutation 0 Gene recruitment enlistment of a changedmutated version of a gene for a function that s different from original funcUon Gene duplication l gene recruitment l evolutionary innovation Citratefeeding e coli Pcpfeeding lrreducible Complexity Not Really Michael Behe said that many structures found in nature were irreduciny complex and couldn t be product of natural processes 0 Thought needed to have intelligent design Reconstructing the Evolution of a Complex System Snake Venom Gene coding for venom crotamine closely related to protein found widely in animal kingdom that provides antibacterial protection defensins Natural selection present in type of venom 0 Tree snake venom more effective on snakes 0 Ground snake more effective on rodents Poison vs venom 0 Poison must be ingested o Venom injected into blood stream From Simple Beginnings The Vertebrate Eye 0 Eye very complex but likely that evolved due to natural selection Vertebrate eye has lightsenesitive photoreceptor cells rods and cones in outermost layer of retina 0 When light hits dissociates into its two components opsin and retinal triggering brain to recognize light Rods night vision cones day vision o GPCRs family of proteins that are involved in sensing external stimuli GPCR mutated to become able to sense different types of light Developed into opsin Opsins differentiated into different types of opsins Eye structure evolved from patches of lightsensing cells on skin to eyes of today 0 Crystallins proteins that comprise lightfocusing lens 0 Transparent and stable 0 Evolved from genes that coded for heatshock proteins 0 Lens itself has heatshock protein properties Modi cation of Gene Expressions Can Change Phenotype o Mutations that change identity of protein not only way to change phenotype o Mutations can change timing of gene or degree to which gene is expressed Can have dramatic results 0 Central Dogma of gene expression 0 DNA is transcribed into RNA and RNA is translated into protein 0 Transcription Factors a protein that binds to speci c DNA sequence and controls how that segment is read 0 What happens to gene when bound to transcription factor Promote facilitates gene transcription Enhancer enhances transcription levelrate Repressor represses transcription levelrate 0 Any of these mutations can increase the production of a gene product decrease it or shut it off Early Development 0 As zygote develops thru cleavages DNA in each new cell is repackaged and modi ed 0 Some genes turn on expressed 0 Some turn off 0 Some code for proteins that turn other genes onoff 0 These proteins are called transcription factors Can be positive or negative 0 As embryo develops genetic instructions give cells instruction and are modi ed into different types of cells Hox Genes and Genetic Toolkits Every embryo has set of genes that determine body axes morphology segmentation limbs etc genetic toolkit ln toolkit are hox genes determine the identity of body segments 0 Expanded into different organisms thru duplication and recruitment 2 major lineages of animals protostomes and deuterstome reversed in body position 0 protostomes worms insects o deuterostomes vertebrates 0 but genes that determine where these systems will develop are homologous inherited from a common ancestor Changing Gene activity Can Change Phenotype How can major differences of beak shapes in nches happen 0 Low level of BMP4 long narrow beaks 0 High level of BMP4 wide deep beak o Calmodultin controls length of beak lowshort highong Placodes disks of skin cells in reptiles turning into feathers 0 Different expressions of placodes cause scale or different kinds of feathers Convergent Evolution evolution of 2 unrelated lineages towards similar form Wolf and tasmainian wolf Human eye and octopus eye Convergences start with different raw material Scientists who study phylogeny use both systematic and taxonomy to organize life into phylogenetic trees Taxonomy naming and classifying organisms Systematics determining evolutionary relationships among organisms Taxon 1 organisms judged by systematists to form a unit 0 Based on evolutionary decent from common ancestor Character a trait used by systematists to help determine evolutionary relationships bw different taxa 0 Character state speci c value of particular character This can be compared to other character states of same trait and be determined a Plesiomorphic primitive or n Apomorphic derived When comparing homologous characters also consider a Symplesiomorphies shared primitive characters a Synapomorphies shared derived characters Phylogenetic Trees Phylogeny evolutionary history of a species Can be represented in a phylogenetic tree 0 Node each branch point represents common ancestor of all taxa above that node on the tree 3 Domains of Life 0 Carl Woese classi ed living organisms into 3 major Domains based on nucleotide sequence of different types of RNA 0 Divergence of RNA can be used as index of how much time has passed since various taxa diverged from common ancestor 0 RNA appropriate bc All living things have RNA rRNA perform essentially same function in all living things rRNA relatively stable in terms of acquiring mutations slow rRNA can be compared across taxa to see where changes have occurred over evolutionary time 0 proposed 3 domains bacteria archaea eukaryote 0 Why Classify Aid to memory easier to remember characteristic of group rather than each individual Aid to prediction if taxon has particular traits likely that new member of that taxon will share some of these traits o Aid to explaining evolutionary relationships 0 To provide a stable relatively unchanging system of internationally recognizable names scienti c names Taxonomy describing naming classifying 0 Before 0 Classi cation based on subjective logic 0 Put like organism together which re ected a quotnatural orderquot kosmos 0 Scienti c names really long 0 Carl von Linne Linnaean System of classi cation 0 Each species nested into successively more inclusive taxonomic groups Domain kingdom phylum etc 0 Scienti c name genus species What is a Taxon Taxon group of organisms that have been classi ed together at any taxonomic level but without specifying that level 3 aspects of a taxon o taxon name dog taxon is carnivore o taxon rank mammalia is class there may be sub or super ranks species is only taxonomic rank with any biological signi cance 0 taxon s content tells us which organisms are believed to be most closely related in terms of evolutionary ancestry classi cation and levels of taxonomy o classi cation ordering of organisms into groups based on their relationships 0 alpha taxonomy describing and naming of species 0 beta taxonomy arranging species into system of higher classi cation 0 gamma taxonomy study of biological aspects of species Nomenclature rules for describing and naming organisms Basic Rules of Biological Nomencalture Commissionscodes are independent of one another Taxon only has one correct name No 2 species may have the same name Must be latin or Iatinized Accepted name based on publication priority whoever describes rst gets to name Name of superfamily must be based on that type genus the rst genus to be described in a given family Practical application of Taxonomy Taxonomy can be used to stop harmful pathogens 0 By identifying speci c species 0 Or identifying group and know how to kill it 0 Finding new species 0 Tracking bioterrorism Systematics reconstructing evolutionary relationships Taxon has dimensions in space geographical range and time evolutionary history systematist interest in both Outgroup analysis method that provides the most parsimonious explanation for which characters are primitive and derived 0 Outgroup is a taxon related to the assemblage of the ingroup but not included within it 0 So all taxa of ingroup should share about same level of evolutionary relationship with the outgroup 0 Characters in ingroup and out group primitive 0 Characters unique to ingroup derived 0 The more synapomorphies common to subsets of ingroup the more recent their common ancestry is Constructing Phylongenies that re ect common ancestry the goal of systematists All members of any taxonomic group should share a common ancestor o Monophyletic taxon all taxa derived from a single common ancestor Sometimes phylogenies don t accurately re ect evolutionary relationships o Polyphyletic taxon taxa derived from more than one common ancestor o Paraphyletic taxon only some of the descendants of a common ancestor Sometimes true evolutionary relationships cannot be determined with available data 0 Form taxon morphotaxon formed on basis of shared similarities in morphology Brief History of Systematics 3 major schools of thought used to classify living organisms o classical evolutionary considers both common ancestry and specialization after branch point so thought monophyletic and paraphyletic taxa were considered acceptable 0 phonetic classi ed on basis of overall similarity with little concern for evolutionary relatedness problem with convergent evolution 0 cladistic system one used today 4 tenets u only quanti able feature of evolution is cladogenesis branching from a common ancestor n all taxa must be monophyletic n all evolutionary relationships must be measured in terms of recency of common ancestor a rank of taxon automatically determined by age of common ancestor only derived characters informative more shared derived traits more recent common ancestry stem taxon gives rise to daughter taxa cladogenesis fossils are extant taxa fossil organism cannot be considered ancestral to an extant taxon if more than one possible cladogram consistent with data choose most parsimonious tree one with fewest steps Forces that Drive Evolution 5 criteria that must be met for a population Not to evolve no mutation no migration no natural selection nonrandom mating inbreeding vs outbreeding small populations meanings of Microevolution genetic change in species over time wo speciation Macroevolution genesis of 2 reproductively isolated taxa from single ancestral taxon random genetic drift changes in relative allele frequency due only to random sampling error mutation When mutant allele inherited new allele added assortative mating 0 positive assortative mating individuals with similar genotype mate more often than the predicted frequencies Results in disproportionate number of homozygotes 0 negative assertive mating opposite Results in disproportionate number of heterozygotes immigrationemigration affects allele frequencies migration natural selection 0 stabilizing selection favor the average state of a trait o directional selection one extreme is favored o disruptive selection 2 extremes favored while average not HardyWeingberg equilibrium genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors 5 factors that can cause a population to evolve mentioned above Know Gene a unit of heredity A or a Allele expression of gene tall or short Population species in same area that breed Deme local population Gene pool polymorphism variants of same trait in a gene pool Homozygous AA aa Heterozygous Aa Tenets of evolution by natural selection 0 Overproduction 0 Variable hereditability 0 Competition 0 Differential reproduction Sexual selection dif From assortative mating 0 based on ability to attract mate 0 Sexual dimorphism when individuals exhibit character that make them more attractive to mates have advantage ghting or attraction Founder effect small sample of breeding individuals from a large population in new area Bottlebeck effect most members of large population remove leaving only few survivors 0 Physiological adaptation vs evolutionary adaptation ony populations evolve o origin of Species and Macroevolution 0 meaning of mutation forwardreverse mutations 0 wild type phenotype most common in wild population 0 exaptation adaptive trait that started out as neutral Classical new bene cial aee formed and continued bc of natural selection Balance maladaptive trait kept alive because has some bene ts Neutral Mutation Model allele is neutral and just went along for the ride central in genetic drift Meaning balanced polyporphism heterozygote advantage frequencydependent selection selective pressure against a particular alee changes with that aee39s relative frequency in the population 0 search image owl develops eye for mice 0 hybrid zone where close species could make hybrids reproduction isolation o hybridization 0 hybrid speciation Calculate Fitness coefficient W genotype that produces most offspring 1 Selection coefficient 1W measure of selective pressures against certain genotype Meaning Gamete sperm and ova Zygote fertilized egg cell Transmission distortion departure from this expected 50 likelihood that any given allele will be inherited Meiotic drive process that results in the overrepresentation of certain alleles in the gametes produced during gametogenesis Postzygotic variability geneticallybased differences in the ability of zygotes to survive Fecundity selection occurs when one genotype is more fertile than another for whatever reason Compatibility selection when combinations of eggs and sperm of a particular genotype are more likely to produce viable offspring than other combinations Mechanisms of reproductive isolation Postzygotic isolating mechanisms 0 Hybrid invariablity sterile breakdown dies Prezygotic isolating mechanisms 0 Behavior temporal geograhic Speciation Allopatric single population divided into 2 by geographic barrier Peripatric new species arises at edge range of orginal population Parapatric gradient of genetic difference develops across a species s range Sympatric speciation occurs without physical separation within range of ancestral population Meanings Anagenesis changes so much just becomes new species Cladogenesis evolves into 2 new species Incipient species species on verge of becoming separated Adaptive radiation When ancestral species creates new ones through cladogenesis and descendent species radiate into new ecological niches Character displacement Altruism scara ce for good of group Group selection sometimes behave for good of group Kin selection assisting relative in rearing of offspring Individual tness the production of offspring by an individual Inclusive tness individual tness PLUS tness gained via kin selection activity
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