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by: Elna Nader


Elna Nader
GPA 4.0


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This 58 page Study Guide was uploaded by Elna Nader on Saturday September 12, 2015. The Study Guide belongs to GENE 3000 at University of Georgia taught by Staff in Fall. Since its upload, it has received 64 views. For similar materials see /class/202265/gene-3000-university-of-georgia in Genetics (Graduate Group) at University of Georgia.

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Date Created: 09/12/15
Terms 982009 60600 PM Biodiversity a variety of life forms at any level of biological systems Evolution change over time change in the form of organisms across generations Great chain of being Aristotle 0 From more spirit to less sprirt 9 God angels demons humans animals plants nonliving matter Adaptation a trait that increases the ability of an individual to survive or reproduce compared with individuals that lack the trait o Derived character that evolved in response to specific selective agent 0 Phenotypic variant that results in highest fitness among set of alternative phenotypes in given population Homology similarity among organisms due to common ancestry Leclerc Uniformitarianism gradual processes which occur today as they did in the past Hutton amp Lyell o Catastrophism today s geological formations resulted from catastrophic events in the past Darwin s 4 Postulates o 1 Individuals within a species vary in phenotype o 2 Some variation is heritable and is passed on to offspring o 3 Individuals vary in their success at surviving and reproducing o 4 Survival and reproduction are nonrandom with respect to phenotypes Theory a hypothesis that has been confirmed or established by observation or experiment Resistance evolutionary consequence of natural selection 0 1 Mutations give rise to variability in resistance and susceptibility in the population 0 2 These mutations are heritable and are passed from parent to offspring o 3 During exposure to AZT or antibiotic some virions or bacteria are better able to survive and reproduce than others People 0 4 The remaining virions or bacteria are those with mutations that make them more resistant The remaining can survive and reproduce in the presence of AZT or antibiotics changing the composition of the population over time Carl Linnaeus o Linnaean taxonomy 9 classified all of nature within hierarchy kingdom phylum class order family genus species 0 Systema Naturae 0 Saw classification as manifestation of divine order James Hutton amp Charles Lyell o Developed uniformitarianism 9 assumes that same natural events occurred in the past as do today at the same rates 0 Replaced catastrophism 0 Earth is 46 billion years old GeorgesLouis Leclerc 0 Common ancestry of organisms based on morphological similarities o Homology similarity among organisms due to common ancestry Alfred Russell Wallace 0 Traveled through Amazon and South Pacific 0 Had a similar theory on evolution but was beaten to press by Darwin Charles Darwin 0 Wrote On the Origin of Species Jean Baptiste de Lamarck 0 First theory of evolution 9 changes in world due to operation of natural law not miraculous intervention Saw progressive change from simple to complex organisms New simple organisms repeatedly created by spontaneous generation Inheritance of acquired characteristics 9 changes in physiology over life of organism can be passed through to offspring by giraffe stretching its neck long necks will be inherited by offspring O O 982009 60600 PM Mutations Macroevolution phenotypic changes great enough to change lineage longterm changes across populations Microevolution shortterm changes within populations Cladogenesis diversification among lineages o Speciation or splitting of lineage Anagenesis genetic changes through time within a lineage Four Evolutionary Forces 0 1 Mutation source of new alleles and genes 0 2 Natural selection sorts among genetic variants in population 0 3 Genetic drift random change in frequency of variants in population 0 4 Migrationgene flow process by which variants move among populations Mutation is fundamental to all evolutionary change 0 Ultimate source of all genetic variation 0 Evolution cannot occur without genetic variation Genotype set of genetic variants for individual 0 Codes for phenotype Phenotype observable traits in individual Gene functional unit of heredity carrying information from one generation to the next Locus chromosomal location of specific gene Allele particular variant of gene Most DNA is noncoding 9 less than 5 encodes proteins Genetic code 0 Redundant 9 same amino acids coded by different codons Three Major Sources of Mutations o 1 Errors in replication 0 2 Errors in segregation of replicated genome in daughter cells 0 3 Chromosome modifications Point mutations random errors in DNA synthesis 0 Synonymous or silent substitutions that do not change amino acid Est O O O O Nonsynonymous or replacement substitutions that do change amino acid Ex sickle cell anemia Both silent and replacement create new alleles Nonsense substitutions that cause stop codons Frameshift indels that aren t multiple of 3 bases Transition point mutation in which purine A or G is substituted for purine or pyrimidine C or T is substituted for pyrimidine Transversion when purine is substituted for pyrimidine or vice versa Transitions are much more common 21 imating mutation rates p O 1 Observe phenotypic changes over generation Ex eye color in fruit flies 2 Sequence DNA at beginning and end of mutation accumulation experiment Yields more accurate mutation rates as it accounts for silent mutations not shown in appearance Pyrosequencing allows for acquisition of massive amounts of DNA sequence data Process 9 maintain lines under benign conditions for many generations and use random individuals to propagate lines Use with selffertilizers Mutations rates are similar in yeast human fruit flies etc Mutation is weak evolutionary force acting alone Lossof function mutations changes in DNA that inactivate a gene leading to complete lack of gene product Ex achondroplasia type of dwarfism and hemophilia impaired bloodclotting Consequence of mutation O 1 Advantageous 9 will go to fixation in population replacing old allele 0 2 Deleterious 9 eliminated by natural selection 0 3 Neutral 9 no influence on phenotype or fitness Most are neutral or slightly deleterious o Origin of New Genes o 1 Genome duplication Due to errors in segregation during meiosis Changes numbers of chromosomes Polyploidy duplication of entire genome n Caused by errors in segregation of chromosomes during meiosis a Can be 4n 6n or 8n n More common in plants because selffertilization is more common a 2n parent 9 mutation causes production of Zn gametes and selffertilization occurs 9 2n 2n gametes 9 4n first generation offspring 9 selffertilizes or mates with 4n sibling 9 2n 2n gametes 9 4n second generation offspring o 2 Gene duplication a Retrotransposition processed mRNA is reverse transcribed to form DNA and integrated back into a chromosome leading to original gene and retrotransposed duplicate b Unequal crossing over occurs at nonhomologous points during meiosis creates extra or deletions of genes Possible fates n 1 Copies retain original function u 2 Copies lose function u 3 Copies diverge in function 0 3 Chromosomal modifications Inversion chromosome segment detaches flips and reanneals in original location o Mutations are random 0 Mutations are not influenced by whether or not the organism is in an environment in which the mutation would be advantageous 982009 60600 PM Variation o Source of variation 0 Ultimate source 9 mutation 0 Over shortterm most genetic differences are result of recombination during sexual reproduction o Processes 1 New combinations of alleles n Crossing over between homologous chromosomes 2 Formation and union of genetically different gametes a Random segregation of chromosomes during meiosis Measuring 1 Examine proteins and DNA a Ex electrophoresis n More variation in noncoding regions than coding regions of DNA a All species are polymorphic 2 Examine phenotypes n Discrete 9 cheek dimples freeattached earlobes n Continuous 9 size length timing rate o Population genetics explains evolutionary change in terms of changes in frequencies of alleles and genotypes 0 Used for discrete phenotypes o Quantitative genetics explains evolutionary change in terms of change in mean andor variance of continuously varying trait 0 Used for continuous phenotypes 0 Mean average value 0 Variance average of distance from mean2 Subtract mean from distance from mean and square then sum the squared amounts and divide by nl o The more loci affecting the trait the greater the number of possible phenotypes o Norm of reaction pattern of phenotypic expression of a single genotype across a range of environments linear reaction 0 Single genotype can produce different phenotypes in different environments 0 o GxE genotype by environment interaction response is different in each environment nonlinear reaction o Causes of phenotypic variation 0 Phenotypes may vary because of genetic differences environmental differences or both 0 Common garden experiment Collect plants from low mid and high elevation and grow them all at mid elevation Differences remain Determines whether variations observed in phenotypes have genetic basis 0 Reciprocal transplant experiment Grow plants from each elevation at all elevation Determines whether trait variations have genetic basis AND whether trait differences were influenced by changes in environment o Partitioning phenotypic variance 0 VPVGVEVGxE 0 VP phenotypic variance 0 VG genotypic variance Part that causes evolutionary change 0 VE other variance Not transmitted from parents to offspring Caused by environmental effects 0 VexE genotypes differ in their response to environmental variation o Heritability O h2 VGVp h2 is not squared Slope of regression line between offspring and parents tells heritability n Offspringparent heritability Only valid for environment in which they are studied 982009 60600 PM Natural Selection o Natural selection nonrandom differences in average reproduction andor survival of different heritable phenotypes in population 0 Evolutionary response only when phenotypic variation is heritable o Four Postulates o 1 Individuals within population are variable 0 2 Variations are passed from parents to offspring o 3 In every generation some are more successful at surviving and reproducing than others Fitness proportional contribution of an individual s genes to future generations n Factors that influence fitness survival reproduction quality of offspring o 4 Individuals that survive and reproduce are those with most favorable variations survival and reproduction are not random o Natural selection acts on phenotypes o Phenotypic trait must be variable among individuals 0 Natural selection must be able to distinguish among varieties 0 Selection can occur without evolution 0 Selection acts on phenotypic variation If no genetic basis for phenotypic variation no evolution Mendelian Genetics o Microevolution any change in allele frequency within a population 0 Population group of interbreeding individuals and their offspring o HardyWeinberg Law Genotype frequency number of individuals with specific genotypeall individuals Must sum to 1 Allele frequency homozygous genotype frequency 12 heterozygous genotype frequency Allele frequencies must sum to 1 Null hypothesis what genotype frequencies look like when there is no selection 0 O O o p2 2pq q2 Allele frequencies are unchanged 0 Assumptions 1 No selection 2 No mutation 3 No migration 4 5 Infinite population size no drift Random mating 0 Change in allele frequency 39 AP P39 P n p observed frequency a p expected frequency o Fitness 1 Viability selection survival from zygotes to adults 2 Sexual selection mating 3 Fecundity selection reproduction 4 Gametic selection 5 Compatibility selection Terms Absolute fitness Ri extent to which an individual contributes genes to future generations n Absolute fitness survival x fecundity n Survival numbers at matingnumbers at birth a Fecundity total offspringnumbers at mating Relative fitness w RiRref a Reference genotype 9 genotype with highest fitness Selection coefficient si strength of selection against relative fitness a S 1 wi Mean population fitness W P2W11 2PqW12 q2W22 0 Function of Phenotype produced by genotype Environment population lives in O O O O O n Same genotype may have different values in different environments o Modes of Selection 0 1 Directional selection homozygote advantage A1 is completely dominant Mean population goes up as p approaches 1 Reduces genetic variation eliminating A2 Populations will always reach highest fitness point when pgtO o 2 Balancing selection heterozygote advantage overdominance Incomplete dominance Ex sicklecell anemia Equilibrium allele frequency n p tSt o p A1 0 s1wA1A1 t 1wA2A2 Maintains genetic variation and neither allele is eliminated from population Populations will always reach highest fitness peak unless p 1 or 0 wlt1 o 3 Disruptive selection heterozygote disadvantage underdominance Incomplete dominance Erodes genetic variation and eliminates A1 or A2 Two fitness peaks Will not always reach highest peak o Frequency dependent selection 0 Negative frequencydependent selection favors alleles when rare maintains genetic variation in populations 0 Positive frequencydependent selection favors more common alleles erodes genetic variation o Mutationselection balance 0 q WitS p mutation rate s selection coefficient against q 0 Only applies to deleterious alleles 1082009 23200 AM Genetic Drift Deterministic process predictable process 0 Ex natural selection Stochastic process random processes about which predictions cannot be made 0 Ex genetic drift and mutation Sewel Wright 0 Evolution by random sampling 0 Adaptive landscape determined by interaction of drift and selection Genetic Drift change in allele frequency due to statistical fluctuations in finite population 0 Removes genetic variation weak negative evolutionary force 0 Magnitude of genetic drift 9 inversely proportional to population size 0 Change in allele frequencies CANNOT be predicted BUT probability that allele frequencies will change CAN be predicted Probability of losing an allele increases with smaller population size Alleles in population become more easily fixed or lost Lose heterozygosity 0 Probability of fixation of allele allele frequency Heterozygosity H proportion of heterozygotes at a locus Drift is important for o 1 Dynamics of rare alleles o 2 Small populations with low migration rates 0 3 Neutral theory of molecular evolution Population bottlenecks significant percentage of population is killed or prevented from reproducing Population reduced in size due to stochastic events Reduces genetic variability Alleles change in frequency due to drift Ex Pingelap Island 9 high frequency of colorblindness Founder effect small population is founded byjust a few individuals 0 O O O O 0 Ex Silvereye birds 9 migrate to islands off Australia o Effective population size Ne number of individuals in theoretically ideal population having the same magnitude of random genetic drift as real population 0 Ne 4Nme NmNf Nm number of breeding males Nf number of breeding females 0 Populations with lower Ne have higher drift rates Rarer sex has disproportionate effect on Ne Bottlenecks have disproportionate effect on Ne Ex Elephant seals 9 hunted to brink of extinction historical and fight to establish harems contemporary Can be smaller than census size because 1 Unequal numbers of males and females 2 Variation in number of progeny produced by males and females 3 Fluctuations in population size 0 0 Migration o Higher population 9 stronger selection drift can be ignored o Lower population 9 stronger drift selection can be ignored o Population group of interbreeding individuals and their offspring o Subdivision takes place on different spatial temporal or geographic scales o Migration gene flow movement of alleles from one population to another by the movement of individuals or gametes o Increases genetic variation 0 Island model 9 individuals move from mainland to island 0 Homogenizes allele frequencies across populations Makes allele frequencies on island equal to original allele frequencies on the mainland Opposite effect of genetic drift 0 Causes averaging of allele frequencies among populations o Population genetic structure arises from variation in allele frequency among populations 0 FST Vq q139q FST extent to which populations are genetically differentiated n Has minimum value of 0 no genetic differentiation and maximum of 1 fixation of allele n FST gt 025 is high q mean frequency of one of alleles across populations Vq variance among populations in its frequency 0 As migration increases FST gets smaller 0 As population size increases FST gets smaller Molecular Evolution o Motoo Kimura 0 Neutral Theory of Molecular Evolution Developed in 1968 Genetic drift not natural selection explains evolution at molecular level Vast majority of base pair substitutions that become fixed in populations are neutral with respect to fitness Substitution K replacement of one allele by another within a population or species fixation of an allele in a Hneage Independent of population size and natural selection Substitution rate equals mutation rate a K H o Coalescence genealogy of gene copies in current population coalesce back to single common ancestor o Controversial 9 adaptive evolution predominates phenotypic evolution so how could drift predominate at molecular level 0 Support 1 Silent substitutions rates higher than replacement substitution rates 2 Genes vary in substitution rates according to functional constraints 3 Proteins that interact with other proteins have lower substitution rates than those that do not 0 4 Molecular clock where accumulation of mutations between taxa is proportional to absolute time o Refutes 1 Abundant evidence for natural selection on coding regions for positive selection like BRCA 2 Codon bias evidence for natural selection on 3rd position of codons and selection in noncoding regions o Tomoko Ohta 0 Nearly neutral model of molecular evolution Highly deleterious mutations are lost rapidly Mildly deleterious mutations are influenced by drift 0 Explains clocklike changes across species of protein evolution Higher mutation rate in larger population but lower chance of drift to fixation Lower mutation rate in smaller population but higher chance of drift to fixation o dNdS ratios 0 dNdS dN rate of nonsynonymous substitution d5 rate of synonymous substitution 0 Purifying selection natural selection against deleterious mutations dN is lower than d5 0 Positive selection natural selection favoring beneficial mutations dN is higher than dS Inbreeding o Inbreeding when the union of gametes is more likely to involve gene copies that are identical by descent than if they joined at random o Consequences o 1 Changes genotype frequencies and heterozygosity o 2 Can cause inbreeding depression Homozygosity for recessive deleterious alleles Homozygosity at overdominant loci where heterozygotes have highest fitness o Coefficient of inbreeding F probability that two alleles in an individual are identical by descent both alleles came from same ancestor allele in previous generation 0 F 412n n number of lines connecting offspring to common ancestors ignoring crosses o Autozygous homozygous and identical by descent o Allozygous heterozygous or homozygous if 2 alleles are not identical by descent o Linkage tendency for alleles at different loci on a chromosome to be inherited together 0 Linkage equilibrium alleles are independent of one another Complete linkage equilibrium 9 D 0 0 Linkage disequilibrium D alleles are linked and are inherited together D 9ABgab gAbgaB g9amete frequency Complete linkage disequilibrium 9 D 1 Genetic recombination 9 reduces linkage disequilibrium o John Maynard Smith 0 Developed null model by comparing fate of individuals that reproduce sexually compared to asexually o Twofold cost of sex Asexual population can double in size every generation Sexual population remains same size o Leigh Van Vaen 0 Red Queenquot hypothesis sex is needed to keep up with constant changing environment 0 Sex purges deleterious recessives accumulated through mutations o Muller s Ratchet o Mutation and genetic drift cause ASEXUAL populations to accumulate deleterious mutations Fittest genotype may be lost due to drift Population cannot regenerate lost genotypes by recombination Complex Traits o Additive genetic variance VA portion of genetic variation transmitted from parent to offspring o If inheritance is purely additive then heterozygotes are perfectly intermediate o Selection on the mean 0 Directional selection change in mean phenotype Reduction in genetic variation Ex Peppered moth 9 changed from light to dark after industrial revolution in response to darkening of trees by soot Selection differential S o Selection on variance 0 Stabilizing selection individuals having intermediate values of traits have highest fitness No change in mean phenotype Reduction in variation Ex birth weight in humans goldenrod gall makers o Disruptive selection individuals with extreme values of traits have highest fitness No change in mean phenotype Increase in variation Ex blackbellied seedcracker 9 birds that have two distinct beak sizes for specialization on different sized seeds o Genetic correlation o 1 Linkage disequilibrium o 2 Pleiotropy one gene affects multiple traits Ex anthocyanin pathway in flowers 9 controls pollinator behavior and resistance to herbivores o Selection and Adaptation o Preadaptationexaption feature that fortuitously serves a new function Ex feathers 9 evolved for thermoregulation but co opted for flight in birds Sexual Selection o Sexual dimorphism difference among members of the same sex 0 Sexual asymmetry 1 Females usually invest more in offspring 2 Male reproductive success is often more variable than female reproductive success 0 Limits of fitness 1 Male success is usually limited more by access to mates a Male gametes are cheap 2 Female success is usually limited more by resource availability a High investment in gametes a High parental care AJ Bateman 0 Cause of sexual selection is stronger correlation in males between number of mates and fertility 0 Predicted results 1 Members of sex under higher selection will compete 2 Members of sex under weaker sexual selection will be choosy Types of sexual selection Intrasexual selection occurs when individuals of one sex can monopolize access to members of other sex 0 Malemale competition Ex combat sperm competition resource guarding infanticide Intersexual selection occurs when individuals of one sex mate nonrandomly with respect to phenotypes of members of opposite sex 0 Femalechoice selection Ex bright colors elaborate morphologies particular courtship behaviors chemical cues Reasons for female preference 0 1 Good genes hypothesis phenotypic traits are direct signals of individual fitness Ex male frogs with long calls produce offspring that survive better o 2 Direct resource enhancement potential mates differ in how many resources they can provide Polyandry multiple mating by females Kin Selection amp Social Behavior Four behaviors cooperative altruistic selfish and spiteful Altruism behavior that decreases fitness of the actor and increases fitness of recipient o Altruism paradox individuals who act altruistically have lower fitness than individuals who do not act altruistically 0 Ex meerkat prairie dog Inclusive fitness individual s total fitness sum of its direct fitness via reproduction and its indirect fitness via reproduction of relatives Relatedness coefficient r probability that alleles at particular locus in two different individuals are identical by descent from common ancestor 0 Full siblings 9 r 12 0 Half siblings 9 r 14 0 First cousins 9 r 18 William Hamilton 0 Hamilton s rule rB gt C n B fitness benefit to recipient a C fitness cost to actor Kin selection 0 Unique behaviors Alarm calling 9 prairie dogs warn of predators only if around those of higher relatedness coefficient Helpers 9 forego reproduction help other parents raise offspring Eusociality many workers never reproduce they are helpers for life 1 Overlapping generation between parents and offspring 2 Cooperative care of offspring 3 Nonreproductive castes o Haplodiploidy males produced from unfertilized eggs 0 O Fathers do not contribute genes to sons 0 Siblicide killing of siblings Masked booby n Nestlings more siblicidal n Evolved response to food shortage n Parents tolerate siblicidal chicks Bluefooted booby n Nestlings less siblicidal n Under shortterm food shortage older chick reduces food intake to help sibling survive a If food shortage continues older chick kills sibling n Parents prevent siblicide 1082009 23200 AM Evolutionary Conflict 1132009 105200 PM o Family conflict 0 Parentoffspring conflict investment by parent in individual offspring which decreases parent s ability to invest in other offspring while offspring s chance of surviving increases Robert Trivers 9 conflict between mother and offspring Parent wants to maximize net benefit amongst ALL offspring Offspring wants to maximize ITS net benefit despite cost to siblings n Trait in offspring can only be selected for if it obeys Hamilton s rBgtC n Prediction 9 POC is stronger in half siblings than full siblings Ex whitefronted beeeaters 9 help at nests of closely related individuals often parents Examples n Postparturition weaning o Mother resists offspring s demand for contact while offspring is more interested in spending time in contact o Ex Rhesus macaques 9 higher conception rate is linked to higher rate of maternal rejection of offspring n In utero motherfetus interactions o Insulin produced by mother transports glucose from blood into cells o Fetus produces human placental lactogen HPL by increasing placental growth to block insulin to keep glucose in blood for higher fetal fitness o In gestational diabetes 9 fetus wins 0 Siblicide death between siblings and indirectly across parentoffspring relationship Parental favoritism parents are equally related to all siblings but do not treat them equally allowing starvation and siblicide n Ex great egrets 9 siblings fight while mother ignores their behavior a Ex brown booby 9 older sibling forces younger sibling from protection of mother where it will die Asynchrony birthing offspring at different times a Can promote sibling conflict Why a 1 Insurance against failure o Younger offspring always die o Parent does not intend to rear two kids o Ex bluefooted booby prevents siblicide while masked booby encourages it n 2 Environmental uncertainty o Good year 9 raise entire clutch o Bad year 9 brood reduction 0 Infanticide killing of young offspring by mature animal of same species Langurs 9 live in groups of one male to several females n Males fight for group of females n Infants often killed by new male taking over group Possible explanations a Overcrowding n Maximize fitness o 1 Males kill unrelated infants o 2 Male kills young so females become fertile sooner and therefore increases reproductive success 0 Behavior favors spread of infanticide genes o Genetic conflict 0 Cytoplasmic male sterility Inherited from mother Found in hybrid production 0 Intragenomic 9 conflict between mothers and fathers o Imprinting signals inherited from mother or father determine expression of gene in offspring Mouse development requires both maternal and paternal genomes Fathers and mothers interests diverge n Fathers extract maximal resources for their offspring from mother a Mothers protect resources for future pregnancies Ex insulinlike growth factor 2 IGFZ n Promotes growth during gestation in mammals a Only expressed from allele inherited from father Sexual conflict two sexes having conflicting optimal fitness strategies concerning reproduction 0 Male manipulation tactics Mate guarding Sperm plugs Alter female attractiveness Seminal fluids Mate harming 0 Ex accessory gland proteins Drosophila n Upregulates females egglaying rate reduces desire to mate with other males and increases ingestion of food a Shortens females lifespan and reduces her fitness 0 Process Adaptation 9 trait aids male but harms female 9 absolute fitness declines 9 counteradaptation 9 relative fitness declines Males have higher optimal mating rate than females and have many adaptations to coerce females to mate with them a rBgtC o b rBgtC o c Benefit of siblicide such as less offspring to care for and possibly poor environmental conditions outweigh the cost of siblicide such as more offspring to carry out traits o a Once BC falls below 1 mothers are forced to wean late as opposed to early This will decrease the mother s production of additional offspring o b The mother would no longer care that BC should drop below 1 She would allow the offspring to wean later as the main purpose for weaning early is for the possibility of production of additional offspring 3 The mother will always want to wean her offspring at BC of 1 so that the cost never outweighs the benefit Full siblings will want be provided milk for longer but will take into account that they are 12 related to their siblings and where the BC will be 12 Half siblings will want to be provided milk for longer but will not care about their siblings fitness as much as they are only 14 related and the BC will be 14 4 It is believed that food shortages are much more common amongst masked boobies and the second chick normally dies of starvation anyway Enough direct fitness benefits are gained by removing competition for food and outweighing indirect fitness cost of killing a sibling Parents acquiesce to siblicide if it increases probability that at least one offspring will survive 1132009 105200 PM Coevolution o Species interact with other species 0 98 of flowering plants require animals for pollination o All animals require plants animals or other organisms as Prey o Coevolution reciprocally induced evolutionary changes in two or more species have parallel phylogenies o Predation Creates strong selection for predation avoidance n Crypsis 9 hide from predators n Aposematism 9 evolve toxicity and advertise Ex nexts produce tetrodotoxin 39I39I39X and snakes evolve resistance to 39I39I39X Batesian mimicry harmless mimic exploits dangerous model a Ex monarch butterfly harmful and viceroy butterfly harmless o Deters predators of both species but prevents predators from learning to avoid o Mutualism interaction between species that benefits both participants Trophic 9 lichen partnership between algae and fungi Defensive 9 antsplants Dispersive 9 pollinatorsplants n Ex yucca and yucca moths o Moths actively pollinate plant and lay eggs in flower while larvae feed of seeds o Plant aborts seeds if moth lays too many eggs o Plant imposes strong selection on moths not to lay too many eggs n Ex fig wasps 9 lay eggs in figs and carry pollen to other trees 0 Parasitism organisms that live off ofget food from single host Usually do not kill host Ex pigeons and lice Virulence extent to which pathogen lowers host fitness 1 n n n n n Ex common cold benign smallpox lethal Horizontal transmission bacterial fungal or viral infection between members of same species o Evolves virulence Vertical transmission infection from mother to child immediately before or after birth o Evolves symbiosis close interactions between different species 1 Coincidental evolution o Ex tetanus 9 lethal soil bacterium but did not evolve in humans 2 Shortsighted evolution enhance withinhost fitness of parasite decrease betweenhost fitness o Ex polio 9 moved to nervous system to more thoroughly affect host but is never transmitted to new host 3 Tradeoff hypothesis enhances parasite s transmission rate even if it eventually kills itself off o Ex myxoma introduced to rabbits 9 killed off most rabbits within a week but consequently killed itself off leading to decrease in virulence o Best virulence is transmitted before killing host ex Huntington s disease o Predictions o 1 Vector borne diseases more virulent than directly transmitted diseases ex mosquitos carrying malaria are more virulent than host to host diseases o 2 Diseases that cause diarrhea will be more virulent 0 Competition sympatric species diverge due to competition for resources Sympatric within same geological area Allopatric amongst different geological areas Character displacement competing species must differ in ecological niche or one will be eliminated o Commensalism o Unreciprocated negative interaction o Species can adapt to environment with no coevolution o Coevolution does not equal specialization o Reciprocity is key o Patterns 0 1 Reciprocal evolution between two species 0 2 Phylogenetic patterns 9 concordant phylogenies for two coevolving taxa 0 Examples Not coevolutionary 9 strong jaws and muscles used by hyenas to crack bones bones have no evolved to resist being eaten Coevolutionary 9 ability of herbivore to detoxify substances produced by plant specifically to deter that herbivore 1 Greater virulence would be disadvantageous in vertical transmission as mother virus would kill off mother before having a chance to pass the virus to the child therefore killing off the virus Greater virulence would be advantageous to a certain extent in horizontal transmission as parasite could be passed throughout a species killing off more and keeping the virus alive longer 2 The plant and pollinator coevolved through dispersive mutualism Take hawk moths out of controlled environment of orchids and other moths and observe over many generations if they evolve to have shorter nectar spurs 3 Female lion will wean children of territory leaders later than those of non territory leaders Observe female lion with cubs of each and observe which is weaned first 1132009 105200 PM Life History o Differences 0 Growth patterns 0 Size at maturity Selection should favor early breeding Costs a Lower growth a Reduced early survival n Tradeoff with latelife fecundity Theory predicts a Low adult survival 9 early maturity a High adult survival 9 late maturity Ex guppies n Guppies in killifish ponds are larger at sexual maturity as killifish eat guppy offspring n Guppies in pikecichlid ponds are smaller at sexual maturity as pikecichlids eat large guppies 0 Age at maturity Ex Labord s chameleon 9 lives one year but 23 of lifespan is spent as egg underground 0 Survival rates 0 Reproduction Number of offspring n Semelparous breed once and die o Produce large broods o Ex Pacific salmon n Iteroparous breed multiple times o Produce smaller broods o Ex Atlantic salmon n Ex Lobelia on Mt Kenya o Adult survival decreases as elevation increases and moisture decreases 9 favoring iteroparity at lower elevations and semelparity at higher elevations Size of offspring n Factors o Tradeoffs 0 Ex fish and fruit flies Egg size is smaller as clutch size becomes larger less resources available to larger clutch size so eggs are smaller o Resource availability 0 Total offspring number of offspring x fraction that survive a Lack clutch best solution is one that maximizes number of offspring surviving to maturity Age distribution and frequency 0 Senescence process of aging o Lifetime reproductive success expected number of daughters 0 R lemx R measure of fitness lX probability of surviving from birth mX number of daughters produced 0 Prevents infinite R 1 Impossible to have zero risk of death 2 Cannot avoid internal damage to organism 3 Deleterious mutations 4 Tradeoffs n Ex fecundity vs mortality 9 higher fertility leads to higher mortality a Ex length of body vs generation time 9 larger the animal the longer it lives but also the longer it takes to evolve 1 Hatcheries produces smaller eggs because smaller eggs are more likely to survive in the predatorfree zone therefore females can produce more eggs and have a higher reproductive success This is not optimal for fish in the wild as smaller eggs are more likely to be eaten by predators and are less likely to survive 2 Lack hypothesis is that selection will favor clutch size that produces the most surviving offspring Research does not support the hypothesis as many birds produce smaller clutch sizes than most optimal as adding eggs reduces longterm survivability 1132009 105200 PM Senescence physiological decline o Oldest human 9 Jeanne Calment of France age 122 amp 12 o Demographic measures of senescence 0 Go underground 9 naked mole rat Learn to fly 9 bats Deter enemies 9 porcupines Get help 9 eusocial ants Grow large 9 elephants Size is good predictor of lifespan o In almost all mammals females live longer than males o Why organisms age 0 Proximate explanations based on trigger stimuli and internal mechanisms Oxidative damage from free radicals n Mitochondria pumps out exhaust in form of free radicals molecules with extra electrons Telomere shortening n Chromosome replication leads to loss of ends of chromosomes n Copied information known as telomeres are located on ends of chromosomes and shorten as chromosomes are copied Breakdown in gene regulation a Genes lose ability to coregulate as organisms age Hormonal regulation a Reduction of caloric intake leads to organisms living longer o The evolutionary theory of senescence 0 Ultimate explanations why specific behavioral trait was favored by evolutionary mechanisms Imagine two mutant alleles that cause their bearers to die when each is activated Imagine that these two alleles exert their deleterious effects at different times Which allele is going to be selected against most strongly O O O The early one 9 late activation alleles have time to reproduce Ex Huntington disease 0 Henry Ford 9 would examine cars in junk yards find what was still functional and tell engineers to make this part cheaper to avoid longevity Sir Peter Medawar Mutation accumulation detrimental mutations that show effect only late in life and are not weeded out by natural selection a Ex House fly lifespan decreases if only young individuals are allowed to breed George Williams Antagonistic pleiotropy selection favors gene if it increases fitness early in life though it may decrease fitness in later life a Ex testosterone in men 9 higher reproductive fitness in younger life but can lead to increased susceptibility to prostate cancer Negative correlation between fecundity and survival Ways to test a Correlations within species a Correlations across species a Artificial selection experiments o Decrease in earlyage fitness should lead to increase in lateage fitness 0 Another way of looking at this NS need not produce parts that will last beyond the point when the organism will normally be dead o Senescence in the wild o Possum Mainland 9 more predators should age faster Island 9 less predators should age slower Mainland populations have higher mortality rates Theory predicts higher rates of senescence in mainland Evolution of menopause O O o Grandmother hypothesis 0 Menopause is adaptation associated with contribution that grandmothers make to feeding grandchildren Women whose mother are still alive have higher fecundity Assumptions of grandmother hypothesis 1 Children dependent on moms well after weaning so reproduction limited by older kids 2 Maternal survival to child s independence decline with age 3 Pregnancy and childbirth risk rise with age 4 As women age daughters start reproducing Conclusions of grandmother hypothesis Older women maximize fitness by ceasing reproduction helping weaned grandchildren Grandmothers face a tradeoff between investment in children and grandchildren o Alternative hypotheses o Menopause is byproduct of senescence o For most human evolution women did not survive past 45 years old 0 No opportunity for selection to favor prolonged non reproductive lifespan o If mother survives offspring survival improves However offspring with nonreproductive grandmothers do m 0 O 1132009 105200 PM Phylogenetics o Systematics classification of organisms o Phylogenetics study of species ancestry o Modern uses 0 HIV transmission Woman accuses Dr Schmidt of mixing blood from HIV patients in his care and injecting during fight Victim s HIV sequences nested within patient s sequences Dr Schmidt found guilty 0 Studying extinct animals Ex dodo 9 grew extinct within 80 years of European contact closely related to pigeons o Comparing phylogenies o Tightly associated taxa might be more likely to show phylogenetic congruence o History of classification 0 Aristotle 9 classified animals amongst characteristics 0 Linnaeus 9 hierarchical classification genus species o Classification 0 Homologous characters trait shared by two species inherited from common ancestor Basis for phylogenies Homologies are nested n Ex placental mammals and marsupials Synapomorphy shared derived characters 0 Homoplasious characters similarity in species of different ancestry convergence Not basis for phylogenies Ex human and octopus eye 0 Monophyletic all species descended from a single common ancestor Ex everything descending from reptiles o Paraphyletic species more closely related to others not in the group Ex all reptiles minus birds o Polyphyletic monophyletic except some descendents placed in other taxa Ex warmblooded mammals and birds 1132009 105200 PM Phylogenetics II Ancestral traits without fossils 0 Ex bees have UV vision and plants produce UV landing strip Parsimony least complex explanation for an observation Homoplasy 0 Ex squid and human eye whale and fish fin 0 Ex cows and langurs have fermentation chambers in their stomachs Rates of evolution 0 Conserved characters Ex organ structure and function are relatively similar in mice and whales Adaptive radiation phenotypes adapt in response to environment 0 Key innovation 0 Ex Darwin s finches 9 beak size Coevolution 0 Ex aphids and symbiotic bacteria 0 Ex lice and humans wearing clothes Ontogeny different species are often more similar during development than as adults 1242009 42600 PM Species o No definition has satisfied all naturalists Darwin o Concepts 0 1 Biological Species Concept Species 9 group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups Ernst Mayr n Have minimal or no gene flow Defined NOT according to similarity of appearance Identifies less species than PSC Examples o Eastern and Western meadowlark 9 look similar but do not interbreed o Queen and worker ant 9 look different but do interbreed and only fulfill different roles o Hydrangeas 9 have blue or pink flowers only changed by pH of soil n n n Problems n Cannot be applied to fossils o Chronospecies different stages of same evolving lineage that existed at different points in time 0 Ex trilobites may have changed over time but each stage shouldn t be considered a new species a Asexuals 9 cannot interbreed o Ex Mexican topminnow rotifers bacteria n Hybrids o Ex Northern pintail Mallard horse donkey wolf coyote o Ring species species with geographic distribution form ring and overlaps at ends extreme ends of range overlap but do not interbreed o Hybridization occurs between species so what marks speciation O O Iquot LA 0 Ex Ensatina salamanders in California o Difficult to apply to many plant groups where hybridization is routine n Allopatric species o Ex North American Elk and Red Deer 9 separated by continents researchers assume they would not interbreed if in contact Test 9 test individual from several populations for ability to mate and produce fertile offspring Morphological Species Concept Species 9 group of morphologically identical organisms Might identify more distinct subspecies as species a Applies to extinct or living species as well as sexual or asexual species Problems n Difficult to apply to archaea bacteria and fungi that have few morphological characters to assess a Cryptic species species independent of one another that appear to be morphologically similar Test 9 compare and contrast morphological characteristics Phylogenetic Species Concept Species 9 cluster of individuals within which there is a parental pattern of ancestry Cracraft n Based on monophyetic groups o Distinguishable if 9 isolated in terms of gene flow and genetically or morphologically divergent Might identify eastern and western species since phylogeny indicates origin of both in North n Identifies more species than BSC Ring species 9 considered one species as they all share the same tip of tree none have different common ancestor from other subspecies Example n African elephants 9 live in two separate habitats and found to be two separate species through PSC Problems n Species could have single basepair difference from related population a Could increase known number of species by huge amount Test 9 sequence two genes and use similarities and differences in base sequences to estimate evolutionary relationships o Modes of Speciation o Prezygotic isolation differences in mating choice or timing of breeding so that no hybrid zygotes are formed Ecological factors habitat choice a Species utilize different resources in habitat n Ex water moccasin lives in aqueous habitat while copperhead lives in terrestrial habitat Behavioral factors a Different mating rituals n Ex fiddler crab 9 mating dances Geographic n Allopatric Speciation physical barrier divides continuous population a Sympatric Speciation occurs without physical separation inside continuous population o Ex Rhagoletis apple maggot flies 9 originally laid eggs in hawthorn tree new species lays eggs in apples Ex Batesian mimicry 9 Monarch and Viceroy butterflies Peripatric Speciation small founding population enters new or isolated niche geographic isolation leads to genetic isolation o Ex genetic drift 9 Drosophila simulans and D sechellia n Parapatric speciation new niche found adjacent to original niche genetic isolation leads to geographic isolation o Ex Sweet vernal grass in Wales 9 lives in uncontaminated soil and mine waste and are divergent in flowering times reproductiver isolated o Ex Ring species 9 Ensatina salamanders Temporal n Mating occurs at different seasons or different times of day Lock and key a Ex Japanese millipedes differ in size and shape and are not physically able to reproduce Gametic incompatibility sperm transfer takes place but egg is not fertilized Sperm competition 0 Postzygotic isolation dysfunctional development or sterility in hybrid forms Hybrid depression 9 no development not viable sterile or reduced fertility n Haldane s rule heterogametic sex is more affected by sterility and inviability o Isolation o Vicariance split species distribution into two or more isolated ranges and prevent gene flow between them Ex rise of mountain range milewide lava flow Ex snapping shrimp separated by isthmus of Panama identified as separated species by all species concepts 0 Dispersal Ex Drosophilia a Each species formed in same branching pattern as Hawaiian islands formed with oldest species being located on oldest island and youngest species on youngest island o Forces for Divergence 0 Natural selection Leads to evolution of genetic differences Causes pre and postzygotic incompatibility 0 Sexual selection Barriers through female preference 0 Reinforcement hybrid offspring have low fitness Leads to assortative mating and prezygotic isolation of populations 0 Genetic drift Peripatry Ernst Mayr o DobzhanskyMuller incompatibilities Ex butterflies n A white a red n B mates only with red b mates with red or white a Hybrid 9 AaBb white mates only with red Homework 2 The morphological species concept uses similar characteristics in groups of individuals to determine species It can be applied to both live and extinct species as well as sexual and asexual species It cannot be applied to some archaea bacteria and fungi as they have few morphological traits to be assessed and cryptic species such as the Monarch and Viceroy as the species may look alike but are genetically different The biological species concept defines a species as being actually or potentially interbreeding It can be applied to species that may morphologically be the same but are different species like the Eastern and Western Meadowlark or morphologically different but the same species like queen and worker ants It cannot be applied to extinct species as it may not be possible for earlier forms of a species to mate with later forms of the same species or asexual species as they do not interbreed The phylogenetic species concept defines a species based on monophyletic groups It can be applied to both live and extinct 5 7 8 11 12 13 species as well as both sexual and asexual species A problem would be that it would define a new species by a change in a single basepair and would easily double the amount of currently existing species It also classifies ring species as only one species as each species shares the same common ancestor Dispersal happens when a group of individuals are separated from the original population like Drosophila on the Hawaiian islands causing gene flow to stop and each population to speciate separately Vicariance is when an obstruction like a mountain range separates a population causing gene flow to stop and each population to speciate separately like the snapping shrimp on each side of the isthmus of Panama The species of snapping shrimp most closely related to the one sampled lived on the other side of the isthmus meaning a vicariance event split each population As individuals are dispersed to a newer island they become geographically isolated and begin to speciate causing genetic isolation The original species began on the oldest island and migrated to the newer island through the years and speciated on each island As for prezygotic barriers ecological factors like belonging to an aqueous versus a terrestrial habitat behavioral factors like mating rituals in Fiddler crabs geographic factors temporal factors like mating in different seasons and gametic incompatibility may affect the two species As for postzygotic barriers zygotes may not form and hybrids may be inviable or infertile Reinforcement happens when hybrids have a low fitness in a population and natural selection leads to prezygotic barriers within populations o Sexual selection promotes divergence because it affects gene flow directly 1242009 42600 PM Web of Life o Tree of life 0 Divergent o Diversifying o Rarely repeating o Divergence with genetic exchange o Web of life 0 Natural hybridization 0 Viral recombination 0 Lateral gene transfer 0 Divergent evolution o Emphasis 9 genetic exchange is widespread and can lead to evolutionary novelty o Evolution of humans 0 Closest relatives 9 chimps and gorillas o Xchromosome suggests genetic exchange between proto humans and protochimps but not protogorillas o Homo species Neanderthals and humans overlap 9 found through artifacts Homo erectus and humans overlap 9 found through evolution of lice 0 Required for genetic exchange Spatial and temporal overlap between lineages involved 0 Our species has genome which is mosaic of protochimp protogorilla and archaic homo gene sequences o Evolution of humanassociated organisms 0 Genetic exchange between Domestic cats and European wildcats Domestic cats and African wildcats Domestic dogs and wolves 0 Citrus species All hybrids all related Sour orange mandarin sweet orange grapefruit pummelo lemon citron lime 0 Coffee cigarettes and chocolate Genetic exchange 9 found by wine yeast 0 Organisms which we depend for food clothing shelter and companionship also possess mosaic genomes o Evolution of disease vectors 0 Mosquitos Vectors for many diseases like malaria Genetic exchange in Southeast Asia 0 Chagas Affects Latin America 0 Organisms with which we battle for survival possess mosaic genomes o Tree of life and web of life are interrelated by vertical and horizontal transfer of genetic information 1242009 42600 PM Biogeography study of geographic distribution of organisms o Overlapping of geology ecology and evolutionary history phylogeny o Patterns can be explained by evolutionary history ecology or both o Ecological biogeography examines patterns of distribution of species communities and ecosystems especially in relation to the current environment 0 Biomes regions classified according to dominant vegetation and adaptations of organisms to that environment Mediterranean shrubland n Mild wet winter and hot dry summer a High biotic diversity n Dominated by shrubs and herbs n Ex Perth Australia San Luis Obispo CA Deserts n Convergent evolution 9 cactus evolves leaves on bark in both Southwestern US and Madagascar o Species not closely related o Historical biogeography examines how past evolutionary and geological events have shaped the distribution of species and groups of related species 0 Key insights 1 Climate and physical environment cannot alone account for the particular species present in a region a Species do not occur everywhere that is suitable for growth and reproduction o Ex plant species in southern Appalachians 9 climate is similar in other regions but plant does not grow there a Endemic species limited to a particular region or locality o Neoendemics due to recent evolutionary origin of species time o Paleoendemics due to fragmentation of formerly extensive range history o Ecological endemics due to ecological characteristics specific adaptations 0 Ex plants adapted to metallic soils 2 Barriers to dispersal are associated with differences in biotas n Terrestrial birds in Galapagos 9 distinct from mainland birds o Separated and speciate a Water birds 9 identical to mainland birds o Greater ability to disperse over waters 3 Related taxa have similar geographic distributions due to common ancestry n Ex Anolis lizards 9 closer related species share common microclimates o Ecology o Abiotic factors 9 temperature precipitation o Biotic factors 9 competitors predators mutualists Wallace s Line 9 communities on Oriental and Australian sides are very different o History 0 Vicariance separation of populations of widespread species due to geological barriers Dispersal movement of individuals Extinction elimination of populations or species Area cladograms If vicariance 9 will track geological history a Phylogeny parallels sequence of separation of geographic areas a Monophyletic groups occupy different areas If dispersal 9 will not track geological history a Paraphyletic pattern of distribution 0 Pangea 9 paleozoic Two super continients Laurasia and Gondwana 200 mya 9 Mesozoic Current continents 9 Cenozoic o Biogeography o Pangaea 200 mya O O O Global distribution of plants 9 some plant taxa only found in Asia and NA Laurasia o Gondwanaland 100 mya Ratite birds 9 found in SA New Zealand and Australia 0 Tertiary 2030 mya Arrival of carnivores in Madagascar 9 separated from Africa 0 Pleistocene 03 mya Humans n Multiregional hypothesis 9 single continuous human species with matching evolution across continents n Replacement hypothesis 9 humans evolved out of Africa onto other continents only to be replaced by newly evolved humans coming again from Africa o Accepted view today 0 Island biogeography theory 1 Islands far from mainland will have fewer species than close islands 2 Smaller islands will have greater extinction than large islands n Speciesarea curve 0 S CAz Homework 1 o The plant family may have evolved just before 200 mya when all the continents were joined as Pangaea Asia and South America were very close and the species may have radiated out of Asia into South America To test this you could find similar ecological regions where the plant is found such as hot and humid and test other areas of the world that occupy the same climate This would prove ecological endemics 2 3 Disjunct distributions in a taxon are where two groups are closely related but are widely separated geographically This could be caused by a vicariance event like the rise of a mountain range or a dispersal event like the drift of a small population to a new location The basic concepts are Smaller islands are prone to more extinction that larger islands and islands further from the mainland are home to less species than those closer to the mainland Moving species to larger islands may help in their conservation 1242009 42600 PM History of Life o Big bang 0 Earth forms 9 46 bya 0 Early oceans form 9 44 bya Experiment show that ocean water when heated yields some of earth s early elements Human body is made up of recycled stars Cyanobacteria 9 35 bya Oxygen builds up in atmosphere 9 2 bya Cambrian explosion 9 500 mya 0 Dinosaurs and small mammals 9 65 mya o Origin of eukaryotes o Symbiosis Ancestral eukaryotic cell engulfs bacterial cell and they begin to reproduce endosymbiotically a Proof 9 mitochondria has 2 cell membranes Eukaryotic cell engulfs ancestral eukaryotic cell that has already engulfed a photosynthetic eukaryote chloroplast a Proof 9 chloroplast has 4 cell membranes a Proof 9 both mitochondria and chloroplasts have genomes that resemble that of bacteria 0 Sexual reproduction 9 1 bya Meiosis and recombination rise First sexual cells are isogamous n Fusion of similar gametes n Mating in yeast types Anisogamous cell evolve n Fusion of dissimilar gametes a Difference in males and females 0 Multicelluarity Chlorella experiment 9 predator introduced and result was chlorella bunch together to become multicellular n Cost 9 reproduce more slowly O O O O o Timeline 0 Archean eon before 2500 mya First prokaryotes o Proterozoic eon 2500542 mya First eukaryotes Precambrian Era 5000570 mya a Life phototropic bacteria cyanobacteria eukaryotes invertebrates o Phanerozoic eon 542 myapresent Paleozoic era 570230 mya 9 vascular plants a Cambrian 5705009 continents shift to southern hemisphere Ordovician 500450 9 radiation of marine organisms 75 of marine species became extinct Silurian 4504209 northern continents ancestors of ferns Devonian 4203509 continents shift northward first gymnosperms first amphibians 75 of marine species became extinct Carboniferous 3503009 terrestrial animals insects abundant Permian 3002509 Pangaea formed mammals diverge from reptiles o Extinction 9 large meteorite hits Australia oxygen depleted by lava over 90 of all species extinct Mesozoic era 23065 mya 9 mammals n Triassic 250200 9 vertebrate lineages reptiles lead to dinosaurs ends with extinction Jurassic 200150 9 Laurasia and Gondwana dinosaur lineages mammals appear Cretaceous 15065 9 Gondwana breaks apart angiosperms o Mass extintion 9 kills vertebrates larger than 25 kg Cenozoic era 65 myapresent 9 humans a Tertiary 9 distinct continents n Quaternary 18 mya present o Pleistocene 1810000 o Holocene 10000present9 Homo erectus to homo sapiens Homework 5 o Archaea Bacteria Eukaryotes 3 1242009 42600 PM Extinction o Diversity 0 Balance between birth rate S and death rate E o Adaptive radiation 0 Release from competitors 0 Extinction of competitors 0 Coevolution o Ecological divergence o Constant extinction rates 0 Red queen hypothesis 0 Average lifespan for species 9 14 my 0 9999 of all species extinct o Mass extinctions o Ordovican 450 mya Devonian 350 mya Permian 250 mya 9 closest to total obliteration Triassic 200 mya Cretateous 65 mya Found reddish clay separating limestone between cretateous and tertiary High concentration of iridium Suggests cosmic impact o Extinction of birds and mammals o Steadily increasing with dramatic increase during last 150 years c Solutions 0 Reduce population growth rate 0 Conserve countryside biodiversity 0 Protect ecosystem services 9 ecotourism Homework o Background extinction extinctions occurring at normal rate 0 Around 96 of all extinctions 0 Not part of big 5 o Mass extinction intense periods of extinction 0 Part of big 5 0 Around 4 of all extinctions 0 Over 60 of species go extinct in the span of 1 million years c Microtektites spherical particles of glass associated with impact sites 0 Related to KT boundary 0 Solidified flight by being ejected from crash instead of cooling in place Iridium 1000 times more likely to be found in space and was found in KT boundary 1242009 42600 PM Evo Devo o Hox Homeobox genes determine segment identity in fertilized e919 0 In same order on chromosome as order of body parts expressed o Predate origin of animals 0 Hox number increased from 3 to 10 prior to Cambrian explosion 0 Core Hox genes remain but pattern of expression has changed 0 Eyes Pax6 9 produces eye tissue a Pax6 from mouse injected into fly and fly developed fly eye tissue a Same gene but convergent evolution 0 Limbs Distalless o Cis or trans effects Create F1 hybrids of two fly species 50 differ due to cis effects 50 differ due to cis and trans effects 0 Ways to limit effects of mutation and environment Genetic canalization genetic capacity to buffer phenotype against mutation Environmental canalization genetic capacity to buffer against environmental perturbation o Hsp90 Heat shock proteins rescue misformed proteins Removed from flies Terms o Homeobox segment identity during early embryonic development 0 Antennapedia hox gene in drosophila that controls placement of legs 0 Pax6 development of eyes and sensory organs


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