Exam 3 Study Guide
Exam 3 Study Guide BIOL 337
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This 7 page Study Guide was uploaded by Carolina Arreola on Sunday May 17, 2015. The Study Guide belongs to BIOL 337 at San Francisco State University taught by Routman in Spring2015. Since its upload, it has received 266 views. For similar materials see Evolution in Biology at San Francisco State University.
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Date Created: 05/17/15
Exam 3 Study Guide BIOL 337 l This evolutionary model states that a female chooses one male over another because that male has something that will directly bene t the female Possible advantages Males can Offer Good territory Protection Horns spikes etc Provide a gift e g Male provides female with bugs to eat Parental care for offspring Ability to avoid predation e g Moving around a lot can make you more susceptible to predation and in order to find a mate a male normally needs to move around a lot putting themselves at risk However if they have bright colors or ornaments then they can show off to potential mates without moving and strategically avoiding predation Abilit to avoid arasitespathogens 2 When the male has a characteristic that will genetically benefit the offspring and therefore indirectly benefit the female Model 1 Fisher s Runaway Sexual Selection a Directional Viability Selection b Heritable genetic female preference relative preference not exact Peacock Tail Length Preference Example Whenever you have sexual selection on the trait and you have female preference you will get runaway selection Assuming tail length is affected by multiple loci let s see the result in the tail length loci in males vs females based off the female preference Then we will look at the result of the offspring s tail length MATINGS TABLE FEMALE MALE Preference Loci AA Aa Random Increase in long tail Tail Length Loc1 Random alleles A Females prefer longer tails so males tend to have longer tails MATINGS TABLE FEMALE MALE Preference Loci aa Random Decrease in long tail Tail Length Loc1 Random alleles A Females don t have a tail length preference so the males tail length will be random but there will be a decrease in long tails Offspring TABLE FEMALE MALE Preference Loci Increase in A Increase in A Tail Length Loci Increase 1n long tail Increase 1n long tall alleles alleles There is a genetic correlation between females preference and the tail length the male offspring have Offspring TABLE FEMALE MALE Preference Loci Decrease in A Decrease in A Tail Length Loci Random Random StalkEyed Flies Experiment This experiment was done to test Genetic Correlation between preference and size of eye stalks The sexual dimorphism in the species relied on eyestalk size where males had much longer eye stalks than females Males use their eye stalks to compete with other males for mating rights Females preferred males with longer eye stalks more details of experiment on iLearn Model 2 Good Genes Model 1 Handicap PrincipleZahavi s When females believe if a male has a handicap but has survived up to this point in life then they must be extra healthy since they are able to survive with the handicap 2 Parasite LoadHamilton amp Zuk When females choose males with characteristics like long tails or bright colors because having these ornaments represent resistance to parasites and these parasiteresistant genes can be passed on to the female s offspring Example Study on Female Choice in Barn Swallows Females prefer males with elaborate ornaments such as long tails because it represents resistance to parasites Control Group 1 Birds feathers were left alone Control Group 2 Birds feathers were cut off then glued back on immediately The birds with extralong tails had fewer mites and found mates the fastest followed by the two controls and the ones with the shortest tails had feathers cut o took the longest amount of time to nd a mate Example2 Study on CrossFostering 9 Divided the male s clutch half of the clutch is raised in one nest by the biological father and the other half is raised by a foster father The dependent variable The of mites on offspring 9 In graphs showing the correlation between the offsprings tail length in comparison to the fathers tail length it showed there was a correlation between the offspring s tail length and the biological father s tail length but there was no correlation between the offspring s and foster father s tail length 3 Sensory Constraints Female choice may be constrained by physiology of sensory systems More like an innate relative preference no actual benef1t Ex When females prefer to incubate the largest egg in their nest if for some reason they are incapable of incubating all of the eggs This is clearly a builtin relative preference since the female gets no benefit either way When the evolution of one species is in response to the revolution of another species When speciation in hosts causes the speciation in parasites In order for cospeciation to exist you must see a phylogeny of the parasite that matches the phylogeny of the hosts examples on iLeam Ex Say a host such as a gopher splits into 2 different species over a period of time The split in species then causes there to be a split in the parasitic species say lice over a period of time Obligate symbioses is when 2 species need one another to survive eg algae and lichens Ex Endosymbiotic theory of eukaryotic cell origin This happened when photosynthetic prokaryotes and aerobic heterotrophic prokaryotes invaded cells over and over again until the cell was unable to live without it 3 Character Displacement When species have a certain phenotype based off the cohabitation of another species When 2 species are sympatric live in the same place they look different When 2 species are allopatric live in different places they look the same When 2 species are allopatric live in different places they look the same If phenotype was based on the environment then we would expect the 2 different species who live in the same area to look similar this is not the case Ex Galapagos Finches The galapagos f1nches evolved to one another when put on the same island One species developed larger beaks and the other species developed smaller beaks This was the 2 species did not have to fight over food options Those with larger beaks ate the bigger nus and those with the smaller beaks ate the small nuts A behavior or phenotype that causes the individual with that phenotype to have a lower 2 3 tness but this in turn increases the tness for someone else hurts me helps you 1 Some have argued that the main driving force behind acts that seem altruistic are actually bene cial to the individual e g noncannibalism some say the reason noncannibalism eXists isn t because of the act of altruism but because being a cannibal can lead to disease and kill you therefore it is bene cial to the individual to NOT be a cannibal When the altruist helps someone out but then another altruist helps that individual out in the future Reciprocal altruism only works when the cost is low and the bene t is high You scratch my back I ll scratch yours Ex Alarm Calls When a bird gives an alarm call to warn others about a predator they are putting them self at risk by attracting attention to themselves cost but they are helping out other by alerting them and giving them the chance to run away and by letting the predator know that they are aware of their presence When considering the tness of an individual you need to consider the tness of the relatives as well Minimizing the amount of help you give to those who are not relatives further helps those who are related to you and helps spread the altruism gene Ex Inclusive Fitness Hamilton Help those who share genes with you do not help those who don t There are 2 ways to do this a Kin Recognition The ability to recognize who is and isn t your relative and adjust your behavior accordingly b No Kin recognition but naturally help relatives more anyways This does require adjustments in behavior in order to help kin or not help nonrelatives AN EXAMPLE OF KIN SELECTION Eusociality in Hymenoptera An individual would give up reproduction in order to help others with reproduction This is due to haplodiploidy and the seX determining gene in Hymenoptera If an egg was fertilized the individual would be female and diploid If an egg was not fertilized it would be male and a haploid With this phenomena it was clear that sisters born from a haploid male and a diploid female would share 75 of their genes with eachother This means the sisters are more related to eachother genetically then they would be to possible offspring 50 Because of this they spread their genes MORE by helping the queen mother make MORE babies than having babies themselves 4 Group selection mimics Individual selection in that it has to do with tness and how many babies you can produce However group selection is thought to not be able to override individual selection because individuals can reproduce a lot faster than groups can reproduce Example of Group Selection Myxoma Virus Rabbits Myxoma virus is like the rabbit Ebola and was essentially used as population control The virus stopped working because the rabbits evolved resistance to the virus and Myxoma evolved a lower virulence meaning it became less and less like Ebola and became more like the common cold This is group selection on the virus If a virulent virus dominates a population then the virus reproduces faster and then kills off the population Less virulent viruses take longer to kill off a population so the rabbits then are able to reproduce a new population that has resistance We will be focusing on the evolution at the DNA level 2 Important observations of molecular techniques Lots of polymorphism at the protein level Molecular Clock The differences among alleles at a locus that tends to be correlated with time The Neutral Theory Motoo Kimuna believe that the molecular polymorphism found in a population at any given time consists mostly of alleles with equivalent effects on tness He argued that mutations that are advantageous or disadvantageous cannot explain variation Most mutations are deleterious 9 Advantageous mutations can be lost due to genetic drift but occasionally the frequency of this mutation can increase over time but can still decrease over time and only rarely become the common allele become the xed allele He is not arguing that the mutations are neutral when they occur Neutrality predicts the level of heterozygosity Criticism of the neutral theory Range of heterozygosity is too small given the range of population sizes given a relatively constant neutral mutation rate Variation is dependent on 2 things Size of Population and Mutation Rate Molecular Clock The idea that the rate at which molecules diverge from one another is proportionate to time 9 An experiment showed pairwise amino acid sequence differences in alpha hemoglobin in 5 vertebrate species It was expected that water vertebrates would be more similar to each other than to land vertebrates this was NOT the case 9 Bony sh had more similarities to humans than they had to sharks and other water vertebrates 9 The neutral theory can explain the molecular clock only if the mutation rate for a gene is constant Mitochondrial Eve Based on sequence differences between haplotypes Relationship of sequence difference to time is calibrated using chimp outgroup and estimates of time of the oldest fossil Homo We expects TMRCA The Most Recent Common Ancestor to be ranked as follows Ylinked ltmtDNA ltsexlinkedlt autosomal Species Concepts Species concepts attempt to define which biological discontinuities are species vs higherorder taxa 9 Both species and higherorder taxa are groups that share a common ancestor 9 Only species have Cohesion Mechanisms Evolutionary forces that make members of a species more similar to each other than to members of other species Biological Species Concepts Species are groups of actually or potentially interbreeding populations that are reproductively isolate from other such groups 9 Cohesion Mechanism IS gene flow Historically gene ow is considered ubiquitous in evolutionary time Therefore studies of a species focused on mechanisms preventing interspecific gene ow Reproductive Isolating Mechanisms Premating isolating barriers save gametes 9 Behavioral Isolation Different mating calls 9 Ecological Isolation Different Habitat breeding time pollinator 9 Mechanical Isolation Can t physically mate Postmating isolating barriers waste gametes 9 Prezygotic gametic incompatibility 9 Postzygotic extrinsic ecological inviability behavioral sterility vs intrinsic hybrid inviability hybrid sterility hybrid breakdown Other Species Concepts Evolutionary Species Concepts 9 A species is an independent evolutionary lineage 9 Cohesion mechanism is gene ow Ecological Species Concepts 9 Individuals of a species occupy the same niche 9 Cohesion mechanism is selection Phylogenetic Species Concepts 9 Individuals of a species are different even if its minorly different 9 Cohesion mechanism is gene ow Cohesion Species Concepts 9 Individuals of a species are held together by some evolutionary force 9 Cohesion mechanisms are gene ow selection or even drift Geographis Modes of Speciation Allopatric Speciation When a single lineage of species is split into 2 or more areas of large species in different locations 1 Macrovariant Speciation Most common mode of speciation according to modern biologists Dumbell Speciation 2 Peripatric Speciation Widespread species were found in areas that were no longer connected by gene ow Meyer argues that speciation occurs on peripheral isolates He argued that on big patches where there s a lot of similarities but gene ow changed on the peripheral isolates This is basically saying speciation occurs among small populations Sympatric Speciation When the descendant species arises within the range of the ancestral species The type of speciation we absolutely know has occurred even though it is NOT the most common 9 Instantaneous Sympatric Speciation Allopolyploidy is when different species hybridize to create the polyploidy Resultant species has chromosomes from parent species and they are easy to identify Autopolyploidy is when a single species undergoes polyploidization A lot of polyploidy species are triploid or other odd ploidy levels Parthenogenesis When females reproduce without the involvement of males or sperm Offspring Clones of mother occurs in lizards snakes and insects 9 Gradual Sympatric Speciation This happens over time and is not instantaneous Disruptive selection and assortative mating is required to get sympatric speciation An example of this is Thorday and Gibson s experiment on Dropsophilia Look on iLeam
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