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Evolutionary Processes and Speciation

by: Bree Scalzo

Evolutionary Processes and Speciation BIOSC

Marketplace > Biology > BIOSC > Evolutionary Processes and Speciation
Bree Scalzo
Foundations of Biology 2
Dr. Swiganova

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These are the book notes that I typed up before the lecture. Then during lecture I used yellow highlighter to emphasize what Swig went over, and then in green highlighter I added what was not in th...
Foundations of Biology 2
Dr. Swiganova
Class Notes
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This 14 page Class Notes was uploaded by Bree Scalzo on Friday March 6, 2015. The Class Notes belongs to BIOSC at a university taught by Dr. Swiganova in Fall. Since its upload, it has received 195 views.


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Date Created: 03/06/15
Chapter 26 Evolutionary Processes 1 Shifts in allele Frequencies that lead to adaptation a Natural Selectionl l increases frequencies of alleles that contribute to reproductive success in a particular environment b Genetic driftl39l causes allele frequencies to change randomly May increase or decrease tness c Gene Flow individuals leave one population join another and breed introducing new alleles d Mutation modi es allele frequencies by continuously introducing new alleles i HardyWeinberg principe 261 1 Analyzing change in Allele frequencies The HardyWeinberg Principle i Populationljgroup of individuals from the same species living in the same area at the same time and can interbreed and vary in possesses traits b The Gene Pool Concept i All the alleles from all the gametes produced in each generation go into a single group called the gene pool and then combine at random to form offspring c Two fundamental claims for the principle For evolution to occur some other factors must come into play 2 The HardyWeinberg Model Makes Important Assumptions v no mutation 1 3 How does the HardyWeinberg Principle Serve as a Null Hypothesis i Allows biologists to see if any evolutionary processes are taking place i 4 step analysis process 1 estimate the genotype frequencies by observation 2 calculate observed allele frequencies from the observed genotype frequencies 3 Use the observed allele frequencies to calculate the genotypes expected according to the Hardy Weinberg principle 4 Compare observed and expected values ii Looking at the data the proportions show that populations differ in allele frequencies Observed are close to expected iii Yes NM blood is in HW proportion and there is no evolutionary advantage to this allele 1 The Goodness of t x2Chi Square c Case Study 2 Are HLA Genes in Humans in HardyWeinberg Equilibrium i HLA codes for haplotypes Notices pathogens in our system ii Mating may not be random with respect to the HLA genotype iii Heterozygous individuals may have higher tness 1 Have wider variety Ch 262 2 How does Inbreeding Affect Allele and Genotype Frequencies a b Inbreeding because allele frequencies do not change in the population as a whole 39 3 How Does Inbreeding Affect Evolution a Can spread the rate of evolutionary change i Increases the rate at which natural selection eliminates recessive deleterious alleles alleles that lower tness from a population 1 Results from two main causes a Many recessive alleles represent lossof function mutations b Many genes especially those involved in ghting disease are under intense selection from heterozygote advantage a selection process that favors genetic diversity Ch 263 1 Natural Selection a If alleles are associated with the favorable phenotypes they increase in frequency while other alleles decrease in Before frequency Resultevolution After 2 How Does Selection Affect Genetic Variation i Genetic variationl l the number and relative frequency of alleles that are present in a particular population b Mode 1 A1 A2 c Mode 2 ol Mode 3 e Mode 4 3 Frequencydependent selectionl lcertain alleles are favored when they are rare but not when they are common 3 Sexual Selection lntersexual selectionl lselection of an individual of one gender for mating by an individual of another gender ii lntrasexual selectionl39l competing with one another of the same gender to obtain mates b Theory The Fundamental Asymmetry of Sex i Pattern and process theory 1 Pattern sexual selection usually acts on males much more strongly than females Traits that attract members of opposite sex are much more highly elaborated in males 2 Process the energetic cost of creating a egg is enormous whereas a sperm contains few energetic resources c Female Choice for quotGood Allelesquot i Most colorful males are the healthiest and best nourished d Female Choice for Paternal Care i Females tend to choose males that care for young or provide the resources required to produce eggs e MaleMale Competition i Territoryljan area that is actively defended and that provides exclusive or semiexclusive use by the owner 1 Large usually win ghts and they father offspring so leads to evolution of large body size f Sexual Dimorphism Results in Sexual Selection g Take Home Message i Ecology environmental selectionl lfavor traits that enable organisms to do things other than obtain mates such as survive in their physical and biological habitats Ch 264 1 Genetic Drift Expected B 5050 45 54 5050 47 51 5050 51 47 b Sampling Errorl l allele frequencies that change due to blind luck i Occurs many times in small populations a Computer Simulations b Genetic markerl39la speci c alleles that causes a distinctive phenotype 4 What Causes Genetic Drift in Natural Populations on the Green Iguana of Anguilla ii Each time a founder event occurred a founder effect is likely to accompany it changing allele frequencies through genetic drift b Genetic Bottleneck on Pingelap Atoll 2 Genetic drift occurs during genetic bottlenecks and causes a change in allele frequencies Ch 265 1 Gene Flow ELF i Equalizes allele frequencies between the source population and the recipient population F 2 Measuring Gene Glow Between Populations 3 Gene Flow is Random with Respect to Fitness 1 Mutation Ch 266 Pquot 4 Mutation as an Evolutionary Process How can they occur i Point Mutations ii Chromosomelevel Mutations iii Lateral Gene Transfer also known as horizontal gene transfer 0 Q Changes in makeup of chromosomes or in speci c DNA sequences do not occur in ways that tend to increase tness or decrease tness It just happens Experimental Studies of Mutation b Fitness Increases in Fits and Starts Studies of Mutation in Natural Population a Lateral Gene Transfer b Gene Duplication TakeHome Messages a 3 main points i Mutation is the ultimate source of genetic variation ii If mutation did not occur evolution would eventually stop Mutation alone is usually inconsequential in changing alees Chapter 27 Speciation Lecture 11 pt1 and 2 Speciationl splitting event that creates two or more distinct ancestral species Results from genetic isolation lack of gene ow and genetic divergence selection genetic drift and mutation proceeding independently in isolated populations Ch 271 1 How are species identi ed i Ways to identify species 1 Biological species concept 2 Morphospecies concept 3 Phylogenetic species concept bWidey applicable i Sexual asexual or fossil species c Disadvantages i May lead to naming of two or more species when there is only one polymorphic species with differing phenotypes 1 May look the same but not really ii Cannot identify cryptic species which differ in traits other than morphology iii The morphological features used to distinguish species are subjective 4 The Phylogenetic Species Concept a Identi es species based on evolutionary history of populations b Monophyletic groupl39lclade or lineage consists of ancestral population all of its descendants and only those descendants c Synapomorphyl ltrait that is found in certain groups of organisms and their common ancestor but missing in more distant ancestors iiEx Lactation and fur distinguish mammals dSpecies are de ned as the smallest monophyletic group on the tree of life fAdvantages i Applied to any population ILogical because different species have different synapomophies only if they are isolated from gene ow and have evolved independently 5 Species De nitions in Actions The Case of the Dusky Seaside Sparrow aimmin new J Eecl EnnLEPH lglfi39ml ninr dimming F i llvl lii uli m i ii 39i l EIEEE Egnn39 igajnw nae n39f39 iii39t39sisajnn i39gpwr Fquot u j F39iut39ni Flu m will arm nanbass quot l39 ll39l39ht39h ll quotarr 1 in delJul gain i ta i39ga39i39l 151 a I tutti Ii wa quotHal 39njtmti ii li a ugxif it Midi ul meal Ci hit Int finalLa 1723 gasauimgu a July iu39wari EZ r 39h l Jr39 nalise IEUIJ 5 Euml i i nu39rd a MC 5 quot39 IquotIquot 39 7 P w Jb39ina quot39i3r iinquotquotnquot ifsgj Ta39 EH ElbaJ aw laquot Ta iriur39ii i amt luff c39 unfit5 s hairquot llnmwi ari HPEJEEJTIE ai9r LED3 1 wta 5 twat a my I an F 39 i gil39n l lt 51W t a l iq wi ergm 1 211quotquot AW Hug5 3 t quotInquot 39sn39imr g rim quotfit 1 aa39itri39i quot1quot Fa quotiu39 39 E af39 wlii mi InfINT ittingUrsa aquot ja EEJun u 13 an winquot lunemagi i 371 WFIEE J55quot 1 Ch 272 1 Isolation and Divergence in Allopatry a Genetic isolation happens routinely when populations become geographically isolatedljallopatry b iii Biogeographyljthe study of how species and populations are distributed geographically Ch 273 1 Isolation and Divergence in Sympatry a Sympatryljwhen populations or species live in the same geographic area or at least close enough to one another to make interbreeding possible b Sympatric Speciationl lspeciation that occurs even though populations live within the same geographical area ii Initiating events 1 External events such as disruptive selection for extreme phenotypes based on ecological niches 2 Internal events such as chromosomal mutations 2 Sympatric Speciation by Disruptive Selection c Niche the range of ecological resources that a species can use and the range of conditions that it can tolerate i Even though species may live close sympatric speciation may occur if there are several different niches 1 Ex Apple and hawthorn ies 3 Sympatric Speciation by Polyploidization 2 Are reproductiver isolated from the original diploid population and thus evolutionary dependent because diploid and tetraploid offspring tend to be sterile 1 Is functioning since it has two complete sets iv Why is speciation by polyploidy so common in plants b Speciation by polyploidization is virtually instantaneous common filwiiwlfquotwquot W quotin i m Mechanism mf gmpmtric p i i n Elma Emmy1E l ku EVEIEE Il n pertain UP 39ii lf 2 Lust m aural 2am NJ fJ39 irtquot 2 In Lif uli l a l 339 2 u39r ass tile Jl Ew j39tlilqiwl Bacallquot fall I39 39E E Dru1 in Us rtsim iquot 395 ix ha 50 is quotman mu 55 mitum 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39E39Zf f i l in irat iugwr39ia Luigi Macg in ii quotEL39 RE a39 59 E I Ch 274 1 What Happens When Isolated Populations Come into Contact 2 Reinforcement a If two populations have diverged extensively and are distinct genetically it is reasonable to expect that their hybrid offspring will have lower tness then their parents a Hybrid zonesl39la geographic area where interbreeding occurs and hybrid offspring are common i Can be narrow wide long or shortlived 4 New Speciation through Hybridization b The hybrid offspring created a third new species that had unique combinations of alleles from each parental species and therefore different characteristics i Creating speciation through hybridization experimentally 1 Mate individuals from the two parental species and raised the offspring in a greenhouse 2 When these hybrid individuals were mature the researchers either mated the plants to other hybrid individuals or backcrossed then to individuals form one of the parental species 3 The breeding program continued for 4 generations before the experiment ended The experimental lines were backcrossed twice and they were mated other hybrid offspring three times c Secondary contact of the two populations can produce a dynamic range of possible outcomes fusion reinforcement hybrid extinction or creation of species


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