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Campbell Bio Unit 4: Mechanisms of Evolution

by: Muhammad Raza

Campbell Bio Unit 4: Mechanisms of Evolution BIL 160

Marketplace > Biology > BIL 160 > Campbell Bio Unit 4 Mechanisms of Evolution
Muhammad Raza
GPA 4.0
Evolution and Biodiversity
Dr. Van Dyken

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About this Document

Campbell Biology chapters 22-25 detailed notes. Great preparation material for the exam on Unit 4!
Evolution and Biodiversity
Dr. Van Dyken
Study Guide
Campbell Biology, Chapter 22, Chapter 23, Chapter 24, Chapter 25
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This 25 page Study Guide was uploaded by Muhammad Raza on Sunday February 1, 2015. The Study Guide belongs to BIL 160 at a university taught by Dr. Van Dyken in Fall. Since its upload, it has received 411 views.

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Date Created: 02/01/15
Chapters 2225 Study Guide 01122015 Evolution The Central Unifying Principle of Biology What is evolution 0 Just like gravity evolution describes patterns facts and the processes that cause these patterns theory 0 Evolution is the change in the genetic code andor phenotypic distribution of a species over time 0 Evolution explains and predicts patterns of biodiversity and organismal design Pattern 0 Life is incredibly diverse Physical Behavioral o Asexual vs sexual o Monogamous vs Polygamous Pattern 1 The Tree of Life 31x10quot9 base pairs per haploid human genome Phylogeny o Humans and chimps 98 similar Humans and old world monkey 93 similar Humans and new world monkeys 89 similar to humans Line species up and make a tree This results in the tree of life in the form of Bacteria Archaea and Eukaryota Tree terminates at kingdom level 0 Fact All life on earth ts on a single phylogeny We call this phylogeny The Tree of Lifequot 0000 Every species on earth uses the exact same genetic code a Same structure for heritable material DNA a Mechanisms of DNA replication n Transcription and translation I Same genetic code a Etc 0 Inference from TOL All life on earth is related by descent from a common ancestor 0 Theory Evolution is the process that generates the pattern of the TOL Putting phenotypes on the TOL o How many cervical vertebrae do these animals have All mammals always have 7 cervical vertebrae 0 Fact Closely related species share structures that are not related to function Homologous structures are anatomical resemblances due to common ancestry not function Tetrapods All had 4 limbs and 5 digits No speci c reason Just existence 0 Homology Single humerus Radius ulna carpals metacarpals and phalanges a Human cat whale and bat all have same basic structure of a limb modi ed to some extent Homologous structures can be used to classify extinct organisms into the phylogenetic tree a Astragalus A type of ankle bone of extinct Pakicetus and extant species of mammal The double humped feature is a homology shared by even toed ungulates Based on this evidence cetaceans are more closely related to ungulates Modi ed wrist bone that looks like a thumb in pandas is homologous to wrist bone in other mammals Evolution works by modifying existing structures Comparative embryology reveals anatomical homologies not visible in adult organisms In Vestigial structures are a special type of homology Vestigiality refers to genetically determined structures or attributes that have apparently lost most or all of their ancestral function in a given species but have been retained through evolution Molecular homology shared gene order synteny a Share the same gene order due to common ancestor a Shared degenerate codonssynonymous nucleotides n Pseudo genesquot Non functional genes 0 Convergent Evolution How NOT to make a tree Convergent evolution is the evolution of similar or analogous features in distantly related groups Analogous traits arise when groups independently adapt to similar environments in similar ways a Coloration of different species in the same environment look the same due to common purpose a Different mutations in garter snakes confer resistance to tetrototoxin from a species of salamanders in different species of garter snakes Evidence of convergent evolution Pattern 11 Tree of Life in Space 0 More closely related species are actually closer to each other geographically Pattern 12 Tree of Life in Time Extinct species resemble extant ones Pattern 2 lntraspeci c Variation Humans differ genetically from one another by about 1 Fruit ies differ genetically from one another by about 1 Pattern 3 Adaptation Organisms appear to be exquisitely designed to live in their environment Pattern 4 Maladaptation Organisms are not perfectly designed They have numerous design aws and defects 0 Design via modi cation of existing structures forces there to be many design compromises that wouldn t occur if you could build each species from scratch Patterns of Life 0 Extraordinary intersoeci c variation MilliOins of extant species Tree of Life All species are related MACROEVOLUTION 11 Tree of Life Iln Sipace Closely related speCIes often clluster geographically 12 Tree of Life iln Timie Extinct species resembllle extant ones 2 Extraordinary intrasoeci c variation Adaptation MICROEVOLUTIDN 4 Maladaptation requires both Macro common descent and Microevolutionarv explanations Macroevolution and macroevolution We can separate the study of evolution somewhat arbitrarily into microevolution and macroevolution o Microevolution studies the patterns and processes of evolution within a species lts pattern is genetic an d phenotypic variation within species lmportantly microevolution tells us all the forces responsible for an action 0 Macroevolution Major evolutionary change The term applies mainly to the evolution of whole taxonomic groups over long periods of time Microevolution The Process of Evolution Evolution of antibiotic resistance Macrolide antibiotics bind bacterial ribosomes inhibiting translation Erythromycin o No drug ribosome tunnel open 0 With drug the ribosome tunnel is blocked 0 Sequence resistant vs non resistant genomes Line up and associate changes between these two types and nd resistance DNA sequence identi es variation in L4 ribosome gene in MRSA O Results in a codon change with is a missense mutation causing the amino acid to change from lysine to glutamic acid OOOOO Samples of staph aureus from general population of g allelestotal of alleles P Frequency of a allele q1p Doesn t tell you about variation We want the probability that you want one to be different allele at the same locus Pqqp2pqH El El El El H for heterozygoisty 2pUp dHdpO12p p12maximum Value of heterozygosity at the maximum is 5 0 Max Pt1P9t DeltapPt1ptO Deltap cannot equal zero for evolution to occur 0 What results in p frequency changing o Mutation 0 Genetic drift chance 0 Natural Selection 0 Gene owmigration Microevolution The change in allele frequency in a population over type Processes of Microevolution Natural selection 0 Genetic drift Mutation 0 Migration Sex and recombination Natural Selection 0 Charles Darwin was the greatest naturalist of all time 0 Over ve decades he collected an incredible amount of biological data 0 His genius lay in identifying patterns in this data and then proposing a theory that provided a simple process that explained all these patterns The process he discovered is natural selectionquot Darwin s four postulates 1 Many more individuals are born every generation than could ever possibly survive to reproduce i Exponential growth of humans 1 Generation time of humans 20 years doubling time 2 Not every individual born can survive to reproduce ii Thomas Malthus is credited with being the rst to express the fact that population growth must be limited by nite resource supply iii To Darwin the limits to population growth implied that there is a struggle for existence over access to resources There are necessarily winners and losers in life 2 Individuals Within a species differ intraspeci c variation i It is the fuel for natural selection ii Variation is the ultimate reality that an ideal type was the illusion 3 Some variants are better able to survive and reproduce than others winners and losers in their struggle for survival are not random i Fitness 1 Measure of reproductive success a De nition The expected umber of offspring an individual produces in its lifetime that survive to reproductive age 2 2 components Fitness is the product of the two a Viability The probability of surviving to reproduce b Fertility The expected number of offspring an individual produces at reproductive maturity 4 Fitness variation can be reliably passed down from parents to offspring i Technical term Heritability traits are heritable Allele Frequency Fitness A P Wa a 1p Wa Wbar PWA 1PWa Wa PWA39Wa Pt1 39Pt PtWAWbar AP PtWA39 thaWbar PtWA39 Pt2WA39WaWbar APP1PMA QMm underlined is the difference in relative tness of the two Bolded tells you about genetic variation Underlined tells you that there must differences in tness Heterozygosity genetic variation in a population 2P1P The strength of natural selection is proportional to heterozygosity 0 We see heritability variation and tness in terms of Darwinian principles 0 Struggle for existence is missing Not necessary for natural selection 0 Heritable variation and differences in tness are what is important 0 Natural Selection 3 Requirements ON EXAM Natural selection requires heritable variation in tness 0 These three criteria are necessary and suf cient for natural selection to occur Variation n Generated by DNA mutation or recombination Differential reproduction n Ecology Heredity a DNA transmission 0 If you have variation and heredity All individuals have equal tness so no aee does better than any other In the equation WAWa is zero so natural selection is O o If you have variation and differential reproduction No natural selection Change within a generation is not passed on to the next generation There is no lasting change P is not existent So equation is unde ned Natural selection requires that tness differences have a genetic basis 0 If you have differential reproduction but no heredity but no variation Fitness is heritable but the population is genetically uniform Crucial Concept Natural selection acts on phenotypes and as a consequence changes the frequency of genotypes in the population Natural selection can only quotseequot the phenotype This is why heritability the correlation between phenotype and genotype is necessary 0 Three types of natural selection 0 Directional Distribution shifts in one direction 0 Diversifying Two extreme types live Intermediate types are selected against bimodal distribution Speciation o Stabilizing Intermediate types are the most t Extremes are selected against Natural selection is the only process that leads to adaptation Populations Gene Pool and Evolution 0 Evolution is the change in allele frequencies in a population over time o Evolutionary processes act on populations not individuals 0 Each life cycle represents a single generation Evolution only occurs if allele frequencies change from generation to the next 0 Evolutionary processes act on speci c phases of the life cycle at different time points for different reasons Genetic Drift Random uctuations in allele frequency 0 Unlike natural selection this process is NOT deterministic repeating this process again will typically lead to a different outcome Mutation does not cause genetic drift Highlighted plants 39 leave pflspr ing Grill 5 tiff 2 quot 39 Grill 2 If ID plants A quot a 1 1D plantc leave vii leave pil39fspring quot 39 ii f l I CECE eneratipan 1 Eeneratian 2 Genra tipn 3 p tirequencv pl Tiff 1 p EIE p 1D a flrequencv pl Ehquot 33 a US a 393th it lFiglulli39 235 Genetic drift This small vvlltlflptver pppulatipn has a stable site of ten plants Supppse that by chance pnlv five plants pl generatipn 1 ithpse highlighted in vellpvv prpduce l er tile pflspring this cpulcl pccur for example ll pnlgr these plants happened tp grew in lipcatipn that provided enpugh nutrients tp tuppprt the prpductlen pf pflspring again lav chance enlv vae plants pl generation 3 leave fertile offspring ts result lav chance the frequency pl the quotfallele first increases in generatipn 2 then falls tp gem in generation 3 7 M I M an F visa the 5m av area m in Mastering iullugy for the planetquot a p animation pn Mechanisms of Evolution Why do allele frequencies uctuate randomly 0 Only a nite number of individuals can persist Darwin s struggle for existence leading to finite sampling variancequot Tons of offspring are produced but only a much smaller fraction will actually survive causing random sampling effects 0 Chance differences among individuals in number of offspring they produce Chance differences among individuals in survival 0 Diploid meiosis just by chance heterozygotes will only pass on one allele at a locus or will pass them on in nonequal proportions 0 Random walks pervade all aspects of life from the microscopic motions of molecules quotBrownian motionquot to the diffusion of heat through a solid to the price of stocks on wall street In fact if you understand the mathematics of genetic drift you can get a job at a hedge fund and buy a yacht Smaller populations have higher genetic drift 0 Allele frequencies undergo a random walk under genetic drift The size of allele frequencies uctuations is inversely related to population size Drift is weaker in larger populations Why a Larger the sample size the lower the deviation from the mean Less sampling error a If genetic drift is the only force acting over a certain period of time it will cause loss of genetic variation and xation of one of the alleles O O u If we look at the process backwards in time you can see that all individuals at one time have a common ancestor in the past 0 Consequences o Allele frequencies uctuate randomly over time 0 Loss of genetic variation one allele will x in the population with probability 1 in in nite time Genetic Bottlenecks Sometimes there are events in a population s history that cause a sudden large reduction in population size for all or a subset of the population 0 Environmental catastrophe ood drought 0 Disease epidemics bubonic plague o Invasive species rapidly outcompetes or over predates an endemic o Colonization event 0 What are the genetic consequences of a bottleneck 0 Major sampling effect 0 Large source population into a smaller sample Cll iglli il 39 Bullieneeiting Summing pepulaLion evem population 1 Figure 23M The bottleneck effett gimme jLISli feeJ r rieir bles Izl39ireuglri the r39iarrtiw netlc Lil a bottle l3 er ialegeua to drastic reduelien in the glee til 3 popule liun By alienate blue r narbles ere merrepre aerated in Lhe ELIWwil g pepulaLien and geld marblee are abaenL The farther you are from source population the more bottlenecking will happen Mutation All heritable variation ultimately comes from mutation 0 Simple DNA replication error DNA polymerase copies 1000 bps DNA polymerase error rate very small Ecoli 1 mutation300 generations Humans 2070 mutationsgeneration n Majority is deleterious harmful Mutations are random Mutation is blind to its tness effect Population does not get a mutation it needsonly get it if it occurs at random 0 Types of errors 0 Point mutation Nonsynonymousmissense Synonymous same amino acid even after a Most subject to pure genetic drift a Natural selection cannot see this Non coding introns or intergenic DNA 0 Insertions and deletions Can cause frame shifts o Duplications Migration 0 Gene ow consists of the movement of alleles among populations Alleles can be transferred through the movement of fertile individuals or gametes Gene ow can increase the tness of a population 0 Consider for example the spread of alleles for resistance to insecticides Insecticides have been used to target mosquitoes that carry West Nile virus and malaria Alleles have evolved in some populations that confer insecticide resistance to these mosquitoes The ow of insecticide resistance alleles into population increase tness and survival rate 0 Gene ow is an important agent of evolutionary change in modern human populations 0 Dairy agriculture resulted in migration and nonlactose intolerance Sex and Recombination Novel gene combinations genotypes can be created by sex and recombination via 3 mechanisms 0 Independent assortment during diploid Meiosis creates novel chromosome combinations in resulting haploid gametes o Crossing 0vertypically 1 event per chromosome arm per meiosis changes allelic combinations within a chromosome 0 Fertilization brings together novel diploid combinations of chromosomes All of this results in reshuf ing of genes Comparing Forces 0 Mutation o 1 tness advantage 0 Genetic Drift 0 Can t say 0 Natural Selection 0 Strongest Mutation and genetic drift are constantly acting in a population they never stop Positive natural selection is much rarer Purifying selection is the most common form of selection 0 There is no one evolutionary force that is more important than the other Maladaptation revisited Species are not perfectly adapted 0 Historical constraints Evolution can only build organisms from pre existing parts 0 Design compromises Making one thing better often has deleterious side effects 0 Actions of other evolutionary forces also constrain natural selection 0 Genetic drift Favorable alleles may be randomly lost 0 Mutation Populations must wait until bene cial mutations occur by chance Deleterious mutations are constantly occurring o Migrant Individuals may disperse into habitats that they are maladapted to The overwhelming majority of selection is negative purifying selection The overwhelming majority of mutations are deleterious Randomly altering a structure is more likely to break it that improve it The equilibrium between recurrent mutation and purifying selection is called mutation selection balance Most of the genetic variation within populations is maintained 0 The strength of natural selection is proportional to heterozygosity 0 TEST QUESTION Diploids and HardyWeinberg equilibrium 0 Sexual dimorphism is ubiquitous 0 Cause sexual selection is natural selection for mating success o It can result in sexual dimorphism marked by differences between the sexes in secondary sexual characteristics Not a process a pattern 2 Types of Sexual Selection lntrasexual selection is direct competition among individuals of one sex often males for mates of the opposite sex lntersexual selection often called mate choice occurs when individuals of one sex usually females are choosy in selecting their mates 0 Male showiness due to mate choice can increase a male s chances of attracting a female while decreasing his chances of survival Fitness tradeoff Makes them more vulnerable to predation a You do one thing that makes your tness go up but it also causes your tness to decrease In Allows predators to better see you as well as being related to high energy costs Evolution of lntersexual Selection Heterozygosity is the genetic diversity of the population 0 A heterozygote is an individual in the population that has two alleles in one locus Why does female choosiness evolve o The good genesquot hypothesis suggests that females chose males that possess traits signaling high genetic quality Traits that are costly to develop and maintain o This can lead to the evolution of female preference for costly male traits that are honest signalsquot of male genetic quality which then leads males to evolve ever more elaborate traits and females to become even choosiereading to quotevolutionquot Speciation Behavioral isolation Habitat isolation Polyploidy Allopolyploid species with multiple sets of chromosomes derived from different ancestral species Why plants 0 O 0 Self fertilization You can t reproduce with anyone else around you More chromosomes more gene products Yields more fruit Hybrid Zones Region in which members of different species mate and produce hybnds Hybrids are the result of mating between species with incomplete reproductive barriers Hybrid zones may form when allopatric subpopulations reconnect this may select for reinforcement active natural selection to prevent hybrids from being viable the populations continue to diverge O O O Hybrids can have low tness leading to little genetic exchange Stability maintenance of two species with a third and natural selection not acting at all all three are good to go Fusion They remate and there is a combining into one species Reinforcement Strengthening reproductive barriers Where reinforcement occurs reproductive barriers should be stronger for sympatric than allopatric species 0 Eg in populations of ycatchers males are more similar in allopatric populations than sympatric populations Selection wants there to be differences in sympatric and doesn t care about allopatric as there is no need they are already divided What must be true about the tness of hybrid offspring in crosses between these two species a Reinforcement is only selected for if hybrid offspring have reduced tness Fusion Weakening reproductive barriers lf hybrids are as t as parents there can be substantial gene ow between species o If gene ow is great enough the parent species can fuse into to Steps in the Origin of Life 0 All life on earth is composed of membrane bound self replicating organic molecules 0 Abiotic synthesis of small organic molecules 0 Joining into macromolecules Origins of organic compounds Earth s atmosphere 46 bya 0 H20 Vapor and volcanic chemicals Very little 02 Lots of N ammonia NO N02 Lots of C02 methane Energy A quotreducingquot atmosphere OOOOO 0 Experiments simulating earth s early atmosphere produce organic molecules aa s nucleotides from inorganic precursors Deep Sea Vents o The rst organic compounds may have been synthesized near submerged volcanoes and deep sea hydrothermal or alkaline vents Rich in hydrocarbons minerals and energy Rocks are porous these pores have lots of catalytic minerals such as iron that can act as sites for chemical rxns Ancient ocean had high pH vents low pH l a pH gradient enabling chemical work Meteorites o A 45 bya old rock landed in Australia in 1969 contained gt 80 aa s in large quantities o MillerUrey Experiment 0 Water vapor goes through ask with methane ammonia hydrogen gas an electrode condenser and cold water 0 The cooled water contained organic molecules 0 In 1953 about 10 amino acids were yielded and in 2008 around 20 0 Good yield as well Dawn of Natural Selection Ribozymes 0 RNA molecules 0 Catalyze many different reactions including Self splicing Self replication autocatalysis Most of the core steps of the central dogma are carrid out by RNA H mRNA tRNA rRNA The RNA World Hypothesis Protocells Macromolecular dilemmas o Diffusion seriously limits rates of biological reactions 0 Self replication requires close proximity of multiple enzymes in suf cient concentration 0 Freely diffusible products of metabolism include enzymes necessary for further reactions are vulnerable to sel sh cheaters Solution Protocells o Protocells are aggregates of abiotically produced 0 Lipids in aqueous solution minimize free energy by spontaneously forming spherical bilayers o This happens spontaneously and are called liposomes 0 Things can diffuse into and out of the lipid bilayer The Origin of Life 0 Organic compounds for life can form spontaneously from inorganic precursors form selfreplicatingautocatalytic polymers and incorporate into spontaneously self replicating protocells which replicators can also build by synthesizing lipids The origin of life is just chemistry 0 Once formed though these primitive replicators are continuously improved by natural selection Radiometric dating 0 How do you know original composition UraniumLead Dating 0 The mineral zircon incorporates uranium but not lead into its crystal lattice when forming o Uranium 238 decays to lead 206 with a half life of 45 billion years Time Periods Hadean Origin of solar system and earth Archaean o Prokaryotes and a little atmospheric o o Proterozoic Multicellular eukaryotes and single celled eukaryotes Prokaryote Evolution and Diversi cation Oldest known fossils stromatolites o 35 billion years ago Photosynthesis and the Oxygen Revolution 0 Most atmospheric OZ is of biological origin 0 OZ produced by oxygenic photosynthesis reacted with dissolved iron and precipitated out to form banded iron formations Lead to banded iron formation Rocks dated around 25 billion years ago Most iron ore comes from these bands in Rocks As soon as oxygen sinks are fully saturated oxygen builds up instantaneously to become atmospheric OZ Takes only 2000 years for OZ to be repopulated in the atmosphere through photosynthesis if all OZ in the atmosphere is taken away 0 Single Celled Eukaryotes o 22 Billion years later after the oxygen revolution 0 Ancient archaea that took up proteobacteria into its cell 0 Archaeal cell became nucleus and proteobacteria became mitochondria 0000 O All mitochondria are related they share a common ancestor This lad to ancestral heterotrophic eukaryote 0 Then it engulfed photosynthetic bacterium leading to the formation of plastids Ancestral photosynthetic eukaryote All Plastids do not share a common ancestor o Endosymbiotic Theory Prokaryotic ancestors of mitochondria and plastids probably gained entry to the host cell has undigested prey or internal parasites Serial endosymbiosis supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events a Mitochondria have their own DNA ribosomes and plasma membrane as do chloroplasts evidence Evolution of Multicellularity First multicellular organisms o 15 bya molecular clock 0 12 bya fossil evidence small algae o Colonial collections of autonomously replicating cells Multicellularity allows evolution of division of labor 0 Some cells specialized for different functions 0 Reproductive division of laborquot separation into germ line and somatic cells Ediacaran biota o Assemblage of larger and more diverse soft bodied organisms 600 mya n Unlike anything else we see today 00 o The Cambrian Explosion o Sudden appearance of fossils resembling modern animal phyla in the Cambrian period 540 mya Get arthropods mollusks annelids brachiopods chordates echinoderms cnidarians and sponges Colonization of Land 0 Plants fungi and animals 500 mya o Symbiotic relationships between plants and fungi Common today Date from this time Plate Tectonics Convection of the mantle driven by heat from the inner core causes plates to move over time o 2cmyear 0 Same rate as nails grow 0 The land masses of Earth have formed a supercontinent three times over the past 15 billion years 11 billion 600 million 250 million years ago Consequences of Plate Tectonics Formation of the supercontinent Pangaea about 250 million years ago had many effects 0 A deepening of Ocean basins o A reduction in shallow water habitat o A colder and drier climate inland Paleozoic Pangaea Mesozoic 2 larger ones a A lot of allopatric speciation n Then into oating close current continents Cenozoic a What we have now present times Mass Extinctions The fossil record shows that most species that have ever lived are now extinct 0 Can be caused by changes to a species environment 0 At times the rate of extinction has increased dramatically and caused a mass extinction Last one was in Mesozoic era under the cretaceous and Cenozoic boundary around 655 million years ago 0 End Permian mass Extinction around 250 million years ago About 96 of all species that existed went extinct End Permian Mass Extinction The mother of all mass extinctions o Likely caused by extraordinary volcanic activity C02 level rise a Global temperature rise a Ocean acidi cation Eutrophication due to Phosphorous a Massive algal blooms Block sunlight 0 Ocean deoxi cation To do increased biological oxygen demand Is a 6th Mass Extinction Under Way Numbers to Know Earth 46 bya Life on earth 38 bya Eukaryotes 22 bya Cambrian explosion 540 mya Colonization of land 500 mya Permian mass extinction 250 million years ago Last mass extinction 655 million years ago Adaptive Radiation Rapid evolution of diversely adapted species from common ancestor upon introduction to new environmental opportunities Tempo of Speciation Punctuated Pattern Gradual pattern 0 Relative time scales issue The punctuated pattern in the fossil record and evidence from lab studies suggests that speciation can be rapid o Proved by extinction The interval between speciation events can range from 4000 years some cichlids to 40000 years EvoDevo 0 An organisms form is determined by its development Evolution modi es form by genetically modifying the organism s developmental program 0 Genes that program development control 0 Rate of 0 Timing of 0 Spatial pattern of Genes expression 0 A mutational change causing a change in patterns of gene expression can in turn change an organism s form as it develops o This creates phenotypic variation possibly leading to a difference in tness between for selection works on variation Changes in Spatial Pattern Genes control placement and organization of body parts Hox genes 0 Hox genes also known as homeotic genes are a group of related genes that control the body plan of an embryo along the anteriorposterior headtail axis Single Gene Speciation Rapid speciation Different chirality in shell 0 Mechanical prevention of insemination parts don t line up this leads up to reproductive isolation Abrupt speciation Most speciation is not like this Changes in Rate and Timing Heterochrony o Evolutionary change in rate or timing of developmental events o Paedomorphosis Retention ofjuvenile characters in the adult Adults look like juveniles n Lactase Persistence in Humans Typically lactase is shut off in mammals after a certain age presumably because it is no longer need post weaning All mammal young drink milk but no adults do 0 Except for in some humans heterochrony About 8000 BCE humans in the middle east invented dairy agriculture milking of cows goats camels and other large domesticated mammal species as a rich source of calories and nutrition 0 The gene MCM6 contains an enhancer of lactase gene meaning that it regulates the expression of lactase n Adults look like juvenile apes Humans are paedomorphic apes Changes in timingPaedomorphosis Adult organism retaining juvenile features as a mature adult 0 Result juvenile species and adult species Progenesis sexual organstissuescells develop faster Neoteny somatic organs develop slower n Neotenic apes Evolution is a heritable change in a population 0 Individuals do not evolve Evolution is the change in allele frequencies in a population over time because they are heritable


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