Notes on lectures 4-6
Notes on lectures 4-6 BIO 160
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This 10 page Class Notes was uploaded by Avi Fox on Friday February 6, 2015. The Class Notes belongs to BIO 160 at University of Miami taught by Dana Krempels in Spring2015. Since its upload, it has received 208 views. For similar materials see EVOLUTION & BIODIVRSITY in Biology at University of Miami.
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Date Created: 02/06/15
Lecture 46 Species Biological species concept all member s of a population that can interbreed in nature Macroevolution speciation Speciation the generation of two or more reproductively isolated new species from an ancestral species Means the 2 new species are reproductively isolated can no longer produce fertile viable offspring Synonymous with macroevolution Can happen quickly or gradual depending on the species Microevolution population that undergoes genetic respect to other populations of the same species but haven t become reproductively isolated Still same species Evidence of Microevolution 1MRSA methicillin resistant Staphylococcus aureus S aureus Normally harmless but there are opportunist bacteria Usually treat staph infection with penicillin s B lactam S aureus became resistant to methicillin by inactivating B lactam ring with the enzyme B lactamase Mutations of the genes encoding these enzymes changed them into the various B lactamases AS antibiotics evolve by humans bacterial enzymes mutate and the beneficial mutations are selected 2 Antibioticresistant Mycobacterium tuberculosis causes tuberculosis in humans In mid 20th century antibiotics nearly eradicated TB New TB came back in developing nations some resistant to antibiotics it was sensitive to Person with AIDS was diagnosed with TB treated him with rifampin and isoniazid and it cleared He came back 2 months later with TB and died New TB came back resistant to rifampin There was both sensitive and resistant strains were present in the patient The variation was heritable Differential reproduction happened because only those with the point mutations survived A nonrandom subset of the original population remained after selection 3 North American House Sparrow body mass and wing surface area House sparrow brought over by Shakespearean society Bergman s rule animals in higher latitudes colder climates tend to have larger bodies than those in lower latitudes Happens not only across species but also within a species across a wide geographic range Northern populations are darker the ones down here are more slender and lighter 4 Evolution of ower size Evidence Macroevolution many speciation events have been observed Evidence what the rocks and fossils tells us Fossils are rare Most dead things are consumed and destroyed relatively soon after they die Fossils come from hard body parts rapid burial protection from scavengersbacteria protection from oxygen Either body parts or trace fossils created by living things like castings gastrolithsstones in the stomach coprolithes poop Molds casts entire body of the organism replaced by minerals Unaltered fossils composed of actual matter from the organism encased in preserving materialamber mummified arid conditions frozen Altered fossils Permineralized spaces in the tissue are filled by minerals over times Mineralized tissues are fully replaced by minerals but keep their shape Relative Dating comparing two strata to determine which ones are older or more recent Doesn t give absolute age Sandstone Limestone Shale nicest fossils Gypsum Conglomerate Stratigraphic column vertical placement of rock layersunits in a particular location Principle of superposition younger layers cover older layers of sediment Principle of Fossil Succession organisms that are similar are going to be found in closer strata Principle of Crosscutting Relationships Principle of Deformation Need radiometric dating for absolute age Homologycharacteristic shared by two species that is similar because of common ancestry Humans didn t evolve from monkeys they share a common ancestor Different Organisms don t evolve from living organisms They give rise to similar species Jaw and bone in middle ear are homologous to the gill arches Morphological shapeform homology species placed in the same taxonomic category show anatomical similarities Ontogenetic ontogenyembryo development homology species placed in the same taxonomic category show developmental embryological similarities Any species that show similar embryonic development show common ancestry Molecular homology species placed in the same taxonomic category show similarities in DNA RNA and protein 1 Morphological Homology Structures derived from a common ancestral structure are called Homologous structures Evolution a process of remodeling a population over the course of many generations Recognizing homologies same basic structures same relationship to others same development skate has fins that fuse into the gill arch and create the dinner shape Phylogenies family trees of living organisms represented as branching diagram called an phylogeneticevolutionary tree Nodes branches on the tree shows extinct closest related ancestor hash marks on the tree show a new evolutionary innovation shared by all the groups under it Shared characters studying both extant and extinct species and comparing their physical and chemical characteristic to tell learn about evolution Primitive characters plesiomorphy something that hasn t changed very much from the ancestral form All vertebrates have a bony tail posterior to the anus Different vertebrates have evolved differently shaped tails Only the presence of a tail is primitive Derived characters apomorphy relatively modified from its original ancestral form The modified shapes of tail or the loss of the external tail May be atavistic reminder human With tail Symplesiomorphy shared primitive character across taxa Synapomorphy shared derived character across taxa The more recent 2 species diverged the more synapomorphies Unique synapomorphies found only in a single group provide strong evidence for the common ancestry of members of that group More useful When trying to figure out common ancestry Clade related group that all branches together Synapomorphies unique to Mammals mammary glands hair and muscular lips Analogous Structures and Convergent Evolution Analogous structures serve the same function in 2 species but aren t derived from a common ancestral structure but from convergent evolution Wing of a butter y and Wing of a bat Convergent Evolution Process in which two distinct lineages evolve a similar characteristic independently of one another This often occurs because both lineages face similar environmental challenges and selective pressures All animals go through the same embryonic sequence Go from zygote to a hollow ball K 7 7 5 fgl i I F I 39 V g Gleavag Eras5 miim bla tula V Ea trurlmmh Archenternn En aderm Ectn erm E Ia itup re aatrrula apwig Paareon Edmatlan II39HG pubii iEl39iing as E39raniamin Wmming a Protostomes blastopores become the mouth Bilaterally symmetrical Deuterostomes blastopores become the anus with a secondary opening becoming the mouth Humans atworms Butter ies are protostomes bats are deuterostomes Most recent common ancestor could have been gastrea grastula with the ability to reproduce or the Urbilateria a simple atworm that was just barely crawling grastula Therefore the bat and butter ies wings must be analogous Wings walking limbs both are in them but they arose independently Craniums of vertebrates and exoskeleton fusiform shape of fish and cetaceans whales and dolphins Sharks swim sideways dolphins swim up and down because it relates to their life out of the water Little genotypic change can lead to big phenotypical expression Stephen Jay Gould Exaptation trait that would accidently come in random events that happened to be good A feature that performs a function but that was not produced by natural selection for its current use Bird feathers the form of feathers is an adaptation for insulation and an exaptation for ight All the stories we hypothesize for the data may just be stories Vestigial characters structures that have marginal if any use to the organism in which it occurs Pelvic spurs in python snakes appendix in humans helps in other taxons in digestion and is larger in embryo of humans semilunar fold in the human eye loss of eyes and vision in cavedwelling animals It becomes vestigial through natural selection because these structures weren t cost effective and those who had them probably didn t reproduce Ontogenetic Homology as a zygote most species look the same and the more related they are the longer they maintain similar development Chimps and humans have the same embryonic development up until towards the end evodevo the study of evolution of development Ontogeny Recapitulates Phylogeny Ernst von Haeckel bent the data He suggested that as we developed we went through less complex animals leading up But the truth is all related species develop together and then begin to branch off More complex adults forms are the result of change in embryo such as changes in timing of character development reduction or loss of embryonic characters greater complexity added as development proceeds Ontogeny the process of embryo development Phylogeny species evolutionary history Timing is everything Differences in ontogeny among taxa are not trivial such changes re ect the evolutionary relationship of those taxa and the modified development that resulted in one species becoming 2 Claws of the baby Hoatzin Transcription factors protein that turns onoff genes on the DNA The amount can change the phenotype Heterochrony changes in the timing of ontogenetic events between related species Can be caused by small genetic changes that may not even be alteration in DNA sequence but in the timing of particular genes being expressed Isometric growth all body parts grow at the approximately the same rate and the adult proportions are about the same as the juvenile Allometric growth different cell linesbody parts grow at different rates resulting in a human adult with proportions different than newborns Somatic cell body cells package that carries germline cells Germline cell one that has potential to undergo meiosis to become a haploid gamete Heterochronic mutation that causes them to reproduce at a younger age Neoteny germ line cell development proceeds at the same rate but the somatic cell development slows down Progenesis somatic cell development remains the same but germline development is accelerated compared to the ancestor Paedomorphy reproductive adult that has a more juvenile form of ancestral species Quickly can cause reproductive isolation 1 Common mudpuppy salamander that retains its juvenile gills as an adult and doesn t leave the water 2 Domestic dog breeds look more like juvenile wolves than adult 3 Homo sapiens re ect a prolonged juvenile period relative to that of chimpanzees Heterochrony zebra stripes being wider or narrower depends on when the genes are turned on Phylum Chordata we are Craniata Cephalochordata and Urochordata Have 4 characteristics in embryoniclarval state Tail posterior to the anus Dorsal Nerve core that starts off hallowneural crest Muscles arranged in bundles sarcomeres 6pack is a remnant of this Cartilaginous notochord Cephalochordata lancelets closest related Pharynx is important in embryonic development for evolutionary relatedness In us notochord becomes the discs between vertebrae Molecular Homology the more recently 2 species descended from a common ancestor the more similar their DNA sequences HOX Genes determine the identity of the body segment Where the appendages go Genes are expressed anterior to posterior Homeodomains transcription factors Chromosomal homology Synteny shows common ancestry from the shared pieces of chromosomes Protein Homology compare amino acid sequences in hemoglobin Level Evolution operate on Individuals don t evolve in a single lifetime we can adapt Populations evolve over generations Evolution is the result of natural selection at the level of the geneRichard Dawkins SELFISH GENE expressing the gene centered view of evolution The more 2 species are related the more genes they will share Genes that promote their own passing on to the next generation can be considered selfish Evolution change over time Organic Evolution change in living organisms over time Microevolution genetic change within a species over generations Change in gene frequency from one generation to the next within a population Do this by measuring allele frequency By the hardyWeinberg equilibrium can determine what it should be if its not under evolutionary change Noticeable population differences depending on where they live Antibiotic resistant bacteria changing allele frequencies and gaining new alleles over generations Macroevolution evolution above the species level including speciation defined by reproductive isolation Reproductive isolation within a population resulting in 2 new species Diversification of major lineages of organisms Evolution on a grand scale Stasis species existing for a long time without change Modification change in traits over time Speciation reproductive isolation Extinction Population all individuals of the same species living in a defined geographic or smaller Organismal area Deme subset of a population in a local actively interbreeding population that shares a distinct gene pool Mostly isolated from one another Isolation of a deme from other conspecific demes can result in the generation of subspeciesmicro or even reproductive isolation macrospeciation Gene pool all the genes at all loci in every member of an interbreeding population Adaptation Physiological adaptation a short term change in physiology morphology metabolism made by an individual organism in response to environmental changes Seasonally changing fur color and density Physiological adaptations are the products of evolutionary adaptation Evolutionary adaptation Process a population evolves to become better suited to its environment Charactertrait that has resulted from the evolutionary process Such as the fusiform shape of a dolphin that is better suited for aquatic existence than that of land dwelling relatives Or specialized teeth of a particular mammal best suited to its diet Causes for why populations evolve Mutation a necessity for evolution Small population size smaller the population the faster change will effect the population Nonrandom assortative mating Migration in or out of the population brings new alleles in or out Natural selection Mutation and Polymorphism Mutation the process by which a gene changes from one allele to another or the end result of that allelic change Depending on the nature and location of a mutation even a small genetic change can have a major phenotypic consequences Without genetic variation there can be no evolution Clones can evolve with genetic recombination Polymorphism more than one form of a particular trait within a population If these multiple phenotypes are heritable and result from different alleles at a particular locus or interacting loci then they are subject to the forces of evolution Wisdom teeth the primitive condition is having a jaw that can fit all the molars It is also a polygenic trait It s no longer maladaptive to have a jaw to short for wisdom teeth because we have the resources to remove them There is no longer any adaptive significance to us having wisdom teeth Morphological polymorphism variation in physical characteristics such as color size patterns Wisdom teeth Chromosomal polymorphism karyotype is usually species specific However non lethal anomalies may be common among the members of a population These include aneuploidies chromosome breakages and fusions polyploidy reciprocal translocations inversions Immunological polymorphism antigen specificities may vary within and among populations Blood groups Protein polymorphisms a codon change will lead to a different protein being created DNA polymorphism Restriction site variation variation in a location of the restriction sequences through restriction endonucleases This means at different locations the DNA will be cut Tandem repeats specific repeats of a DNA sequence Complete sequence variation over time long sequences of DNA have varied between organisms Polymorphism in a single gene locus at different positions genes can vary in their polymorphism at different locations Mutations in somatic cells are not heritable Germ line cells create the gametes and mutations here can be passed down to the next generation Animals they have a determinate growth there is a defined juvenile period and then once we reach maturity somatic growth slows or stops Plants have indeterminate growth meaning they grow new tissues from meristems essentially stem cells The meristems stay pluripotentcan become many different kinds of cells but not all The meristem creates the roots and shoots which create the germ line cells So if it mutates in the meristem can be passed to offspring Fungi also exhibit inderminate growth The mushroom we see are the Protists single celled organisms that passes on their entire genome so any mutations can be inherited Prokaryotes Types of mutations Point mutation can have big consequences Mutations at the chromosome there could be a deletion duplication of segments or genes inversions rearrangement and translocations swapped pieces of chromosomes Euploidy the normal amount of homologous pairs Aneuploidy to few or to many of a homologous pair Trisomy 21 Down syndrome Monosomy only one of the homologous pair Trisomy three homologs are present Nullisomy the entire pair is deleted Mutations at the chromosome set Level Haploid cell with one set of nuclear chromosomes sperm and eggs Diploid Have 2 sets Polyploid cell with more than 2 sets Alternating generations one individual organism that is diploid creates a gametophyte haploid and the haploid gametophytes create a sporophyte diploid offspring Haploidy some animals such as the honeybees the male are haploid and the females are diploid organisms Polyploid organisms very common in plants but until recently thought it was rare in animals Autopolyploidy a plant has a problem in meiosis and creates a new species Comes from the same species Allopolyploidy one possible way is 2 species come together with two different amount of chromosomes but they are close enough that they can create a hybrid A problem in meiosis occurs and it doesn t split This then goes back with another normal gamete Creating a Viable new species Comes from 2 different species Hybrid organisms produces by genetically dissimilar parents This can result in speciation Polyploid individuals are usually larger than the parents If a polypoid organism can selffertilize it can give rise to speciation Population genetics Measuring Evolutionary Change Traits Discretequalitative either or traits that are usually monogeniceither you can or canthitch hikers thumb or rolling tongue Continuous quantitative polygenic depends on multiple genes It results on a continuum Such as skin color in humans depends on levels of melanin Mendelian genetics Molecular genetics Population genetics Genetic variations exists Within a population Between geographically close populations Florida tree snails Between geographically distant populations Clinal variation different populations in different locations show different traits such as skin color Heterozygosity proportions of genes present in the heterozygous condition Average heterozygosity the average percent of loci that are heterozygous in a population Hardy Weinberg equation p2 2pq q2 p is homozygous dominant pqheterozygous q homozygous recessive 5 conditions must be met 1 No mutations The populations must be very large Random mating must occur No entering or leaving individuals No genotype has a reproductive advantage over another no natural selection 9593 Heterozygosity and deleterious alleles can be advantageous such as the sickle cell anemia example as well as in HIV
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