Bio 102: Ch. 26 & 27
Bio 102: Ch. 26 & 27 Bio 102
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This 7 page Class Notes was uploaded by Sierra Barton on Sunday September 27, 2015. The Class Notes belongs to Bio 102 at University of South Carolina taught by Dr. Mihaly Czako in Fall 2015. Since its upload, it has received 27 views. For similar materials see Biological Principles II in Biology at University of South Carolina.
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Date Created: 09/27/15
Chapter 26 Phylogeny and the Tree of Life evolutionary history of a species or group of related species classifies organisms and determines their evolutionary relationships scientific discipline concerned with classifying and naming organisms Binomial Nomenclature Created by Carolus Linnaeus 2 part names for species amp hierarchical classification 0 first part genus first letter capitalized 0 second part specific epithet o entire species name is italicized taxonomic groups domain kingdom phylum class order family genus species taxonomic unit at any level of hierarchy Linking Classification amp Phylogeny used to show the evolutionary history of a group of organisms represents hypothesis about evolutionary hypothesis each represents the divergence of 2 species groups that share immediate common ancestor includes a branch to represent the last common ancestor of all the taxa in the tree 0 diverges early in the history of a group and originates near the common ancestor of the group 0 branch from which more than 2 groups emerge o in some trees length of branch can reflect of genetic changes that have taken place in a particular DNA sequence in that lineage 0 in others branch length can represent chronological time amp branching points can be determined from fossil record Why we can amp cannot learn from Phylogenetic Trees 0 show patterns of descent NOT phenotypic similarity 0 do not indicate when species evolved or how much change occurred 0 shouldn t be assumed that a taxon evolved from the taxon next to it Morphological and Molecular Homologies phenotypic and genetic similarities due to shared ancestry similarities due to convergent evolution occurs when similar environmental pressures and natural selection produce similar analogous adaptations in organisms from different evolutionary lineages analogous structures or molecular sequences that evolved independen y structures can be distinguished by comparing fossil evidence and degree of complexity Cladistics group organisms by common descent group of species that includes an ancestral species and all its descendants o a valid clade is signifying that it consists of the ancestor species amp all of its descendants o grouping consists of an ancestral species amp some but not all of the descendants o grouping includes distantly related species but does not include their most recent common ancestor Shared Ancestral amp Shared Derived Characters originated in an ancestor of the taxon evolutionary novelty unique to a particular clade species or group of species that is closely related to the the various species being studied 0 out group diverged before in group a character can be both ancestral amp derived Maximum Parsimony amp Maximum Likelihood assumes tree required the fewest evolutionary events appearances of shared derived characters is the most likely given certain rules about how DNA changes over time a tree can be found that reflects the most likely sequence of evolutionary events Organism s Evolutionary History is Documented in it s Genome DNA that codes for rRNA changes slowly amp is useful for investigating branching points a long long time again mtDNA evolves rapidly and can be used to explore recent events Gene Duplications and Gene Families increases of genes in the genome providing more opportunities for evolutionary changes 0 repeated ones result in gene families found in a single copy in the genome and are homologous between species 0 can diverge only after speciation o widespread amp extend across many widely varied species result from gene duplication so are found in more than one copy in the genome 0 can diverge within clade that carries them amp can evolve new functions Molecular Clocks uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change calibrated against branches whose dates are known from fossil record if most of the evolutionary change in genes amp proteins has no effect on fitness then the rate of molecular change should be regular like a clock potential problems 0 does not run as smoothly as expected if mutations were neutral 0 irregularities result from natural selection in which some DNA changes are favored over others 0 estimates evolutionary divergences older than fossil record have a high degree of uncertainty 0 use of multiple genes or genes that evolved in different taxa may improve estimates dating HIV 0 descended from viruses that infect primates o spread to humans more than once 0 evolved in clocklike way From 2 Kingdoms to 3 Domains early taxonomist classified all species as plants or animals later 5 kingdoms recognized o Monera prokaryotes Protista Plantae Fungi and Animalia Then 3 domains 0 Bacteria Archaea amp Eukarya Horizontal Gene Transfer Tree of life shows eukaryotes and archaea are more closely related to each other than to bacteria 0 Based on rRNA genes movement of genes from one genome to another 0 Occurs by exchange of transposable elements and plasmids viral infection and fusion of organism 0 Played key role in evolution of prokaryotes amp eukaryotes Chapter 27 Bacteria and Archaea Masters of Adaptation Prokaryotes Prokaryotes thrive almost everywhere places too acidic salty cold or hot for other organisms Most are microscopic More in a handful of fertile soil than the of people who have ever lived Divided into 2 domains bacteria amp archaea Most likely Earth s first organism Most are unicellular Most cells are 055 um Cells have a variety of shapes 0 Most common are spheres coccus cocci rods bacillus bacilli and spirals Cell Surface Structures maintains shape protects cell and prevents it from bursting in hypotonic environment 0 Eukaryotic cell wall made of cellulose or chitin 0 Bacterial cell wall contain a network of sugar polymers cross linked by polypeptides o Archaea contain polysaccharides and proteins lack peptidoglycan used to classify bacteria by cell wall composition have simpler walls with large amount of peptidoglycan have less peptidoglycan and an outer membrane that can be toxic to us polysaccharide or protein layer that covers prokaryotes allow prokaryotes to stick to their substrate or other individuals in a colony or sex pili larger than fimbriae allow prokaryotes to exchange DNA Motility ability to move toward or away from a stimulus Most bacteria propel themselves by flagella scattered about the surface at one or both ends 0 Flagella is composed of different proteins and likely evolved independently o Flagella is composed of a motor hook and filament o Flagella is an example of existing structures take on new forms through descent with modification Internal Organization amp DNA 39 Some prokaryotic cells have specialized membranes that perform metabolic functions 0 Usually in folding of plasma membrane Prokaryotic genome has less DNA than eukaryotic Most consist of circular chromosome 0 Not surrounded by membrane 0 Located in nucleoid region smaller rings of DNA Reproduction Reproduce quickly can divide every 13 hours Key features 0 Small 0 Reproduce by binary fission 0 Short generation times Prokaryotes have considerable Generic Variation 3 factors contribute 0 rapid reproduction I offspring cells generally identical I short generation time allows them to evolve quickly 0 mutation I mutation rates are low but can accumulate rapidly 0 genetic recombination combing of DNA from 2 sources I can be brought together by transformation transduction and conjugation Transformation and Transduction when a prokaryotic cell can take up amp incorporate foreign DNA from surrounding environment movement of genes between bacteria by viruses that infect bacteria Conjugation and Plasmids process where genetic material is transferred between prokaryotic cells DNA transfer is ONE way in bacteria Donor cell attaches recipient by pilus pulls it closer and transfers DNA A piece of DNA called the is required for production of pili F Factor as Plasmid 0 Cells containing the F plasmid function as DNA donors during conjugation 0 Cells without it function as DNA recipients o F factor is transferable during conjugation F Factor in Chromosome 0 A cell with the F factor built into its chromosomes functions as a donor during conjugation 0 Recipient becomes recombinant bacterium with DNA from 2 different cells R Plasmids carry genes for antibiotic resistance 0 Through natural selection the fraction of bacteria with genes for resistance increases in a population exposed to antibiotics Prokaryotes Categorized by How They Obtain Energy amp Carbon Phototrophs obtain energy from light Chemotrophs obtain energy from chemicals Autotrophs require C02 as a carbon source Heterotrophs require organic nutrient to make organic compounds Energy amp carbon sources are combined to give 4 major modes of nutrition 0 Photoautotrophy o Chemoautotrophy o Photoheterotrophy o Chemoheterotrophy Prokaryotic metabolism varies with respect to 02 o require 02 for cellular respiration o poisoned by 02 and use fermentation or anaerobic respiration o can survive with or without 02 Nitrogen Metabolism Nitrogen is essential for production of amino acids amp nucleic acids some prokaryotes convert nitrogen NZ to ammonia NH3 Metabolic Cooperation Cooperation between prokaryotes allows them to use environmental resources they could not use as individual cells Occurs between different prokaryotic species in surfacecoating colonies called Bacteria Include vast majority of prokaryotic species familiar to most people Proteobacteria o Gram negative bacteria include photoautotrophs chemoautotrophs and heterotrophs 0 Some anaerobic some aerobic Subgroup alpha proteobacteria o Scientist hypothesize that mitochondria evolved from aerobic alpha proteobacteria through endosymbiosis o parasites that live within animal cells 0 Can cause blindness through sexual transmission helicalheterotrophs 0 Can cause syphilis amp lyme disease Cyanobacteriaphotoautotrophs that generate 02 0 Plant chloroplasts likely evolved from cyanobacteria by process of endosymbiosis Grampositive bacteria 0 Actinomycetes decompose soil Bacillus anthracis cause of anthrax Clostridium botulinum cause of botulism Staphylococcus amp streptococcus can be pathogenic Mycoplasms smallest known cells O O O O Archaea Share certain traits with bacteria amp other traits with eukaryotes live in extreme environments live in highly saline environments thrive in very hot environments live in swamps amp marshes amp produce methane as a waste product 0 Strict anaerobes amp are poisoned by 02 Chemical Recycling Chemoheterotrophic prokaryotes function as breaking down dead organisms amp waste products Ecological Interactions ecological relationship in which 2 species live in close contact a larger host amp a smaller symbiont both symbiotic organisms benefit 1 organism benefits while neither harming nor helping the other in any significant way organism called parasite harms but does not kill its host 0 Parasites that cause diseases are called Mutualistic Bacteria Human intestines are home to about SOD1000 species of bacteria Many break down our food undigested by our intestines Pathogenic Bacteria Cause about half of all human disease Transmitted by other species Cause disease by releasing o Exotoxins secreted and cause disease even if prokaryotes that produce them aren t present 0 Endotoxins released only when bacteria die amp their cell walls break down Prokaryotes in Research amp Technology Bacteria can be used to make natural plastics Principal agents in use of organism to remove pollutants from environment Can produce vitamins antibiotics amp hormones Can produce ethanol from agricultural amp municipal waste biomass switch grass amp corn
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