Ch 26 Phylogeny and the Tree of Life Monday June 16 2014 10 57 AM Phylogeny Systematics The evolutionary history of a species or group of related species An analytical approach to understanding the diversity and relationships of organisms Concept 26 1 phylogenies show evolutionary relationships Taxonomy The ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences Binomial Nomenclature Carolus Linnaeus The two part format of the scientific name of an organism The binomial name consists of Genus and species These are always written in a different font eg italics Genus is always capitalized species is always lowercase eg Homo sapiens Hierarchical Classification Linnaeus also introduced the system for grouping species in decreasingly broad categories Domain Kingdom Phylum Class Order Family Genus Species Linking Classification Phylogeny Systematists depict evolutionary relationships in branching phylogenetic trees Each branch point node represents the divergence of two species Lines represent lineages Concept 26 2 phylogenies are inferred from morphological and molecular data Morphological Molecular Homologies Phylogenetic history can be inferred from similarities in homologous structures and genes when compared among organisms Generally Similar morphology and similar DNA sequences closely related species But beware of analogous structures or molecular sequences aka homoplasies E2 Notes Page 1 But beware of analogous structures or molecular sequences aka homoplasies Similarity may be due to convergent evolution analogy not shared ancestry homology Concept 26 3 shared characters are used to construct phylogenetic trees Cladistics Cladogram Clade within a cladogram A valid clade is monophyletic A diagram depicting patterns of shared characteristics among species A group that includes and ancestral species and all of its descendants Monophyletic grouping Paraphyletic grouping Polyphyletic grouping Made up of an ancestral species and all of its descendants Consists of an ancestor and some but not all of that ancestor s descendants Grouping that lacks the common ancestor of the species in the group Shared ancestral shared derived characteristics Shared ancestral characteristic Homologous structure that predates the branching of a particular clade from other members of that clade Ex backbones in mammals All mammals have backbones but a backbone doesn t distinguish mammals from other vertebrates because all vertebrates have backbones So this character originated in an ancestor of mammals and vertebrates Shared derived characteristic Evolutionary novelty unique to a particular clade Ex hair in mammals All mammals have hair but none of their ancestors have hair So hair is an evolutionary novelty that is unique to mammals Concept 26 4 an organism s evolutionary history is documented in its genome Gene Duplications Gene Families Gene duplication The production of multiple copies of a gene within the genome This is an important type of mutation in evolution because it increases the number of genes in the genome Orthologous Paralogous genes Orthologous genes Genes found in a single copy in the genome Diverge only when a new species is formed Paralogous genes Result from gene duplication More than one copy in the genome Can diverge within the species that carries them and can have new E2 Notes Page 2 Can diverge within the species that carries them and can have new functions The Fossil Record Sedimentary rocks are the richest source of fossils Record is based on the sequence in which fossils have accumulated in strata Fossils show ancestral traits that may have been lost over time Different Types of Fossils Paleontologists study a wide variety of fossils in addition to fossils preserved in sedimentary rock E2 Notes Page 3 Ch 27 Prokaryotes 11 43 AM Monday June 16 2014 Prokaryotes are unicellular Range in size from 1 5 um No membrane bound organelles Circular chromosomes Concept 27 1 Structural and functional adaptations contribute to prokaryotic success Prokaryotic cells have a variety of shapes The three most common are spheres cocci rods bacilli and spirals spirilli Cell Surface Structures Cell wall Maintains cell shape provides physical protection prevents cell from bursting in a hypotonic environment Composed of peptidoglycan in bacteria May also have an outer phospholipid membrane A capsule a sticky layer of polysaccharide or protein may cover the cell wall of many prokaryotes Fimbriae and Pilli allow prokaryotes to stick to their substrate or other individuals in a colony Motility Motile bacteria move by means of flagellae Bacteria exhibit taxis ability to move toward or away from certain stimuli e g Positive chemotaxis moving toward a chemical stimulus Internal organization Prokaryotes do not have membrane bound organelles Some do have specialized membranes that perform metabolic functions Genomic organization Prokaryotic chromosome circular DNA found in the nucleoid region Not within a nucleus Plasmid smaller circular DNA rings Additional genes not always necessary for basic survival e g antibiotic resistance Reproduction Prokaryotes reproduce quickly by binary fission Can divide every 1 3 hours Form of asexual reproduction Produces genetically identical daughter cells Concept 27 2 Rapid reproduction mutation and genetic recombination promote genetic diversity in prokaryotes Bacteria reproduce asexually leading to genetically identical daughter cells Rapid reproduction leads to large populations high mutation rates High genetic diversity rapid evolutionary rates E2 Notes Page 4 High genetic diversity rapid evolutionary rates Genetic Exchange Bacterial conjugation Transfer of genetic material between two bacteria Not necessarily the same species horizontal gene transfer Plasmids are usually transmitted from donor to recipient through a sex pilus Transformation Transduction Transformation Uptake of foreign DNA from the environment Transduction Viruses carry bacterial DNA from one host cell to another Concept 27 3 Diverse nutritional and metabolic adaptations have evolved in prokaryotes Metabolic Relationships to Oxygen Prokaryotic metabolism can vary with respect to oxygen availability Obligate aerobes Require oxygen Facultative anaerobes Can survive with or without oxygen Fermentation when no oxygen present Obligate anaerobes Are poisoned by oxygen Always perform fermentation Anaerobic respiration Substances other than
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