Chapter 26 Phylogeny and the Tree of Life Phylogeny the evolutionary history of a species or group of related species Systematics 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 The two part format of the scientific name of an organism The binomial name consists of o Genus and species o These are always written in a different font e g italics o Genus is always capitalized species is always lowercase o E g Homo sapiens Hierarchical Classification Linnaeus also introduced the system for grouping species in increasingly broad categories Keep Pipes Clean OF GaS Kingdom Phylum Class Order Family Genus Species Kindly Professors Cannot Often Fail Good Students Kingdom Animalia i Phylum Chordata ii Class Mammalia iii iv Order Primates v vi Genus Homo vii Family Hominidae Species Homo sapiens Linking Classification Phylogeny Systematists depict evolutionary relationships in branching phylogenetic trees Each branch point node represents the divergence of two species Deeper branch points represent greater amounts of divergence Lines represent lineages Interpreting Phylogenetic Trees INSERT PICTURE Interior nodes represent common ancestors Taxa at tips represent living species groups Rotating around any node leaves a phylogeny unchanged Which taxon on the tree below is most closely related to taxon C A B D B and D are equally closely related to C All of the above are equally closely related to C i ii iii iv v Which taxon on the tree below is most closely related to taxon A i ii iii iv B C D All of the above are closely related to A Which of the following represents the correct order of taxa from the most inclusive to the least inclusive i ii iii iv Domain Kingdom Phylum Class Order Family Genus Species genus family order class phylum kingdom Class domain family genus kingdom order phylum Domain phylum order family class genus 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 a k a homoplasies o 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 a diagram depicting patterns of shared characteristics among species Clade within a cladogram a group of species that includes an ancestral species and all of Made up of an ancestral species and all of its descendants Only monophyletic groups qualify as legitimate taxa in cladistics Consists of an ancestor and some but not all of that ancestor s descendants Polyphyletic Grouping Grouping that lacks the common ancestor the species in the group its descendants Monophyletic Grouping Paraphyletic Grouping Shared Ancestral Shared Derived Characteristics Shared ancestral characteristic homologous structure that predates the branching of a particular clade from other members of that clade Shared derived characteristic evolutionary novelty unique to a particular clade Which shared derived character allows us to infer that stink bugs beetles lobsters is a clade i ii iii iv 1 pair antennae Large claws Compound eyes 6 legs Which of the following is not a shared ancestral trait of the stink bugs beetles lobsters clade i ii iii iv molt skeleton 6 legs 1 pair of antennae simple eyes Is the similarity between the Australian mole and the North American mole due to homology 1 Yes they share a recent common ancestor 2 No they are similar due to random factors 3 No they are similar due to convergent evolution analogous Concept 26 4 An organism s evolutionary history is documented in its genome Gene Duplications and Gene Families Gene duplication the production of multiple copies of a gene within the genome 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 o Diverge only once speciation takes place Paralogous genes result from gene duplication o More than one copy in the genome o Can diverge within the clade that carries them Paralogous Genes The Globin gene family has resulted from several gene duplication events Choose the pair of paralogous genes from the following list 1 A human alpha hemoglobin and chimpanzee alpha hemoglobin orthologous homologous 2 Two alleles of the human alpha hemoglobin gene different variety of same gene 3 Mouse insulin gene and yeast mating type gene not connected in any way 4 Two different olfactory receptor genes paralogous Chapter 27 Prokaryotes One thing that E coli and other bacteria have in common with eukaryotes is the presence of 1 Chloroplasts 2 Mitochondria 3 Nucleus 4 Ribosomes Concept 27 1 Structural and functional adaptations contribute to prokaryotic success Prokaryotes are unicellular o Some colonial forms Range in size from 1 5 micrometers No membrane bound organelles Circular chromosomes o Thiomargarita namibiensis 750 micrometers Prokaryotic cells have a variety of shapes The three most common are spheres cocci rods bacilli and spirals spirilli Cell Surface Structures Cell Wall o Maintains cell shape provides physical protection prevents cell from bursting in a hypotonic environment o Composed of peptidoglycan in bacteria o May also have an outer phospholipid membrane Cell Surface Structures prokaryotes A capsule a sticky layer of polysaccharide or protein may cover the cell wall of many Fimbriae and pilli allow prokaryotes to stick to their substrate or other individuals in a colony Motility Motile bacteria move by means of flagellae o Structurally different from eukarotic flagella In a heterogenous environment bacteria exhibit taxis ability to move toward or away from certain stimuli o Positive chemotaxis moving toward a chemical stimulus Gram negative bacteria have peptidoglycan than gram positive cells and their cell walls are complex structurally 1 More more 2 More less 3 Less less 4 Less more Groups of Staphylococcus aureus look like 1 Corkskrews 2 Filaments 3 Rods 4 Clusters of grapes because of the
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