The evolutionary history of a species or group of related species ○Phylogeny•An analytical approach to understanding the diversity and relationships of organisms○Systematics•Concept 26.1: phylogenies show evolutionary relationshipsThe ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences○Taxonomy•The two part format of the scientific name of an organism•Genus and species○These are always written in a different font (eg italics)○eg Homo sapiens Genus is always capitalized; species is always lowercase○The binomial name consists of •Binomial Nomenclature (Carolus Linnaeus)Domain ○Kingdom○Phylum○Class○Order○Family○Genus○Species○Linnaeus also introduced the system for grouping species in decreasingly broad categories•Hierarchical ClassificationSystematists depict evolutionary relationships in branching phylogenetic trees •Each branch point (node) represents the divergence of two species•Lines represent lineages•Linking Classification & PhylogenyConcept 26.2: phylogenies are inferred from morphological and molecular dataPhylogenetic history can be inferred from similarities in homologous structures and genes when compared among organisms•Similar morphology and similar DNA sequences = closely related species○Generally,•But, beware of analogous structures or molecular sequences (aka, homoplasies)•Morphological & Molecular HomologiesCh. 26 Phylogeny and the Tree of LifeMonday, June 16, 201410:57 AM E2 Notes Page 1Similarity may be due to convergent evolution (analogy), not shared ancestry (homology) ○But, beware of analogous structures or molecular sequences (aka, homoplasies)•Concept 26.3: shared characters are used to construct phylogenetic treesA diagram depicting patterns of shared characteristics among species○Cladogram•A group that includes and ancestral species and all of its descendants○Clade within a cladogram•A valid clade is monophyletic •CladisticsMade up of an ancestral species and all of its descendants•Monophyletic groupingConsists of an ancestor and some, but not all, of that ancestor's descendants •Paraphyletic groupingGrouping that lacks the common ancestor of the species in the group•Polyphyletic groupingHomologous structure that predates the branching of a particular clade from other members of that clade○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 Ex backbones in mammals○Shared ancestral characteristic•Evolutionary novelty unique to a particular clade○All mammals have hair, but none of their ancestors have hairSo hair is an evolutionary novelty that is unique to mammals Ex; hair in mammals○Shared derived characteristic•Shared ancestral & shared derived characteristicsConcept 26.4: an organism's evolutionary history is documented in its genomeThe production of multiple copies of a gene within the genome ○Gene duplication•This is an important type of mutation in evolution because it increases the number of genes in the genome •Gene Duplications & Gene FamiliesDiverge only when a new species is formedGenes found in a single copy in the genome○Result from gene duplicationMore than one copy in the genomeCan diverge within the species that carries them, and can have new Paralogous genes○Orthologous genes •Orthologous & Paralogous genes E2 Notes Page 2Can diverge within the species that carries them, and can have new functions Record is based on the sequence in which fossils have accumulated in strata○Fossils show ancestral traits that may have been lost over time ○Sedimentary rocks are the richest source of fossils•The Fossil RecordPaleontologists study a wide variety of fossils in addition to fossils preserved in sedimentary rock •Different Types of Fossils E2 Notes Page 3Concept 27.1: Structural and functional adaptations contribute to prokaryotic successProkaryotes are unicellular•Range in size from 1 - 5 um •No membrane-bound organelles•Circular chromosomes•The three most common are spheres (cocci), rods (bacilli), and spirals (spirilli) •Prokaryotic cells have a variety of shapesCell 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 •Cell-Surface StructuresMotile bacteria move by means of flagellae•e.g. Positive chemotaxis - moving toward a chemical stimulus ○Bacteria exhibit taxis (ability to move toward or away from certain stimuli)•MotilityProkaryotes do not have membrane-bound organelles•Some do have specialized membranes that perform metabolic functions•Internal organizationNot within a nucleus○Prokaryotic chromosome (circular DNA found in the nucleoid region •Additional genes not always necessary for basic survival○e.g., antibiotic resistance ○Plasmid (smaller circular DNA rings) •Genomic organizationCan divide every 1-3 hours○Prokaryotes reproduce quickly by binary fission•Produces genetically identical daughter cells ○Form of asexual reproduction•ReproductionConcept 27.2: Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotesRapid reproduction leads to large populations & high mutation rates○High genetic diversity & rapid evolutionary rates ○Bacteria reproduce asexually leading to genetically identical daughter cells•Ch. 27 ProkaryotesMonday, June 16, 201411:43 AM E2 Notes Page 4High genetic diversity & rapid evolutionary rates ○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 ○Bacterial conjugation•Genetic ExchangeUptake of foreign DNA from the environment○Transformation•Viruses carry bacterial DNA from one host cell to another ○Transduction•Transformation & TransductionConcept 27.3: Diverse nutritional and metabolic adaptations have evolved in prokaryotes Require oxygenObligate aerobes○Can survive
View Full Document
Unlocking...