20-1 Chapter 20 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Classification of Organisms The problem with common names – Different in every language – Different names can be used to identify the same organism. Organisms must have names that all scientists can identify. Naming organisms involves two different activities. – Taxonomy The naming of organisms – Phylogeny Demonstrating how organisms are related evolutionarily

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Taxonomy The science of naming organisms and grouping them into logical categories – Taxis = arrangement Scientific names of organisms are in Latin.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Taxonomy Organism names follow the binomial system of nomenclature. – Introduced by Linnaeus – Uses two Latin names The genus and the specific epithet A genus is a group of closely related organisms. A specific epithet identifies the particular species to which the organism belongs. Binomial names are italicized or underlined. The first letter of the genus is capitalized; the specific epithet is not. Thamnophis sirtalis

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Taxonomy Three sets of rules determine how organisms are named. – International Rules for Botanical Nomenclature – International Rules for Zoological Nomenclature – International Bacteriological Code of Nomenclature Organisms are organized into logical groups. – These groups are hierarchical. – Domain, kingdom, phylum, class, order, family, genus, species

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Three Domains of Life

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylogeny The science that explores the evolutionary relationships among organisms – Seeks to reconstruct evolutionary history Taxonomists use phylogeny to classify organisms whenever possible. Phylogenists use a variety of data to establish evolutionary relationships. – Fossils – Comparative anatomy studies – Life cycle information – Biochemical and molecular studies

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fossils Different types of fossils – Whole organisms that have been preserved intact – Bones embedded in rock – Impressions left in rock – Found in sedimentary rock, not igneous or metamorphic Some organisms fossilize more easily than others. – Those with hard parts vs. those with soft bodies – Those that live in water and can be buried in sediment

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fossils Fossils can be placed in a time sequence. – Established by the order that the organisms appear in the layers of sediment Deeper layers were laid down first. – Rocks can be aged by analyzing radioactive isotopes. Older rocks have fewer radioactive isotopes.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Comparative Anatomy Studies The anatomy of fossilized organisms can be compared to that of living organisms. – Allows for the classification of fossils – Those organisms that have similar structures are presumed to be related. – Examples Plants with flowers are related. Animals with hair and mammary glands are related.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Life Cycle Information Larval stages can provide clues about the relatedness of organisms. – Barnacles and shrimp The anatomy of eggs also provides clues. – Birds and reptiles The anatomy of seeds can be used as well. – Peas, peanuts and lima beans

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Biochemical and Molecular Studies New DNA technologies have allowed phylogenists to use DNA sequence comparisons to determine relatedness. These analyses have clarified phylogenetic relationships that previously could not be confirmed. – Storks, flamingoes and geese – Green algae and plants

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display A Current Phylogenetic Tree

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display A Brief Survey of the Domains of Life Eubacteria, Archaea and Eucarya – Eubacteria and Archaea are prokaryotic. – Eucarya is eukaryotic. Order of appearance – Eubacteria evolved first. – Gave rise to Archaea – Eucarya evolved most recently.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Domain Eubacteria “True bacteria” Unicellular Small (1-10  m) Prokaryotic (no nucleus) – Contain a single, circular chromosome – Reproduce asexually

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Domain Eubacteria Cell walls made of peptidoglycan – One component, muramic acid, is only found in bacteria. Can be rods, spheres or spirals Move via slime or flagella Varied metabolic requirements – Some are aerobic, some are anaerobic. – Some are decomposers, others are parasites; some are commensals. – Some are autotrophs, others are chemosynthetic.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Domain Archaea Unicellular Prokaryotic – Single circular chromosomes – Have several genes that are different from eubacteria and eucarya No peptidoglycan in their cell walls Have unique cell membranes Can be spheres, spirals, filaments or flat plates

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Domain Archaea Metabolically labeled as extremophiles – Methanogens Produce methane Found in sewage, guts of ruminants, intestines of humans – Halobacteria Live in extremely salty environments Photosynthetic – Thermophiles Live in high temperatures or areas with high sulfur concentrations

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Habitat for Thermophilic Archaea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Domain Eucarya Eukaryotic Appear to have evolved through endosymbiosis of prokaryotic cells Larger than prokaryotes Contain specialized membranous organelles

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Kingdom Protista Diverse – 60,000 species Live in freshwater, marine, terrestrial Some are parasitic, commensalistic or mutualistic. Some reproduce asexually via mitosis. Some are autotrophic, others are heterotrophic. May not be a cohesive phylogenetic unit Include algae, protozoa and slime molds – Amoeba, Paramecium

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Kingdom Fungi Most are non-motile Have a thin, rigid cell wall composed of chitin Heterotrophic – Most are saprophytes that secrete enzymes that break down the material they live on. – Decomposers – Some are parasitic, others are mutualistic. – Can form lichens

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Kingdom Fungi Most are multicellular. – A few are unicellular. Yeast Made up of filaments Include – Athlete’s foot – Plant pathogens – Ringworm

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Kingdom Plantae Photosynthetic – Green because of chlorophyll Non-motile Terrestrial Likely evolved from green algae – Non-vascular plants first – Then vascular Cone-bearing Flowering

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Kingdom Plantae Multicellular Contain a cellulose cell wall Exhibit alternation of generations – Multicellular gametophyte stage produces gametes via mitosis. – Multicellular sprorophyte stage produces spores via meiosis. – Able to reproduce sexually and asexually

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Kingdom Animalia Are thought to have evolved from protozoa Over a million species identified Range from microscopic to very large Common traits – Heterotrophs – Multicellular – Motile – Can reproduce sexually

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Acellular Infectious Particles Living organisms are made of cells. – Have cell membranes – Use nucleic acids as genetic material – Have cytoplasm – Contain enzymes – Contain ribosomes – Use ATP as their source of energy Particles that show some of these characteristics, but not all, are called acellular. – Most of these cause disease. – Viruses, viroids and prions

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Viruses An infectious particle consisting of a nucleic acid core surrounded by a coat of protein. Are obligate intracellular parasites – Because they cannot live outside of a living cell Not technically “living” Some cause disease, some do not Vary in size and shape – Rod-shaped, spherical, coil, helix – Most are extremely small.

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display How Viruses Cause Disease Viruses are host-specific. – Only infect one type of cell that has specific receptor sites on the cell membrane This is where the virus attaches. Is usually a glycoprotein Viruses must get their nucleic acids into the cell. – Once attached, viruses either enter the cell whole, or inject their nucleic acid into the cytoplasm.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display How Viruses Cause Disease Viruses don’t have many enzymes. – They depend on their hosts to replicate their DNA and make their proteins. After viruses are replicated they leave the cell. – Frequently, this process kills the cell.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Viral Invasion of a Bacterial Cell

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Viroids: Infectious RNA Infectious particles – Simply single strands of RNA Only found to infect plants Viroid infections cause stunted growth May cause plant death

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Prions: Infectious Proteins Infectious proteins All prion diseases cause brain tissue to become “spongy”. – Cause spongiform encephalitis – Mad cow (BSE), scrapie (sheep), Creutzfeld- Jakob and Kuru (human) Can be transmitted from one animal to another

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display How Prions Cause Disease How do prions form and how do they multiply? – Normal prion proteins exist in the brain. – Infectious prions come in contact with normal prions and cause them to change shape. Called conversion Makes the normal prions infectious – The infectious proteins aggregate and form plaques. These plaques disrupt brain function and kill brain cells. Where cells die, a hole is formed. Causes infected brain tissue to look “spongy” Some people are more resistant to prion disease than others.