Classification + Diversity of Life

Unit Outline Classification (Chapter 17.1) introduction Linnaeus and binomial nomenclature modern taxonomy dichotomous keys Diversity (Chapter 17.2 and 18) Six Kingdoms of Life Viruses Bacteria

Introduction to Classification classification - grouping of objects or information based on similarities taxonomy - branch of biology that groups and names organisms based on their characteristics (science of classification) Aristotle’s system - animal or plant This system stayed in place until a more useful one was developed in the 1700s.

Carolus Linnaeus aka Karl von Linne developed a system known as binomial nomenclature consists of a Genus and species name written in Latin italicized or underlined first name capitalized, second lower case tells something about organism

Modern Taxonomy combines Linnaeus’s system of classification due to similarities and combines it with evolutionary thought. phylogeny - the evolutionary history of organisms organisms are grouped based on “shared derived characteristics” and “most recent common ancestors”

Hierarchical Taxonomic System began with Linnaeus and has been constantly modified since.

Complete Classification of Homo sapiens

Dichotomous Keys

What is a Virus? Infectious particle consisting of a genome either single- or double-stranded either RNA or DNA inclosed in a capsid - protein that surrounds it. Replicate using metabolic machinery of host cells: bacteria, plant, animal Possibly evolved from plasmids or transposons

Structural components of viruses Genome: genes are contained on a single linear or circular nucleic acid molecule Capsid: protein shell, often large numbers of identical subunits (capsomeres) rod-shaped (helical) polyhedral complex Envelope: derived from membranes of hosts

What is a “phage”? Bacteriophage: complex viruses that attack bacteria Host Range: proteins on the outside of virus only recognize a few specific receptors on host cell surfaces.

Three patterns of Genome Replication DNA viruses RNA viruses retroviruses reverse transcriptase

Viral Life Cycles Lytic cycle Lysogenic cycle

Defenses against Infection restriction enzymes barriers antibodies vaccines

Bacteria short generation span aids their evolutionary adaptation to changing environments circular bacterial chromosome found tightly packed in a region called the nucleoid. 100x the DNA of a virus 1/1000 of the DNA of a eukaryote plasmids are also found in many strains genetic recombination produces new strains

Binary Fission replication of chromosome proceeds in two directions from the single point of origin prior to binary fission. most bacteria in a colony are identical (clones)

Genetic Recombination: Bacteria Transformation: (recall Griffith’s exp.) bacteria take up naked DNA Transduction: (recall Hershey and Chase) phages transfer genes from one bacterium to another generalized and specialized transduction Conjugation and Plasmids 2 cells temporarily join by appendages called sex pili

Most Common Shapes cocci: spherical bacilli: rod-shaped spirilli and spirochetes: helical

Bacterial Cell Wall Structure contain peptidoglycan: matrix of sugars with polypeptide cross-links gram-positive gram-negative capsule

Bacteria Adapt Rapidly short generations transduction, transformation, conjugation antibiotic resistance endospores

Four Metabolic Categories photoautotrophs chemoautotrophs photoheterotrophs chemoheterotrophs saprobes parasites nitrogen fixing bacteria = Rhizobium Relationship to oxygen

Ecological Impacts decomposers symbiosis: symbiont and host mutualism commensalism parasitism Research and Technology

Disease and Bacteria opportunistic pathogens Koch’s postulates Bacterial Pathogens exotoxins endotoxins

Classification Quiz What is taxonomy? Who is the father of taxonomy? What is binomial nomenclature? List the 7 taxa (levels) in order from most to least inclusive (biggest to smallest). Write a scientific name using the correct rules we learned in class.

Quiz-cont’d. Finish this sentence: A dichotomous key is used to _________________________. See Dichotomous Key… See Cladogram …