Taxonomy & Classification Organization of Life Taxonomy & Classification

Vocabulary Classification: grouping objects or info based on similarities Biodiversity: the variety of organisms considered at all levels from populations to ecosystems Taxonomy: science of describing, naming, and classifying organisms Taxon (plural taxa): any particular group w/in a taxonomic system Binomial nomenclature: system of 2 part names for organisms consisting of genus and species

More Vocab Dichotomous key: key for the identification of organisms based on a series of choices between alternative characteristics Unicellular: organisms consisting of a single cell Multicellular: organisms consisting of more than one cell

More Vocab: Autotroph: an organism that produces its own nutrients from inorganic substances or from the environment instead of consuming other organisms Heterotroph: organism that obtains organic food molecules by eating other organisms or their byproducts and that cannot synthesize organic compounds from inorganic molecules Cladistics: a phylogenetic classification system that uses shared derived characteristics and ancestry as the sole criterion for grouping taxa Phylogeny: evolutionary history of a species or taxon

History of Classification Why do we classify: to better understand the organisms that we coexist with How do we classify: based on similarities Taxonomy: science of grouping and naming organisms based on their similarities and differences

History of Classification Aristotle (384-322 B.C.) Developed the 1st widely used system of classification Classified organisms into plants and animals Subdivided plants into herbs, shrubs, trees based on size and structure Subdivided animals by characteristics such as habitat & physical differences Did not use evolutionary history as a basis for classification

History of Classification Aristotle classified the organisms below into the same category, make sense?

History of Classification Linnaeus (1707-1778) System still used today Based on physical and structural similarities in organisms His groupings revealed relationships b/t organisms Grouped organisms into hierarchical categories, the lower the level the more closely relate the organisms in it Used binomial nomenclature to name organisms

History of Classification Binomial Nomenclature 2 word naming system, italicized or underlined 1st word: genus of the organism, 1st letter upper case 2nd word: species of the organism This sometimes describes a specific characteristic of the species that denotes it from others of the same genus i.e.: homo sapiens: homo = genus, sapiens = wise which distinguishes humans from other organisms in the homo genus

History of Classification Modern Classification Builds on Linnaeus’s work Tries to use evolutionary relationships Compares internal and external characteristics, geography & genetics

Taxonomy Science of describing, naming and classifying organisms Taxon: group w/in a taxonomic system Taxa are bases on the closeness of the organisms in them

Taxonomy Modern levels of classification, from broadest (organisms w/in share the least similarities, to the narrowest, organisms are extremely similar) (highest level )Domain  kingdom  phylum  class  order  family  genus  species (lowest level) From the highest, each level includes all of the organisms grouped in the taxa below it

Modern Taxonomy

Taxa: Kingdom 6 different kingdoms Organisms placed in kingdoms based on differences primarily in: Cellular structures Methods of obtaining energy

Kingdom Eubacteria “true bacteria” Prokaryotic – lack nucleus and other organelles Cell wall w/ peptidoglycans & cell membrane w/ fatty acids Unicellular Heterotrophic and autotrophic by chemosynthesis or photosynthesis i.e.: salmonella, streptococci, cyanobacteria

Kingdom Eubacteria

Kingdom Archaebacteria “ancient bacteria” Prokaryotic Cell wall & cell membrane w/ hydrocarbons in addition to fatty acids Unicellular Heterotrophic & autotrophic by chemosynthesis i.e.: Methanosarcina, Halobacterium

Kingdom Archeabacteria

Kingdom Protista (aka Protists) Eukaryotes that aren’t plants, animals, fungi Eukaryotic – have nucleus & organelles Cell wall w/ cellulose & cell membrane w/ fatty acids Mostly unicellular, multicellular forms lack cellular organization Autotrophic by photosynthesis, some heterotrophic by phagocytosis, some both i.e. unicellular: amoebas & paramecia i.e. multicellular: some seaweeds & molds

Kingdom Protista

Kingdom Fungi Eukaryotic Cell wall w/ chitin & cell membrane w/ fatty acids Unicellular & multicellular Heterotrophic by secreting digestive enzymes, absorb nutrients, don’t ingest About 70,000 species i.e. mushrooms, puffballs, rusts, smuts

Kingdom Fungi

Kingdom Plantae Eukaryotic Cell wall w/ cellulose & cell membrane w/ fatty acids Multicellular & develop from embryos Autotrophic by photosynthesis, few parasitic i.e. mosses, ferns, conifers, flowering plants

Kingdom Plantae

Kingdom Animalia Eukaryotic Cell membrane w/ fatty acids Multicellular, develop from embryos Mostly symmetrical body organization Heterotrophic by phagocytosis i.e. humans, bees, shrimp, birds

Kingdom Animalia

Identifying Species Dichotomous key is one way to identify an unknown species Uses pairs of contrasting descriptive statements of physical characteristics to lead to the id of an organism or object Uses the principle of forced choice, you must choose one description or the other Does not evaluate evolutionary relationships

ID these: 1. a. wings covered by an exoskeleton ………go to step 2 b. wings not covered by an exoskeleton ……….go to step 3 2. a. body has a round shape ……….ladybug b. body has an elongated shape ……….grasshopper 3. a. wings point out from the side of the body ……….dragonfly b. wings point to the posterior of the body ……….housefly

Phylogenetics Phylogeny: evolutionary history of a species or taxon Phylogenetics: analysis of evolutionary or ancestral relationships among taxa Systematists: people who study phylogenetics Use physical characterists, embryonic development, chromsomes and macromolecules (like nucleic acids) Used a phylogenetic diagram or tree to represent relationships

Phylogenetics

Cladistics System of phylogenetics that uses only shared and derived characteristics for grouping taxa Shared characteristic: all members of a group have (hair in mammals) Derived characteristic: evolved only w/in the group under consideration (feathers in birds)

Cladistics Assumes organisms that share 1 or more derived characteristics come from a common ancestor Clade: group of organsims that includes an ancestor plus all of its descendants Use cladograms to represent relationships Show probable evolutionary relationships Two groups on diverging branches share 1 or more characteristic

Cladogram