TAXONOMY & CLASSIFICATION

Organization of Life

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 animalsSubdivided plants into herbs, shrubs, trees

based on size and structureSubdivided animals by characteristics such as

habitat & physical differencesDid 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 todayBased on physical and structural similarities in

organismsHis groupings revealed relationships b/t

organismsGrouped 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 underlined1st word: genus of the organism, 1st letter upper

case2nd 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 ClassificationBuilds on Linnaeus’s workTries to use evolutionary

relationshipsCompares 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 structuresMethods 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 phylogeneticsUse 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 relationshipsShow probable evolutionary relationshipsTwo groups on diverging branches share 1 or

more characteristic

Cladogram