Classification of Organisms
Classification of Organisms
•The study of the kinds and diversity of organisms and their evolutionary relationships is called systematics or taxonomy▫Taxonomy is the work involved in the
original description of a species.▫Systematics is the assigning of species
into evolutionary groups.
Father of Modern Classification
•The modern classification system originated with the work of Carolus Linnaeus ▫he recognized the different species could be
grouped into broader categories based on shared characteristics
▫any grouping of animals that shares a particular set of characteristics forms an assemblage called a taxon
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CLASSIFICATION
•OBSERVATION:•Many kinds of organisms:•Some similar to each other.
▫wood frog, ▫leopard frog, ▫bull frog
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CLASSIFICATION•Others less
similar▫fish, ▫ frogs, ▫snakes
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CLASSIFICATION
•Others very dissimilar▫people, ▫pine trees, ▫protozoans
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CLASSIFICATION•Why are some kinds similar and
others NOT similar? Question to be answered later?
•How can we make sense of (explain) this diversity?
•How can we organize what we know about these organisms?
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Answer: CLASSIFY
•Similar “types” (species) grouped together, separated from other species.
•Then, group similar groups together, •etc.
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CLASSIFICATION
•Species = kind of organism▫fundamental unit in evolution and
ecology▫more precise definition soon
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CLASSIFICATION
•Necessary? YES !!~ 1 million species of plants,5-10 million species of animals+ fungi, protists, bacteria
no good estimates of numbers of species•Human mind needs to organize
information.
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CLASSIFICATION•Classification system organizes
biological knowledge.•Classification itself is HYPOTHESIS
about relationships, similarity because of common ancestry.
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HYPOTHESIS of relationship
Modern taxonomists use 7 taxa:•kingdom, phylum, class, order, family,
genus and species ▫as taxa increase organisms get more
specific
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CLASSIFICATION = Sequence of levels. Linnaean system, from Carolus Linnaeus, 1740's
Kingdom Phylum Class Order Family Genus Species
King Phil called old fat George stupid.
Kingdoms and DomainsBacteriaBacteria ArchaeaArchaea EukaryaEukarya
BacteriaBacteria ArchaeaArchaea ProtistaProtista PlantaePlantae FungiFungi AnimaliaAnimalia
MoneraMonera ProtistaProtista PlantaePlantae FungiFungi AnimaliaAnimalia
The three-domain systemThe three-domain system
The six-kingdom systemThe six-kingdom system
The traditional five-kingdom systemThe traditional five-kingdom system
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CLASSIFICATIONWoese, 1985
Domain Kingdom Phylum Class Order Family Genus SpeciesDid King Phil call old fat George
stupid ?
Kingdoms of Life
•In 1969, Robert H. Whitaker classified kingdoms based on cellular organization and mode of nutrition
▫this lead to the formation of the 5 kingdoms
5 Kingdoms of Classification:
Monera: comprised of bacteria and cyanobacteria• distinguished by being single cell prokaryotes
Protista: comprised of Amoeba, Paramecium etc….
• distinguished by being single celled eukaryotes
Plantae: multi-cellular photosynthetic eukaryotes• plants have cell walls and are non-motile
5 Kingdoms of Classification:Fungi: multi-cellular heterotrophic
eukaryotes• fungi have cell walls and usually non-motile•digest organic matter extra-cellularly (outside
of cell) and absorb the breakdown products
Animalia: multi-cellular heterotrophic eukaryotes
•animal cells lack a cell wall and usually motile
• feed by ingesting other organisms or parts of other organisms
MoneraMonera prokaryoteprokaryote single-cellsingle-cell
ProtistaProtista eukaryoteeukaryote multi-cell multi-cell
PlantaePlantae eukaryoteeukaryote multi-cellmulti-cell autotrophicautotrophic
FungiFungi eukaryoteeukaryote multi-cellmulti-cell heterotrophic, heterotrophic, external digestionexternal digestion
AnimaliaAnimalia eukaryoteeukaryote multi-cellmulti-cell heterotrophic, heterotrophic, internal digestioninternal digestion
DOMAINS???
•Many taxonomists have pushed the idea that the five kingdom system isn’t enough▫they feel that organisms share too much
similarities and need to be grouped otherwise
• the push has led to the addition of 3 domains
3 Domains
1. Archae: bacteria that live in extreme conditions
2. Eubacteria: “true bacteria”
3. Eukarya: all eukaryotic organisms
Taxonomic Diagrams
MammalsMammals TurtlesTurtles Lizards and Lizards and SnakesSnakes
CrocodilesCrocodiles BirdsBirds MammalsMammals TurtlesTurtles Lizards and Lizards and SnakesSnakes
CrocodilesCrocodiles BirdsBirds
CladogramCladogramPhylogeneticPhylogeneticTreeTree
BioEd OnlineBioEd Online
Binomial Nomenclature:•when a species is talked about only the
genus and species names are used▫this is called the scientific name ▫unique to each type of organism
•Required by the International Code of Zoological Nomenclature
Writing Scientific Names
•the genus names is always capitalized• both names are either italicized or
underlined ▫leave a space in the underline between names
ex. Homo sapienFelis leoQuercus rubra
Ursus americanusUrsus americanus
American Black BearAmerican Black Bear
Often Latin names contain clues about the type of organism being described.
Canis domesticus :And closely related organisms are often in the same genus, also giving clues about their names
Canis lupus: Some names are given after the discoverer, or the discovery location, or even a Latinized descriptive term in English
ConclusionThe classification system for organismshave been around for a long time. It hasendured several changes and is quitecomplex. Without it modern biology couldnot exist, much in the same way thata grocery store would go out of businessif it did not have a classification system.