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taxonomy notes bI
Taxonomy
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Carolus Linnaeus
Taxonomy - study of classifying organisms
Taxonomists are scientists who study classifying
Taxon ( taxa-plural) is a category into which related organisms are placed
Reasons to Classify:
Shows evolutionary relationships
Accurately & uniformly names organisms
Prevents misnomers such as starfish & jellyfish that aren't really fish
Uses same language (Latin) for all names
Prevents duplicated names because all names must be approved by
International Naming Congresses (International Zoological Congress)
Naming rules are followed called the International Code for Binomial
Nomenclature
Early Taxonomy:
Aristotle was the first taxonomist dividing organisms into land, sea, & air
dwellers
John Ray was the first to use Latin for naming
Linnaeus developed the modern system of naming known as binomial
nomenclature, a two-word name (Genus & species)
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Scientific names should be italicized in print or underlined when writing
Always capitalize the genus name, but write the species in lower case
The scientific name for man is Homo sapiens
The genus name may be abbreviated, but not the species (H. sapiens)
Taxonomic categories:
Linnaeus placed organisms into related groups called taxa (taxon-singular)
based on their morphology (similar structure & function)
The broadest taxon is called the kingdom
Linnaeus put all organisms into one of two kingdoms --- Plantae or Animalia
The other six taxa from broadest to most specific are --- Phylum, Class,
Order, Family, Genus, & species
A sentence to help remember these taxa is --- "King Phillip Came Over For
Gooseberry Soup."
Each taxa is a proper noun &should be capitalized except species
Each level or taxon groups together organisms that share more
characteristics than the level above
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Botanists use the term division instead of phylum for classifying plants
Plant species are subdivided into varieties, while bacteria are subdivided into
strains
Basis for Modern taxonomy:
Modern taxonomists classify organisms based on their evolutionary
relationships
Homologous structures have the same structure, but different functions &
show common ancestry
The bones in a bat's wing, human's arm, penguin's flipper are the same
(homologous), but the function is different
Analogous structures have the same function, but different structures & do
not show a close relationship (insect wing & bird's wing)
Similarity in embryo development shows a close relationship (vertebrate
embryos all have tail & gill slits)
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Similarity in DNA & amino acid sequences of proteins show related organisms
Modern Taxonomic System:
Modern taxonomy uses six kingdoms --- Archaebacteria, Eubacteria,
Protista, Fungi, Plantae, & Animalia
Archaebacteria & Eubacteria are unicellular prokaryotes lacking a nucleus,
while Protista, Fungi, Plantae, & Animalia are all eukaryotes with a nucleus &
membrane-bound organelles
All members of Plantae & Animalia are multicellular organisms
Fungi & Animalia are heterotrophs, while Plantae are all autotrophs capable of
making their own food
Archaebacteria live in harsh environments like very salty lakes; intestines of
mammals; and hot, sulfur springs & may be autotrophs or heterotrophs
Eubacteria are true bacteria some of which cause disease
Protista are mainly unicellular with a few multicellular organisms and may be
autotrophic (Euglena) or heterotrophic (Ameba)
Fungi include multicellular mushrooms, mold, unicellular yeast, etc. & are
absorptive heterotrophs (digest food & then absorb it)
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Animalia are ingestive heterotrophs that take in food & then digest it inside
their multicellular bodies.
Plantae includes all plants & are the only all multicellular, autotrophic kingdom
Phylogeny (evolutionary history):
Phylogenetic trees are branching diagrams showing how organisms are
related
Also called family trees
Fossil records help establish relationships on a phylogenetic tree
Organizes living things based on their evolution (systematics)
Common ancestor is shown at the base of the tree
Most modern organisms shown at tips of branches
Each time a branch divides into a smaller branch, a new species evolves
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Cladograms shows how organisms are related based on shared, derived
characteristics such as feathers, hair, scales, etc.
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Three Domain System:
Based on comparing sequences of ribosomal RNA in different organisms to
determine ancestry
All organisms placed into three broad groups called domains
Domain Archaea (kingdom Archaebacteria) contains chemosynthetic bacteria
living in harsh environments
Domain Bacteria (kingdom Eubacteria) contains all other bacteria including
those causing disease
Domain Eukarya (kingdoms Protista, Fungi, Plantae, & Animalia) contains all
eukaryotic organisms
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