Organization of Life
Vocabulary
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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
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More Vocab:
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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
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History of Classification
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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
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Aristotle classified the organisms below into
the same category, make sense?
History of Classification
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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
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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
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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
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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
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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
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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
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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
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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
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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
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ID these:
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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
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 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)
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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
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 Show probable evolutionary relationships
 Two groups on diverging branches share 1
or more characteristic
Cladogram