Ch 18- Classification
• Why do biologists organize living organisms
into groups that have biological meaning?
– Study the diversity of life
• Use classification system to name organisms
and group them in logical manner
• Taxonomy- discipline of classifying organisms
and assigning each organism a universally
accepted name
Scientific Names
• Why don’t scientists use common names?
• Use Latin and Greek
• Bionomial nomenclature- two word naming system
– Each species given two-part scientific name
– Carolus Linnaeus
– First word is capitalized, second word is lowercased,
written in italics
– Ursus arctos- grizzly bear
• Ursus- genus to which organism belongs
– Genus- group of closely related species
• artos- unique to each species within the genus
Linnaeus’s System of Classification
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Linnaeus’s hierarchical system of classification uses seven taxonomic categories
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Species
Genus
Family
Order
Class
Phylum
Kingdom
Taxon- taxonomic category
Family- genera that share many characteristics
– Ursidae
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Order- broad taxonomic category composed of similar families
– Carnivora
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Class- composed of similar orders
– Mammalia
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Phylum- several classes that share important characteristics
– Chordata
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Kingdom- largest and most inclusive categories
– Animalia
Sec 2- Modern Evolutionary
Classification
• Phylogeny- evolutionary relationships among
organisms
• How are evolutionary relationships important in
classification?
– Organisms are grouped into categories that represent
lines of evolutionary descent, or phylogeny- not just
physical similarities
• Evolutionary classification- grouping organisms
together based on their evolutionary history
Classification Using Cladograms
• Cladistic analysis identifies new characteristics
that arise as lineages evolve over time
• Derived characters- characteristics that appear in
recent parts of a lineage but not in its older
members
– Evolutionary innovation, or new characteristics
• Cladogram- diagram that shows evolutionary
relationships among group of organisms
– Help understand how one lineage branched from
another
– Use derived characters
Similarities in DNA and RNA
• All organisms use DNA and RNA to pass on information
• How can DNA and RNA help scientists determine
evolutionary relationships?
– Genes of many organisms show important similarities at
molecular level
– Can be used to determine classification and evolutionary
relationships
• Similar genes
– Human muscles and yeast
• DNA evidence
– More similar DNA sequence of two species, the more recently
they shared a common ancestor
– American vulture, African vulture, stork
Molecular Clocks
• Uses DNA comparisons to estimate the length
of time that two species have been evolving
independently
• Relies on mutations
• Comparison between DNA sequences can
reveal how dissimilar the genes are- indicates
how long ago two species shared a common
ancestor
Sec 3- Kingdoms and Domains
• How many kingdoms of life are there?
• What are the 6 kingdoms?
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Eubacteria
Archaebacteria
Protista
Fungi
Plantae
Animalia
• Domain- taxonomic category larger than kingdom
– Eukarya- composed of protists, fungi, plants, animals
– Bacteria- Eubacteria
– Archaea- Archaebacteria
Domain Bacteria and Archaea
• Bacteria- unicellular and prokaryotic
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Thick, rigid cell walls
Ecologically diverse- free living to deadly parasites
Some photosynthetic, some not
Some depend on oxygen, some not
• Archaea- unicellular and prokaryotic
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Most extreme environments
Many survive only in absence of oxygen
Cell walls lack peptidoglycan
Unusual lipids in cell membranes, not found in any
other organism
Domain Eukarya
• All have nucleus
• Protista, Fungi, Plantae, Animalia
• Protista- display greatest variety
– Unicellular and multicellular
– Photosynthetic and heterotrophic
• Fungi- heterotrophs
– Feed on dead or decaying organic matter
– Unicellular or multicellular
• Plantae- multicellular organisms that are photosynthetic
autotrophs
• Animalia- multicellular and heterotrophic
– Incredible diversity