classification. taxonomy science of grouping organisms according to their presumed natural...
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Classification
Taxonomy
Science of grouping organisms according to their presumed natural relationships
Artificial
May change with new evidence
History of Classification
Aristotle
Either plant or animal
Animals where they lived
Land Dwellers
Water Dwellers
Air Dwellers
Plants based on stem differences
Herbs
Shrubs
Trees
18th Century
New discovered organisms didn’t fit
Used Latin Descriptions - Cumbersome
Common Names
• Everyday name given to organisms–Don’t describe accurately– Same name for two organisms–May have more than one common name
Carolus Linneaus
Swedish Naturalist – 1707 -1778
Grouped organisms into a hierarchy
Developed system called Binomial Nomenclature
Linneaus’ Hierarchy
KingdomPhylum
ClassOrder
FamilyGenus
Species
Binomial Nomenclature
Means “two names”
Uses Genus and Species
Also called Scientific Name
Rules for Scientific Names
• Describes organism, its range, or honors another scientist
• Name is always Latinized
• Genus – capitalized; Species – Lower Case
• Always italicized or underlined
Levels of Classification with Human Taxonomy
• Kingdom – Animalia• Phylum – Chordata• Class – Mammalia• Order – Primates• Family – Hominidae• Genus – Homo “Man”• Species – Sapiens “Wise One”
The Taxonomist’s Subgroups
Subspecies – morphologically different; geographically separated
Variety – morphologically different; not geographically separated
Strain – biochemically dissimilar group in a species; microorganisms
Domains
• Bacteria – Kingdom Eubacteria
• Archea – Kingdom Archaebacteria
• Eukarya – Kingdoms Protista, Fungi, Plantae, and Animalia
Evidence used in Classification
• Comparative Morphology (Anatomy)• Embryological Evidence• Genetic Similarities• Biochemical Comparisons• Physiological Studies
Comparative Morphology
• Based on physical features• Looks at structural similarities• May or may not be completely accurate• Identification often uses a Dichotomous Key– Set of written choices leading to organism’s name– Branches; selections become more specific
Embryological Evidence
• Usually used for upper categories – Phylum, Class, etc.
• Looks at origin of body organs
• Homologous Organs – common origin, similar function – bat’s wing, human’s arm
• Analogous Organs – Different origin, similar function – insect’s wing vs bird’s wing
Genetic Similarities
• Looks at DNA sequences – related species have more similarities
• Comparison of Karyotypes – picture of organism’s chromosomes
• Chromosome counts• Chromosome shapes
Biochemical Comparisons
• Comparisons of amino acid sequences in common proteins in different species
• More similarities indicate closer relationship
Physiological Studies
Useful in Bacterial Classification
Looks at what chemical bacteria may use as food
May look the same but have different physiologies
Phylogeny
Evolutionary history of a species
Uses evidence of probable evolutionary relationships
Phylogenetic Tree (Cladogram) – model of inferred evolution
Phylogenetic Tree
• Species at branch ends – most recently evolved organisms
• Main Branches and Trunk – organisms which gave rise to more recent organisms
• Close branches imply close evolutionary history
Biosystematics
• Study of reproductive compatibility and gene flow
• Reproductive compatibility used to infer evolutionary relationship
• Studies speciation – evolution of one species into two new species
Kingdom Classifications
Two KingdomsPlants
Animals
Three KingdomsPlants
Animals
Protists
Kingdom Classifications
Four KingdomsPlantsAnimalsProtistsMonera
Five KingdomsPlantsAnimalsProtistsMoneraFungi
Kingdom Classifications
Six KingdomsPlants
AnimalsProtistsFungi
EubacteriaArchaebacteria
Criteria for Defining Kingdoms
• Cell Structure – Prokaryote or Eukaryote
• Number of Cells – Unicellular or Multicellular
• Nutrition – Autotrophs or Heterotrophs
• Reproduction – Asexual or Sexual
Kingdom Characteristics
ArchaebacteriaProkaryoticUnicellular – Cell Walls
without peptidoglycanAutotrophs and
HeterotrophsAsexual/SexualLive in extreme
environments
EubacteriaProkaryoticUnicellular – Cell Walls
with peptidoglycanAutotrophs and
HeterotrophsAsexual/SexualTypical Bacteria
Kingdom Characteristics
ProtistaEukaryoticUnicellular some
MulticellularAutotrophs and
HeterotrophsAsexual/SexualAquatic or Moist Habitats
FungiEukaryoticMulticellular some
UnicellularHeterotrophic by
AbsorptionSexual/AsexualMostly terrestrial, some
aquatic
Kingdom Characteristics
PlantaeEukaryoticMulticellularAutotrophicSexual/AsexualAquatic and terrestrialUsually remain in one
place
AnimaliaEukaryoticMulticellularHeterotrophic by ingestionSexual/Asexual (lower
species)Aquatic and terrestrialMost move about
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