Chapter 10 CLASSIFICATION

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Chapter 10CLASSIFICATION

• Classification an orderly grouping of organisms
• The study of classifying organisms is called
  taxonomy
• Provides universal names for organisms
• Provides a reference for identifying organisms
• There are tow approaches to classification

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Convenience vs. Phylogenetic Classification

• THE CLASSIFICATION SCHEMES IN PLACE TODAY ARE
  MAINLY BASED ON THE CONVENIENCE METHOD.
• ANY PHYLOGENY IS ASSUMED AND NOT PROVED
  SCIENTIFICALLY.

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History of Kingdom

• WHITTAKERS FIVE KINGDOM CLASSIFICATION - A
  CONVENIENCE METHOD.
• THE HISTORY OF KINGDOM CLASSIFICATION SCHEMES
• THE FIRST CLASSIFICATION SCHEME WAS DEVELOPED BY
  ARISTOTLE 2000 YEARS AGO.
• PLANTS AND ANIMALS.

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History of Kingdom (continue)

• IN THE LATE 1800S, A THIRD KINGDOM WAS ADDED
  PROTISTA
• IN THE 1950S, A FORTH KINGDOM WAS ADDED MONERA
• PROCARYOTIC AND EUCARYOTIC CELL STRUCTURE

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History of Kingdom

• IN 1969, A FIFTH KINGDOM WAS ADDED FUNGI

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Taxonomy

• 1735 Plant and Animal Kingdoms
• 1857 Bacteria fungi put in the Plant Kingdom
• 1866 Kingdom Protista proposed for bacteria,
  protozoa, algae, fungi
• 1937 "Prokaryote" introduced for cells "without a
  nucleus"
• 1961 Prokaryote defined as cells in which
  nucleoplasm is not surrounded by a nuclear
  membrane
• 1959 Kingdom Fungi
• 1968 Kingdom Prokaryotae proposed
• 1978 Two types of prokaryotic cells found

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The Basis of Five Kingdom

• WHITTAKERS FIVE KIGNDOM CLASSIFICATION RELATED
  ALL ORGANISMS ON THE BASIS OF
• 1. MODES OF NUTRITION
• 2. POSITION IN THE ECOLOGICAL FOOD CHAIN
• A. PRODUCER
• B. CONSUMER
• C. DECOMPOSER

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The Basis of Five Kingdom (continue)

• 3. CELLULAR ORGANIZATION
• A. SINGLE CELL
• B. MULTICELLULAR
• C. PROCARYOTIC/EUCARYOTIC
• 4. EVOLUTIONARY TREND
• WITHIN THE INDIVIDUAL KINGDOMS, ORGANISMS ARE
  FURTHER GROUPED INTO SMALLER GROUPS AS FOLLOWS

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The Basis of Five Kingdom (continue)

• PHYLUM/DIVISION
• CLASS
• ORDER
• FAMILY
• GENUS
• SPECIES
• STRAIN/VARIANT/SUBSPESCIES

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THE PHYLOGENETIC APPROACH

• ORGANISMS THAT ARE GENETICALLY RELATED WILL HAVE
  MORE CHARACTERISTICS IN COMMON THAN ORGANISMS
  THAT LOOK A LIKE.
• CARL WOESE AND FRIENDS HAVE BEEN WORKING SINCE
  1970 TO PUT IN PLACE A PHYLOGENETIC
  CLASSIFICATION SCHEME.

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THE PHYLOGENETIC APPROACH (continue)

• COMPARE HEREDITARY MOLECULES OF ORGANISMS.
• THEY SELECTED RIBOSOMAL RNA BECAUSE
• ALL CELLS HAVE IT AND PLENTY OF IT.
• ITS FUNCTION IS THE SAME IN ALL CELLS.
• ITS NITROGEN BASE SEQUENCE IS MODERATELY
  CONSERVED FROM GENERATION TO GENERATION.

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THE PHYLOGENETIC APPROACH (continue)

• WOESE SEPARATED ORGANISMS IN THE MONERA INTO TWO
  GROUPS
• - ARCHAEABACTERIA
• - EUBACTERIA
• ARCHAEABCTERIA TEND TO THRIVE IN EXTREME
  ENVIRONMENTS, EUBACTERIA DO NOT.
• ALSO, THERE ARE STRUCTURAL DIFFERENCES BETWEEN
  THESE TWO GROUPS OF BACTERIA.

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The Three-Domain System