Transcript classification - De Anza College

CLASSIFICATION
• WHAT DOES CLASSIFICATION MEAN?
• IT MEANS “AN ORDERLY GROUPING OF
ORGANISMS”.
• THE STUDY OF CLASSIFICATION IS
CALLED TAXONOMY.
• THERE ARE TWO APPROACHES TO
CLASSIFICATION.
• 1. CONVENIENCE CLASSIFICATION
– ARTIFICIAL CLASSIFICATION
– PHENOTYPIC CHARACTERISTICS
• 2. PHYLOGENETIC CLASSIFICATION
– NATURAL CLASSIFICATION
– GENOTYPIC CHARACTERISTICS
• THE CLASSIFICATION SCHEMES IN PLACE TODAY
ARE MAINLY BASED ON THE CONVENIENCE
METHOD.
• ANY PHYLOGENY IS ASSUMED AND NOT PROVED
SCIENTIFICALLY.
• WHITTAKER’S 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
• IN THE LATE 1800’S, A THIRD KINGDOM
WAS ADDED: PROTISTA
• IN THE 1950’S, A FORTH KINGDOM WAS
ADDED: THE MONERA OR THE
PROCARYOTAE.
• PROCARYOTIC AND EUCARYOTIC CELL
STRUCTURE AND PHYSIOLOGY WAS
DISCOVERED.
• IN 1969, A FIFTH KINGDOM WAS ADDED:
FUNGI
• WHITTAKER’S 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
3. CELLULAR ORGANIZATION
A. SINGLE CELL
B. MULTICELLULAR
C. PROCARYOTIC/EUCARYOTIC
4. EVOLUTIONARY TREND - PHYLOGENY
• WITHIN THE INDIVIDUAL KINGDOMS,
ORGANISMS ARE FURTHER GROUPED
INTO SMALLER GROUPS AS FOLLOWS:
KINGDOM
•
•
•
•
•
•
•
PHYLUM/DIVISION
CLASS
ORDER
FAMILY
GENUS
SPECIES
STRAIN/VARIANT/SUBSPESCIES
• 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.
• 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.
• WOESE SEPARATED ORGANISMS IN THE MONERA
INTO TWO GROUPS:
- ARCHAEABACTERIA
- EUBACTERIA
• ARCHAEABACTERIA TEND TO THRIVE IN
EXTREME ENVIRONMENTS, EUBACTERIA DO
NOT.
• ALSO, THERE ARE STRUCTURAL DIFFERENCES
BETWEEN THESE TWO GROUPS OF BACTERIA.