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01 July 2016

#147 Classification

Classification is arranging different kinds of organisms into groups.













Taxonomy
Taxonomy is the study and practice of classification, which involves placing organisms in a series of taxonomic units, or taxa.





Bacteria
Archaea
Eukarya

prokaryotic
eukaryotic
nucleus
absent
present
membrane-bound organelles
absent
present
DNA
- circular “chromosome”
- no histone proteins associated
- smaller circular DNA molecules: plasmid
- inside the nucleus
- arranged as linear chromosomes
- has histone proteins
- mitochondria and chloroplasts have circular DNA
ribosomes
70S < eukaryotes
70S < eukaryotes
similar features
80S in cytosol > prokaryotes
cell wall
present,
peptidoglycan
present, no peptidoglycan
some do, some don’t
cell division
binary fission
mitosis
reproduction
sexually/asexually
unique

extremophiles – inhabit extreme environments
great diversity of forms
- unicellular
- colonial
- multicellular organisms





1. Kingdom Protoctista (eukaryotic)
  • mostly single-celled or groups of similar cells
  • some are protozoa: have animal-like cells (no cell walls) 
  • some are algae: have plant-like cells (cellulose cell wall and chloroplasts)

2. Kingdom Fungi (eukaryotic)
  • no chlorophyll --> does not photosynthesise
  • heterotrophic nutrition: use organic compounds (carbon) made by other organisms as its source of energy and molecules for metabolism from                                                                                                 - dead and deccaying matter                                                                                                             - feeding as parasites on living organisms
  • reproduce by spores
  • simple body form: unicellular or made of long threads called hyphae (with or w/o cross walls)
  • cell walls of chitin (not cellulose)
  • no cilia or flagella



Kingdom
Plantae
Animalia

- multicellular eukaryotes
- cells differentiated to form tissues and organs
specialised cells
few types
many types
chloroplasts
ü photosynthetic organism
û
vacuole
- large, permanent
- for support
- small, temporary
nutrition
autotrophic
heterotrophic

cells sometimes contain flagella
cells sometimes contain cilia and flagella
unique
- complex bodies
- highly branhed above and below ground
- communication by nervous system


Virus
  • microorganisms, only visible under an electron microsope
  • acellular (cellular structure unlike bacteria and fungi)
  • show none of the features traditionally used for classification
Some features:
  • have particles made of protein and nucleic acid
  • in free environment, viruses are infectious, but have no metabolism
  • when viruses infect cells --> use biochemical machinery of host cell to copy their nucleic acid and make proteins to destroy the host cell
  • energy provided by respiration in host cell
Taxonomy system - classified by:
  • which disease the virus causes
  • type of nucleic acid (RNA or DNA)
  • whether nucleic acid is single or double stranded



  Syllabus 2016-2018

18.2 Classification

Organisms studied locally may be used to show how hierarchical classification systems are organised.

a) describe the classification of species into the taxonomic hierarchy of domain, kingdom, phylum, class, order, family, genus and species 

b) outline the characteristic features of the three domains Archaea, Bacteria and Eukarya 

c) outline the characteristic features of the kingdoms Protoctista, Fungi, Plantae and Animalia 

d) explain why viruses are not included in the three domain classification and outline how they are classified, limited to type of nucleic acid (RNA or DNA) and whether these are single stranded or double stranded

3 comments:

  1. What do those green and red u's stand for in the table?

    ReplyDelete
  2. Domain Archaea has DNA which exists as circular chromosomes and DOES HAVE HISTONE PROTEINS ASSOCIATED WITH IT

    ReplyDelete