Classification of organisms

  • Created by: Katrina
  • Created on: 14-05-12 16:49


at least 10-100 million different kinds of organisms of Earth today

scientists classify organisms in order to make sense of this great diversity of species

organisms are classified according to evolutionary similarities in: morphology (anatomical structures), physiology (function) and biochemistry (chemical pathways)

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International Classification (Taxonomy)

Taxon Example

Kingdom Animalia

Phylum Chordate

Class Mammalian

Order Primate

Family Homonidae

Genus Homo

Species Homo sapiens

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the grouping of organisms according to how they are believed to have diverged from a common ancestor

classification is uncertain and constantly changing due to constant new evidence

taxonomic heirarchy is the successive grouping of organisms-each group is a taxon

a taxon is each level-each level is an assembly of different organisms sharing some basic features

organisms are more closely related as we progress from kingdom to species

genus is several closely related species which share many homologous characteristics

species is the basic unit of biological classification-organisms of the same species have numerous physical feature in common-they can interbreed and produce viable, fertile offspring

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Naming Organisms

a binomial system-a 2 word Latin name

organisms named by genus (capital letter) and species (lowercase letter) e.g. Homo (generic name) sapiens (species name)-common name 'human being'; Locusta miratoria, Rosa canina

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Features Prokaryotae Protoctista Fungi Plantae Animalia

Cell type prokaryotic  simple eukaryotic eukaryotic eukaryotic eukayotic

Cell wall peptidoglycan some chitin cellulose NONE

Uni/multicellular unicellular unicellular uni/multicellular multicellular multicellular

Mode of nutrition auto/heterotrophic auto/heterotrophic hetero(sapro)trophic autotrophic heterotrophic

Chloroplasts/phyll some some no yes no

Motile some some no no yes

Examples bacteria amoeba, plasmodium yeast, mushroom confers, moss human

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small (0.5-5.0um)

circular DNA, free in cytoplasm

no true nucleus

small ribosomes

no ER, few organelles (non-membrane bound)

peptidoglycan cell wall (murein)

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simple eukaryotic organisms

unicellular/colonies or identical cells

no tissues formed, little or no specialisation of cells

larger cells (40um)

true nucleus (contains DNA), DNA associated with protein

larger ribosomes

many single/double membrane-bound organelles

organelles carry out varying functions

e.g. amoeba, water mould, slime mould, algae

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eukaryotic cells

saprotrophic enzymes secreted onto food substrate, digested outside of the cells and nutrient solution absorbed into cell (heterotrophic)


cell wall of chitin

unicellular (yeast) or multicellular (mushroom)

similar cells joined together to make threads called hyphae (sing. hypha)

whole mass of hyphae called mycelium

reproduction by spores e.g. penicillium, yeast, mushroom

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autotrophic-feed via photosynthesis

cell walls of cellulose

sap filled vacuoles

chloroplasts in some cells

e.g. mosses, liverworts, ferns, confers, flowering plants

main plant phyla:

non-flowering plants e.g. ferns

flowering plants (most dominant phyla) known as angiosperm,  including major crops-most important food source.  Flowers have seeds enclosed in fruit

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heterotrophic (take organic molecules into body, digest them and synthesise new molecules for own use)

no cell walls

no sap filled vacuoles

show nervous coordination

2 main groups:

non-chordates (invertebrates) are animals without a vertebral column e.g. worms, molluscs, arthrophods, jellyfish

chordates (vertebrates) are animals with a vertebral column e.g. fish, amphibians, reptiles, birds, mammals

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