1.4 Three Domains of life

. Three Domains of life Three domain classification was proposed by Carl Woese ( ) and his co-­workers. They classified organisms based on the difference in 16S rRNA genes. The three domain system adds the taxon ‘domain’ higher than the kingdom. This system emphasizes the separation of Prokaryotes into two domains, Bacteria and Archaea, and all the eukaryotes are ARCHAEA (Extremophiles) Methanogens, Halophiles, Thermoacidophiles BACTERIA Cyanobacteria, Eubacteria, beneficial& pathogenic EUKARYA (Eukaryotes) Protista, Fungi, Plants and Animals THREE DOMAINS (Carl Woese, ) XI Std Biology-Zoology Chapter- and harmful pathogenic bacteria which are diversely populated. Cyanobacteria are photosynthetic blue green algae which produce oxygen. These had played a key role in the changes of atmospheric oxygen levels from anaerobic to aerobic during the early geologic periods. . Domain Eukarya (Eukaryotes) Eukaryotes are animals which have true nucleus and membrane bound organelles. DNA in the nucleus is arranged as a linear chromosome with histone proteins, ribsosomes of 80S type in the cytosol and 70S type in the chloroplast and Table . Five Kingdom Classification KINDS OF KINGDOM