Five Kingdom Classification

You will thus find that three- and four-kingdom classifications were able to remove some of the anomalies of the two-kingdom classification system. These systems however, were not able to place appropriately the Fungi -a group of organisms which lack chlorophyll. They were classified inappropriately under protista in the four system classification despite the fact that they differed from the protista totally in form, function and behaviour. Also they could neither be considered plants nor animals, so in 1969 Whittaker erected a separate kingdom, 'Fungi', for them, thus proposing the 'Five-King Classification' which is generally used at present. Whittaker's classification retained the: basic prokaryote - eukaryote distinction. Thus, the Kingdom Monera contains the prokaryotes. The eukaryotes are classified into four remaining kingdoms.

Figure: Five Kingdom Classification

The Kingdom Protista contains the unicellular eukaryotic organisms (Protozoa and unicellular eukaryotic algae). The multicellular organisms are split into three kingdoms on the basis of mode of nutrition and other fundamental differences in organization. The Kingdom Plantae includes multicellular, photosynthesizing organisms, higher plants and multicellular algae. Kingdom Fungi includes the moulds, yeasts and mushrooms etc. which do not have chlorophyll but obtain their food by absorption. The non chordates and the chordates make up Kingdom Animalia. Most of these forms ingest their food and digest it internally, although some parasitic forms are absorptive. The evolutionary relationship of the five kingdoms are shown in Figure. The protists are believed to have given rise to all the multicellular organism, which have evolved independently.