Whittaker’s System of Classification
It is the five kingdom classification. In the 20th century, advances in cell biology and interest in evolutionary biology led scientists to question the two or three-kingdom classification schemes. In 1969, Robert H. Whittaker proposed a system which recognizes five kingdoms of living things: Monera (Bacteria), Protista, Fungi, Plantae and Animalia (Table 8.1).
Whittaker’s system of classification is based on 1) complexity of cell structure 2) mode of nutrition 3) body organization 4) phylogenetic or evolutionary relationship.
Monera: This kingdom includes all prokaryotic organisms. Unicellular microorganism such as Mycoplasma, Bacteria, Actinomycetes and Cyanobacteria are grouped under kingdom Monera.
Protista: This kingdom includes eukaryotic unicellular Protozoans, slime molds and algae. The kingdom is made up of more than 250000 species. These organisms have typical eukaryotic cell organization.
Fungi: This kingdom includes non green, non photosynthetic eukaryotic fungi. molds, mushroom, toad stools, puffballs and bracket fungi are grouped under this kingdom. They are multicellular and consist of specialized eukaryotic cells arranged in a filamentous form.
Plantae: It includes all multicellular plants of land and water. They use photosynthesis to synthesize their organic molecules.
Animalia: This kingdom includes all multicellular eukaryotic animals. They are also referred to as Metazoans. Animals ingest their food through one of any ingestion portal and then use digestive enzymes to break food particles into absorbable fragments (Figure 8.3).
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