Different system of classification recognize two to six kingdoms. For centuries, there are only two kingdoms in which living organisms have been classified PLANTS AND ANIMALS. Plants are the living organism that can make their own food from simple inorganic material can called AUTOTROPHS. They store their food in their body. While animals are the living organism that cannot make their own food can called HETEROTROPHS. And depend upon autotrophs and other animals to fulfill their need. Bacteria were introduce in the kingdom of plants.
Many biologist are satisfy from this system but many found it unworkable for unicellular organism that have both plant like and animal like characteristics example EUGLENA. This system also not explained the difference of prokaryotic and eukaryotic cells. The classification of fungi is also not satisfactory such as bread, mold, yeast, mushrooms etc. fungi resembles to plant in many ways but are not autotrophs. Fungi are special heterotrophs that obtain food by decomposing and absorption from surrounding. They possess chitin in their cell wall.
SYSTEM OF CLASSIFICATION:
In 1866, ERNST HACKEL proposed kingdom protista for euglena type organisms. In 1937, E-CHATTON suggested two different terms prokaryotic and eukaryotic. ROBERT WHITTAKER give five kingdom classification depend upon principal modes of nutrition PHOTOSYNTESIS, ABSORPTION, INGESTION.
- MONERA (prokaryotic unicellular bacteria)
- PROTISTA (eukaryotic unicellular euglena, amoeba)
- PLANTAE (eukaryotic multicellular)
- FUNGI (reducer)
- ANIMALIA (consumers)
LYNN MARGULIS and KARLENE SCHWARTZ (1988) modified five kingdom classification of WHITTAKER by considering cellular organization, mode of nutrition, cytology, genetics and organelles of symbiotic origin.