Over thousands and millions of years, a bewildering variety of species has evolved on the earth. Classification of these organisms was a serious challenge for the biologists. Many researchers had come forward with different categories to classify living things. Among them, Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) are few whose contributions are notable. Modern-day of taxonomy has accepted the five kingdom classification of R. H. Whittaker. The basis of his classification is cell structure, mode, and source of nutrition and body design. Monera, Protista, Fungi, Plantae, and Animalia are the five kingdoms which were introduced by Whittaker.
Let’s learn about kingdoms Monera, Protista, and Fungi.
- Kingdom Monera comprises of unicellular organisms with a prokaryotic cell organization.
- They lack well-defined cell structures including the nucleus and other cell organelles.
- Cyanobacteria, bacteria, and mycoplasma are few members of this kingdom.
- The general characteristic features of Monerans are: some have cell walls while some do not, they have an autotrophic mode of nutrition i.e., they can synthesize food on their own while some other have a heterotrophic mode of nutrition.
- Protista includes unicellular eukaryotes.
- Amoeba, protozoan, diatoms, euglena, algae, and paramecium are few members of this kingdom.
- Like monerans, protists also include both autotrophic and heterotrophic mode of nutrition.
- Some protists like protozoan possess appendages for locomotion such as cilia and flagella.
- All members of Protista kingdom reproduce through an asexual mode of reproduction either through binary fission and spore formation.
- Fungi are eukaryotic organisms.
- They consist of both unicellular (e.g. Yeast, Molds) and multicellular (e.g. mushrooms) organisms.
- Like plant cells, fungi have cell walls made up of a complex sugar called chitin. But they do not perform photosynthesis.
- They have a heterotrophic mode of nutrition. Few species are saprophytes i.e., they feed on dead and decaying organic matters.
- Some fungi are parasitic while some are symbionts. They can live in symbiotic relationship with algae like blue-green algae. These are called lichens.
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