The Five Kingdom Classification system by R.H. Whittaker, introduced in 1969, divides living organisms into five major kingdoms based on their cell structure, nutritional modes, and other key characteristics. These kingdoms are:
- Monera: This kingdom includes all prokaryotic organisms, such as bacteria and cyanobacteria (blue-green algae). They are unicellular organisms without a distinct nucleus.
- Protista: This kingdom contains unicellular eukaryotic organisms, such as protozoans, algae, and slime molds. These organisms have a defined nucleus and may be autotrophic (like algae) or heterotrophic (like protozoa).
- Fungi: Fungi are multicellular (except for some yeasts) and are heterotrophic organisms that absorb nutrients from their environment. They have a cell wall made of chitin and reproduce via spores. Examples include molds, mushrooms, and yeasts.
- Plantae: This kingdom consists of multicellular, autotrophic organisms that carry out photosynthesis. Plants have cell walls made of cellulose and are non-motile. Examples include mosses, ferns, conifers, and flowering plants.
- Animalia: Animals are multicellular, eukaryotic organisms that are heterotrophic and usually motile at some stage in their life. They lack cell walls and reproduce sexually. This kingdom includes all animals, from sponges to humans.
Whittaker’s classification provided a clearer distinction between organisms based on both their morphological and nutritional differences, as opposed to earlier systems which were less comprehensive.
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