3-Class, 4-Order, 5- Family, 6- Genus, 7- Species.
In biology, a kingdom is the top-level, or nearly the top-level, grouping of organisms in a scientific classification. Originally, two kingdoms were distinguished, the Animalia (animals), which typically, they are multicellular in composition and capable of both movement and responding to their surroundings. Animal don’t photosynthesize, instead using plants or other organisms to grow and sustain themselves.
Another kingdom is the Plantae (plants), which typically could not move but they are able to photosynthesize, they have their own kingdom classification. A third kingdom is minerals. Each kingdom was divided into classes, and then into phyla for animals and divisions for plants. This is a simple classification but a new development started once single-celled organisms were first discovered, they were divided into the two kingdoms: motile forms were placed in the phylum Protozoa, they are single celled creatures with nuclei they usually associated with animals, while colored forms (algae) and bacteria were categorized in several divisions of plants. A number of forms ended up being placed in both - for example Euglena and slime molds.the result of this is a third kingdom creat , the Protista, was created to hold these groups.
The fourth kingdom for bacteria introduced by Copeland, bacteria is a certain type of single celled micro organism characterized by the lack of a memberance bound nucleus and membrane-bound organelles. Bacteria are among the oldest and most numerous living things and are found in the soil, water, and inside and outside most multicellular organisms. The fungi, which he included among the Protoctista, were given their own kingdom by Whittaker. Thus, he had three kingdoms for multicellular organisms, depending on whether they were autotrophic (Plantae), apostrophic (Fungi), or heterotrophic (Animalia), and two for unicellular or colonial organisms (Protista and Monera). With some variation in the exact circumscription of these groups, this five-kingdom system has been standard for a long time, and is still used in many works.
However, newer findings have led to alternative systems. Most notable was the finding by Carl Woese that prokaryotes comprised two distinct groups, which he called Eubacteria and Archaebacteria but are now called Bacteria and Archaea, which are not or are not much closer related to each other than they are to the eukaryotes. This prompted the three- domain system, with each of these groups is treated as a domain. The domains were originally a replacement for kingdoms, but are more commonly used as a higher level rank, with the Eukaryota divided into several different kingdoms. Alternatively, some have simply treated the Bacteria and Archaea as two kingdoms in place of the Monera. This six-kingdom system has replaced the five-kingdom system in some books.
The Protista have long been recognized as a junk-basket category for organisms that don't fit into the other eukaryotic kingdoms, and as a result some workers have promoted various protist groups to kingdoms. The most notable of these is the kingdom Chromista, proposed by ThomasCavalier-Smith, which corresponds essentially to the heterokonts and includes groups like brown algae,diatoms, and water molds. He also proposed a kingdom Archezoa for primitive eukaryotes that lack motochondria, but this gained little support due to the group's implausible heterogeneity, and in later revisions he abandoned both it and the Archaebacteria. Other groups which have been considered kingdoms, though considerably less often, include the alveolates and euglenozoa.
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Refrences :
1-) Campbel and Reece Biology International Edition (6th Ed), Benjamin,
Cummings,Publishing Co..
2-) Google Surch /Biology/ Taxonomy
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