A Short Note On Classification Of Organisms

Taxonomy refers to the process of classifying organisms. ‘Taxis,’ which implies ‘arrangement,’ and ‘Nomos,’ which means ‘method,’ are the two terms that make-up taxonomy and classification in biology. A 5 Kingdom Classification was proposed by R.H. Whittaker in 1969. Monera, Protista, Fungi, Animalia and Plantae were the kingdoms he defined.  He uses cell structure,  nourishment, Body organisation, and reproduction as criteria for the classification. 

Organisms are classified using a structural hierarchy, which is a multi-level structure wherein every group is layered or contained within a bigger group. The highest level groups are the biggest and most broad, containing a diverse range of living creatures. These are broken down into smaller groupings of organisms that are similar. Each smaller group is subdivided further, resulting in organisms with increasingly more identical characteristics: A big group of plants, for example, might have smaller groups of plants that are similar, such as trees, shrubs, mosses, blooming plants, and so on. Each of these categories would be subdivided further; for example, the tree category may be subdivided into broadleaf trees and conifers.

The Linnean categorization system or classification in biology contains eight levels of taxa, ranging from the broadest to the most specific:

• Domain 
• Kingdom 
• Phylum 
• Class, 
• Order, 
• Family, 
• Genus
• Species 

Each level exists within the level above it.  A genus, for example, contains a single or more species; the category family has one or more general, an order has one or more families, etc. The domain is the biggest group and is at the greatest level of organisation.

Now let’s discuss,

 The 5 kingdoms of classification in biology are as follows: 

• Monera includes unicellular organisms, for example, bacteria.
• Protista is analogous to monera which is unicellular but much more complicated and developed. It has a nucleus in it.
• Plantae This kingdom studies all plants, from the tiniest (algae) to the biggest trees.
• Fungi are eukaryotic creatures that include yeasts, moulds, mushrooms as well as other microbes. This kingdom’s species do not produce their food; they are essentially parasites.
• Animalia is a term that refers to all multicellular and eukaryotic organisms.  Metazoa is another name for it.

Kingdom Monera

• The Kingdom Monera is essentially, entirely bacterial microorganisms.  
• They are the most commonly found microorganisms on the planet. Bacteria may be found practically anywhere. A handful of dirt contains hundreds of microorganisms. 
• They also exist in harsh environments like hot springs,  snow, deserts, and deep oceans, where only a few other species can survive.  Many of these bacteria live in/on other species, as parasites. 
• The spherical Coccus, the comma-shaped Vibrium,  the rod-shaped Bacillus and the spiral Spirillum are the four types of bacteria, which are classified based on their form.

Kingdom Protista

• Protista includes all single-celled eukaryotes, however, the kingdom’s limits aren’t firmly defined. To one biologist, a eukaryote may be a  photosynthetic Protista,  but to another, it may be a plant. Chrysophytes, Euglenoids, Dinoflagellates, Slime Moulds, and Protozoans are all classified as Protista.   
• Protista is largely an aquatic phylum.
• This kingdom is linked to other kingdoms such as Kingdom Plantae, Animalia, and fungi. 
• The cell body of a protista like other eukaryotes has a well-defined nucleus as well as other membrane-bound organelles. Some may have flagella or cilia, whereas others don’t. 
• Cell fusion & zygote development are used by protists for reproduction which is both, sexual and asexual.

Kingdom Fungi

• Fungi are a distinct kingdom of heterotrophic creatures. They exist in a wide range of forms and various environments. 
• You’ve probably seen fungus on stale bread and rotting fruit. Fungi include the ordinary mushroom you eat as well as toadstools and the white patches on mustard leaves (due to parasitic fungus). 
• Some unicellular fungi, such as yeast, are utilised in the production of bread and beer. 
• Other fungi produce illnesses in animals and plants; Puccinia, which causes wheat rust, is a good example. Penicillium, for example, is a source of antibiotics. 
• Fungi are widely distributed and may be found in the air, water, soil, and on plants and animals.

Kingdom Plantae

• Plantae refers to all eukaryotic organisms that contain chlorophyll and are typically referred to as plants. 
• A few members, such as insectivorous plants and parasites, are somewhat heterotrophic. Insectivorous plants such as bladderwort and Venus flytrap exist, while Cuscuta is a parasite. 
• The cells of plants are eukaryotic, having significant chloroplasts and cellulose-based cell walls.

Kingdom Animalia

• This kingdom (Animalia) is made up of heterotrophic eukaryotic organisms which are multicellular and do not contain cell walls. 
• They rely on plants/vegetation for food, which is consumed directly or indirectly. Food is digested in an interior cavity, and food reserves are stored as glycogen/fat. Their form of nourishment is holozoic, which means they consume/ingest.  
• They have a distinct development pattern and mature into adults with distinct shapes and sizes. Higher forms of animals have more complex sensory and motor neural mechanisms. The majority of them can move about (perform locomotion). 
• Sexual reproduction is through male and female mating, which is succeeded by embryological development.

Conclusion

Aristotle was the first to propose the biological taxonomy of animals and plants based on simple physical characteristics. All living organisms were eventually divided into two kingdoms by Linnaeus: Plantae and Animalia.  Whittaker offered a five-kingdom classification which includes Monera, Fungi,  Protista, Plantae, and Animalia.  Cellular structure, body organisation, mechanism of nourishment and reproduction, and evolutionary links were the major factors for the five-kingdom categorization/ classification in biology.