Kingdom Monera,Protista,Mycota,Plantae and Animalia

Prokaryotic and Eukaryotic microorganisms

Evolution in electron microscopy in 1940 exposed much more of the internal structure of cells than made with the light microscope.A particularly important discovery in terms of taxonomy was that microbial cells could be divided into two types based on how the nuclear substances survive within the cell: Eukaryotic cells possess a nucleus separated from the cytoplasm by the nuclear membrane, where prokaryotic cells harbor nuclear material not enclosed within a membrane. The basis dissimilarity in the basis for separation of bacteria from other kinds of microorganisms and from all other cells, plant or animal. Bacteria have a prokaryotic cell structure and are prokaryotes.

Kingdom Monera

• The organism of this kingdomare unicellular. These organisms lack the nucleus.Besides, all those membranes bound organelles such as mitochondria, chloroplast, lysosome, etc.are absent from the monera cell. The photosynthetic microorganism has pigment enclosed by ingrowths of the plasma membrane.
• The ribosome is the only cytoplasmic organelles present in the organisms.
• Peptidoglycan is the main element of the cell wall.
• Flagellated ones have the single thread like a procession .The flagella lack 2+9 arrangement of microtubules i.e they are simple.
• The organisms under this group show variation in nutrition. These may be autotrophic or heterotrophic. Many heterotrophic types are important in causing decay and decomposition.
• Sexual reproduction sometimes occurs in these organisms.Most organisms reproduce vegetative or asexually.Sometimes gene recombination may occur.
• Only a single naked chromosome is found in the cell. DNA component in it is circular with no chromosomal proteins.
• Bacteria, Cyanobacteria (Blue-green algae), archaebacteria are included in this kingdom.

Kingdom Protista

• The organisms are usually unicellular or colonial unicellular eukaryotes.
• These are usually aquatic.
• Cell wall when present in made mainly of cellulose.
• Flagella if present shows 2+9 arrangement.
• Nutrition in these organisms is not usually photosynthetic (autotrophic).
• Few are predatory and feeds on other protists.
• They reproduce by asexual and sexual reproduction.
• The DNA component associated with basic protein is known as histones. Example-Protozoans, Euglenoid.

Mycota

• These are uni or multicellular achlorophyllous, spores possessing thallophytes.
• A major element of the cell wall may be fungus cellulose or chitin or both.
• When a multicellular thread like structures branched in various orders called mycelia (singular-mycelium) constituent the thallus. Individual branch of it is known as hypha (plural hyphae)
• These are heterotrophic usually saprophytic or parasitic. Some are symbiotic in that lifestyle.
• Mode of nutrition is adsorptive which assumes the enzymes secreted by hyphae digest complex nutrients of the host. The simplified nutrients then absorbed by these organisms.
• The reproduction may be vegetative, asexual and sexual. Asexual reproduction takes place within favorable conditions.
• The reserve food materials are glycogen. Example: Aspergillus, Penicillium, Saccharomyces (yeast)

Plantae

• It possesses multicellular, eukaryotic and autotrophic organisms.
• The cell possesses cell wall, which is made up of the element called cellulose.
• The cells contain one or two large vacuoles and no structure like centrosome.
• These organisms bear photosynthetic pigments in their cells and therefore are producers.
• The reserve food material is generally starch.
• The tree generally grows being attached to the soil.
• Reproduction is usually vegetative, asexual or sexual.

Examples:- Multicellular algae, bryophytes, Pteridophytes, Phanerogams.

Animalia

• All the heterotrophic multicellular organisms are places in this kingdom.
• Higher animals show organ system of organization.
• The cell wall is absent.
• Cells lack central vacuole. Vacuole if present is small and multiple in number.
• Animal mostly shows locomotion.
• Reproduction occurs in higher animals by sexual techniques.
• Reserve food ie stored in the form of glycogen.
• Growth occurs equally in all parts of the body.

Merits of Five-kingdom classification

• This system of classification is formulated on origin and evolution of the organisms, hence phylogenetic one.
• Since prokaryotes are a lot different from all other organisms, they were given the status of the kingdom.
• Likewise, fungi are the organism with cell wall but the component of the wall and their psychological and nutritional properties are distinctly different.Therefore,the organisms were kept in a separate kingdom.

The five kingdom system of classification of the living organisms was based on three different criteria:

1. Cellular organization: Organisms with prokaryotic and eukaryotic cellular structure were separated
2. Body organization: The organisms were arranged in different kingdom according to their body complexity (arrangement from unicellular and simple structure to multicellular complex body)
3. Mode of nutrition: Mode of nutrition were given due consideration while grouping the organisms.The autotrophic organisms and heterotrophic organisms were given different position. Ecological role of the organisms was also taken into account in classifying the word of living beings.

This system classifies the organisms into five kingdoms namely Monera, Protista, Mycota, Plantae, and animals.

Microorganisms were separated in the kingdoms-monera, Protista, and Mycota. Fungi were given the place of a separate kingdom upper than the protests. According to these systems, the primitive prokaryotic organisms under Monera gave evolved to unicellular, Protists. The kingdoms of mycota, Planeta and animelia developed in three independent types.

The characteristic feature of the kingdoms is given above.

References

Arvind, Keshari K. and Kamal K Adhikari. A Textbook of Biology. Vidyarthi Pustak Bhander.

Michael J.Pleczar JR, Chan E.C.S. and Noel R. Krieg. Microbiology. Tata Mc GrawHill, 1993.

Powar. and Daginawala. General Microbiology.

Rangaswami and Bagyaraj D.J. Agricultural Microbiology.