Five Kingdom System of Classification

• Taxonomy identifies, names, and classifies organisms by similarity and evolutionary relationships.
• Taxonomy is multidisciplinary, advancing with progress in fields like morphology, histology, and genetics.
• A taxonomic system classifies every living species.
• Taxonomic classification groups organisms into categories (taxa) based on shared features.
• Taxa are arranged hierarchically from species to domain.
• The five kingdom system is a widely accepted biological classification.
• R.H. Whittaker proposed the five kingdom system in 1969.
• The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.
• Kingdoms are delineated by cell structure, cellular organization, and nutrition mode.
• Ecological roles and reproduction modes are also important characteristics.

Five Kingdom System of Classification

• Monera/Prokaryotae: Prokaryotic cells, cell walls of polysaccharides and amino acids, unicellular organization, variable nutrition (phototrophic, heterotrophic, or chemo-autotrophic), primarily asexual reproduction, and variable ecological roles.
• Protista: Eukaryotic cells, present cell walls with cellulose in some, unicellular or multicellular organization, phototrophic or heterotrophic nutrition, asexual and sexual reproduction (without embryonic stage), and variable ecological roles.
• Fungi: Eukaryotic cells, cell walls with no cellulose, unicellular or multicellular organization, heterotrophic nutrition (absorption), asexual and sexual reproduction (with spore formation), and decomposer ecological role.
• Plantae: Eukaryotic cells, cell walls with cellulose, multicellular organization (tissues/organs/organ systems), autotrophic nutrition (photosynthesis), asexual and sexual reproduction (with embryonic stage), and producer ecological role.
• Animalia: Eukaryotic cells, absent cell walls, multicellular organization (tissues/organs/organ systems), heterotrophic nutrition (ingestion), primarily sexual reproduction (with embryonic stage), and consumer ecological role.
• Diploblastic describes invertebrate animals derived from two embryonic germ layers (endoderm & ectoderm).
• Triploblastic describes multicellular animal development from three embryonic layers (endoderm, ectoderm & mesoderm).
• Body symmetry is the arrangement of body parts giving a balanced form.
• Asymmetry is an irregular body form without orderly arrangement of parts.
• Radial symmetry has proportional arrangement of similar parts around a central axis.
• Bilateral symmetry divides the body into two mirror-image halves.
• A coelom is a fluid-filled body cavity formed from the mesoderm.
• Acoelomate: lacks a coelom.
• Pseudocoelomate: has a pseudocoel between the gut and body wall.
• Coelomate: has a coelom between the body wall and digestive tract.
• Parazoa: animals lacking tissues.
• Metazoa (Eumetazoa): multicellular animals with cells in tissues and organs.

Viruses

• D.I. Ivanosky (1892) identified viruses as the cause of tobacco mosaic disease.
• Viruses are small enough to pass through bacteria-preventing filters.
• Beijerink named them 'virus' (Latin for poison) in 1898.
• Viruses require electron microscopy for study.
• Frobisher classified viruses into plant, insect, mammalian, and bacterial groups in 1957, based on host specificity.
• Viruses are classified by envelope presence (enveloped or non-enveloped).
• Viruses are classified by nucleic acid type (DNA or RNA viruses).
• Viruses lack cellular structures.
• Viruses are parasitic, requiring a host cell to reproduce.
• Viruses exist on the boundary between living and non-living.
• Viruses are specific to their host.
• Virus sizes vary from 20nm (foot and mouth disease) to 300nm (smallpox).
• Viruses have a simple structure: nucleic acid (DNA or RNA) with a capsid.
• Capsids are made of capsomeres and can have a lipid envelope from the host cell.
• Virus shapes include helical, icosahedral, prolate (enveloped), and complex.
• Approximately 2000 viruses are known, with about 400 attacking plants.
• Bacteriophages are viruses that attack bacteria, reproducing rapidly.
• T4 bacteriophage infects Escherichia coli.
• Bacteriophages consist of a polyhedral head, neck, collar, core (DNA or RNA), sheath, endplate, and tail fibers.
• The sheath is contractile, aiding core penetration into the bacterium.
• Tobacco mosaic virus (TMV)has nucleoproteins and is rod-shaped, measuring 300nm x 15nm.
• Viruses require in-vivo cultivation (developing chick embryo, bacteria, laboratory animals).
• Viruses cause diseases in plants (mosaic disease) and animals (mumps, smallpox, AIDS).

Kingdom Monera

• Monera includes unicellular prokaryotes like bacteria and cyanobacteria, with no nuclear membrane.
• Bacteria are abundant microorganisms found almost everywhere.
• Bacteria inhabit diverse environments, including extreme conditions.
• Bacteria are mostly single-celled prokaryotic microorganisms in soil, plants, and aquatic habitats.
• Some bacteria are symbionts; others cause plant or animal diseases.
• Many bacteria are used in commercial and manufacturing processes.
• Anthony Von Leuwenhook (1683) discovered bacteria, calling them "tiny animacules".
• Ehrenberg (1829) established the genus 'Bacteria'.
• Bacteria are unicellular, achrolophyllous (non-chlorophyllous).
• Bacteria are autotrophic, using carbon dioxide and light, saprophytic, obtaining nutrients from non-living matter, and parasitic, benefiting at the expense of the host.
• May be motile or non-motile due to flagella.
• Structurally are primitive cells without a nucleus or nuclear membrane.
• Reproduce via binary fission (sexual reproduction recently reported in Escherichia coli).
• Bacteria grow in all environments.
• They range from 0.5µm to 10µm in size.
• Cohen divided bacteria into cocci (spherical), bacilli (rod-shaped), spirilla (spirals), and vibrio (comma-shaped).
• Cocci arrangement divisions: micrococci (single), diplococci (pairs), streptococcus (chains), staphylococcus (bunches), sarcinae (cuboidal), tetracocci/gaffkya (groups of four).
• Bacilli may be in pairs (diplobacilli), chains (streptobacilli), or palisade arrangements.
• The Spirillum represents spirals of helical structures.
• Vibrio are comma shaped.
• Flagellation: bacteria are motile with flagella.
• Flagella arrangements: monotrichous (single flagellum), lephotrichous (many flagella at one pole), amphitrichous/multitrichous (flagella at both ends), and peritrichous (flagella all around).
• Some move via cellular contraction or ‘swelling of the slime'.
• Structurally enveloped by a capsule/slime layer, cell wall, and plasma membrane.
• Capsule/slime layer is a protective layer that is pathogenic.
• The bacterial cell wall is a strong structure that protects the cell, composed of amino acid sugars.
• Gram-positive bacteria have thicker cell walls.
• The cell membrane is a phospholipid and protein layer involved in respiration.
• The cytoplasm contains salts, sugars, and ribosomes.
• Chromotophore in photosynthetic bacteria contains photosynthetic pigments.
• The nucleic region has a primitive nucleus, a single circular chromosome of DNA and protein, and may contain plasmids.