Systematics

• branch of biology cataloguing biological organisms (plants, animals, etc.) into categories.

  Systematics
• “Names” were basically biological description of the organism
• Systematics may be defined as the study of the kinds and diversity of organisms and the relationships among them
• Taxonomy is the theory and practice of identifying, describing, naming, and classifying organisms.
• Early classifications were concerned entirely for easy identification of useful and harmful plants and animals
• 430-377 BC Hippocrates (the Father of medicine) and Aristotle (384-322 BC, father of zoology) arranged animals on the basis of habitat into aquatic, terrestrial, aerial animals
• On the basis of single character, Greek scholars divided animals into four major groups— insects, birds, fishes and whales
• Theophrastus (father of botany, У10-285 BC) divided plants on the basis of form, texture and habit into four groups— trees, shrubs, under-shrubs and herbs
• Theophrastus (father of botany) described 480 plants in his book ‘Historia Plantarum’
• Pliny the Elder (28-79 A.D.) introduced the first system of artificial classification. His book, Historia Naturalis (c75 AD), mentions over 1,000 economic plants with about 2,000 items. More and more organisms were discovered and named.
• John Ray (1627-1705), English naturalist, described about 18600 plants in three volumes ‘Historia Generalis Plantarum’ between 1686-1704
• The naturalist introduced the word “species” in its present sense for the first time. John Ray defined species as an assemblage of individuals with similar par­entage and having ability to pass the parental traits to the offspring.
• Swedish naturalist Carolus Linnaeus developed the scientific system of naming species known as the “Binomial System of Nomenclature”. Linnaeus described 5900 species of plants in his book Species Plantarum (1753) and 4326 species of animals in Systema Naturae (1758).
• Basics of Systematic Study

  Characterization, Identification, Classification, Nomenclature
• Characterization - The organism to be studied is described for all its morphological and other characteristics.
• Identification - Based on the studied characteristics, the identification of the organ­ism is carried out to know whether it is similar to any of the known group or taxa.
• Classification - The organism is now classified on the basis of its resemblance to different taxa. It is possible that the organism may not resemble any known taxa or groups. A new group or taxon is raised to accommodate it.
• Nomenclature - After placing the organism in various taxa, its correct name is determined. If the organism is new to systematics, it is given a new name based on rules and conventions of nomenclature
• Systematics is the study of the diversity of an organism on the basis of its evolutionary relations
• 3 Domains of Life

  Bacteria, Archaea, Eukarya
• Archaea are prokaryotic cells.
• Unlike the Bacteria and the Eukarya, the Archaea have membranes composed of branched hydrocarbon chains (many also containing rings within the hydrocarbon chains) attached to glycerol by ether linkages
• The cell walls of Archaea contain no peptidoglycan, and are genetically different among the other organisms
• Archaea contain rRNA that is unique to the Archaea as indicated by the presence molecular regions distinctly different from the rRNA of Bacteria and Eukarya.
• Woese et al., 1990 describe Archaebacteria as:

  (1)the presence of characteristic tRNAs and ribosomal RNAs

  (2)the absence of peptidoglycan cell walls, with in many cases, replacement by a largely proteinaceous coat

  (3)the occurrence of ether linked lipids built from phytanyl chains and (4) in all cases known so far, their occurrence only in unusual habitats
• Archaea often live in extreme environments and include methanogens, extreme halophiles, and hyperthermophiles
• Membrane lipids of Archaea is Ether link
• Membrane Lipids of Bacteria and Eukarya is Ester link
• Also known as eubacteria or "true bacteria“, are prokaryotic cells that are common in human daily life, encounter many more times than the archaebacteria.
• Like the Eukarya, they have membranes composed of unbranched fatty acid chains attached to glycerol by ester linkages
• The cell walls of Bacteria, unlike the Archaea and the Eukarya, contain peptidoglycan.
• Bacteria contain rRNA that is unique to the Bacteria as indicated by the presence molecular regions distinctly different from the rRNA of Archaea and Eukarya.
• Cell wall of Gram positive bacteria has thick Peptidoglycan layer
• Gram negative bacteria has thin Peptidoglycan layer with outer lipopolysaccharide (LPS)
• Archaea are extremophiles, living at high temperatures, low pH, high salt concentrations, etc.
• Like the Bacteria, Eukarya have membranes composed of unbranched fatty acid chains attached to glycerol by ester linkages
• Not all Eukarya possess cells with a cell wall, but for those Eukarya having a cell wall, that wall contains no peptidoglycan.•
• Eukarya contain rRNA that is unique to the Eukarya as indicated by the presence molecular regions distinctly different from the rRNA of Archaea and Bacteria.
• Kingdoms of Eukarya

  Protoctista, Fungi, Plantae, Animalia
• Geological Time Scale- extensive interval of time occupied by the geologic history of Earth.