BIOL 1020 Classification 2022 PDF

Diversity of Life I BIOL1020 Microbial Classification Lecturer: Dr. Bidyut Mohapatra Dept. of Biological and Chemical Sciences [email protected]  Topics for this week Microscopy Microbial Classification – The need for classification...

Diversity of Life I BIOL1020 Microbial Classification Lecturer: Dr. Bidyut Mohapatra Dept. of Biological and Chemical Sciences [email protected]  Topics for this week Microscopy Microbial Classification – The need for classification Carl Linnaeus Standardisation in science History of the organisation of diverse organisms – The science of taxonomy How organisms are classified The process of classification  Definitions Taxonomy: Science of biological classification – Classification: « Natural »: mutual similarities Phylogenetic: evolutionary relationship – Nomenclature: attribution of names to taxonomic groups in accordance with the published rules – Identification: Practical aspect of taxonomy. Process by which it is determined that a particular isolate belongs to a known taxon. Biological classification systems Two Kingdoms System Five Kingdoms System Six Kingdoms System Eight Kingdoms System Universal Phylogenetic Tree (The Tree of LIFE)  Criteria for the classification of organisms Morphological Physiological Metabolic Ecological Genetic (Molecular) Carl Linnaeus In the time of Carl Linnaeus, it was an age of exploration (18th century) Members of the European community set off across the oceans to ‘discover’ new worlds and the organisms which lived there The diversity of organisms was on an unimaginable scale To bring some type of order to the chaos, Carl Linnaeus came up with a method of classification to standardise the naming process  Classification Linnaeus devised a hierarchical (relationship based) classification structure that helped to identify (name) the organism as well as relate it with others His classification structure resulted in the naming of an organism with two Latin derived epithets (Binomial nomenclature) Binomial nomenclature a burger bug is Escherichia coli  Classification Linnaeus’s classification system consists of seven taxonomic ranks The criteria for inclusion within each successive taxonomic rank becomes increasingly more specific Physical and structural, characteristics were considered Classification  Classification Carl Linnaeus based his taxonomic ranking system on natural, mutual similarities between organisms. Example: when Linnaeus first described his system he used the two kingdoms first designated by Aristotle: – Animalia – Plantae Inclusion into one of these two Kingdoms was based on specific characteristics.  Two Kingdom System Animalia Plantae Two Kingdoms Classification  Two Kingdoms System However, as the diversity of the newly discovered organisms increased, so too did the diversity of their characteristics Not all organisms could fit exactly Euglena gracilis into the two Kingdom scheme  Five Kingdoms System In 1969, after some alteration to the Linnaean system, including – The inclusion of a new rank- Empire (Domain) This separated organisms based on the presence (Eukaryote) or absence of a nucleus (Prokaryote) The separation of Protista into Monera and Protista. Robert Whittaker debuted his five kingdoms system.  Five Kingdoms System CLASSIFICATION CRITERIA Mode of Nutrition Metabolism Mode of Reproduction Type of Motility Morphology  Six Kingdoms System Monera or Prokaryotae were divided into two kingdoms: – Eubacteria – Archaea Classification  Eight Kingdoms System Two Empires and eight Kingdoms. Empire Bacteria: Eubacteria & Archaea. Empire Eukaryota: Six eukaryotic Kingdoms. Two new Kingdoms: Archezoa: Unicellular eukaryotes (Giardia) no Golgi, mitochondria, chloroplasts or peroxisomes. Chromista: photosynthetic, chloroplasts in the lumen of RER. (Diatoms, Brown algae, Cryptomonads & Oomycetes). RER = rough endoplasmic reticulum RECENT CLASSIFICATION PROKARYOTES EUKARYOTES  The Three Domains* *based on rRNA gene diversity  The Phylogenetic domains Phylogenetic classification is based on evolutionary relationships as established or implicated by genetic analysis (molecular similarities) According to molecular analysis although eukaryote groups such as plants, fungi, and animals may look different, they are more closely related to each other than they are to either the Eubacteria or Archaea. It was also found that the eukaryotes are more closely related to the Archaea than they are to the Eubacteria. RECENT CLASSIFICATION Phylogenetic tree  Universal phylogenetic tree Bacteria: – prokaryotes – membrane lipids : diesters of diacyl-glycerol – Ribosomes: 70S – rRNA: 16S Archaea: – prokaryotes – membrane lipids : tetraethers of diglycerol or diethers of isoprenoid-glycerol – Ribosomes: 70S – rRNA: 16S Eukaryota: – eukaryote – membrane lipids : diesters of acyl- glycerol – Ribosomes: 80S – rRNA: 18S. BACTERIA ARCHAEA EUKARYA