taxonomy and classification

• Earth formed approximately 4.6 billion years ago
• First prokaryotes likely arose at least 3.5 to 3.8 billion years ago
• Stromatolites are layered rocks formed by the incorporation of mineral sediments into microbial mats, mainly by cyanobacteria
• Evolution of prokaryotes is based on the characterization of small subunit ribosomal RNA sequences, divided into Bacteria and Archaea
• Eukaryotes arose from prokaryotes around 1.4 billion years ago, with two major hypotheses: invagination of plasma membranes or endosymbiotic theory
• Endosymbiotic theory suggests eukaryotes arose from a fusion of ancient bacteria and archaea, supported by data showing bacterial-like ribosomes and single, circular chromosomes
• Taxonomy involves classification based on behavioral, genetic, and biochemical variations, nomenclature, and identification to determine if an isolate belongs to a recognized taxa
• Classification systems include natural, phenetic, phylogenetic, and genotypic classifications
• Kingdoms of Life: Carolus Linnaeus proposed Plantae and Animalia, Ernst Haeckel added Protista, and Robert Harding Whittaker introduced the 5 Kingdom concept in 1969
• Whittaker's 5 Kingdoms include Animals, Plants, Protista, Monera, and Fungi
• Woese's Three Domain Scheme includes Bacteria, Eukarya, and Archaea, based primarily on rRNA analysis
• Kingdom Bacteria consists of true bacteria with peptidoglycan in the cell wall, metabolically and morphologically diverse, divided into 23 phyla
• Kingdom Archaea lacks peptidoglycan in the cell wall, has a different membrane lipid composition, and colonizes extreme habitats
• Kingdom Eukarya includes self-replicating organelles like chloroplasts and mitochondria, more closely related to archaebacteria and eukaryotes
• Prokaryotic cells are more primitive, lack a defined nucleus, and have circular chromosomes, while eukaryotic cells are more complex, have true nuclei, and contain membrane-bound organelles
• Taxonomy is the science of biological classification, consisting of taxa, classification, nomenclature, and identification
• Systematics studies organisms to characterize and arrange them, assisting in understanding phylogenetic relationships and evolutionary history
• Taxonomic ranks organize organisms into groups based on specific features, with taxa sharing common characteristics
• Defining prokaryotic species involves collections of strains with similar characteristics that differ from other groups, with strains being descendants of a single pure microbial culture
• Binomial system of nomenclature by Carolus Linnaeus assigns each organism two names: genus name (italicized and capitalized) and species epithet (italicized but not capitalized)
• Importance of taxonomy includes organizing knowledge, making predictions, facilitating scientific communication, and accurate identification of organisms