Diversity of life

• Diversity of Life


  Variety of living organisms
• The Greek philosopher Aristotle was the first to classify organisms almost 2000 years ago
• Aristotle's classification of animals

  • Land dwellers
  • Water dwellers
  • Air dwellers
• Aristotle's classification of plants


  • Herbs
  • Shrubs
  • Trees
• Many organisms were placed in groups to which they had no real relationship with the other members of the group in Aristotle's system
• The use of common names was very confusing in Aristotle's system, for example, catfish or jellyfish
• Many new organisms were being discovered and needed to be classified
• Linnean Classification System


  Classification system based on structural similarity, with organisms assigned a scientific name (binomial nomenclature)
• Two-Kingdom System(Linnaeus)


  Organisms divided into two kingdoms: plant and animal, with further subdivision into smaller groups
• As the knowledge of the properties of various groups of microbial life exploded around the middle of the 19th century, it became apparent that a division of the living world into two kingdoms cannot really be maintained on a logical and consistent ground
• Three-Kingdom System


  Kingdoms: Protista, Plantae, and Animalia, based on morphological complexities, tissue system, division of labor, and mode of nutrition
• Four-Kingdom System


  Kingdoms: Monera, Protoctista, Plantae, and Animalia, with Monera accommodating lower protists (bacteria and blue-green algae)
• Unicellular organisms were challenging to classify
• Five-Kingdom System


  Evidence that all living things seem to fall naturally into three broad groups
• Three-Domain System/Six-Kingdom System


  Domains (superkingdoms) are a higher taxonomic level than kingdoms, with Domains: Bacteria, Archaea, and Eukarya
• Domains are needed as a higher taxonomic level to better classify the diversity of living organisms
• Eight-Kingdom System


  Kingdoms divided based on ultrastructural characteristics and rRNA sequences, with two Empires and seven kingdoms
• Monerans are distributed widely
• Kingdom Protista


  • Eukaryotic, unicellular or colonial, aquatic, photosynthetic or non-photosynthetic, possess cell organelles, reproduce sexually and asexually
• Kingdom Fungi


  • Fungi are ubiquitously found in any conceivable habitat.
• Fungi have economic importance
• Fungi


  • Heterotrophic and absorb food from the environment through extracellular digestion.
• Fungi can colonize environments
• One-to-all known fungi are heterotrophic and absorb food from the environment through extracellular digestion
• Phylogeny


  The evolutionary history of an organism
• Phylogenetic tree


  A type of family tree that depicts the evolutionary relationships between various groupings of species
• Evidences Used for Modern Taxonomy

  • Morphology (Structural Similarities)
  • Cellular Organization
  • Evolutionary Relationships
  • Biochemical similarities
  • Genetic similarities
  • Embryological similarities
• Molecular clock


  Used to plot the period and time that organisms are related by the identification of repeating occurrences of mutations present in the genes
• Dichotomous key


  A useful scientific tool for identifying various organisms based on their observable characteristics, made up of a series of statements, each with two options, that guide users to the proper identification
• Linnaeus proposed a 2-Kingdom classification system
• Microscopic observations and other modern techniques added up to the knowledge, thus, modifying the early classification systems
• Embryological similarity evidence investigates the features of embryos and their development, and how their resemblances across species indicate relatedness
• Nomenclature


  The art of naming the object
• International Code of Botanical Nomenclature (ICBN)


  The set of rules and recommendations dealing with the nomenclature of plants, fungi and a few other groups of organisms, all those "traditionally treated as algae, fungi, or plants"
• International Code of Nomenclature for Cultivated Plants (ICNCP)


  Gives rules and recommendations that supplement the ICN for the naming of...
• International Code of Nomenclature of Prokaryotes (ICNP)


  Gives rules and recommendations that supplement the ICN for the naming of bacteria
• Generic epithet


  Always a noun showing colour, name in honour of person or adjective
• Species


  An adjective e.g. for white colour it is alba, red-rubra, green-viridis black colour-nigrum etc. for cultivated one it is sativa, edible one esculenta etc.
• Species


  May also be a pronoun, e.g., americana, indica, benghalensis, etc. It may characterize shape of a leaf (character of plant), e.g., hastata, cordata, sagitata etc. name of other scientist to whom the plant is dedicated, e.g., pangteyana, sahnia, etc
• Principle I: (Straight forward Principle) Botanical nomenclature is independent of zoological nomenclature