Classification

• A micrograph of Hemimastix kukwesjijk, the newly described hemimastigote
• Hemimastigote


  A newly discovered kingdom, neither animal, plant, fungus nor familiar protozoan, a strange microbe that sits in its own "supra-kingdom" of life
• The species points to the influence of biodiversity on classification and that the classification itself is not permanent
• In a paper published in The Quarterly Review of Biology (September 2017), researchers from the University of Arizona had estimated that there were roughly 2 billion living species on Earth - over a thousand times more than the then (2017) current number of described species
• Species


  Organisms that can exchange genes (i.e., interbreed)
• Life (bio) is therefore quite diverse (diversity) OR there are millions of variety of life forms around us
• Taxonomy

  The branch of biology that names, describes and classifies species into groups (taxonomic units/taxa) of increasing breadth
• Broadest units of classification

  • Domains
  • Kingdoms
• This is a scientific classification, that is, a method of scientific taxonomy used to group and categorize life (i.e., species) hierarchically
• The classification of domestic cat has the species name Felis catus
• 3 Domains

  • Bacteria
  • Archaea
  • Eukarya
• Puma have several common names (e.g., cougar, panther or mountain lion)
• Puma's scientific name

  Felis concolor
• All life forms seemed to have similar structures, for example, the forelimbs of the organisms
• Classification enabled taxonomists to see that all life forms are biologically related, and to different degrees

  
• Birds are related to reptiles (particularly crocodiles) than man. Proof? Birds and reptiles share several features: four-chambered hearts, song (call), nest building, and brooding (incubating)

  
• Both birds and reptiles fall under the same class - Reptilia - in the classification of vertebrates
• A classification system based on two (2) kingdoms: Animal and Plant kingdoms scheme was first proposed by Linnaeus, based on shared physical characteristics. It lasted for more than 2 centuries
• Studies showed that many genes of Archaea were found to be more similar to those of Eukaryotes rather than to Bacteria
• A classification system based on five (5) kingdoms: Whittaker used, for instance, species similarities and differences in morphology to produce Plant, Animal, Fungi, Monera & Protista kingdoms
• A classification system based on three (3) domains: Woese and other scientists reviewed kingdom Monera and drew from, for instance, DNA sequencing methods to produce the 3 known domains today, namely Archaea, Bacteria, and Eukarya
• Species


  The basic unit of classifying organisms, representing organisms that can exchange genes (i.e., interbreed)
• Binomial nomenclature


  Carolus Linnaeus' system of taxonomy based on resemblances, with two-part names for species and hierarchical classification
• The American black bear's scientific name is Ursus americanus
• The specific epithet may be used for many unrelated species, e.g., the yellow–billed cuckoo is Coccyzus americanus
• Division replaces phylum in plants
• Today some taxonomic levels have been added to distinguish groups with specific feature(s) from other members of a given species, such as variety (a.k.a. subspecies, strains, races, breeds, etc.)
• Homo sapiens sapiens (to distinguish modern human beings from the archaic ones [Homo sapiens]) and Canis lupus familiaris (to distinguish domestic wolf-dog from the domestic dog [Canis familiaris])
• Phylogeny


  The evolutionary history of a species or group of related species
• Systematics


  The discipline that classifies organisms and determines their evolutionary relationships
• Systematists use fossil, molecular, and genetic data to infer evolutionary relationships and depict them in branching phylogenetic trees
• Homologies are organisms with phenotypic (observable characteristics) and genetic (inheritable) similarities, which are likely to be more closely related than organisms with different structures or DNA sequences
• Homology can be distinguished from analogy by comparing fossil evidence and the degree of complexity, as the more complex two similar structures are, the more likely it is that they are homologous
• Phylogenetic trees emphasise the similarities between animals to show how they are related, while dichotomous keys emphasise the differences between animals to separate them
• Dichotomous keys


  Use "either-or" technique to help identify and classify individuals or groups of organisms
• Plants

  • Plants that bear flowers
  • Plants that do not bear flowers
• Plants


  • Plants that have true roots, stems or leaves
  • Plants that have no true roots, stems or leaves
• Plants


  • Plants that have some roots, stems or leave structure
  • Plants that have no roots, stems or leave structure
• Then numbers will enable you to classify and to identify organisms

  
• Dichotomous Key


  A tool used to classify and identify organisms