Where we fit in the world and how we came to be here

Classification

• Nomenclature: naming of organisms
• Binomial: biological name of an organism → Genus species (eg Homo sapiens)
• Taxon: set of organisms within a category / taxonomy / study of biological classification
• Different levels of taxons: species, genus, family, order, class, phylum, kingdom
  • Right side of spectrum → highest number of species
  • Left side of spectrum → most similar organisms
• Five Kingdoms:
  • Prokaryotae
  • Protoctista
  • Fungi
  • Plantae
  • Animalia
• Background Knowledge
  • There is a new three-domain system:
    • Domain Eukarya - contains the four kingdoms
      • Animalia
      • Pkantae
      • Fungi
      • Protista
    • Domain Archaea
    • Domain Bacteria
• Unicellular: Single cell; Colonial: Groups of cells; Multicellular: Many cells
• Autotrophs produce energy from inorganic sources
  • Phototrophs from photosynthesis/sunlight
  • Chemotrophs from simple inorganic (oxidative) processes
• Heterotrophs digest and absorb organic molecules
• Human classification
  • Kingdom: Animalia (no cell wall, eat other organisms)
  • Phylum: Chordata
  • Class: Mammalia (produce milk from mammary glands)
  • Order: Primates
  • Family: Hominidae
  • Genus: Homo
  • Species: sapiens

Species

• Most basic unit of biological classification
• Members of a species are similar (phenotype) to each other but different from other species
  • Similarity can be
    • physical (branching pattern of trees)
    • biochemical (haemoglobin structure)
    • immunological (antibody against an antigen equally effective)
    • development (similar growth of embryos)
    • ecological (occupy identical ecological niche)
• Members of a species are able to reproduce giving fertile offspring
  • Each species is reproductively isolated from every other species
    • Prevents exchange of genes
    • Species keep special characteristics that distinguishes them

Evidence of classification

• Biochemical
  • Cytochrome c
    • Protein used in cellular respiration and found in mitochondria
    • Count number of amino acids that organisms differ by
    • Higher number, more distant ancestor
  • DNA hybridisation
    • Unzip DNA from 2 different species
    • Mix them to allow complementary base pairing
    • Higher similarity, more base pairing, more energy required to separate hybrid DNA strands
• Anatomical
  • Similar anatomical structure, more closely related
• Embryological
  • Similar stages of development due to common ancestor
• Immunological
  • Human blood serum is injected into a test animal
  • Test animal recognizes foreign proteins (antigens) and produces antibodies
  • Serum blood of immunized test animal is added to all test tubes
  • Add human serum to one test tube (control)
  • Add serum of other organisms to other test tubes (compare with control)
  • Antigen-antibody complexes form and precipitate from solution
  • Higher amount of precipitation, closer related to humans
• Behavioural
  • Similar behaviour due to common ancestor
  • Primates live in social groups, communicate by facial expression, long parental care