Taxonomy through the Ages

Taxonomy

• Ancient Taxonomy: Organised life in a straight line, with humans at the top, based on similarities.
  • Humans: rational soul
  • Animals: sensitive soul
  • Plants: vegetative soul
  • Minerals: inanimate, no soul
• Medieval Taxonomy: Humans in the centre, with God at the top, and beings organised into realms (spiritual/material).
  • Man divided into clergy, nobles, and peasants.
  • Animals, plants, and minerals remained in the same categories.
• Modern Taxonomy: Grouped living things based on shared characteristics, specifically cell structure.
  • Every living thing is made of cells.
  • A system of classifying organisms with hierarchical categories (Domain, Kingdom, Phylum, etc.).
  • Cladistics (another modern system) organizes based on evolutionary relationships.
  • Two main domains:
    • Eukarya (complex cells with a nucleus): Includes protists, fungi, plants, and animals
    • Bacteria (simple cells without a nucleus): Includes prokaryotes living in various environments (e.g. harsh ones).

Additional Biological Classification

• Kingdoms (e.g., Animalia, Plantae, Fungi).
  • Each kingdom has characteristics (e.g., multicellular, heterotrophic).
• Phylum: Animals divided into groups called phyla (e.g., Chordata).
  • Animals sharing common characteristics (e.g. a backbone in Chordata).
• Further subdivisions within these categories (Class, Order, Family, Genus, Species).
• Modern taxonomy uses characteristics of cells and embryonic development, rather than just the overall form of the creature.
  • Vertebrates (a sub-group of animals) have a backbone.
  • Other examples from the text include Arthropods (with exoskeleton), Echinodermata (radial symmetry), Mollusca (often having a shell).
• Classification schemes are adapted/updated. For example, "Protista" is no longer considered a kingdom.