Lecture Notes: Biological Classification (Taxonomy)

Introduction to Taxonomy

• Definition: Grouping of living organisms based on shared characteristics.
• Purpose: Understanding the biological classification of an organism reveals much about it.
• Origin:
  • Developed by Swedish botanist Carolus Linnaeus in the 1700s.
  • Known as Linnaean classification.
• Evolution: Initially based on observable characteristics; now enhanced by DNA analysis.

Hierarchy of Biological Classification

1. Domain: Most inclusive category.
   • Three Domains: Bacteria, Archaea, Eukarya.
   • Eukarya includes plants, animals, fungi, and protists.
2. Kingdom: Subdivision within domains.
3. Phylum: Singular is phylum.
4. Class: Grouped within phyla.
5. Order
6. Family
7. Genus
8. Species: Most specific; organisms that can breed and produce fertile offspring.

Mnemonic Devices for Classification

• Example: "Do Kangaroos Prefer Cake Or Frosting, Generally Speaking?"
  • D: Domain
  • K: Kingdom
  • P: Phylum
  • C: Class
  • O: Order
  • F: Family
  • G: Genus
  • S: Species

Examples of Classification

Human Classification

• Domain: Eukarya
• Kingdom: Animalia
• Phylum: Chordata
  • Characteristics: Notochord, dorsal hollow nerve cord, postanal tail.
• Class: Mammalia
  • Characteristics: Fur, milk production.
• Order: Primates
• Family: Hominidae
• Genus: Homo
• Species: Sapiens

Dog Classification

• Domain: Eukarya
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Order: Carnivora
• Family: Canidae
• Genus: Canis
• Species: Lupus
  • Subspecies: Familiaris (domestic dogs)

Binomial Nomenclature

• Definition: A two-name system using genus and species.
• Formatting:
  • Genus capitalized, species lowercase.
  • Italics if typed, underlined if handwritten.
  • Abbreviation after first use (e.g., H. sapiens).
• Example: Canis lupus (underline separately if handwritten).

Importance of Scientific Names

• Provide descriptive information about organisms (e.g., Haliaeetus leucocephalus, meaning "white head").
• Can be named after people or based on characteristics.

Differences in Arthropods: Insects vs. Arachnids

• Both belong to Phylum Arthropoda.
• Insects:
  • Three body segments: Head, thorax, abdomen.
  • Six legs.
  • Have antennae.
• Arachnids:
  • Two body segments: Cephalothorax, abdomen.
  • Eight legs.
  • Have pedipalps, not antennae.

Conclusion

• Biological classification helps in understanding similarities and differences among organisms.
• Next lecture topic: Evolution, focusing on natural selection.