Lecture Notes on Taxonomy and Linnaeus

Introduction to Taxonomy

• Taxonomy: The science of classifying living things.
• It reveals the story of life on earth, showing relationships between organisms.
• All living organisms are related through a common ancestor.
• The goal is to organize and categorize life to understand evolutionary relationships.

The Phylogenetic Tree

• Also known as the Tree of Life.
• Illustrates evolutionary relationships between species.
• Around 2 million known species, potentially up to 100 million.
• New species are continually discovered, adding complexity to the tree.
• The system isn't perfect and often requires updates.

Carl Linnaeus and His Contributions

• Born in 1707; a botanist who recognized the chaotic state of nomenclature.
• Developed a system based on morphology (physical form and structure).
• His system grouped organisms by homologous traits (common evolutionary ancestor) versus homoplasic traits (independent origins).
• Introduced binomial nomenclature (two-part naming system in Latin).
• Published classifications in 'Systema Naturae'.

Linnaeus's Taxonomic System

• System still in use: Kingdom, Phylum, Class, Order, Family, Genus, Species.
• Binomial nomenclature: Genus and species name.

Modern Taxonomy

• Incorporates new technologies like genetic testing.
• Added a new taxon: Domain.
• Three Domains: Bacteria, Archaea, and Eukarya.
  • Bacteria and Archaea are prokaryotes (no nucleus).
  • Eukarya includes life forms with a nucleus.

Kingdoms under Eukarya

• Protista: Single-celled, mix of autotrophs and heterotrophs.
• Fungi: Includes mushrooms, molds; have chitin cell walls.
• Plantae: Autotrophs via photosynthesis, cellulose cell walls.
• Animalia: Multicellular heterotrophs.

Examples in Taxonomy

• Cats: Followed taxonomy from Kingdom Animalia to species Felis catus.
• Demonstrates how taxonomy reflects evolutionary relationships.

Conclusion

• Taxonomy helps us understand common ancestry and evolutionary history.
• Despite its complexity and imperfections, it remains a foundational organizational tool in biology.