Overview
This lecture introduces biological classification (taxonomy), explaining how living things are grouped from domains down to species, and the reason for using scientific names.
Introduction to Classification
- Classification is grouping organisms based on shared characteristics.
- Taxonomy is the science of naming and classifying organisms.
- Classification systems change as new DNA and structural evidence is discovered.
Historical Foundations
- Carl Linnaeus developed formal classification and introduced binomial nomenclature (two-part scientific names).
- Early systems did not recognize differences among protists, bacteria, or DNA.
Hierarchy of Biological Classification
- Classification hierarchy moves from most inclusive to least: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
The Three Domains
- Bacteria: Prokaryotes, include disease-causing, decomposing, nitrogen-fixing, and digestive bacteria.
- Archaea: Prokaryotes with unique DNA/structure; many are extremophiles (live in extreme environments like high salt, temperature, or low oxygen).
- Eukarya: All eukaryotes (organisms with complex cells, including protists, fungi, plants, and animals).
Eukaryote Kingdoms Overview
- Protista: Diverse group; includes "animal-like," "plant-like," and "fungi-like" organisms, both autotrophs and heterotrophs, mostly unicellular.
- Fungi: Heterotrophs, mostly multicellular (some unicellular), cell walls made of chitin.
- Plantae: Autotrophs (make glucose from sunlight), multicellular, cell walls made of cellulose.
- Animalia: Multicellular, heterotrophs, no cell walls (includes humans and hydra).
Binomial Nomenclature & Scientific Naming
- Scientific names have two parts: Genus (capitalized, italics) and species epithet (lowercase, italics).
- Binomial nomenclature ensures consistent naming across languages and regions.
- Example: Mountain lion (common names: puma, cougar, etc.) has a single scientific name.
Key Terms & Definitions
- Taxonomy — science of classifying and naming organisms.
- Domain — largest classification group (Bacteria, Archaea, Eukarya).
- Kingdom — next level below domain (e.g., Plantae, Animalia).
- Prokaryote — organism without a nucleus (Bacteria, Archaea).
- Eukaryote — organism with a nucleus (Protista, Fungi, Plantae, Animalia).
- Extremophile — organism living in extreme conditions (many Archaea).
- Binomial nomenclature — two-part scientific naming system.
Action Items / Next Steps
- Memorize the hierarchy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
- Practice writing and identifying scientific names using binomial nomenclature.