Overview
This lecture introduces biological classification, explaining how organisms are grouped by shared characteristics and detailing the hierarchy used in taxonomy.
Taxonomy and Its Origins
- Taxonomy is the science of classifying living organisms based on shared characteristics.
- The term comes from Greek roots: "taxis" (arrangement) and "nomia" (method).
- Carolus Linnaeus developed the first systematic method of classification, known as Linnaean classification.
Hierarchical Classification System
- The hierarchy includes: Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species.
- Domains are the most inclusive group; species are the most specific.
- Three biological domains: Bacteria, Archaea, and Eukarya.
- Kingdoms, phyla, and other groups further subdivide organisms by shared traits.
Examples of Classification
- Humans: Domain Eukarya > Kingdom Animalia > Phylum Chordata > Class Mammalia > Order Primates > Family Hominidae > Genus Homo > Species sapiens.
- Dogs: Domain Eukarya > Kingdom Animalia > Phylum Chordata > Class Mammalia > Order Carnivora > Family Canidae > Genus Canis > Species lupus > Subspecies familiaris.
Scientific Naming (Binomial Nomenclature)
- Binomial nomenclature uses two names: genus (capitalized) and species (lowercase).
- Genus and species names are italicized when typed, underlined separately if handwritten.
- After first mention, genus can be abbreviated (e.g., H. sapiens).
Meaning and Use of Scientific Names
- Scientific names often describe characteristics (e.g., leucocephalus means "white head").
- Names can also honor people (e.g., a fern genus named "gaga" after Lady Gaga).
Comparing Organism Classification
- Organisms in the same phylum share major characteristics but differ in specifics (e.g., insects vs. arachnids in Arthropoda).
- Insects: three body segments, six legs, antennae.
- Arachnids: two body segments, eight legs, no antennae.
Key Terms & Definitions
- Taxonomy — the science of classifying organisms.
- Linnaean classification — hierarchical method for grouping organisms by shared traits.
- Domain — most inclusive taxonomic group.
- Binomial nomenclature — two-name system for scientific naming (genus + species).
- Species — group of organisms capable of breeding and producing fertile offspring.
Action Items / Next Steps
- Review hierarchy of biological classification and memorize order.
- Look up and practice a mnemonic for classification order.
- Prepare for the next lecture on evolution and natural selection.