Overview
This lecture explains how and why species are classified, the evolution of classification systems, major taxonomic ranks, and how to remember them.
Problems with Early Classification
- Early classification was based on appearance, which led to confusion and inconsistent naming.
- Different cultures used different names for the same species, causing more confusion.
- Simple names did not show how species are related.
The Linnaean System
- Carl Linnaeus proposed classifying organisms by shared features and bone structure in the 1700s.
- Linnaean classification groups species into hierarchical ranks: Kingdom, Phylum, Class, Order, Family, Genus, Species.
- Scientific names are in Latin to be universally understood.
- The binomial naming system uses genus and species (e.g., Homo sapiens for humans).
- Binomial names are written in italics, with only the genus capitalized.
The Three-Domain System
- Carl Woese introduced the three-domain system in the 1990s based on RNA evidence.
- The three domains are: Eukaryota (organisms with eukaryotic cells), Bacteria (true bacteria), and Archaea (primitive bacteria).
- Domains are above kingdoms in the classification hierarchy.
Evolutionary Trees
- Evolutionary trees show relationships between organisms by linking them to common ancestors.
- A split in a tree branch represents a common ancestor splitting into new species.
- Relationships are determined using structures, DNA, and fossil records.
Remembering the Order
- Mnemonics help remember taxonomic ranks (e.g., "Dear Kate Please Come Over For Great Spaghetti" for Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species).
Key Terms & Definitions
- Binomial naming system — system using two Latin names (genus and species) for each organism.
- Domain — highest taxonomic rank above kingdom, introduced by Carl Woese.
- Evolutionary tree — diagram showing evolutionary relationships and common ancestors.
- Eukaryote — organism with complex cells containing a nucleus.
- Prokaryote — organism with simple cells lacking a nucleus (includes Bacteria and Archaea).
- Mnemonic — memory aid to recall information.
Action Items / Next Steps
- Find or create a mnemonic for remembering taxonomic ranks.
- Review examples of binomial names and practice writing them correctly.
- Explore evolutionary trees and identify how species are related.
- (If applicable) Visit the provided website for practice questions and resources.