6.4 Classification of Living Organisms

Classification is the process of grouping organisms based on their shared characteristics.

Why classify:

• Easier to find or add new species
• Shows evolutionary relationships
• Makes studying them easier
• Hierarchies - smaller groups within later groups

Linnaeian System

Traditionally, living things have been classified into groups depending on their structure and characteristics in a system developed by Carl Linnaeus.
Linnaeus was a racist. He tried to classify via race because of course.

• Kingdom (Animalia, Plantae, Fungi, Protista, Prokaryota)
• Phylum
• Class
• Order
• Family
• Genus (e.g., Homo, always capitalised and in italics, underline in exams)
• Species (e.g., Homo sapiens)

Woeseian System

The Woeseian System is a more modern approach to classification based on genetic relationships.
It was developed by Carl Woese and is based on evidence now available (microscopes and DNA sequencing).
Everything is categorised into three domains:

• Archaea (primitive bacteria usually living in extreme environments)
• Bacteria (true bacteria)
• Eukaryota (including protists, fungi, plants, and animals)