3-Domain Classification System
Biology: Cambridge International A Level, topic 18.2.1
New Classification Systems
Technological advancements have led to new, more accurate classification systems.
Technological advancements
- New technologies have allowed extensive sequencing of the DNA and proteins of organisms.
- More closely-related organisms have DNA with a more similar base sequence and proteins with a more similar amino acid sequence.
3-domain system
- Carl Woese proposed the 3 domain system. This classifies organisms based on chemical analysis.
- The 3 domains are:
- Archaea - primitive bacteria.
- Bacteria - true bacteria.
- Eukaryota - organisms possessing complex sub-cellular structures (protists, fungi, plants & animals).
Viruses
- Viruses are not classified as living so they do not feature in the 3-domain system.
- Viruses are not seen as living as they rely on other cells to reproduce and have no metabolism.
- Virus classification is based on their:
- Nucleic acid (DNA or RNA).
- Whether these nucleic acids are single- or double-stranded.
Test yourself on 3-Domain Classification System
Who devised the traditional classification system, which categorises organisms based on their structure and characteristics?
Linnaean Classification