BRAINCAKEThe Three Domain System
A domain is the highest taxonomic rank.
There are three domains: Bacteria, Archaea and Eukarya.
Bacteria are single-celled prokaryotes with no membrane-bound organelles, 70S ribosomes, murein (peptidoglycan) cell walls and a single loop of DNA with no histones. Their RNA polymerase contains 5 proteins.
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Key terms in this lesson
- organelle
- A membrane-bound structure within a cell with a specific structure suited to a specific function.
- mitochondrion
- An organelle with a double membrane, the inner one folded into cristae, that is the site of aerobic respiration and ATP production.
- prokaryotic cell
- A cell with no nucleus or membrane-bound organelles, found in bacteria.
- eukaryotic cell
- A cell with a nucleus and membrane-bound organelles, found in animals, plants, fungi and protoctists.
- gene
- A length of DNA that codes for a specific polypeptide.
More in Classification and Evolution
- Fungi
- Plantae
- Animalia
- Classification
- Archaebacteria and Eubacteria
- Phylogeny
- Advantages of Phylogenetic Classification
- Theory of Evolution
All 36 lessons in Classification and Evolution · All OCR AS-level Biology topics