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.Archaea are single celled prokaryotes with their genes and proteins more similar to eukaryotes. They have 70S ribosomes (the same size as bacterial ones but with a different rRNA and protein composition), their membranes are made of branched hydrocarbon chains (not fatty acids) linked to glycerol by ether linkages, their cell walls do not contain murein and they have a more complex form of RNA polymerase than bacteria.Eukarya are organisms with eukaryotic cells. They have 80S ribosomes, membrane bound organelles such as mitochondria and chloroplasts and cell walls, if any, do not contain murein(peptidoglycan).
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Specification: AQA Biology (7401), AS-level, 3.4.7 Investigating diversity and 3.4.5 Species and taxonomy. Topic: Biodiversity.
Key terms in this lesson
- ribosome
- A small organelle, made of RNA and protein, that is the site of protein synthesis.
- prokaryotic cell
- A cell, such as a bacterium, that lacks a nucleus and membrane-bound organelles and has a single loop of circular DNA.
- eukaryotic cell
- A cell that has a nucleus and membrane-bound organelles.
- gene
- A length of DNA that codes for a polypeptide or a functional RNA molecule, at a specific locus on a chromosome.
More in Biodiversity
- Binomial System of Naming
- Courtship Behaviour
- Classification
- Taxonomy
- Kingdoms
- Phylogeny
- Index of Diversity
- Example Index of Diversity
All 33 lessons in Biodiversity · All AQA AS-level Biology topics