Introduction to Molecular Biology: Universal Features of Cells
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What Molecular Biology Studies & The Three Domains of Life
Molecular biology studies how molecules interact with one another in living organisms to perform the functions of life.
Life started ~3.5 billion years ago. All life is organized into three major domains (based on genome comparisons):
| Domain | Nucleus? | Cell type | Examples |
|---|---|---|---|
| Bacteria (Eubacteria) | No | Prokaryote | E. coli, Salmonella, Cyanobacteria |
| Archaea | No | Prokaryote | Asgard archaea |
| Eukaryota | Yes | Eukaryote | Animals, plants, fungi |
- Prokaryotes = NO nucleus; Eukaryotes = HAVE a nucleus (the defining distinction).
- Two key endosymbiosis events shaped eukaryotes: mitochondrial symbiosis and chloroplast symbiosis.
- Insects dominate known species diversity (~1.05 million of ~2.15 million total).