Biology
The Five Kingdoms and the Bacteria: Quick Revision
A brief note on The Five Kingdoms and the Bacteria: why two kingdoms failed, Whittaker's five kingdoms and their features, the shapes and groups of bacteria, archaebacteria, and how bacteria feed, help and harm. With a worked example, practice, a program and questions to check yourself.
Written by StemPy LabA brief note on The Five Kingdoms and the Bacteria. Try each question at the end before you open its answer.
From two kingdoms to five
- Linnaeus's two kingdoms did not separate prokaryotes from eukaryotes, one cell from many, or photosynthetic from non-photosynthetic organisms.
- Whittaker (1969): Monera, Protista, Fungi, Plantae, Animalia, by cell structure, body organisation, nutrition, reproduction and relationships.
| Kingdom | Cell | Wall | Food |
|---|---|---|---|
| Monera | prokaryotic | not cellulose | both |
| Protista | eukaryotic, one cell | in some | both |
| Fungi | eukaryotic | chitin | absorbed |
| Plantae | eukaryotic | cellulose | made |
| Animalia | eukaryotic | none | taken in |
Bacteria
- The only members of Monera; the most abundant organisms. No nuclear membrane.
- Shapes: coccus (ball), bacillus (rod), vibrio (comma), spirillum (spiral).
- Reproduce mostly by binary fission; some form spores in bad times.
- Archaebacteria: halophiles (salt), thermoacidophiles (hot acid springs), methanogens (marshes, cattle gut, biogas). A different cell wall.
- Eubacteria: a rigid wall, some with a flagellum.
- Cyanobacteria photosynthesise; some fix nitrogen in heterocysts. Chemosynthetic bacteria oxidise inorganic substances. Heterotrophs are the largest group: decomposers, curd, antibiotics, nitrogen in legume roots, and diseases.
- Mycoplasma: the smallest cells, no cell wall.
A worked example
A slimy green-blue colony grows on wet soil after the rains. Under the microscope, its cells have no nucleus, and some larger cells sit along its threads.
- No nucleus. A prokaryote, so kingdom Monera.
- Green-blue and on wet soil. It makes food in light: a cyanobacterium, such as Nostoc.
- The larger cells. Heterocysts, which fix nitrogen from the air and enrich the soil.
Practice with new numbers
A program to try
The program sorts six organisms with the simple key and counts each kingdom.
Mistakes to avoid
- Putting fungi with plants. Fungi have no chlorophyll and a wall of chitin.
- Calling every one-celled organism a bacterium. Protists have a true nucleus.
- Calling cyanobacteria algae in the strict sense. They are bacteria, with no nucleus.
- Thinking bacteria are only harmful. Most are decomposers, and many help us.
Check yourself
- Which kingdom has cell walls of chitin?
- Name the three kinds of archaebacteria.
- Why do farmers grow pulses between cereal crops?
- What shape is a coccus?
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