Monera
Many biologists now divide Monera into the Eubacteria and Archeobacteria (Three division). Monera individuals are single celled and may or may not move. They have a cell wall however they don’t have chloroplasts, organelles or a nucleus, they are usually very tiny and are green in colour. They absorb nutrients through the cell wall or produce their own by photosynthesis, but there is no visible feeding mechanism.
Protista
Protists are single celled and usually move by cilia, flagella, or by amoeboid mechanisms. They usually don’t have cell walls but they have organelles including a nucleus and they could have chloroplasts. Some protists may be green. They get nutrients by photosynthesis or by ingestion of other organisms
Fungi
Fungi are multicellular, they have a cell wall and organelles including a nucleus, however they don’t have chloroplasts. They vary in size from microscopic to very large such as mushrooms. They get their nutrients by absorption of decaying material.
Plantae
Plants are multicellular and most don't move, although some may move using cilia or flagella. They have cell walls and organelles including a nucleus and chloroplasts. They acquire their nutrients by photosynthesis.
Animalia
Animals are multicellular, and move with the aid of cilia, flagella, or muscular. They have organelles including a nucleus, but no chloroplasts or cell walls. Animals acquire nutrients by ingestion.
There are currently 10,000 species of monera, 250,000 species of protista, 100,000 species of kingdom fungi, and 250,000 species of kingdom plantae.
We can determine what kingdoms organisms belong to using the following mini-key:
- 1. Is it green or does it have green parts?
- Yes - go to 2
- No - go to 3
- 2. Could be a plant or a protist, or blue-green bacteria. Make sure that the green is really part of the organism, though. An animal might have eaten something green, for example.
- Single-celled? go to 6
- Multicellular? Plantae. Look for cell walls, internal structure. In the compound microscope you might be able to see chloroplasts.
- 3. Could be a moneran (bacteria), protist, fungus, or animal.
- Single-celled - go to 4
- Multicellular (Look for complex or branching structure, appendages) - go to 5
- 4. Could be a moneran or a protist. Can you see any detail inside the cell?
- Yes - Protista. You should be able to see at least a nucleus and/or contractile vacuole, and a definite shape. Movement should be present, using cilia, flagella, or amoeboid motion. Cilia or flagella may be difficult to see.
- No - Monera. Should be quite small. May be shaped like short dashes (rods), small dots (cocci), or curved or spiral shaped. The largest them that is commonly found in freshwater is called Spirillum volutans. It is spiral shaped, and can be nearly a millimeter long. Except for Spirillum, it is very difficult to see Monerans except in a compound microscope with special lighting.
- 5. Animalia or Fungi. Is it moving?
- Yes - Animalia. Movement can be by cilia, flagella, or complex, involving parts that contract. Structure should be complex. Feeding activity may be obvious.
- No - Fungus. Should be branched, colorless filaments. May have some kind of fruiting body (mushrooms are a fungus, don't forget). Usually attached to some piece of decaying matter - may form a fuzzy coating on or around an object. In water, some bacterial infections of fish and other animals may be mistaken for a fungus.
- 6. Most likely Protista. If it consists of long, unbranched greenish filaments with no apparent structure inside, it is blue-green bacteria (sometimes mistakenly called blue-green algae), a Moneran.
Three domain system
The three-domain system divides cellular life forms into archaea, bacteria, and eukaryote domains. It also divides prokaryotes into two groups called Eubacteria and Archaebacteria. Woese argued that, on the basis of differences in 16S rRNA genes, these two groups and the eukaryotes each arose separately from an ancestor. Using molecular data, he saw that the there are two types of prokaryotes, one that is bacteria, and another that is different to bacteria- the archaea.
Each of the three cell types have a specialty or a role. Bacteria tends to be the most prolific reproducers, Archaeans tend to adapt quickly to extreme environments, And Eukaryotes are the most flexible with regard to forming cooperative colonies.
The picture below shows the three domains:
So to conclude Woese used molecular data to classify organisms and he saw that single celled organisms were very different from bacteria, therefore he proposed the archaea, the five kingdom system couldn’t accommodate for this therefore he added a level above kingdoms ;domains, to include bacteria,( which are prokaryotes that are truly bacteria), Archaea (that are prokaryotes but are different to bacteria) and Eukarya (organisms with a nuclei in their cell)
