6. Describe briefly the four major groups of Protozoa.
All protozoans are single-celled, cell-wall lacking, heterotrophic organisms that live as predators or parasites. Protozoans are considered to be primitive relatives of animals. Protozoa are divided into four groups based on their organ of motility.
1. Amoeboid protozoa- This type of protozoa are found in fresh water, sea water or moist soil. They can move and capture their prey with the help of pseudopodia. The pseudopodia are the extensions of the cell membrane. Example: Amoeba
2. Flagellated protozoa- These protozoa can be parasitic or free-living. They use their flagella for movement. Example Trypanosoma causing sleeping sickness.
3. Ciliated protozoa- These protozoa possess a number of cilia all over their bodies for movement. Ciliated protozoa are characterised by the presence of two nuclei i.e. macronuclei and micronuclei. Example: Paramoecium
4. Sporozoa- These protozoa include organisms that have an infectious spore-like stage in their life cycle. Sporozoans do not possess cilia or flagella. They are mostly endoparasites. E.g. Plasmodium. ???????