Protozoans

• They are heterotrophs (predators or parasites).
• They are believed to be primitive relatives of animals.
• There are 4 major groups of protozoans:
  

  a. Amoeboid protozoans:

• They live in fresh water, sea water or moist soil.
• They move and capture prey by putting out pseudopodia (false feet). E.g. Amoeba.
• Marine forms have silica shells on their surface.
• Some of them are parasites. E.g. Entamoeba.
  

  b. Flagellated protozoans:

• They are either free-living or parasitic.
• They have flagella.
• The parasitic forms cause diseases such as sleeping sickness. E.g. Trypanosoma.
  

  c. Ciliated protozoans:

• They are aquatic, actively moving organisms with the help of thousands of cilia.
• They have a cavity (gullet) that opens to the outside.
• Due to the coordinated movement of cilia, the water with food enters into gullet. E.g. Paramoecium.
  

  d. Sporozoans:

• They include organisms that have an infectious spore-like stage in their life cycle. E.g. Plasmodium (malarial parasite) which causes malaria.