1. Chapter 22: Kingdom Protista Leaving Certificate Biology Higher Level

2. Amoeba Amoeba is a unicellular organism that lives in freshwater –For this reason, osmosis poses a problem for Amoeba Amoeba feeds heterotrophically meaning it takes in food from other animals and plants – it is also an omnivore

3. Structure of Amoeba Single cell with nucleus, granular protoplasm (due to many food vacuoles) and characteristic pseudopods for movement and feeding The protoplasm is made up of an outer cytoplasm (ectoplasm) and inner cytoplasm (endoplasm) –Ectoplasm is more viscous (harder) than the endoplasm –Endoplasm is clearer in nature and more granular then the ectoplasm

4. Structure of Amoeba

6. Feeding in Amoeba Amoeba feeds by extending its pseudopods around target and engulfing it much the same way in which macrophage/phagocytes belonging to the immune system engulf pathogens Once engulfed, the area in which the food is held is called the food vacuole – digestive enzymes are released and the food is broken down and used by the Amoeba

7. Osmoregulation in Amoeba Amoeba lives in freshwater and so its cytoplasm has more dissolved solutes than the surrounding environment meaning that the water concentration is lower inside Amoeba than outside Water moves by osmosis down its concentration gradient so water will move into Amoeba continuously This poses a problem – Amoeba would burst if it was not able to regulate water content Amoeba regulates water content by having a large central ‘contractile vacuole’ in which excess cytoplasmic water is pumped out Once the contractile vacuole is full it moves to the surface of the cell and fuses with the membrane spilling its contents back out to the environment

8. Osmoregulation in Amoeba H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O