You will need:

• water
• a small, solid, plastic ball
• a small plastic bag
• scissors
• four packets of gelatine

Introduction:

Amebas are single-celled protists. Giant amebas are just big enough for you to see without a microscope. An ameba takes in its food by wrapping itself around it. The ameba then absorbs the food through its outer cell membrane.

 Danger: Hot water can scald you! Ask a grown-up to help you with this experiment.

Procedures:

1. Ask an adult to help you dissolve the gelatin in some hot water. Add enough warm water to make a jelly that will set. Leave the jelly to cool for a few minutes.

2. Pour half of the jelly into the plastic bag. Keep the rest of the jelly warm, while the jelly in the plastic bag sets. It will set more quickly in a cool place.

3. When the jelly in the bag is partly set, put in the plastic ball. Then add the rest of the jelly. Tie a knot in the bag to seal it and trim off the ends. This is roughly the shape of an animal cell. The plastic bag is like the membrane. The plastic ball is like the nucleus, and the jelly represents the cytoplasm. You can use the model cell described above to show how an ameba moves.

4. Hold the model steady with one hand and pull one side of the plastic bag out with your other hand.

5. Now squeeze the gelatin into the part of the bag you have pulled out.

6. Repeat this several times, and you will see that your model has moved forwards a little way.

Discussion:

1. The food floats inside the ameba's body until it is absorbed. Then any waste can pass out through the membrane.