Irritability

If we place a crystal of table salt at the edge of a drop of hay infusion the Paramecia will immediately retreat to that part of the drop where the salt content is less. If we put another drop of salt -free hay infusion, near the drop, and connect the two, the Paramecia will migrate into the salt-free drop.

Now, if we introduce bacteria into the drop of water the Paramecia are irritated by the presence of salt and bacteria. They try to escape from the former and move nearer to the latter. The reaction of animals to outside influences is called irritability.

Reproduction

In the warmer seasons when there is much food in the pond, the Paramecia grow fast and then divide. Each of the nuclei divides into two, and a groove appears across the middle of the body. It deepens and the body separates into two approximately equal parts. The "daughter" cells then grow to their maximum size and again divide about a day later.

Encystment

If the water in the pond where the Paramecia live dries out suddenly, they die. They cannot exist without water. Water is essential for all their vital processes nutrition, excretion, etc. If the drying out process is slow the body of the Paramecium takes a round shape and forms a hard resistant wall, a cyst. This condition is known as encystment. The Paramecium does not take in food and remains immobile. Life seems suspended, but the animal does not die. If a gust of wind carries the cysts into another reservoir they burst and the Paramecia become lively and active again. The cysts are capable of withstanding drought, low temperatures, and other unfavourable conditions.

Their Importance

By eating up bacteria Paramecia clean up reservoirs, in their turn, they serve as food for fish, crustaceans, molluscs, etc. Reproducing fast, the Paramecia in their millions play an important part in the life of Nature.

Tasks

1. Write down whether the following statements are true or false. Give extensive answers.

1. Leeuwenhoek discovered tiny animals in 1678.

2. A paramecium is harder to detect under a microscope than other Protozoa.

3. Paramecia are commonly found in wet or moist places.

4. Paramecium has a soft body which helps it to maintain a constant shape.

5. The paramecium is one-celled living organism with one nucleus.

6. It has foot-like organs which drives the animal forward.

7. The Paramecium feeds on organic matter.

8. It assimilates the digested food as well as the undigested remains.

9. The Paramecium respires through its body surface.

10. Paramecia don’t react to outside influence.

11. In the warmer seasons the Paramecia grow fast and divide into several unequal parts.

12. Water isn’t essential for Paramecia’s life.

13. The cysts are capable of withstanding drought, low temperatures and other unfavourable conditions.

14. The paramecia don’t play an important part in the life of Nature.

2. Complete the sentences using the text and translate them into Russian.

1. While examining a drop of rainwater under a microscope he saw …

2. … after which it was named (Slipper Animalcule)

3. Only a small degree of magnification is needed …

4. … which helps the Paramecium to maintain a constant shape.

5. Like all other animal cells …

6. … while at the same time its body rotates upon its own longitudinal axis.

7. By beating its cilia, the Paramecium sets up a current …

8. … dissolved and absorbed by the protoplasm.

9. Water dissolved oxygen is brought …

10. Water which accumulates in the protoplasm …

11. … discharging the waste solutions into the vacuole.

12. If we place a crystal of table salt …

13. … the Paramecia are irritated by the presence of salt and bacteria.

14. Each of the nuclei divides into two …

15. … and forms a hard resistant wall, a cyst.

16. If a gust of wind carries the cysts …

17. In their turn, they serve as … .