the mud that clings to the feat of birds. Encystment not only furthers the distribution of protozoa but also enables them to live in habitats they otherwise could not invade.
Within the hard walls of their cysts, some protozoa can withstand the heat and drought of summer in the desert. After the first rain the cysts burst and the protozoa move about, frequently encysting again after only an hour of activity.
About fifteen thousand species have already been described, though it is probable that many more remain to be discovered.
The Classes of Protozoa
Protozoa are divided according to their means of locomotion into four classes:
1. Those that move by means of temporary projections of their protoplasm called pseudopodia ("false feet,f).
2. Those that move by means of whiplike structures called flagella.
3. Those that move by means of hairlike structures called cilia.
4. Those that have no organs of locomotion, these protozoa are known as sporozoa.
Tasks
I. Write down whether the following statements are true or false. Give extensive answers.
1. Protozoa live in a dry soil.
2. Many species of protozoa aren't able to endure the absence of water.
3. They are carried by animals and plants.
4. They can't withstand the heat and drought of summer in the desert.
5. Protozoa are divided according to their means of locomotion into two classes.
II. Complete the sentences using the text and translate them into Russian.
1. With very few exceptions ....
2. The ability of protozoa to survive is enhanced by ... .
3. Encystment not only furthers the distribution of protozoa but... .
4. ... frequently encysting again after only an hour of activity.
5. Those that move by means of whiplike structures ....
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