I. What tense forms are the verbs in italics in the following sentences? Comment on the tense form usage in these sentences

1. Membrane-bound organelles occur only in eukaryotic cells.

2. Russian scientist and academecian A.I. Oparin, in 1922, hypothesized that cellular life was preceeded by a period of chemical evolution.

3. In this class we will use light microscopes for our laboratory observations.

4. Many Americans are turning now to herbal remedies to ease arthritis pain, improve memory, as well as improve our moods.

5. The students were working in the laboratory the whole morning yesterday.

6. The nurse will be giving medicine to the patients at 11 am tomorrow.

7. A lot is known about living things today. For example, anatomists and taxonomists have studied the forms and relations of more than a million separate species of plants and animals.

8. The nurse had taken the patients’ temperature before the doctor made the morning round.

9. Next month they will have already been working for a year on the problem of side effects of the new vaccine.

II. Put the verbs in brackets into the correct tense form

1. In the past few decades, many developments in physiology and embryology (result) from studies in cell biology, biophysics, and biochemistry.

2. A good science experiment simultaneously (not test) several variables.

3. In 1838 Mattias Schleiden (conclude) all plant tissues consisted of cells.

4. Probably the greatest biological problem of the future, (be) to find ways to curb environmental pollution without interfering with man's constant effort to improve the quality of his life.

5. The compound light microscope, shown in Figure 8, (use) two ground glass lenses to form the image.

6. The nurse (prepared) the instruments for the operation by the time the doctor came.

7. I hope next year she (enter) the Medical University.

8. The changes that (take) place since the origin of the cell are also thought to have occurred as a result of natural selection.

LISTENING COMPREHENSION

I. You will hear a text about cells’ movement. Before listening discuss the words and expressions in the box with your fellow students and teacher

glide thrash whip fertilization oar to extrude to anchor

flagellum (flagella) cilium (cilia) to propel oneself to swallow respiratory tract inhaled dust basal body

to search for food dense, hairy appearance a current of mucus temporary pseudopodium to pursue and devour prey to roam the bloodstream to stalk and engulf a bacterium or virus

II. Listen to the text and answer the questions below

1. Why do cells have to move?

2. What adaptation do they use for this purpose?

3. What is the difference between prokaryotic and eukaryotic flagella?

4. What eukaryotic cells use flagella as a means of motion?

5. Give an example of an organism that cilia for motion?

6. What functions do cilia perform in cells which do not move?

7. What are basal bodies?

8. Describe the principle of amoeboid motion?

9. Which types of motion in cells are faster and which are slower?

10. In what conditions is amoeboid motion most effective?