1. Water may also penetrate the aggregates and be held to the clay particles by chemical forces.
2. The crumb structure of a clay soil can be improved by growing grass on it for a year or two.
3. A biologist is to know thoroughly the stages of matter and the physical laws which govern the behavior of matter in various states.
4. Do the students have to make a great number of experiments to acquire good knowledge in biology?
5. Water may pass through in a few minutes, a meal of carbohydrate such as porridge may be retained less than an hour, and a mixed meal containing protein and fat may be in the stomach for one or two hours.
VII. Rewrite and translate the following sentences into Russian, pay attention to different meanings of the words.
1. Plants differ from the more highly evolved animals in that hormones are secreted by unspecialized tissues.
2. One can improve the structure of the soil by proper treatment.
3. Give me a book on zoology, please. Which one? The one which is lying near the thermometer.
4. It was not easy to measure the rate of photosynthesis.
5. You know that experiment has been conducted at our laboratory and you also know what has been established in it.
VIII. Put in some, any, something, anything, nothing, nobody, anybody translate the sentences into Russian.
1. I know... about hereditary diseases.
2. There are... protozoa that have no organs of locomotion (sporozoa).
3. Is... doing any experiments in biochemistry?
4. We knew... about crossing-over twenty-five years ago.
5. Can you name... types of food and their functions?
IX. Make plural forms of the following nouns.
1. One bacterium - two...
2. One wolf-two...
3. One mouse - two...
4. One insect-two...
Variant 3
I. Read the text and answer the questions in written form.
Algae: the simplest green plants
1. The main difference between green plants and other living things is their ability to make food - complex starch and sugar molecules from simple carbon dioxide and water. They do this by the process of photosynthesis which requires the presence of chlorophyll, the material that produces the color in all green plants.
2. Algae are the simplest organisms in the plant kingdom that possess chlorophyll and can make their own food. Algae vary in size: they may consist of a single cell, or a row of cells joined together to form a filament. The largest algae consist of a plant body called a thallus, which is made of many cells and gives the plant a ribbon-like appearance. AIgae live in both fresh and salt water and may swim, float or fasten themselves to a firm surface. Some of them live in the soil and a few are parasites on animals and plants. All algae possess chlorophyll, but their green color may be masked by other pigments. This provides a way of classifying them according to color, for instance green algae (Chlorophyceae), brown algae (Phaeophyceae).
3. Algae reproduce in various ways. Sexual reproduction may occur, resulting in the formation of a new individual by the fusion of two sex cells. Sometimes asexual reproduction takes place, in which spores are produced, or a single-celled alga splits into two. Vegetative reproduction occurs when a filament or thallus breaks into two parts to form new plant bodies.
4. Diatoms are single-celled algae (Bacillariophyceae) that live in fresh and salt water. They grow in enormous numbers, and make up a great part of the floating community of organisms called plankton which is found in all seas and is the food supply for many aquatic animals.
Questions:
1. What is the main difference between green plants and other living things?
2. What are algae?
3. What do we call a thallus?
4. Where do algae live?
5. What provides a way of classifying algae according to color?
6. How do algae reproduce?
7. What algae can live both in fresh and salt water?
8. What is the food supply for many aquatic animals?
