I. Read the text and answer the questions in written form. Algae: the simplest green plants

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?

Date: 2015-12-13; view: 555; Нарушение авторских прав