1.10 To study the important role of plants in the ecosystem

Natural sciences

Ecosystems and the environmental balance

Educator section

Memorandum

Assignment 15:

1. Plants and animals die

2. Plants and animals produce waste material

3. Decomposers degrade the waste material and use some parts of it as food

4. Other parts are degraded as chemicals and then released into the air or soil

5. The chemicals are absorbed by other plants and taken up into the food chain

Leaner section

Content

Activity: to study the important role of plants in the ecosystem [lo 1.2, lo 2.3]

Plants (producers) simply take non-living material (water, sunlight, carbon dioxide and minerals) and produce plant food. This process is called photosynthesis, of which you will learn a great deal in the next module. Oxygen is released simultaneously.

Design two more food chains with plants as the producers.

(a) The role of fungi in the ecosystem

Fungi are regarded as the “poor” family members of the plant kingdom because they do not contain green colouring. The green colouring, chlorophyll, enables green plants to produce their own food from carbon dioxide and water. Green plants are therefore self-sufficient and do not depend on other living things for food. Fungi and bacteria, on the contrary, are as dependent as animals on the food that plants have to prepare for them.

When a plant or an animal dies, the energy stored in them is not lost. Microscopic fungi and bacteria live on the dead bodies and thereby break them down. In this way, such dead material becomes part of the soil once more. Plants that do this are called decomposers because of the unique role they play in nature.

Assignment 15

Study the following diagrammatic representation of the process of decay. It shows how dead organisms are broken down and recycled by decomposers. Read the captions that are provided below and copy them into the appropriate spaces. Take note of the fact that the captions are not given in the correct order:

• Plants and animals produce waste material, e.g. leaves.
• Decomposers break down the waste material and use part of it as food.
• Other parts are broken down into chemicals and are released into the air or the soil.
• Plants and animals die.
• The chemicals are absorbed by other plants and are again taken up into the food chain.

(i) The structure of fungi

Fungi consist of branched threads that may be divided into sections (e.g. bread mould) or may be combined in a large, solid body (e.g. mushrooms). Many fungi are edible, but some are extremely poisonous. It is much safer to eat well-known mushrooms only. The mushroom is pushed up from below the soil as a small, round button. When it grows bigger, it stretches out on a stem and eventually opens up like an umbrella.

Below the umbrella the spore-bearing gills radiate from the stem. In the common edible button mushrooms these gills are pale pink when the fungus is young and become blackish-brown as the fungus matures. None of the poisonous toadstools have this colour, so the colour provides the best indication to whether you are dealing with a poisonous toadstool or an edible mushroom. One should never eat a fungus that looks like a mushroom but has white gills, because this could lead to death.