SYSTEM — WHAT ARE ITS COMPONENTS?

-SYSTEM — WHAT ARE ITS COMPONENTS? All organisms such as plants, animals, microorganisms and human beings as well as the physical surroundings interact with each other and maintain a balance in nature. All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem. Thus, an ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals.

For example, if you visit a garden you will find different plants, such as grasses, trees; flower bearing plants like rose, jasmine, sunflower; and animals like frogs, insects and birds. All these living organisms interact with each other and their growth, reproduction and other activities are affected by the abiotic components of ecosystem. So a garden is an ecosystem. Other types of ecosystems are forests, ponds and lakes.

These are natural ecosystems while gardens and crop-fields are human- made (artificial) ecosystems. You might have seen an aquarium. Let us try to design one. What are the things that we need to keep in mind when we create an aquarium?

The fish would need a free space for swimming (it could be a large jar), water, oxygen and food. We can provide oxygen through an oxygen pump (aerator) and fish food which is available in the market. If we add a few aquatic plants and animals it can become a self- sustaining system. Can you think how this happens?

An aquarium is an example of a human-made ecosystem. Can we leave the aquarium as such after we set it up? Why does it have to be cleaned once in a while? Do we have to clean ponds or lakes in the same manner?

Why or why not? We have seen in earlier classes that organisms can be grouped as producers, consumers and decomposers according to the manner in which they obtain their sustenance from the environment. Let us recall what we have learnt through the self sustaining ecosystem created by us above. Which organisms can make organic compounds like sugar and starch from inorganic substances using the radiant energy of the Sun in the presence of chlorophyll?

All green plants and certain bacteria which can produce food by photosynthesis come under this category and are called the producers. Organisms depend on the producers either directly or indirectly for their sustenance? These organisms which consume the food produced, either directly from producers or indirectly by feeding on other consumers are the consumers. Consumers can be classed variously as herbivores, carnivores, omnivores and parasites.

Can you give examples for each of these categories of consumers? Imagine the situation where you do not clean the aquarium and some fish and plants have died. Have you ever thought what happens when an organism dies? The microorganisms, comprising bacteria and fungi, break-down the dead remains and waste products of organisms.

These microorganisms are the decomposers as they break-down the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants. What will happen to the garbage, and dead animals and plants in their absence? Will the natural replenishment of the soil take place, even if decomposers are not there? While creating an aquarium did you take care not to put an aquatic animal which would eat others?

What would have happened otherwise? Make groups and discuss how each of the above groups of organisms are dependent on each other. Write the aquatic organisms in order of who eats whom and form a chain of at least three steps. Would you consider any one group of organisms to be of primary importance?

Why or why not? Trophic levels