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CONTENT: (a) Autotrophy and Heterotrophy (i) Producers (ii) Consumers (iii) Aquatic and Terrestrial

In this topic, the question a wise student will ask is; what is ecosystem? First of all, the word ‘eco’ simply means ecology so, it is ecological system. Let us consider this illustration, in a freshwater habitat where you have aquatic plant such as spirogyra, animals such as tilapia, frogs and toads. All this living things interact with the non- living environment which includes the water where they are, the atmosphere, and the soil beneath it. These living things in the environment together with the non-living environment constitute an ecological system or ecosystem. Therefore, an ecosystem is defined as the interrelationship between the living things and their non-living environment


In an ecosystem, there are two major parts; the biotic or living and abiotic or non-living part. Then from the functional point of view, we have three kinds as producers, consumers, and decomposers. The producers are always green plants; the consumers are the animals, while the decomposers are the saprophytes.

Under the consumers we have the following:

  1. Primary consumers, e.g. grasshopper, rat etc.
  2. Secondary consumers, e.g. cat, lizard etc.
  3. Tertiary consumer, e.g. hawks, snakes.
  4. Omnivores, e.g. man, domestic fowl.

Decomposers are organisms which feed on the carcasses of dead producers and consumers and in the process bring about the decay of such carcasses. Large decomposers such as insects and earthworms are called macro decomposers, whereas small decomposers, such as certain bacteria and fungi are known as micro decomposers.


In the process of decomposition, dead organic matter is broken down physically and chemically, and this is done in stages. Now, the product of this decomposition is inorganic compounds like carbon (iv) oxide, ammonium, ammonium compound as well as salts of elements present in the organic matter. Some gaseous products such as carbon (iv) oxide, ammonia and hydrogen sulphide can be identified as organic matter decomposes. Intermediate products of decomposition include sugars, and complex organic compound derived from protein.


The role of decomposers is the recycling conversion of materials of dead organic materials into inorganic materials which are available to the producers in the ecosystem.


Carry out an activity to show that heat is released during decomposition

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