Class 9 Science Note


There is a continuous cycle of interrelationship between a community and its physical environment that causes the formation of complex and permanent relationship. Such kind of phenomenon that occurs in the nature is known as ecosystem. So, an ecosystem can be defined as an overall integration of the whole mosaic of interacting organisms and their physical environment in particular areas.

An ecosystem includes biotic factors like producer, consumers, decomposers and abiotic factors like soil, rock, water, heat, light etc.



An ecosystem includes abiotic factors like soil, rock, water, heat, light etc. It helps for the circulation of the ecosystem properly. It also helps in the balance of ecosystem. They are responsible for the survival of the living organisms


All living beings in nature fall under biotic factors. The factors indicate a biological community of particular area. A biological community can be divided into producer, consumer and decomposer on the basis of flow of energy in the ecosystem.


Producers: Producers are those living organisms of the ecosystem which are capable of synthesizing their own food from inorganic compound. For example, grasses, trees, Aquatic green plants, etc.

Consumers: Consumers are the heterotrophs of the ecosystem which feed on other living organisms. For example, cats, insects, fish etc. They are divided into three categories:

  1. Primary consumers.
  2. Secondary consumers.
  3. Tertiary consumers.

Decomposers: Decomposers are also called saprophytic organisms. Some micro-organisms feed on dead and decaying organic matters and decompose them into simpler compounds. These compounds are then utilized by the producers for the synthesis of their food. So decomposers are responsible for the regular cycling of the materials in the ecosystem. Some examples of decomposers are bacteria, fungi, etc.

Relationships between producer consumer and decomposer

There is a close relationship between producer consumer and decomposers.  Ecosystem includes biotic factors like producer, consumer, decomposer and abiotic factors like soil, rock, water, heat, light etc. All the living organisms fall under biotic factor. The producers or plants use abiotic factors to make or synthesize their food. The herbivores or primary consumers feed on green plants. The herbivores are eaten by carnivores. When these living components die, they are converted into simpler form with the help of decomposers and get mixed on the soil. When they are mixed in the soil, they are absorbed by the green plants for their growth and development. In this way, the phenomenon occurs in nature continuously.


Food chain

In the food chain, producers are the base in ecosystem. Consumers get nutrition from plants and ultimately it reaches up to decomposers. There are different types of consumers in an ecosystem. Insects eat herbs. Insects are eaten by birds. Birds are eaten by hawks and eagles. Thus nutrition reaches up to higher trophic level from producers. After the death of plants and animals, they are decomposed by the decomposers and minerals are released in the soil and in turn, plants use the minerals as the constituents of their food. Thus transfer of food energy from producer to consumers and consumers to decomposers by the process of eating and being eaten is known as food chain. In the food chain each source of food energy is named as trophic level.

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