Ecosystem and its structure

A. G. Tansley was invented the term ‘ecosystem’ in 1935. An ecosystem is a region of the landscape that forms such as forest, grassland, desert, wetland or coastal area.

An Ecosystem defines as “the living community of plants and animals in any area together with non-living components of the environment such as soil, air and water, constitute the ecosystem”.

All the ecosystems of the Earth are connected, e.g., the river system is connected with the ecosystem of the ocean, and a small ecosystem of dead logs is part of a large ecosystem of a forest.

Structure of an Ecosystem:

It has two main components: 1. Abiotic           2. Biotic


These are the non-living components of the ecosystem. It includes basic inorganic elements and compounds, such as soil, water, oxygen, calcium carbonates, phosphates and a variety of organic compounds. It also includes such as solar radiation, wind currents. The energy of the sun is a significant energy source for the ecosystem.  There are two types a) Climatic factors such as rain, temperature, the light, wind, etc. b) Edaphic factors such as soil, pH, minerals, etc.

Biotic :

The living organisms such as plants, animals and micro-organism (Bacteria and Fungi) that form the biotic components. On nutrition-based, there are two basic components :

1. Autotrophic components :

This includes all green plants which fix the radiant energy of the sun and make food from inorganic substances.

2. Heterotrophic components :

This includes non-green plants and all animals which take food from autotrophs.

The biotic components can be classified into three main classes:

1. Producer

2. Consumers

3. Decomposers or Reducers and transformers


The green plant in the ecosystem is called producers. The green plants have chlorophyll with the help of which they catch solar energy and change it into the chemical energy of carbohydrates using inorganic compounds, i.e. water and carbon dioxide. This process is called photosynthesis. The green plants’ make their own food they are known as Autotrophs.

The chemical energy stored by the producers is used partly by the producers for their own growth and survival, and the remaining is stored in the plant parts for their future use.


The animals lack chlorophyll and are inadequate to synthesis their food. Therefore, they depend upon the producers for their food. There are four types :

1. Primary consumers

2. Secondary consumers

3. Tertiary consumers

4. Parasites, scavengers and saprobes

1. Primary Consumers

The primary consumers are herbivores. Some common herbivores are insects, birds and mammals in the terrestrial ecosystem. Elton named herbivores of an ecosystem as “key industry animals”. These serve as the chief food source for carnivores.

2. Secondary Consumers

Those animals that depend on the primary carnivores for food are called secondary consumers—E.g. sparrow, crow, fox, snakes

3. Tertiary consumers

These are the top carnivores which prey upon other carnivores, omnivores and herbivores. These are considered as tertiary or top consumers. E.g. Lions, tigers, hawk, vulture

4. Parasites, scavengers and saprobes

Besides different classes of consumers, the parasitic plants and animals utilise the living tissues of different plants and animals. The scavengers and saprobes utilise dead remains of animals and plants as their food.

Decomposers and transformers

The detritus food chain begins with dead organic matter.  The decomposers are a heterotrophic organism, mainly fungi and bacteria. They meet their energy and nutrient requirements by degrading dead organic matter or detritus are known as saprotrophs. Decomposers secrets digestive enzymes that breakdown dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them.

Source: NCERT, biologydiscussion

MPSC – Mains Topic GS1 paper

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