What is an Ecosystem?

An ecosystem can be simply defined as a community of living beings in concurrence with nonliving components in which they will interact. It is a chain of interaction between organisms and its environment.

An ecosystem can vary in size it can either be small as an oasis or vast as an ocean encompassing precisely limited spaces. They are usually controlled or influenced by external and internal factors as well. External factors such as climate can be considered as a prime material that forms soil and topography that controls the entire configuration of the ecosystem.

There are mainly two components in an ecosystem, namely biotic and abiotic components.

Biotic Components

They are living components of the ecosystem. It includes biotic factors such as producers, consumers, and decomposers.

  • Producers include all autotrophs (plants), they produce their own food by making use of energy that is obtained from the sunlight. All living beings are dependent on plants for oxygen and food.
  • Consumers include the primary consumers and secondary consumers. Top carnivores and apex predators make up the tertiary consumers.
  • Decomposers include saprophytes (fungi and bacteria), that converts the dead matter into nitrogen and carbon dioxide. They are essential for recycling of nutrients to be used again by the producers.

Abiotic Components

They are the nonliving component of an ecosystem such as light, air, soil, water, and nutrients. Below figure demonstrates a simple food chain.

Food Chain

The sun is the ultimate source of energy on earth which powers all plant life. This energy is utilized by the plants through photosynthesis to produce food. That is, light energy is converted into chemical energy. This energy is passed up through successive levels – from producers to consumers. This energy flow from the producer to the apex predator is called the food chain.

The dead and decaying matter, along with organic debris is broken down into smaller bits by scavengers. These molecules are then absorbed by the reducers. After gaining the energy, the reducers liberate molecules to the environment in the form of chemicals that are utilized again by the producers.


Ecological Pyramids

Ecological Pyramids

The biomass, number, and energy of organisms ranging from the producer level to the consumer level represented in the form of a pyramid. This pyramid is known as the ecological pyramid.

An ecological pyramid is the graphical representation of the number, energy, and biomass of the successive trophic levels of an ecosystem. Charles Elton described how the ecological pyramid works in the year 1927.

The base of the ecological pyramid comprises of the producers, followed by the primary and secondary consumers. The tertiary consumers hold the apex. The producers generally outnumber the primary consumers, and similarly, the primary consumers outnumber the secondary consumers. And lastly, apex predators also follow the same trend as the other consumers, wherein, their numbers are considerably lower than the secondary consumers.

For example, grasshoppers feed on crops such as cotton and wheat, which are plentiful. These grasshoppers are then preyed upon by common frogs, which are comparatively less in number. These frogs are then preyed upon by snakes such as cobras, with numbers even smaller than that of the frogs. Snakes are ultimately preyed on by apex predators such as the brown snake eagle.

In essence: Cotton-> Grasshopper -> Common Frog -> Cobra-> Brown snake eagle

Nutrient Cycling

Carbon Cycle

The cycle of carbon between abiotic and biotic systems is known as the carbon cycle. Carbon dioxide is found both in the air and water, and it is the main source of carbon. The content of carbon dioxide in the air is 0.03% and it remains constant.

The carbon flows in the biotic system in three forms.

  • Photosynthesis

Carbon dioxide (CO2) is required by green plants for photosynthesis, which is used to produce glucose. The glucose is used in the synthesis of different kinds of lipids, carbohydrates, and proteins, most of which contains carbon. These compounds are then stored in plant tissues and delivered higher up the food chain. When herbivorous animals eat these plants, the carbon enters their system. Eventually, the carbon enters the body of carnivores when herbivores are preyed on.


  • Formation of shell

Carbon dioxide is dissolved in the sea and consumed by marine animals such as corals, protozoans, molluscs for the formation of their shell. Calcium carbonate forms from carbon dioxide, which is the essential component of shells.

CO2+H2→H2CO3 (Carbonic acid)

H2CO3→H++HCO3 (Bicarbonate)

HCO3+Ca+→H++CaCO3 (Calcium carbonate)

  • Coal

Billions of years worth of biomass get trapped under the earth and over time, the intense heat and pressure deep inside the earth converts it to coal. Carbon eventually returns to atmosphere from coal in the form of CO2 through weathering and combustion.

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Practise This Question

Energy flow in an ecosystem is ____.