An ecosystem can be visualised as a functional unit of nature, where living organisms i.e. producers, consumers and decomposers interact among themselves and also with the surrounding physical environment.

The biotic and abiotic components of an ecosystem interact amongst themselves and function as a unit, which gets evident during the processes of nutrient cycling, energy flow, decomposition, and productivity.

There are many ecosystems such as ponds, forests, grasslands which are examples of natural ecosystem. Apart from this artificial ecosystem includes cultivated land, aquarium.

The two components of an ecosystem are:

1. Biotic Components: It is the living component of an ecosystem that includes biotic factors such as producers, consumers, decomposers, etc.

a. Primary producers: Primary producers are basically green plants, certain bacteria and algae that carry out photosynthesis. They contain chlorophyll pigment, which helps them carry out the process of photosynthesis in the presence of light. Thus, they are also called converters or transducers.

b. Consumers: Consumers are incapable of producing their own food. They depend on organic food derived from plants, animals or both.

Consumers can be divided into two groups namely:

I. Primary Consumers: Herbivores are primary consumers which feed mainly on plants.

II. Secondary consumers: They feed on primary consumers it includes carnivores and omnivores. Carnivores which feed on both primary and secondary consumers are called tertiary consumers e.g. lion which can eat wolves, snakes etc. Omnivores are organisms which consume both plants and animals e.g. man, bear, etc.

c. decomposers: They are bacteria and fungi which obtain energy and nutrients from dead organic substances (detritus) of plant and animals. The products of decomposition such as inorganic nutrients which are released in the ecosystem are reused by producers and thus recycled. Earthworm and certain soil organisms (such as nematodes, and arthropods) are detritus feeders and help in the decomposition of organic matter and are called derivers.