FOOD CHAIN - Series of organisms feeding on one another at various level forms a food chain.                       or
The sequence of living organism in which one organism eats another is called a Foodchain .
                 Each step of level of food chain forms a trophic level .

BIOTIC FACTOR Biotic components of the ecosystem refer to any living component and their interactions. 
Example --- soil ,topography ,moisture , etc .

ABIOTIC FACTOR Abiotic component are those which refer to any non living component in the ecosystem. 
Example--- sunlight ,oxygen ,temperature,etc.

ECOSYSTEM -An ecosystem includes all of the living things (plants, animals and organisms) in a given area, interacting with each other, and also with their non-living environments (weather, earth, sun, soil, climate, atmosphere). 
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Biotic Biotic refers to the living organisms. Abiotic Abiotic refers to the non living organisms Ecosystem The interconnection between living organisms , plants and animals is known as ecosystem.
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