Food chain : The biotic factors of the ecosystem are linked together by food. For example, the producers form the food for the herbivores. The various steps in a food chain are called trophic levels. Owing to repeated eating being eaten, the energy is transferred from one trophic level.

Food Chain:
The process of eating and being eaten is called a food chain. It refers to the transfer of energy and nutrients from one organism to another in an ecosystem. The food chain is a sequence of living organisms in which each organism is the food of the next one in the chain.

Components of a Food Chain:
A food chain consists of three main components:

1. Producer: The first organism in the food chain is the producer, which synthesizes organic matter from inorganic substances through photosynthesis or chemosynthesis. Example: Plants.

2. Consumer: The second organism in the food chain is the consumer, which feeds on the producer or other consumers. Consumers are further classified as primary, secondary, tertiary or quaternary depending on their position in the food chain. Example: Herbivores, carnivores, omnivores, etc.

3. Decomposer: The third organism in the food chain is the decomposer, which breaks down dead organic matter into simpler substances and returns nutrients to the soil. Example: Fungi, bacteria.

Types of Food Chain:
There are two types of food chains:

1. Grazing food chain: In this type of food chain, the energy flows from the producer to the herbivore and then to the carnivore. Example: Grass → Rabbit → Fox.

2. Detritus food chain: In this type of food chain, the energy flows from the dead organic matter to the decomposer and then to the detritivore. Example: Dead leaves → Earthworm → Bird.

Importance of Food Chain:
The food chain is an important concept in ecology as it helps us to understand the interdependence of living organisms in an ecosystem. It also helps us to understand the flow of energy and nutrients through the ecosystem. The food chain also plays a vital role in maintaining the balance of nature.

Answer is B