What is Food Chain : Definition, Types, Examples

Key Concepts

• Food chain
• Trophic level
• Producers
• Consumers
• Decomposers
• Scavengers
• Predator
• Prey
• Predator (grazing) food chain
• Detritus (decomposer) food chain

Introduction

From the last topic, we have come to know that depending upon the food habits, animals and human beings are classified into three groups. These are herbivores (plant-eating organisms), omnivores (both plant and animal eating organisms) and carnivores (animal-eating organisms). 

Food chain: 

The food chain is a transfer of materials and energy from their ultimate source in plants as producers through a series of organisms, each of which eats a smaller preceding one and is eaten by a larger succeeding one. 

Trophic level: 

Each food chain is a possible pathway that energy and nutrients can follow in the ecosystem. Organisms in food chains are grouped into categories called trophic levels. These levels are divided into producers (first trophic level), consumers (second, third, and fourth trophic levels), and decomposers. 

Producers: Producers are any kind of green plant. Green plants make their food by taking sunlight and using the energy to make sugar (food). At the base of almost every food chain is a producer. 

Consumers: Consumer is a category that belongs within the food chain above the producers of an ecosystem.   It refers predominantly to animals. Consumers are unable to make their food, and instead rely on the consumption and digestion of producers or other consumers, or both, to survive. 

We can again divide consumers into the following categories: 

• Primary consumers are herbivores. Their food source is the first trophic level organism. Primary consumers represent the second trophic level. 

• Secndary consumers nearly always consume both producers and primary consumers and are, therefore, usually classed as omnivores. Secondary consumers make up the third trophic level of the food chain. Examples of secondary consumers are earwigs, ants, badgers, snakes, rats, crabs. 
• Tertiary consumers can be either omnivorous or carnivorous. They feed on primary and secondary consumers and may also eat producers. Tertiary consumers make up the fourth trophic level of the food chain. Examples of tertiary consumers are hawks, snakes, crocodiles, and some big cats. 

Decomposers and scavengers break down dead plants and animals. They also break down the waste of other organisms. Decomposers are very important for any ecosystem. If they were not present in the ecosystem, the plants would not get essential nutrients, and dead matter and waste would pile up. 

Decomposers: Decomposers are organisms that act on dead plants and animals and convert them into a dark-colored substance called humus. Bacteria and some fungi act as decomposers. 

Scavengers: Some animals eat dead animals or carrion. They are called scavengers. They help break down or reduce organic material into smaller pieces. Decomposers then eat these smaller pieces. Examples of scavengers are hyenas, vultures, crows, etc. 

The trophic level of decomposers and scavengers: 

Decomposers are those organisms that break down the dead and decaying organic matter, and scavengers are those organisms that eat dead animals. So, these organisms consume organisms in the consumer levels below them and have no predators. They are at the top of the food chain, i.e., they are the quaternary consumers or apex predators that belong to the fifth trophic level. 

Types of food chains: Food chains are broadly categorized into two based on the energy produced: 

1. Grazing or Pasturing food chain: This food chain starts from green plants (producers), passes through the herbivore (primary consumers) and ends with carnivore (secondary or tertiary consumers) 

2. Saprophytic or Detritus food chain: In this food chain, the ecosystem’s dead organic matter or organic wastes go to the microorganisms and finally to detritus feeding organisms known as detrivore. The energy stored in detritus serves as a source of energy for detrivore. This type of food chain is less efficient as the major portion of the energy is lost to the ecosystem without being properly used. 

Role of decomposers in a food chain: 

Decomposers are saprophytic organisms that obtain their nourishment from organic remains. They grow on the dead and decaying organisms and help break down the complex organic molecules into simpler ones by releasing various enzymes, which are biological catalysts. These decomposers complete the food chain. 

Example of an aquatic food chain: 

A food chain in a pond ecosystem include: 

Algae →protozoans →small crustaceans →small fishes →large fishes 

Example of a terrestrial food chain: 

Grass → grasshopper → frog → snake