Describe different types of food chains that exist in an ecosystem.

Food chain: Organisms belonging to different trophic levels form food chain. Energy passes from one trophic level to another trophic level. There are three types of food chains:
1. Grazing food chain
2. Parasitic food chain
3. Detritus food chain
 

1) Grazing food chain (predator food chain): Green plants, herbivores, primary carnivores and secondary carnivores, occupy I to IV trophic levels.
Examples: 

• Rose bush – Aphids – Spiders – Small birds – Hawk
• Grass – Grasshopper – Frog – Snake – Hawk

2) Parasitic food chain: It also begins with the producers. Food energy passes from large organisms to small organisms.
Example: 

• Tree - Many birds - Many parasites which live on birds.

3) Detritus food chain: It begins with dead organic matter made up of decomposers like bacteria and fungi.
Examples:

• Detritus – earthworms – frogs – snakes
• Dead animals – flies – frogs – snakes

Food Web: In an ecosystem, the feeding relationships are not so simple. The food chains have interconnections and form a network called food web.