Food Chain
The food chain refers to the transfer of food energy from green plants (producers) through a series of organisms in which each organism is eaten by the next.
For example: Grasses → Grasshopper → Frog → Snake → Hawk/Eagle
Each stage or step in a food chain is called a trophic level.
- In the above example, grasses are at the first trophic level and the eagle represents the fifth trophic level.
As energy flows through the food chain, some of it is lost as heat at each step, reducing the energy available for higher levels. This limits most food chains to 4 or 5 trophic levels.
Trophic Levels in a Food Chain
1) Autotrophs (Producers)
- Green plants and certain bacteria that produce food using solar energy through photosynthesis.
- The total energy captured by producers is called Gross Primary Production (GPP).
- Plants use some of this energy for their own metabolism, and the leftover energy stored as food is called Net Primary Production (NPP) — available for consumers.
2) Herbivores (Primary Consumers)
- Animals that eat plants directly, such as insects, birds, rodents, and ruminants.
3) Carnivores
- Animals that eat other animals.
- Secondary consumers: feed on herbivores (e.g., frogs, dogs).
- Tertiary consumers: feed on other carnivores (e.g., tigers, hawks).
4) Omnivores
- Animals that eat both plants and animals (e.g., humans, pigs, bears).
5) Decomposers
- Bacteria and fungi that break down dead organic matter from all trophic levels, recycling nutrients back into the ecosystem.
Types of Food Chains
There are two main types of food chains in an ecosystem:
- Grazing food chain: Starts with green plants eaten by herbivores, which are then eaten by carnivores. (Producers → Herbivores → Carnivores)
- Detritus food chain: Starts with dead organic matter (detritus) eaten by detritivores, which are then eaten by protozoans and carnivores. (Producers → Detritus Feeders → Carnivores)
In most ecosystems, these two types of food chains are interconnected, forming a Y-shaped food chain, illustrating the flow of energy through both living and dead matter.