13.3 Food Chain

Definition:

• The flow of food energy through different trophic levels in an ecosystem is known as the food chain.

• Green plants are the primary producers, and their activity is crucial for sustaining herbivores and carnivores in the ecosystem.

• Without the food produced by plants, herbivorous and carnivorous animals would not survive.

Example of a Food Chain:

1. Grass (Primary Producer): Green plants such as grass begin the food chain by producing food through photosynthesis.

2. Grasshopper (Primary Consumer): Herbivorous animals like grasshoppers feed on the grass, obtaining energy.

3. Toad (Secondary Consumer): The toad consumes the grasshopper, gaining energy from it.

4. Snake (Tertiary Consumer): The snake feeds on the toad, obtaining energy from it.

5. Gui Snake (Top Consumer): If a larger predator, like the gui snake, consumes the smaller snake, it becomes the top consumer in the food chain.

Food Chain Classification:

Food chains can vary depending on the type of interaction between organisms. They can be classified into three main types:

1. Predator Food Chain:

• In a predator food chain, organisms at lower trophic levels (like primary consumers) are preyed upon by higher-level consumers.

• Example: The food chain above is an example of a predator food chain, where grass → grasshopper → toad → snake → gui snake represents a series of predator-prey relationships.

2. Parasitic Food Chain:

• In this type of food chain, parasites (such as parasitic plants and animals) obtain food from a host organism that is much larger than them.

• Sometimes, smaller parasites may rely on other parasites for their food.

• The food chain may be incomplete, as the primary producers do not always appear at the beginning of the chain.

• Example: Man → mosquito → Dengue virus. In this case, the female Aedes mosquito sucks blood from a human, but this does not provide nutrients for the mosquito; instead, it helps in the development of its eggs.

3. Saprophytic Food Chain:

• A saprophytic food chain involves the decomposition of dead organisms.

• The energy flows from dead organisms to decomposers, such as fungi and earthworms.

• Example: Dead body → fungi → earthworm.

• This type of food chain is also incomplete since it lacks primary producers. Saprophytic and parasitic food chains depend on predator food chains for energy flow.

Key Points:

• Incompleteness: Parasitic and saprophytic food chains are incomplete because they do not have a producer at the start.

• Dependence on Producers: All food chains, regardless of type, ultimately depend on the energy produced by green plants through photosynthesis. These producers are the foundation of every food chain.