(1) Food chain in a pond: In a pond, floated or rooted plants and algae are responsible for performing photosynthesis to prepare food for other member of ecosystem. They represent producers in the food chain (Figure 39.2). Unicellular algae are consumed by protozoan, water flies, snail, mosquito larvae and tadpoles. These small organisms represent primary consumers. These organisms are eaten by hydra, dragonfly larvae, giant insects and small fishes. These are secondary consumers. Large fishes and frog fed on these organism and represent tertiary consumers. Frog and fishes are eaten by snakes, birds and these are quaternary consumers. Death of all these organism become the food for bacteria and fungus to produce simple inorganic materials for reuse by the producers.

 

Figure 39.2: Food Chain in Pond.

(2) Food chain on land:  A typical land food chain is given in Figure 39.3. In land food chain, grass and tree are the producers. Grass is eaten by rabbit and other herbivorous. They represents the primary consumers. Rabbit is eaten by cats (secondary consumers), which in-turn eaten by wolves (tertiary consumers). Both cat and wolves will be consumed by tigers and other big carnivorous (quaternary consumers). Death of all these organism become the food for bacteria and fungus to produce simple inorganic materials for reuse by the producers.