Pond is an aquatic ecosystem. The food chain can be defined as the transfer of energy from plants through a series of organisms with repeated eating and being eaten Or who eats whom .At each trophic level a large portion of the potential energy is lost as heat. The number of steps in a food chain is usually limited to four or five, since the energy decreases during the transfer from one step to another.
In any food chain, energy flows from producers to primary consumers, from primary consumers to secondary consumers, from secondary consumers to tertiary consumers and so on. Producers prepare their own food using solar energy and convert it to chemical energy.
In a pond ecosystem the food chain starts from phytoplankton and goes through zoo plankton, smaller fish, bigger fish, and birds and so on.
The producers in a pond ecosystem are macrophytes and phytoplanktons.The phytoplankton when present in abundance, gives the pond water a greenish colour.The phytoplankton usually comprises diatoms, blue green algae, green algae etc.
In pond the macro consumers are the animals. They can be categorized into:
1. Primary consumers
2. Secondary consumers
3. Tertiary consumers
The primary consumers feed on living plants or plant remains. The primary consumers are the zoo planktons and benthos. The zooplanktons include dianoflagellates, heliozoans, and copepods while Mollusca and annelids form the bottom dwelling forms. The secondary consumers are the carnivores which feed on primary consumers like predaceous insects, small fishes, frogs etc. The tertiary consumers are some large fish like game fish that feed on the secondary consumers.