A pond ecosystem is a lentic, freshwater, self-regulating and self-sufficient ecosystem within which biotic and abiotic components of nature interact and energy flow from one trophic level to another.

1. Structural organization

They are the physical component of the ecosystem that contains biotic and abiotic components.

a. Abiotic components

They are the non-living factors of the environment.

Main abiotic component- water

On the basis of depth of pond, pond water is divided into 2 main zones;

i. Litteral zone

-Water keeps on circulating.

-Temperature keeps on changing

- Oxygen rich with enough light

ii. Limnetic zone

-Water generally doesn't circulate

-More or less, temperature doesn't keep on changing.

iii. Benthic zone

-Lowest part of the pond

- No direct sunlight

Other abiotic components include- sunlight, dissolved minerals, dissolved gases, edaphic factors, organi and physio-chemical factors.

b. Biotic components

-Determined by abiotic components

-Divided into:

I. Producer

Producers are the living organisms that prepare food for whole other biotic components directly or indirectly by converting inorganic into organic components. It includes"

• Macrophytes: They are the plants whose body is differentiated into roots, leaves and stem. Eg: Pistia, Trapa, Lotus, etc.
• Microphytes: They are the minute free floating or submerged lower plants. Eg: Volvox, Nostoc, Spirigyra, etc.

II. Consumers

They are the heterotrophic organisms that cannot prepare their own food and depend upon other organisms.

• Primary consumers: They depend upon producers for food. Eg: Euglena, tadpole, mites, etc.
• Secondary consumers: They depend upon primary consumers for food. Eg- Small fishes, insects, etc.
• Tertiary consumers: They depend upon secondary consumers for food. Eg- crocodile, frog, etc.

III. Decomposers

The saprophytic microorganisms that convert organic compounds into inorganic and recharge the nutrients in the ecosystem are called decomposers. Eg: bacteria, fungi, etc..

2. Functional components

It is the process which helps in smooth functioning of the ecosystem. In this organization, all producers prepare food by photosynthesis and the light energy is converted into chemical energy by all autotrophic plants. Besides this, some chemotrophic bacteria also convert inorganic molecule into organic. The food prepared by producers is transferred to different levels of consumers by process of eating and being eaten. After the death of producers and consumers, the complex nutrients in their bogy is converted into simpler and absorbable form in ecosystem by process of decomposition and this is carried out by decomposers. So bacteria and fungi recharge the nutrient in ecosystem for next producer and next generations.

Food chain

The process of transfer of energy from one trophic level to another by repeated process of eating and being eaten is called food chain.

Food web

Various food chains are inked together and interact with each other to form a complex network called food web.

Ecological pyramid

Ecological pyramid is a graphical representation of parameters like number, biomass or energy in different trophic level of an ecosystem in a pyramid.

Types:

a. Pyramid of number-Upright

b. Pyramid of energy- Upright

c. Pyramid of biomass- Inverted