Which organisms represent the base of an ecological pyramid?

Hint: Ecological pyramid is a relation between the producers and consumers in an ecosystem that can be represented graphically in the form of a pyramid. These are of three types – pyramid of number, pyramid of energy, pyramid of biomass.

Complete answer:
The sun is the only source of energy for all ecosystems on earth. Only 50% of it is photosynthetically active radiation. The plants only capture 2-10 percent of the PAR and this sustains the entire living world. So, the energy flows in the unidirectional way i.e. from the sun to producers then to the consumers.

The energy is transferred in an ecosystem in the form of food which is degraded and lose major part of food energy as heat during metabolic activities and only a very small fraction becomes stored as biomass. Green plants in the ecosystem which can trap the solar energy by the help of chlorophyll, a green color pigment present on the leaves to convert it into chemical bond energy and are called producers. All the animals or consumers depend on plants for their survival or food.

So, we say that the base of an ecological pyramid represents the producers or first trophic levels i.e. plants.

Note: There are various limitations of ecological pyramids –
- It never takes into account the same species belonging to two or more trophic levels.
- It assumes a simple food chain, which never exists in nature.
- In spite of the vital role played by decomposers, they are not given any position in ecological pyramids.