Ecological Pyramid

This concept is often associated with description of food chains and food web. An ecological pyramid is an illustration of the reduction in energy as we move through each feeding (tropic) level in the ecosystem. The base of the pyramid is large since ecosystem’s energy factories (the plant producers) are converting solar energy into chemical energy through photosynthesis. A food chain can also depict a reduction in energy at each tropic level if the arrow drawn at different levels; continue to be reduced in size.

Ecological pyramid can be represented in three ways:

(1)   Pyramid of numbers: it can be generated by counting all the organisms at different feeding levels. This is a difficult task as we are not just identifying each species in the ecosystem but also counting how many of each species are present. Sometimes this may not work. For example, one tree (a producer) can represent an ecosystem and harbor numerous populations of herbivores and carnivores. Thus, the bottom of pyramid would be very small and not broad.

(2)   Pyramid of biomass:

This is generated when organisms from each trophic level are collected, dried and then weighed. This dry weight (biomass) represents the amount of organic matter (available energy) of the organisms. Please note that there are alternate, non lethal ways to determine biomass. While using this approach can generate a pyramid that illustrates energy flows but its use also generate as inverted pyramid. For example, in aquatic ecosystems. Phytoplankton could reproduce and then be eaten by rapidly reproducing zooplankton. Therefore, it would be possible to have few herbivores and a lot of carnivores when a collection is taken.

(3)   Pyramid of Energy Flow: This pyramid tends to resolve the above mentioned problems. This approach necessitates measuring the caloric value of the different organisms that make up the community. It nicely shows how energy is continually decreasing along the food chain from producers to top level carnivores. In summary there are three models used in ecology – food chains, food webs, and ecological pyramids –t hat can illustrate how energy moves through an ecosystem.

Energy Flow: Solar radiation is the basic input of energy which enters the ecosystem. This solar energy passes step by step through each trophic level and ultimately becomes output from ecosystem as energy lost through respiration from each trophic level.

Biosynthesis is the process of the formation of organic tissue which represents the transformation of solar energy into chemical or food energy.

Biodegradation is the process of breakdown and decomposition of organic matter and thus this process refers to release of nutrients and food (chemical) energy it the form of heat. The energy flow in the ecosystem is unidirectional and is non-cyclic i.e. not available for reuse.