The ecosystem can sustains itself, if there is a balance between the producers, the consumer and the decomposers. Energy is a major link which binds all the above components in an ecosystem. Thus, there is a fixed position or level of a particular type of organisms in an ecosystem. How we can know or decide that position? To explain it, a graphical structure has been proposed by the environmental biologists, known as Ecological Pyramid.
What is an Ecological Pyramid
An ecological pyramid is a graphical representation of the relationship between various trophic levels organisms in a Food Chain. It was first designed by Charles Elton and are called Eltonian Pyramid or Food Pyramids.
Types of Ecological Pyramids
Ecological Pyramids are three types: Pyramid of Number, Pyramid of Biomass and Pyramid of Energy.
1. Pyramid of Number
As the name says, in this type of pyramid number of organisms are counted and accordingly respective volume to each trophic level is allotted in the pyramid. Characteristic features of pyramid of number are.
- Number of producers are higher in number than the consumers present in other trophic levels.
- Number of individuals in each trophic level decrease when we go from bottom to top in a pyramid.
- Collectively the living organisms present in each of the trophic levels are known as standing crop.
- Normally the pyramid of number is an upright one Ex. Grassland ecosystem, Aquatic ecosystem.
- Sometimes inverted pyramids are also found in this case.
- A mixed or spindle shaped pyramid is also observed in case of forest ecosystem.
2. Pyramid of Biomass
Biomass is the total dry weight of the animals as well as plants present in the ecosystem at any point of time. Like pyramid of numbers it may be upright one or inverted one. In case of a forest and grass land ecosystem it is upright and in cases of a pond ecosystem inverted pyramids are observed.
3. Pyramid of Energy
The Food Chain and Food Web systems are existed for the energy requirement and energy transfer between the living organisms in an ecosystem. It is the most important type of ecological pyramid. The amount of energy being transferred from the lower trophic level towards the upper ones become less and less. Thus, longer the pyramid in height, lesser will be the amount of energy to reach the organisms present in the topmost trophic level. Only 10% of the energy is being transferred to the subsequent upper trophic level organisms.
For example, if the producers generate 1000 kilo calorie amount of energy, the primary consumers will receive 100 kcal, the secondary consumer will get 10 kcal and only 1 kcal amount of energy will reach to the tertiary or topmost level of consumers.
In this way a pattern of upright Pyramid of Energy will be developed for all types of ecosystems found in the Nature. This is the universal formula. Energy pyramid can never be an inverted one or spindle shaped found in other types of ecological pyramid structure. The shape of the pyramid of energy is not affected by the size, biomass, number or the metabolic rate of the organisms.
Limitation of Ecological Pyramids
Some limitations are also observed in the studies of ecological pyramids. That can be described as follows:
- The position of certain organisms are not fixed in one ecological pyramid. That may vary in same or may be in a different ecosystem.
- There is no consideration of seasonal changes, while studying the pyramids
- Role of detrivores are not represented in an ecological pyramid.
However, it can be said that the pyramid of energy is very accurate and gives a true picture of the ecosystem.
