Define ecological pyramids and describe with examples, pyramids of number and biomass.
Solution and Explanation
An ecological pyramid is a graphical representation of various ecological parameters such as the number of individuals present at each trophic level, the amount of energy, or the biomass present at each trophic level. Ecological pyramids represent producers at the base, while the apex represents the top level consumers present in the ecosystem.
There are three types of pyramids:
(a) Pyramid of numbers
(b) Pyramid of energy
(c) Pyramid of biomass
Pyramid of numbers: It is a graphical representation of the number of individuals present at each trophic level in a food chain of an ecosystem. The pyramid of numbers can be upright or inverted depending on the number of producers. For example, in a grassland ecosystem, the pyramid of numbers is upright. In this type of a food chain, the number of producers (plants) is followed by the number of herbivores (mice), which in turn is followed by the number of secondary consumers (snakes) and tertiary carnivores (eagles). Hence, the number of individuals at the producer level will be the maximum, while the number of individuals present at top carnivores will be least.
On the other hand, in a parasitic food chain, the pyramid of numbers is inverted. In this type of a food chain, a single tree (producer) provides food to several fruit eating birds, which in turn support several insect species.
Pyramid of biomass
A pyramid of biomass is a graphical representation of the total amount of living matter present at each trophic level of an ecosystem. It can be upright or inverted. It is upright in grasslands and forest ecosystems as the amount of biomass present at the producer level is higher than at the top carnivore level. The pyramid of biomass is inverted in a pond ecosystem as the biomass of fishes far exceeds the biomass of zooplankton (upon which they feed).
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Concepts Used:
Ecological Succession
Ecological succession is the steady and moderate change in a species of a given area with respect to the changing environment. Our nature consists of both biotic and abiotic factors. When these biotic and abiotic factors interact with each other to develop natural communities they give rise to such successions.
Ecological Succession:
When land is left on its own for years, it starts being occupied by microorganisms followed by wild shrubs and other large plants, which gives rise to a new ecosystem. The series of stages is quite predictable and inescapable. In order to understand the primary and secondary succession, we need to be very much clear about what ecological succession is as they are its types. This succession mainly focuses to bring about equilibrium in the ecosystem. When the target is achieved, it is called a climax community.
The number of species to survive is then decided based on achieving the equilibrium. In a community, these changes happen in a sequence, and such a community is known as a seral community which further is an intermediate stage of ecological succession advancing towards the climax community. All the succession begins with an instigating species. The instigate species or the first species build an initial biological community that is simpler in form. The initiation of this ecological succession separates it into the following three types –
- Primary succession
- Secondary succession
- Cyclic Succession