Pyramid of numbers, pyramid of biomass and pyramid of energy are usually referred to as ecological pyramids. Ecological pyramids represent the trophic structure and also trophic function of the ecosystem. In ecological pyramids, the producer forms the base and successive trophic levels make up the apex.
Pyramid of Numbers
Pyramid of numbers is a graphical representation that shows the number of organisms at each trophic level. It is usually an upright pyramid because in an ecosystem, the producer are always more in number than organisms in the successive trophic levels. At higher level, no predator can be as common as its prey, otherwise the population of both animals will soon be wiped out. This pyramid was advanced by Charles Elton (1927), who pointed out the great difference in numbers of organisms involved in each step of the food chain.
The pyramid of numbers does not take into consideration the biomass of organisms, it does not also indicate transferred or use of energy by the organism involved. The lake ecosystem is usually a perfect example for pyramid of number.
The pyramid of numbers is usually used as a basis for ecosystem’s quantitative analysis, because through it you can tell how the population of a given species can affect others.
Types of Pyramid Of Numbers
Upright pyramid of number: This type of pyramid of numbers is common in grassland ecosystem, whereby there are numerous autotrophs that support less number of herbivores. The herbivores then eventually support a smaller number of carnivores.
Partly upright pyramid of number: This type of pyramid of number is found in forest ecosystem. In Forest ecosystem, the producers are larger-sized trees, which sit at the base of the number pyramid. The herbivores such as fruit eating birds or elephants make the primary consumers. They are more in numbers than the producer.
The inverted pyramid of number: In this type of pyramid, individual number increase at each successive trophic level. This type of pyramid is common in parasitic food chains. In these food chains, there is usually one producer supporting many parasites, the parasites then eventually support other more hyper-parasites.
Pyramid of Biomass
What Is A Pyramid Biomass?
Biomass in ecology refers to the total mass of all living or organic matter that inhibit an ecosystem at any given point of time. Therefore, the pyramid of biomass is a graphical representation which shows the biomass existence per unit area in all the different trophic levels of the ecological system. The lowest level of this pyramid is occupied by producer, and the top of the pyramid is occupied by the carnivores.
The pyramid of biomass shows the relationship between biomass available in each trophic level of an energy community at a given time. A pyramid of biomass is shaped such that it is largest at the base and diminishes as it goes to the top.
Pyramid of biomass is usually ascertained by collecting all organisms occupying each trophic level separately and measuring their dry weight. Each trophic level has a certain mass of living material at a particular time referred to as standing crop, which is measured as the mass of living organisms (biomass) or the number in a unit area.
Graphical representation of the flow of energy and mass in the ecosystem is one of the best ways to understand whether or not there is any sort of imbalance in the system.
Types of Pyramid of Biomass
Upright Pyramid of Biomass: Many ecosystems found on land have an upright pyramid of biomass whereby there is a large base of primary producers with smaller trophic level perched on top, hence the upright pyramid of biomass.
Inverted Pyramid of Biomass: A good example of pyramid of biomass is the pond ecosystem, where the mass of phytoplankton, the major producers will always be lower than the mass of heterotrophs like fish and insects.
Pyramid Of Energy
Pyramid of energy is a graphical representation of the rates of flow of energy through the different trophic levels of an ecosystem. Each bar of the pyramid represents the amount of energy per unit area or volume which flows through that trophic level in a given time period. The different trophic levels represent groups of organisms that might compose a food chain. From the bottom-up, they are as follow:
- Producers bring energy from nonliving sources into the community.
- Primary Consumer Eat the producers.
- Secondary Consumers eat the primary producers.
- Tertiary Consumers eats the secondary producers
An energy pyramid’s upward shape shows how the amount of useful energy that enters each level- chemical level in the form of food, decreases as it is used by the organism in that level. In other words, Energy decreases as one moves through the trophic levels from bottom to the top of the pyramid. Thus, the energy pyramid is always upward.
Pyramid Of Numbers Vs. Pyramid Of Biomass Vs. Pyramid of Energy In Tabular Form
|BASIS OF COMPARISON||PYRAMID OF NUMBERS||PYRAMID OF BIOMASS||PYRAMID OF ENERGY|
|Description||It is a graphical representation that shows the number of organisms at each trophic level.||It shows graphical representation of the relative amount of biomass at each trophic level.||It is a graphical representation of the trophic levels, by which the incoming solar energy is transferred to the ecosystem.|
|Importance||It is usually used as a basis for ecosystem’s quantitative analysis, in that it helps to estimate how the population of a given species can affect others.||It expresses the total dry weight of the organisms existing in the trophic level.||It shows the total energy flow in the ecosystem.|
|Inverted Pyramid||There can be an inverted pyramid of numbers.||There can be an inverted biomass pyramid.||An inverted pyramid of energy does not exist.|
|Assigning Of Organisms||The organisms can be easily assigned to a particular trophic level in this pyramid.||The organism can be easily assigned to a particular trophic level in this pyramid.||The assignment of creatures to a particular level in this pyramid is difficult.|
Importance of Ecological Pyramids
Limitations of Ecological Pyramids
- It does not accommodate a food web.
- Saprophytes are not given any place in ecological pyramid even though; they play an important role in ecosystem.
- It assumes a simple food chain, something that almost never exists in nature.
- It never takes into account the same species belonging to two or more trophic levels.