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Ecology @ 9:05 PM
6) What are ecological pyramids? Describe the different types of ecological pyramids.
Ecological pyramids can be used to compare trophic levels in a food chain.The three ecological pyramids:
1) Pyramid of numbers
2) Pyramid of biomass
3) Pyramid of energy
1) Pyramid of numbers
The pyramid of numbers allows us to compare the number of organisms present in each tropic level at a present time.
There are also pyramids of numbers which are inverted. It occurs when:
-Organisms on one trophic level are parasitic on organisms on another trophic level.
-Many small organisms of one trophic level feed on a large organism of another trophic level.
2) Pyramid of biomassA pyramid of biomass allows us to compare the mass of organisms present in each trophic level at a particular time.
An ecological pyramid of biomass shows the relationship between biomass and trophic level by quantifying the amount of biomass present at each trophic level at any one time. This is called the standing mass of organisms.
The pyramid of biomass is more accurate than the pyramid of numbers, as the pyramid of numbers may be inverted in some cases while the pyramid of biomass, is based on standard mass. Thus, most of the time it will be broad at the bottom and narrow at the top.
The biomass pyramid may also be 'inverted' which happens when the producer has a very fast rate of reproduction which is fast enough the replace the organisms eaten by the primary consumers.
3) Pyramid of energy
The energy in the various trophic levels of a food chain can be represented in the form of a pyramid. It is known as the pyramid of energy.
The pyramid of energy is constructed based on the total energy level in each trophic level over a certain period of time. A huge amount of energy is lost to the environment as food is transferred from one trophic level to the next. Energy may be lost to the environment in a few ways:
-as heat during respiration at every trophic level
-in uneaten body parts
-through undigested matter egested by consumers
-through waste products excreted by consumers, for example, urea.
Heat energy is wasted as it cannot be recycled in any way in the ecosystem.
Loss of energy occurs as the food chain continues. The total energy at the first trophic level is the highest while the energy at the lowest trophic level is the lowest. Hence, a pyramid of energy is always broad at the bottom and narrow on top. About 90% of the energy is lost during energy transfer from one trophic level to another. The greatest amount of energy lost is during the transfer of energy from producer to primary consumer.
