I MSc

1. Ecological pyramids
and recycling

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• A graphical representation of the biomass or bio productivity
at each trophic level in a given ecosystem is known as an
ecological pyramid.
• Ecological pyramids start at the bottom with producers and
work their way up through the trophic levels (such as
herbivores that eat plants, then carnivores that eat flesh, then
omnivores that eat both plants and flesh, and so on).
• The apex of the food chain is the highest level.
• G.Evylen Hutchinson and Raymond Lindeman were the ones
who introduced it.

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Types of Ecological Pyramid
1. Pyramid of Numbers
• The total number of individuals (population) present at each
trophic level is represented by a pyramid of numbers.
• Elton John popularised the term "pyramid of numbers" in 1972.
Except in rare cases, such as the detritus food chain, where many
creatures feed on a single dead plant or animal, the number
pyramid is normally vertical.

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Pyramid of Biomass
• Biomass is the amount of living material present in
an individual or a group of individuals per unit area
product.
• Each level of this form of ecological pyramid
accounts for the amount of biomass present in each
trophic level.
Except in oceans, where enormous numbers of
zooplanktons rely on a relatively small number of
phytoplankton, the biomass pyramid is also upright.

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Pyramid of Energy
• The energy pyramid is a vertical pyramid that
depicts the transfer of energy from producers to
consumers.
• As energy transmission in a food chain is always
unidirectional, the energy pyramid is the only type of
ecological pyramid that is always upright.
• In addition, as the trophic level rises, some energy
is lost to the environment.

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Energy Flow in an Ecological Pyramid
• When one creature feeds another and obtains energy-rich
molecules from its prey's body, energy is transmitted between
trophic levels.
• Some of the energy that enters a trophic level is stored
as biomass, which is a component of organisms' bodies.
• As only energy stored as biomass can be eaten, this is the
energy available to the next trophic level.

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Significance of Ecological Pyramid
• They illustrate the nutrition of several organisms in various
habitats.
• It demonstrates the effectiveness of energy transmission.
• The ecosystem's state can be monitored, and any additional
damage can be avoided.

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Limitations of the Ecological Pyramid
Several species may occupy multiple trophic levels.
Even though saprophytes are a significant feature of many ecosystems,
they are not included in any of the pyramids.
These pyramids don't provide any information about seasonal and
climate changes.
They don't take into account the possibility of many species existing at
various levels.