Ecological Pyramids
Ecological Pyramids
Ecological Pyramids
Ecological Pyramids
o Pyramid of Numbers
o Pyramid of Biomass
o Pyramid of Energy
o Ecological Efficiency
o Limitations of Ecological Pyramids
Pollutants and Trophic Level – Biomagnification
o Chlorinated Hydrocarbons (CHC)
o Bioaccumulation
o Biomagnification
Ecological Pyramids
1. Pyramid of numbers,
2. Pyramid of biomass, and
3. Pyramid of energy or productivity.
Pyramid of Numbers
Pyramid of numbers represents the total number of individuals of different
species (population) at each trophic level.
Depending upon the size, the pyramid of numbers may not always be
upright, and may even be completely inverted.
It is very difficult to count all the organisms, in a pyramid of numbers and so
the pyramid of number does not completely define the trophic structure for an
ecosystem.
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Pyramid of Biomass
Pyramid of biomass is usually determined by collecting all organisms
occupying each trophic level separately and measuring their dry weight.
This overcomes the size difference problem because all kinds of organisms at
a trophic level are weighed.
Each trophic level has a certain mass of living material at a particular time
called the standing crop.
The standing crop is measured as the mass of living organisms (biomass) or
the number in a unit area.
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Pyramid of Energy
Ecological Efficiency
It does not consider the same species belonging to two or more trophic levels.
It assumes a simple food chain, something that seldom exists in
nature; it does not accommodate a food web.
Moreover, saprophytes (plant, fungus, or microorganism that lives on
decaying matter) are not given any place in ecological pyramids even though
they play a vital role in the ecosystem.
CHCs are hydrocarbons in which one or more hydrogen atoms have been replaced by chlorine
(dichlorodiphenyltrichloroethane), endosulfan, chloroform, carbon tetrachloride, etc.
CHCs are used in the production of polyvinyl chloride (a synthetic plastic polymer used to make
Chloroform, dichloromethane, dichloroethane, and trichloroethane are useful solvents.
These solvents are immiscible with water (not forming a homogeneous mixture when mixed wit
effective in cleaning applications such as degreasing and dry cleaning.
DDT, heptachlor and endosulfan are were widely used as pesticides.
Effects of CHC
Dioxins (toxic by-products produced when organic matter is burned in the presence of chlorine
natural processes such as volcanic eruptions and forest fires), and some insecticides, such as DDT, a
organic pollutants.
DDT was widely used a few decades ago as an effective pesticide and insecticide.
It was later identified as a persistent organic pollutant, and its usage was phased out in almos
countries.
It accumulated in food chains and caused eggshell thinning in certain bird species.
In India, it is still being used by civic administrations as a mosquito repellent (disease vector co
In India, traces of DDT spray used three decades ago can still be found on the walls of homes.
Crops that are grown in fields that were sprayed with DDT in the last decades show substantial
insecticide.
DDT residues continue to be found in mammals all across the planet.
In Arctic areas, particularly high levels are found in marine mammals.
The traces of persistent organic pollutant are found in human breast milk.
In some species of milk-producing marine mammals, males typically have far higher levels, as fe
concentration by transfer to their offspring through lactation.
Endosulfan, one of the most widely used pesticide, is an endocrine disruptor (enhances the eff
causing reproductive and developmental damage in both animals and humans).
Because of its threats to human health and the environment, a global ban on the manufacture a
endosulfan was negotiated under the Stockholm Convention in 2011.
1. Bioaccumulation
2. Biomagnification
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Bioaccumulation
Bioaccumulation is the gradual accumulation of pollutants, chemicals
(chronic poisoning) or other substances in an organism.
Bioaccumulation occurs when the rate of loss of the substance from the body
of the organism through catabolism (breakdown of complex molecules in living
organisms), or excretion is lower than the rate of accumulation of the substance.
As persistent organic pollutants like DDT are long-lasting, the risk of
bioaccumulation is high even if the environmental levels of the pollutant are not
high.
Biomagnification
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