Ecological pyramids

Presentation

By

Jhansirani.R AP/ECE

Definition

• Graphic representation of trophic structure and function of an ecosystem, starting with producers at the base and successive trophic levels forming the apex is known as an ecological pyramid

• An ecological pyramid is a diagram that shows the relationship amounts of energy or matter contained within each trophic level in a food web or food chain.

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ECOLOGICAL PYRAMIDS

• Food chains and food webs do not give any information about the numbers of organisms involved.

• This information can be shown

through ecological pyramids.

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Types of pyramids

• Pyramid of numbers

• Pyramid of biomass

• Pyramid of energy

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PYRAMID OF NUMBERS

• Shows the number of organisms at each trophic level per unit area of an ecosystem with producers forming the base and top carnivores the tip.

• The shape of the pyramid of numbers vary from ecosystem to ecosystem.

• We may have upright or inverted pyramid of numbers, depending upon type of ecosystem and food chain.

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Pyramid of Numbers

Pyramid of numbers displays the number of individuals

at each level.

1 owl

25 voles

2000grass plants

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Pyramid of Numbers

• Pyramid of Numbers in a Grassland Ecosystem

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Pyramid of Numbers

• Pyramid of Numbers in a Aquatic Ecosystem

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Pyramid of Numbers• In a parasitic food chain, for

e.g., an oak tree, the large tree provides food to several herbivorous birds. The birds support still larger population of ectoparasites leading to the formation of an inverted pyramid.

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• When a large tree support larger number of herbivorous birds which inturn are eaten by carnivorous birds like falcon and eagle, which are smaller in number, it forms a spindle shaped pyramid.

Pyramid of Numbers

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Pyramid of bio mass

The total amount of matter present in organisms of an ecosystem at each trophic level is biomass.

Biomass is preferred to the use of numbers of organisms because individual organisms can vary in size. It is the total mass not the size that is important.

Pyramid of biomass records the total dry organic matter of organisms at each trophic level in a given area of an ecosystem.

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Pyramid of bio mass• In a terrestrial ecosystem, the maximum biomass occurs in producers,

and there is progressive decrease in biomass from lower to higher trophic levels. Thus, the pyramid of biomass in a terrestrial ecosystem is upright.

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Pyramid of bio mass• In an aquatic habitat the

pyramid of biomass is inverted or spindle shaped where the biomass of trophic level depends upon the reproductive potential and longivity of the member.

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Pyramid of energy• Shows the amount of energy input to each

trophic level in a given area of an ecosystem over an extended period with producers forming the base and the top carnivores at the tip.

• Pyramid of energy is always upright

• It is so because at each transfer about 80 - 90% of the energy available at lower trophic level is used up to overcome its entropy and to perform metabolic activities. Only 10% of the energy is available to next trophic level

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Energy PyramidEnergy PyramidIn nature, ecological efficiency varies from 5% to 20% energy available between successive trophic levels (95% to 80% loss). About 10% efficiency is a general rule.

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Energy flow in an ecosystem

Energy flow in an ecosystem

• Flow of energy in ecosystem takes place through the food chain and it is the energy flow which keeps the ecosystem going

• Energy flow is a one-directional process.• Nutrients like carbon, nitrogen, phosphorus

move in a cyclic manner and are reused by the producers after flowing through the food chain

• Energy is not reused• Flow of energy follows the two laws of

thermodynamics

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The Laws of Thermodynamics • sun---> heat (longer wavelengths) --->

biochemical energy by plants ---> consumers

• FIRST LAW of THERMODYNAMICS:

• Energy can be converted from one form to another, but cannot be created or destroyed.

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SECOND LAW of THERMODYNAMICS

• Transformations of energy always result in some loss or dissipation of energy

or• In energy exchanges in a closed system, the

potential energy of the final state will be less than that of the initial state

• Loss of energy takes place through respiration, locomotion, running, hunting and other activities

• 90% loss of energy takes place at every trophic levels.

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Energy flow models

• Flow of energy through various trophic levels can be explained with various energy flow models

Universal energy flow modelSingle channel energy flow modelDouble channel or Y- shaped energy

flow model.

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Primary productivity

• Primary productivity is the rate of energy capture by producers.

• the amount of new biomass of producers, per unit time and space

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• Gross primary production (GPP)

= total amount of energy captured

• Net primary production (NPP)

= GPP - respiration

• Net primary production is thus the amount of energy stored by the producers and potentially available to consumers and decomposers.

• R= Respiratory loss• NU = energy not used• NA = energy not assimilated • A= assimilated energy• P= energy used for production• D= Dead matterJhansirani.R AP/ECE

Energy flow model

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UNIVERSAL MODEL

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Single channel Energy flow model

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Y-SHAPED OR DOUBLE CHANNEL ENERGY FLOW MODEL

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Nutrient cycling

Definition

• The elements which are essential for the survival of both plants and animals are called nutrients

• The cyclic flow of nutrients between the biotic and abiotic components is known as nutrient cycle or biogeochemical cycles.

• Nutrients enter into producer and move through food chain and reach consumer. The bound nutrients of consumer, after death, are decomposed and converted into inorganic substances which are readily used by the plants and the cycle starts again.Jhansirani.R AP/ECE

Types

• Hydrological cycle• Carbon cycle• Nitrogen cycle• Phosphorus cycle

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The Water Cycle

• Water is essential to all organisms• movement of water in a cyclic manner is

known as hydrological cycle.

• 97% of the biosphere’s water is contained in the oceans, 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater

• Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater

Precipitationover land

Transportover land

Solar energy

Net movement ofwater vapor by wind

Evaporationfrom ocean

Percolationthroughsoil

Evapotranspirationfrom land

Runoff andgroundwater

Precipitationover ocean

Carbon cycle

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• Carbon is stored on our planet in the following major pools:

• As organic molecules in living and dead organisms found in the biosphere

• As the gas carbon dioxide in the atmosphere• As organic matter in soils

• In the lithosphere as fossil fuels and sedimentary rock deposits such as limestone, dolomite and chalk

• In the oceans as dissolved atmospheric carbon dioxide and as calcium carbonate shells in marine organisms.

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• Carbon is exchanged between the active pools due to various processes

• Photosynthesis and respiration between the land and the atmosphere

• Diffusion between the ocean and the atmosphere.

• Carbon, in form of carbon dioxide is taken by plants for photosynthesis, through which variety of carbohydrates and other organic substances are produced.

• Through the food chain it moves and when the consumer is dead the organic matter present in the dead is returned to the atmosphere as carbon dioxide by microorganisms which is again used up by plants.

• Increasing level of CO2 in atmosphere due to burning fossil fuels etc., causes an in balance in natural cycle and leads to global warming.

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Nitrogen cycle• Nitrogen (N2) makes up 78% of the

atmosphere.

• All living things needs nitrogen to build proteins, nucleic acids, etc.,

• Nitrogen is a component of amino acids, proteins, and nucleic acids

• Most living things, however, can not use atmospheric nitrogen to make amino-acids and other nitrogen containing compounds.

• They are dependent on nitrogen fixing to convert N2 into NH3(NH4

+), (NO3).Jhansirani.R AP/ECE

Nitrogen cycle

• The nitrogen cycle consists of four natural processes

• Nitrogen Fixation• Nitrification• Denitrification• Decay Processes

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• Nitrogen Fixation

There are two main ways nitrogen is 'fixed’

• Fixation by LightningThe energy from lightning causes nitrogen (N2) and water (H2O) to combine to form ammonia (NH3) and nitrates (NO3). Precipitation carries the ammonia and nitrates to the ground, where they can be assimilated by plants.

• Biological FixationAbout 90% of nitrogen fixation is done by bacteria. Cyanobacteria convert nitrogen into ammonia and ammonium.N2 + 3 H2 -> 2 NH3

• Ammonia can be used by plants directly. Ammonia and ammonium may be further reacted in the nitrification process.

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• Nitrification

Is the process in which ammonia in the soil is converted to nitrates. Nitrification is performed by nitrifying bacteria. Plants absorb the nitrates and use them to make proteins.

• Denitrification

Is the reverse of the combined processes of nitrogen fixation and nitrification. It is the process by which nitrogen compounds, through the action of certain bacteria, give up nitrogen gas that then becomes part of the atmosphere. The amount of gas released by this process is relatively small.

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• Decay Processes

Are those by which the organic nitrogen compounds of dead organisms and waste material are returned to the soil. These compounds are chiefly proteins and urea. The many bacteria and fungi causing decay convert them to ammonia and ammonium compounds in the soil.

• Thus, through the nitrogen cycle, food-making organisms obtain the necessary nitrogen through nitrogen fixation and (to a greater extent) through nitrification. At the same time, nitrogen compounds are returned to the soil through decay and nitrogen is returned to the air through denitrification and cycle goes on.

• If the nitrogen cycle does not supply enough nitrogen to support plant growth, artificial fertilizers, containing nitrates or ammonium compounds, are needed.

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Phosphorus cycle

• The atmosphere does not play a significant role in the movements of phosphorus, because phosphorus and phosphorus-based compounds are usually solids at the typical ranges of temperature and pressure found on Earth.

• The phosphorus cycle is long and slow, but it is an important part of the environment. It helps plants grow, and is used by farmers to fertilize them.

• Phosphorus can be found on earth in water, soil and sediments. 

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• It is in these rocks where the phosphorus cycle begins.

• When it rains, phosphates are removed from the rocks (via weathering) and are distributed throughout both soils and water.

• Plants take up the phosphate ions from the soil.• The phosphates then moves from plants to

animals when herbivores eat plants and to carnivores.

• The phosphates absorbed by animal tissue through consumption eventually returns to the soil through the excretion, as well as from the final decomposition of plants and animals after death.

• Runoff may carry them back to the ocean or they may be reincorporated into rock. Jhansirani.R AP/ECE

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