Ecological Pyramids 311j31

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.

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.

Types of pyramids • Pyramid of numbers • Pyramid of biomass • Pyramid of energy

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.

Pyramid of Numbers Pyramid of numbers displays the number of individuals at each level.

1 owl

25 voles 2000 grass plants

Pyramid of Numbers

• Pyramid of Numbers in a Grassland Ecosystem

Pyramid • Pyramid of Numbers of in aNumbers Aquatic Ecosystem

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 still larger population of ectoparasites leading to the formation of an inverted pyramid.

Pyramid of Numbers • When a large tree 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 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.

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.

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.

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

Energy Pyramid In 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.

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

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.

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.

Energy flow models • Flow of energy through various trophic levels can be explained with various energy flow models • Universal energy flow model • Single channel energy flow model • Double channel or Y- shaped energy flow model.

Primary productivity • Primary productivity is the rate of energy capture by producers. • the amount of new biomass of producers, per unit time and space

• 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 matter

Energy flow model

UNIVERSAL MODEL

Single channel Energy flow model

Y-SHAPED OR DOUBLE CHANNEL ENERGY FLOW MODEL