3. ecosystem- functioning, biogeochemical cycles
TRANSCRIPT
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- Structure and Function II
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TROPHIC STRUCTURE
e pro ucers an consumers are arrange n t e ecosystem n a
definite manner and their interaction along with population size are expressed
together as trophic structure
The flow of ener is mediated throu h a series of feedin
relationships in a definite sequence or pattern which is known as food chain.
Nutrients and energy too move along the food chain.
Trophic Level/Feeding level
Each food level is known as trophic level and the amount of living
ma er a eac rop c eve a a g ven me s nown as s an ng crop or
standing biomass.
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FOOD CHAINS
food chain.
ii. All organisms, living or dead, are otential food for some other organism
and thus, there is essentially no waste in the functioning of a natural
ecosystem.
iii. Each organism in the ecosystem is assigned a feeding level or
trophic level depending on its nutritional status.
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II. Detritus food chain
Starts with dead organic matter
Detritivores and decomposers follow the order
Even the detritivores are consumed by decomposers
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Food chains in ecosystems are rarely found to o erate as isolated
linear sequences.
Usually interconnected and form a complex network with several
linkages and are known as food webs.
Definition:
Food web is a network of food chains where different types of
organisms are connected at different trophic levels, so that there are a
number of options of eating and being eaten at each trophic level.
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a. Energy flow and nutrient cycling
b. Maintenance and re ulation of o ulation
size of different animals
c. Maintenance of ecological balance
d. Biological magnification
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ECOLOGICAL PYRAMIDS
Graphic representation of trophic structure and function of an
ecosystem, starting with producers at the base and successive trophic
.
Ecological pyramids are of three types:
A. Pyramid of numbers
.
C. Pyramid of Energy
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Pyramid of numbers
It represents the number of individual organisms at each trophic level
Upright or inverted pyramid , depending upon the type of ecosystem
Fig: Grass land ecosystem Fig: Forest ecosystem
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Pyramid of biomass Represents the total biomass (dry matter) at each trophic level in a food chain
,
Forest Ecosystem Pond Ecosystem
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Pyramid of Energy
Represents the amount of energy present at each trophic
Always upright
At ever successive tro hic level there is a hu e loss of ener about 90%
Energy loss in the form of heat, respiration etc.
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ENERGY FLOW IN AN ECOSYSTEM
The energy flow is always unidirectional
The flow of energy follows the two laws of Thermodynamics:
energy can neither be created nor be destroyed but it can be
transformed from one form to another.
energy dissipates as it is used or in other words, its gets converted
from a more concentrated to dispersed form.
As energy flows through the food chain, energy dissipates at every
trophic level
The loss of energy takes place through respiration, loss of energy in
locomotion, running, hunting and other activities.
t every eve t ere s a out oss o energy an t e energy
transferred from one trophic level to the other is only about 10%.
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Productivity of Ecosystem
Primary productivity : The rate at which radiant energy is converted into
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producers.
i Gross rimar roductivit
It refers to the total rate of photosynthesis including the organic matter used
up in respiration, i.e., amount of CO2 fixed/g chl/hour.
(ii) Net primary productivity NPP = GPP R
It is the rate of storage of organic matter in plant tissues in excess
of the respiratory utilization by plants.
SECONDARY PRODUCTION
The amount of organic matter stored by the herbivores or carnivores (in excess of
respiratory loss) is known as secondary production.
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CYCLES
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Water Cycle
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Oxygen Cycle
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Nitrogen cycle
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Carbon Cycle
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Phosphorus cycle
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Sulphur cycle