Ecosystem : Concepts
Ecosystem
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Sir A. Tansely
Biotic community + physical environment
“ as a structural and functional unit of
biosphere/segment of nature consisting of community
of living beings and the physical environment both
interacting and exchanging materials between them.”
Ecosystem
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Self sufficient interacting system
Small /large
Open system
Varied (distinct community)
Not an isolated unit
eg leaves falling in river water
Types of Ecosystem
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Natural
 Terrestrial
 Aquatic
Saltwater
Fresh
water
Lentic
Lotic
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Man-made/Artificial
Components of Ecosystem
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Abiotic
Biotic
 Autotrophs/Producers
 Terrestrial
 Deep aquatic
 Shallow water
 Heterotrophs
 Consumers
 Herbivores/first order consumers
 Carnivores/primary carnivores/second order consumers
 Secondary Carnivores/third order consumers
 Tertiary Carnivores/ fourth order consumers
 Top carnivores
 Decomposers/micro consumers - Mineralization
Components of Ecosystem
Abiotic Components
Climatic factors
 Inorganic substances
 Organic substances
 Biogeochemical cycles –minerals & gases
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Structure of Ecosystem
Species composition- forest/desert
 Stratification- tropical rain forest
 Tropic organization- food relationships
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 T1,T2,T3
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and so on…….
Nutrients
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Standing Stage- amount of abiotic materials
present in an ecosystem at a given time .
Standing Crop - amount of biotic materials present
in an ecosystem at a given time .
 Expressed
area
as number/biomass of organism per unit
Functions of Ecosystem
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Productivity- g/m2/year
 Primary
 GPP
(Gross primary productivity)
 NPP (Net primary productivity)
 NPP=GPP-Loss due to respiration & maintenance
 Secondary
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Decomposition /Nutrient cycling
Energy flow - Law of thermodynamics
 Unidirectional
 Energy
decreases with successive trophic levels
 10%of GPP
Energy flow
Flow of Energy
Food chain
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The transfer of food energy from the source in plants
through a series organism with repeated steps of eating
and being eaten is referred as food chain
The transfer of energy from one trophic level to the next
trophic level is called food chain
Food chains were first introduced by the African-Arab
scientist and philosopher Al-Jahiz in the 9th century and
later popularized in a book published in 1927 by
Charles Elton, which also introduced the food web
concept
Types of Food chains
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Grazing Food chain
Starts with producers, passes through consumers to
decomposers
 A typical food chain here could be :Grass > Rabbit > Fox
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Detritus Food chain
Starts with dead organic matter and passes through detritus
feeding organisms in soil to organisms feeding on detritus
feeders and their predators
 A typical food chain here could be :mangrove leaves > microbes>crabs>shrimps>small fish
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Detritus food chain
Y shape flow of energy
SUN
HERBIVO
RES
PREDATORS
GFC
PLANTS
DETRITUS
CONSUMERS
DFC
PREDATORS
Food Web
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A network of food chains which are interconnected at
various trophic level so as to form a number of
feeding connections among different organisms of a
biotic community called food web.
Alternate pathways for flow of energy
Complexity > diversity
Stability
food web
Significance of food chains & food
webs
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Energy flow and nutrient cycling take place through
them
Ecological Balance- population size
Unique property of biological magnification
Can an ecosystem regulate itself?
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Human beings should try to keep ecosystems within
the homeostatic plateau.
Should not contribute to positive feedbacks
otherwise ecosystem will collapse
Ecological pyramid
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An ecological pyramid is a graphical
representation designed to show the ecological
parameters (biomass /number/energy) at each
trophic level in a given ecosystem.
1927 Charles Elton – Eltonian pyramids
Ecological pyramids begin with producers on the
bottom and the highest level is the top of the food
chain
Upright/Inverted/spindle shape
Ecological pyramid
Pyramid of Number
 Pyramid of Biomass
 Pyramid of Energy
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Pyramid of Number
Pyramid of Biomass
Pyramid of Energy
Major Ecosystems
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Forest Ecosystem
 Tropical
rain forest
 Tropical deciduous forest
 Coniferous forest
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Abiotic
 Inorganic
 Climate
 litter
and organic substances present in soil
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Biotic
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Producers – trees ,diff species ,shrubs and ground
vegetation
TRF – Teak( Tectona grandis), Dhak (Butea frondosa),Sal
 Coniferous – Abies, Spruce, Deodar,Pine
 Temperate forest – Quercus (oak)
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Consumers
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Primary Consumers
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Small animals feeding on trees beetles, flies,bugs,spiders,leafhoppers, ants
Large animals – elephants, deer, moles, squirrels, mangooses etc
Secondary Consumers – snakes, birds, lizards, fox etc
 Tertiary Consumers – lion, tiger etc
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Decomposers
fungi(Aspergillus,Fusarium,Alternaria,Trichoderma)
 bacteria (Bacillus, Pseudomonas,Clostridium)
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Major Ecosystems
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Pond Ecosystem
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Abiotic
 Inorganic
 Climate
and organic substances present in soil
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Biotic
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Producers – Phytoplankton and Macrophytes
Phytoplankton – Ulothrix,Spirogyra,Oedogonium,Chlamydomonas,
Vovox,Anabaena
 Macrophytes –
Hydrilla,Utricularia,Vallisneris,Wolfia,Lemna,Eichhornia,Pistia,Azoll
a, Typha
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Consumers
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Primary Consumers
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Zooplankton – Copepods and Daphnia
Benthos – annelids, molluscs
Secondary Consumers – insects and fish
 Tertiary Consumers –large fish
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Decomposers
fungi(Aspergillus, Phythium)
 bacteria (Bacillus, Pseudomonas)
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