Ecosystem:Structure and Function is meant for the students of CBSE Class 12 and 10.

2.  The
term ecosystem was first coined by
A.G.Tansely.
 Ecosystem consists of two Words :
Eco
Environment
System
Interaction
Ecosystem

3. According to E.P.Odum, an American ecologist, the
ecosystem is the basic functional unit of organism and
their environment interacting with each other and with
their own components.
 e.g. Grassland, Forest, Aquarium, Pond, Lake, River and
Ocean.

Grassland Ecosystem
Forest Ecosystem
Ocean Ecosystem

4. Ecosystem
Terrestrial
Aquatic
Eg.Forest,
Grassland and
Desert
Eg. Pond, Lake,
Wetland, River and
Estuary

5. Abiotic
non-living
Eg. soil, water, light,
inorganic nutrients and
weather
Ecosystem
Biotic
living
Eg. producers and
consumers

6. 
From nutrition point of view, the biotic components
of ecosystem can be grouped into three categories:
Biotic components of
Ecosystem
Producers
Consumers
Decomposers

7.  The
vertical distribution
of different species
occupying different
levels is called
stratification.
 Eg. Trees occupy top
vertical strata or layer of
a forest, shrubs the
second, herbs and
grasses occupy the
bottom layers.

8. The components of the
ecosystem are seen to function
as a unit when we consider the
following aspects:
 Productivity
 Decomposition
 Energy flow
 Nutrient cycling

9. PRODUCTIVITY
Productivity - The rate of biomass production is
called productivity.
Units: g–2 yr –1 or (kcal m–2) yr–1
 Gross primary productivity - The rate of production
of organic matter during photosynthesis is called gross
primary productivity.
Gross PP (GPP) = total energy fixed
Net PP (NPP) = GPP – respiration
 Secondary productivity – The rate of formation of
new organic matter by consumers is called secondary
productivity .


11. 
The breakdown of complex organic matter into
inorganic substances like carbon dioxide, water and
nutrients and the process is called decomposition.
Steps in decomposition
Fragmentation
Leaching
Catabolism
Humification
Mineralization

12. Decomposition cycle in a Terrestrial Ecosystem

13.  The
flow of energy is one way
direction from producer to
consumers, and ends in
decomposition process.
 However, a part of the energy is lost
as heat and agrees with the
phenomenon of second law of
Thermodynamics.

14. Man
(Secondary
consumer)
Goat (Primary
Consumer)
Grass (Producer)

15. Detritus Food Chain
Detritus is non-living particulate organic material
includes the bodies or fragments of dead organisms
as well as fecal material.
 Decomposers are heterotrophic organisms also
called saprotrophs. Eg. Fungi and Bacteria.


16. A
food web
depicts various
feeding
connections in
an ecological
community.
 Natural
interconnected
food chains
make a food
web.

17. The trophic level is the position of an organism it occupies
in the community or a food chain.

18. Energy flow in different Trophic Levels

19. 
An ecological pyramid is a graphical representation of
trophic levels in a given ecosystem.
Pyramid
of
Number
Ecological
Pyramids
Pyramid
of
Energy
Pyramid
of
Biomass

20. PYRAMID OF NUMBERS

The pyramid of biomass in sea is also generally
inverted because the biomass of fishes far exceeds
that of phytoplankton.

21. PYRAMID OF BIOMASS

The pyramid of biomass in sea is also generally
inverted because the biomass of fishes far exceeds
that of phytoplankton.

22. PYRAMID OF ENERGY
Pyramid of energy is always upright.
 It can never be inverted.
