2. Ecological System Concept
(Concept of Ecosystem)
Ecosystem is the basic structural andEcosystem is the basic structural and
functional unit of ecology.functional unit of ecology.
“Ecosystems are the basic units of
nature
on the face of the earth”.
An ecosystem is an ecological unit, or a
subdivision of the landscape, or a geographic area that
is relatively homogeneous and reasonably distinct from
adjacent areas.
J.W. Marr, 1961
Tansley, 1935
Definition
3. Ecosystem – another view
• Ecosystem is a spatial functional structure
• The space may be geographically large or
small
• Largest ecosystem. e.g., Planet earth
• Smallest ecosystem (microcosm):
• e.g. a handful of soil and moss in a sealed
jar.
4. Components of an Ecosystem
Abiotic components-
(geographical, climatic,(geographical, climatic,
physicochemical characteristics)physicochemical characteristics)
Biotic
components-
(Plants, animals, microbes)(Plants, animals, microbes)
7. Mountain ecosystem – Removal of forest cover
Evergreen forests – Over exploitation of forest resources
Coral reefs – Human interference, Dynamite fishing
River ecosystem – Pollution
Land ecosystem – Dumping solid wastes
Specific influence of human
beings on sensitive Ecosystems
8. Properties of Ecological
Systems
1. Networks –Interdependence, diversity,
complexity
2. Boundaries- Scale and limits
3. Cycles – Recycling of resources and
partnership
4. Flow –through – Energy and resources
5. Development – Succession and co-evolution
6. Dynamic balance- Self – organization,
flexibility, stability, sustainability
11. Plant Cow Man
Input
Sunlight
Output - Input
Chemical
energy in
leaves
Output - input
Chemical
energy
in meat
of cow
Output
Heat
given
off during
Series open system components
12. System X Y Z
Subsystem
X
Subsystem
Y
Subsystem
Z
Inputs Outputs
Open system with components
13. Features of an open systemFeatures of an open system
Open systems process inputs and produce
outputs
The amount of output produced is directly
related to the amount of input received.
14. Features of Complex systems
• Complex systems are composed of many
interconnected and interacting subunits.
• They are capable of adaptation and self-
organization.
15. Open systems
All living systems are open systems.
A cell is an open system because it
constantly acquires food from outside
itself and eliminates wastes.
It gives off heat as it carries on
chemical processes (respiration).
21. Solar energy
Photosynthesis
Solar energy is converted to chemical energy
Respiration
Chemical energy is used to do work
Ecosystem
Degraded Waste Energy
Energy flow in an Ecosystem
22. Ecological Pyramids
Pyramid of numbers:
No of individuals at each trophic level
Graphic representation of tropic structure and
function of an ecosystem.
Hawks
Hyperparasites (microbes)
Frogs
Parasites (Lice, bugs)
Insects
Birds
Grasses
Trees
23. Pyramid of biomass:
Total biomass (dry matter) at each tropic level
Fox
Rabbit
Herbs
Pyramid of energy:
Amount of energy present at each trophic level.
Top Carnivores
Carnivores
Herbivores
Producers
26. At every trophic level there is 90% loss of energy (respiration, activity).
Only 10% energy is transferred from one trophic level to the other.
There is one-way flow of energy.
Nutrient Cycling
Nutrients like C, N, S, O, H, P etc.
Move in circular paths.
Hydrological cycle
Nitrogen cycle
Carbon cycle
Phosphorous cycle
Energy flow in an ecosystem
27. Functional Attributes
Food chains
The sequence of feeding relationships in
an ecosystem is called food chain.
Trophic structure
Each organism in the ecosystem is
assigned a feed level or trophic level.
28. Simple food web model
Producer : Pond grass
Herbivore : Water insects
Carnivore : Large fish
Herbivore : Small fish
Carnivore : Duck
Top Carnivore : Man
30. Kinds of food chain
1. Grazing food chain – Starts with green plants and ends with
carnivores.
Grass → Rabbit→ Fox
2. Detritus food chain – Starts with dead organic matter and
ends with predators.
Mangrove ecosystem
Leaf litter →Saprotrophs / detritivores (crabs) →Small carnivorous fish →
Large Carnivorous fish
- a complex inter connected network of food chains
at different trophic levels.
Food web
31. Significance of food chain
1.Food chains maintain energy flow and nutrient cycling.
2.Food chains maintain ecological balance by regulating
population size.
3.Food chains biologically magnify toxicity of some
chemicals.
32. Kinds of Ecosystems
Ecosystem
Terrestrial
Aquatic Man-engineered
e.g. Forest, Desert
Grassland, Steppe,
Savanna
e.g. Agricultural land use,
Urban / industrial land use
Freshwater
Marine
Lentic Lotic
e.g. Ponds,
Lakes
e.g. Streams,
Rivers
Coastal ecosystems
Mangrove ecosystems
Seagrass ecosystems
Coastal lagoon ecosystems
Coral reef ecosystems
Delta ecosystems
Estuarine ecosystems
Sandy beach ecosystems
Rockyshore ecosystems
Coastal upwelling
34. Threats from Agricultural
Ecosystems
Ecological simplicity – large
monocultures.
Ecosystem instability.
High degree of biological
uniformity (minimum genetic
variability).
Widespread disease outbreaks or
pest infestations.
Depletion of fertilizers
(nutrients) and energy (fossil
fuels).
Elimination of other crop species
and other ecosystems.
