1) An ecosystem is a community of living organisms that interact with each other and their non-living environment. It includes biotic components like producers, consumers, and decomposers, as well as abiotic components like sunlight, water, and nutrients. 2) Energy and matter move through an ecosystem via food chains and food webs. Producers use photosynthesis to capture energy from the sun which is then consumed by herbivores, carnivores, and decomposers in a trophic pyramid, with less energy being transferred at each higher trophic level. 3) Ecosystems can be characterized by their primary productivity, the rate at which producers capture energy, and secondary productivity, the rate

1. Ecosystem
By, Dr. Sanjay Vyas

2. Contents
What is an Ecology & Ecosystem
Three major principles of ecosystem
Components of an ecosystem
Abiotic components
Biotic components
Movement of energy and nutrients
Food chain
Food webs
Trophic levels, biomass and biome.
Energy flow pathway.

3. What is an Ecology & Ecosystem
Ecology
the study of interactions between
organisms and organisms
organisms and their environment
Ecosystem
An ecosystem is a community of living organisms in
conjunction with the nonliving components of their
environment (things like air, water and mineral soil),
interacting as a system. These abiotic and biotic
components are regarded as linked together through
nutrient cycles and energy flows.

4. Abiotic components
They form the environment and determine
the type / structure of ecosystem.
Sunlight (temperature)
Nutrients
• Rainfall, minerals, carbon, nitrogen,…..

5. Biotic components
Producers (Autotrophs):
All green plants. They use solar energy, chlorophyll,
inorganic nutrients and water to produce their own food.
(Photosynthesis)
Consumers:
They consume the organic compounds in plant and animal
tissues by eating.
• Herbivores (plant feeders) Primary consumers
• Carnivores (meat eaters) Secondary consumers
• Omnivores (general feeders)
Decomposers
They are tiny organisms includes bacteria and fungi, which
turn organic compounds in dead plants and animals into
inorganic materials.

6. Components of an ecosystem

7. Tropical organization
The trophic level of an organism is the position it occupies
in a food chain.
A food chain represents a succession of organisms that eat
another organism and are, in turn, eaten themselves.
The number of steps an organism is from the start of the
chain is a measure of its trophic level.

8. Trophic Levels
A trophic level means a feeding level.
First level – all producers
Second level – all herbivores
Third level – first level carnivores
Fourth level – second level carnivores.

9. Trophic levels
Energy and Nutrients passed through the
ecosystem by food chains and webs from lower
trophic level to the higher trophic level.
However, only 5% to 20% energy and nutrients
are transferred into higher trophic level
successfully.
For this reason, first trophic level has the largest
number of organisms, and second trophic level is
less than first one; the third level is less than
second level, and so on.

10. Movement of energy and
nutrients
Food chain
Food webs

11. Food Chain
A food chain is a linear sequence of
organisms through which nutrients and
energy pass as one organism eats another.
Decomposers

12. Food chains are of three types:
1. Grazing food chain
2. Parasitic food chain
3. Saprophytic or detritus food chain

13. 1. Grazing food chain
The grazing food chain
starts from green plants
and from autotrophs it
goes to herbivores
(primary consumers) to
primary carnivores
(secondary consumers)
and then to secondary
carnivores (tertiary
consumers) and so on.
Eg; Producer→ Primary
consumer→ Secondary
consumer→ Tertiary
consumer

14. 2.Parasitic food chain:
It goes from large
organisms to smaller
ones without outright
killing as in the case of
predator.
Eg; Tree→herbivore
bird→ parasites→
hyperparasites

15. 3. Detritus food chain
The dead organic remains and
metabolic wastes derive from
producer and consumers are
generally called detritus. The
energy contained in a detritus
serve as a source of energy for a
group of organisms called
detritivores. The main source of
energy is the detritus. So, the
food chain starts with detritus to
detrivores and to their
predators.
Eg; Detritus→Earthworm→
Birds

16. Food web
Food webs consist of
many interconnected
food chains and are
more realistic
representation of
consumption
relationships in
ecosystems.

17. Biomass
Biomass means the total combined weight
of any specified group of organisms.
The biomass of the first trophic level is the
total weight of all the producers in a given
area.
Biomass decreases at higher trophic levels.

18. Biomass

19. Biome
This is a total different concept apart from
Biomass.
Biome are defined as
“the world’s major communities, classified
according to the predominant vegetation and
characterized by adaptations of organism to that
particular environment.

20. Energy flow pathway
1. Single-Channel Energy Models
2. Y- Shaped energy flow Model

21. SINGLE CHANNEL ENERGY FLOW MODEL

22. Y-shaped or double channel energy flow
model

23. Ecological Efficiency:
Percent of energy transferred from one trophic
level to the next.
Example: Assume 500 units of energy are produced by trophic level 1.
One half of that is lost to non-predatory death, while the other half
(250 units) is ingested by trophic level 2.
One half of the amount ingested is expelled through defecation,
leaving the other half (125 units) to be assimilated by the organism.
Finally one half of the remaining energy is lost through respiration
while the rest (63 units) is used for growth and reproduction. This
energy expended for growth and reproduction constitutes to the net
production of trophic level 1.

24. Three categories of transfer efficiency are
required to predict energy flow from PP (pri.
productivity) to
SP1 to SP2(sec. productivity)…
1) Consumption efficiency
2) assimilation efficiency
3) production efficiency

25. 1) consumption efficiency (CE)
% of total productivity at one trophic level
that is consumed by the next highest level

26. 2) assimilation efficiency (AE)
% of ingested food energy that is assimilated
(i.e. digested), and thus potentially available
for growth, reproduction.

27. 3) Production efficiency (PE)
% of assimilated energy that is incorporated
into new biomass (growth, reproduction).

28. Exploitation efficiency
When production and consumption are not
balanced  energy accumulates in ecosystem
Exploitation efficiency is the proportion of
production on one trophic level that is consumed
by organisms in next higher level
Ecological = gross production x exploitation
efficiency efficiency efficiency

29. Ecosystem Energy Budgets:
Primary Productivity (PP)
Secondary Productivity (SP1, SP2)

30. • Photosynthesis powers primary productivity.
Primary Productivity (PP)
• The annual productivity of an area is determined
primarily by sunlight, temperature, and moisture.
• Rate at which energy or biomass is produced
per unit area by plants (primary producers)

31. Secondary Productivity (SP1, SP2…)
• Rate of production of new biomass from PP
by heterotrophic organisms
(primary and secondary consumers)