There are two laws of thermodynamics. On the other hand in our universe sun is the source of energy. Green plants are the only producer. Plants make their own food by sunlight with the help of water and carbon dioxide. Other animals get energy by consuming green plants, plant products and other animals. Hence the energy is cycle. So the ecosystem proves the two laws of thermodynamics.

1. Mridul Bora
Animal Ecology & Wildlif Biology
Gauhati University

2. Energy Flow in an Ecosystem
 Laws of thermodynamics describes the
energy flow in an Ecosystem.
 1st law of thermodynamics- Energy can not
be created or destroyed, only transformed
from one step to another.
 2nd law of thermodynamics- In the path of
energy transformation some energy loss in the
form of heat and the entropy increases.

3. 1st law of thermodynamics in
Ecosystem

4. Energy From Sun to Plant
 Chlorophyll of
green plants
traps the light
energy from sun
and produce
food with the
help of water,
CO2 and
minerals.

5. Energy users
Producers– Green plants use light energy (sunlight)
to produce food (chemical energy).
Primary consumers– Feed on herbivores and get
energy from plants (Carnivores).
Secondary consumers– Feed on primary consumers
and get energy form them.
Tertiary consumers- Feed on secondary consumers
and get energy.
 Decomposers- Break down dead or decaying
organism (decomposition) and get energy.

6. 
Food chain or food web support the 1st law
of thermodynamics

7. Energy Recycling
Plants or
Producers
1st tropic
level
Energy
Sun
The energy
house
Energy
Consumers
2nd tropic
level
Decomposers
3rd tropic
level
E
n
e
r
g
y
Energy
Soil, Air, Water
with matter
Heat

8. 2nd Law of Thermodynamics

9. In the path
of energy
transforma
tion some
energy loss
in the form
of heat and
the entropy
increases.

10. The Path Way of Energy Loss
 Not all food consumed by heterotrophs
(consumers) is transformed into biomass.
At each tropic level about 90% of energy is loss to
perform metabolic activities.
 Entropy increases.

11. What is Entropy?
According to Great Physicist Peter Higgs,
Entropy is the every types of error or
unrestrained activities of a system.

12. Different Forms of entropy among
organisms

13. What happens to the energy
in the end?
Solar energy is used by
plants for food production.
That energy transformed
from green plants to
decomposers in different
steps. In the energy
transformation path, energy
is lost into space in the form
of heat. That is used in
endothermic reaction(an
animal that is dependent on
the internal generation of
heat).

14. Conclusion
 Sun is the ultimate energy source of ecosystem
(excluding chemoautotrophs).
 Energy transformed from sun to decomposers.
 In each tropic level maximum energy is released as
heat.
 Ecosystem obeys 1st and 2nd law of
thermodynamics.