The document discusses energy flow through ecosystems. It begins by explaining that the sun is the primary energy source for ecosystems and that plants convert the sun's radiant energy into chemical energy through photosynthesis. This chemical energy then passes through food chains, with approximately 10% of the energy being transferred to each higher trophic level. Various models and laws are described that illustrate principles like the one-way flow of energy and the inefficiencies of transfers between trophic levels. Overall, the summary emphasizes that sunlight powers ecosystems by being converted to chemical energy by plants and then traveling through food webs in a step-wise, 10%-losing manner.

1. TOPIC: ENERGYFLOWPATHWAYIN Ecosystem
-ANURAGpandey

2. INTRODUCTION
An ecosystem consists of all the organisms living in a community as well as all the
abiotic factors with which they interact.
The dynamics of an ecosystem involve two processes: energy flow and chemical
cycling.
Energy is the capacity to do work.
Energy exists in two forms potential and kinetic.
Potential energy is the energy at rest {i.e., stored energy).
Kinetic energy is the energy of motion (free energy).
The source of energy required by all living organisms is the chemical energy of
their food.
The chemical energy is obtained by the conversion of the radiant energy of sun.
In any ecosystem there should be unidirectional flow of energy.

3. Primary source of energy in all ecosystem is the sun.
Approximately 57% of sun energy is absorbed in the atmosphere and scattered in
the space.
Some 35% is spent to heat water and land areas and to evaporate water.
Approximately 8% of light energy striking plant surface, 10% to 15% is reflected,
5% is transmitted and 80 to 85% is absorbed.
An average of only 2% (0.5 to 3.5%) of the total light energy striking on a leaf is
used in photosynthesis and rest is transformed into heat energy.
The movement of energy through the trophic levels of a food chain is called as
energy flow.
This energy flow is based on two important Laws of Thermodynamics

4. The first law of Thermodynamics:
It states that the amount of energy in the universe is constant.
It can neither be created nor destroyed, but it may change from one form to
another.
The solar energy of the sun is converted in to chemical energy of carbohydrate.
The second law of thermodynamics:
The Second Law of Thermodynamics is about the quality of energy.
It states that as energy is transferred or transformed, more and more of it is
wasted
It occurs at each trophic level, 90% energy is lost ( as heat and in metabolic
processes) and only 10% is transfer from one trophic level to another.

5. ENERGY FLOW IN AN ECOSYSTEM:
Living organisms can use energy in two forms radiant and fixed energy.
Radiant energy is in the form of electromagnetic waves, such as light.
Fixed energy is potential chemical energy bound in various organic substances
which can be broken down in order to release their energy content.
Producers: Organisms that use the solar energy to produce their own food.
E.g. plants, algae and some bacteria.
 Consumers: All animals depend on plants (directly or indirectly) for their food
needs. Hence, they are called consumers and also heterotrophs.
Decomposers: The heterotrophic organisms, mainly fungi and bacteria, which
obtain their energy and nutrient requirements by degrading dead organic matter
or detritus are called decomposers

6. SUN PRODUCERS
CONSUMERS
DECOMPOSERS
RADIENT
ENERGY
HEAT
ENERGY
HEAT
ENERGY
ENERGY FLOW IN AN ECOSYSTEM
HEAT
ENERGY

7. Productivity
It is the rate at which organic matter is produced by producers.
It is usually expressed in units of mass per unit area (or volume) per
unit time (mass/unit area/unit time).
Primary productivity: It is the rate at which biomass produced
per unit area by the primary producers (both photoautotrophs and
chemoautotrophs).
Gross primary productivity (GPP): The total rate of
photosynthesis, including the biomass used up in the respiration
during the period of measurement.
Net primary production (NPP): The rate of the storage of
biomass in the plants that exceeds the respiratory used up in the
respiration during the period of measurement.
NPP = GPP - R

8. Trophic level
The producers and consumers in
ecosystem can be arranged into
several feeding groups, each known as
trophic level (feeding level).
In any ecosystem, producers represent
the first trophic level, herbivores
present the second trophic level,
primary carnivores represent the third
trophic level and top carnivores
represent the last level.

9. Food chain-:-
It is the relation between one trophic level to
adjacent trophic level.
The transfer of energy and nutrients through a
succession of organisms through repeated
process of eating and being eaten.
In food chain initial link is a green plant or
producer which produces chemical energy
available to consumers.
Food chain in any ecosystem runs directly in
which green plants are eaten by herbivores,
herbivores are eaten by carnivores and
carnivores are eaten by top carnivores.
 Food chains are of three types:
1) Grazing food chain
2) Parasitic food chain
3) Saprophytic or detritus food chain

10. Food web
Many food chains exist in an
ecosystem, but these food chains
are not independent.
A complex of interrelated food
chains makes up a food web.
Food web maintains the stability
of the ecosystem.
The greater the number of
alternative pathways the more
stable is the community of living
things.

11. Energy Flow models
Single Channel Energy Flow Models:
The flow of energy takes place in a
unidirectional manner through a single
channel of green plants to herbivores and
carnivores.
The energy which is passed to the next
trophic level is never reverted back to the
lower level.
Y-shaped Model of Energy Flow :
It is also called double channel model.
In nature, both grazing and detritus food
chains operate in the same ecosystem.
It explain the connection between a
grazing and a detritus food chain. Y-shaped model of energy flow

12. THE TEN PERCENT LAW
This law was introduced in context to
energy flow in ecosystems by Raymond
Lindeman.
According to this law, during the transfer of
energy from organic food from one tropic
level to the next, only ten percent of the
energy from organic matter is stored as
flesh.
The remaining is lost during transfer, broken
down in respiration, or lost to incomplete
digestion by higher trophic level.
The ten percent law gives us a basic
understanding on the cycling of food chains.
This law shows the inefficiency of energy
capture at each successive tropic level

13. Ecological pyramid
The concept was first introduced by Charles Elton.
It is a graphic representation of the relationship between organisms
at various trophic levels in a food chain.
The basis of an ecological pyramid is biomass, energy, and number.
Types of ecological pyramid :
a. Pyramid of number: It represent the total no. of individuals of
different species belonging to each trophic level in an ecosystem.
b. Pyramid of mass : It represent the total dry weight of the living
beings of different species at each trophic level at a particular time.
c. Pyramid of energy : It shows the flow of energy from one
trophic level of a community to the next.

14. Pyramid of biomass
Pyramid of numbers Pyramid of energy

15. CONCLUSION
Sun is the ultimate source of energy.
Energy flow in an ecosystem is always unidirectional.
Energy in an ecosystem is never destroyed but it is converted from
one form to another.
Plants play a vital role in converting the solar energy to the chemical
energy, making the sun’s energy available to the organisms at higher
tropic levels.
Only 10 % of energy is passed to the successive tropic level.
If any of the link in a food chain or food web (interconnected food
chains) is removed efficient energy flow will not occur.