Energy flow in ecosystem, biogeochemical cycles, succession,

1. Environmental Studies
&
Disaster Management
Somanath Sarvade
Assistant Professor (Agroforestry)
College of Agriculture Balaghat
E-mail: somanath553@jnkvv.org
Jawaharlal Nehru Krishi Vishva Vidyalaya,
Jabalpur

2. CONCEPT OF ENERGY IN ECOSYSTEM
• Energy is the capacity to do work.
• Biological activities require consumption of
energy which ultimately comes from sun.
• Except for the deep-sea hydrothermal
ecosystem, sun is only the source of energy
for all ecosystem on Earth.
• Of the total incident solar radiation less than
60% of it is photo-synthetically active
radiation (PAR).
• Solar energy of sun is transformed into
chemical energy (Adenosine triphosphate)
by the process of photosynthesis, then it is
stored in plant tissues and then transformed
into mechanical and heat form of energy
during metabolic activities.

3. Components of the energy flow in Ecosystem
Sun – The energy used for all plant life processes is derived from solar
radiations and all animals are further dependent on plants. About 34%
of the sunlight reaching the Earth’s atmosphere is reflected back (by
clouds and dust), 10% is held by ozone layer, water vapor and other
atmospheric gases. The rest 56% reaches the earth’s surface and out
of that only 2 to 10% is used by plants and the remaining is absorbed
as heat by water or ground.

4. Producers – The green
plants in the ecosystem-
terminology are called
producers. In a terrestrial
ecosystem major producers
are herbaceous and woody
plants. Likewise, primary
producers in an aquatic
ecosystem are various
species like phytoplankton,
algae and higher plants.

5. Consumers – All animals
depend on plants (directly or
indirectly) for their food
needs. Hence, they are
called consumers and also
heterotrophs.

6. Decomposers – The heterotrophic organisms, mainly fungi
and bacteria, which meet their energy and nutrient
requirements by degrading dead organic matter or detritus are
called decomposers. They are also known as saprotrophs

7. • Plants capture only 2 to 10 % of the PAR and this small
amount of energy sustains the entire living world!
• So, it is very important to know how solar energy captured
by plant flows through different organisms of an ecosystem.
• This can be shown by the following schematic diagram
Sun
Radiant energy
Producers Consumers
Decomposers
(metabolism)
Heat energy
(metabolism)
(metabolism)
Heat energy
Heat energy

8. ECOLOGICAL ENERGETICS
• Ecological energetics include energy
transformation which occur within the
ecosystems.
• In ecological energetics, we consider –
i. Quantity of energy reaching an ecosystem
per unit of area per unit time.
ii. Quantity of energy trapped by green plants
and converted to a chemical form
(photosynthesis).
iii. The quantity and path of energy flow from
green plants to organisms of different tropic
levels over a period of time in a known area (
energy flow from producers to consumers).

9. LAWS GOVERNING ENERGY TRANSFORMATION IN ECOSYSTEM
• Energy transformation in ecosystem can be explained by the laws of
thermodynamics.
• Ecosystem follows the first law of thermodynamics, which states that energy
may be transformed from one form to another but it can neither be
created nor be destroyed. This is also true in the case of an ecosystem, when
an organism dies its energy is not destroyed but is dissipated in the
surrounding through decomposers.
• Further, ecosystem is not exempt from the Second law of thermodynamics
which states that processes involving energy transformation does not
occur spontaneously unless there is degradation of energy from a non-
random to a random form. The energy in living organisms is in non-random
form i.e. in the form of chemical bonds of biomolecules, but when their
decomposition occurs the non-random energy is converted to random form by
the decomposers to simpler form.

10. INTERCONNECTION AMONG ORGANISMS
• All the organisms in an ecosystem are connected in a very intricate
manner and the energy flow occurs through these interconnections.
• These interconnections can be depicted by food chains to
understand the basic connection between organisms (In reality they
are lot more complexly interconnected).
• There are many types of food chains operating in nature, major one
among them are grazing food chain (GFC) and detritus food chain
(DFC). A simple GFC is depicted
below :-

11. 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 consumed/used during
transfer, broken down in respiration, or
used to incomplete digestion by higher
trophic level.

12. The ten percent law gives us a basic understanding on the cycling of
food chains.
• Furthermore, this law shows the inefficiency of energy capture at
each successive tropic level.

13. 1. Energy is “used up” for daily life activities.
2. Not all organisms that die are eaten by
animals in the next trophic level.
3. Not all parts of an organism are eaten and
digested for energy.
3 Reasons for decrease in available
energy

14. REPRESENTATION OF ENERGY FLOW IN ECOSYSTEM
• Tropic level – Organisms occupy a place in the natural surroundings or
in a community according to their feeding relationship with other
organisms. Based on the source of their nutrition or food, organisms
occupy a specific place in the food chain that is known as their tropic level.
A given organism may occupy more than one tropic level simultaneously.
• Organisms at each tropic level depend on those at the lower tropic level
for their energy demands.
• Standing crop - Each tropic level has a certain mass of living material at
a particular time called as the standing crop. It is measured as the biomass
of an organism or their number in a unit area.
• Pyramid of energy - Any calculations of energy content, biomass, or
numbers has to include all organisms at that tropic level.

16. Cycles of Elements
Nutrients (water, nitrogen, carbon) are cycled
through the Earth in cycles called the
biogeochemical cycles.
Law of Conservation of Mass
• Matter cannot be created or destroyed in
chemical reactions it simply changes forms
• No new sources of matter on Earth instead it
continuously cycles through
• Matter simply changes in the way that the
elements are bonded together

17. Hydrological cycle (Water cycle)
Defined: Movement of water through the atmosphere
• 75% of the earth is water
• 99% of water undrinkable (salty & frozen)
• Makes up 60-70% of your body

19. Water rises into the atmosphere in two ways:
◦ Evaporation: Heat changes water from a liquid to a gas
◦ Transpiration: Water evaporates from the leaves of plants
through openings called stomata
Warm, moist air rises and eventually cools
◦ Condensation: process where water vapor turns into a liquid
• Rain, snow, sleet, or hail falls when water drops become
heavy (Precipitation)

20. 1. Reservoir – oceans, air (as water vapor), groundwater, lakes
and glaciers; evaporation, wind and precipitation (rain) move
water from oceans to land
2. Assimilation – plants absorb water from the ground, animals
drink water or eat other organisms which are composed mostly of
water
3. Release – plants transpire, animals breathe and expel liquid
wastes

21. Oxygen cycle
Autotrophs: Release O2 into atmosphere via photosynthesis
• All life: Absorbs O2 to be used during cellular respiration
◦ Respiration: creates ATP energy for cells

22. Carbon cycle
Carbon = (organic molecules) carbohydrates, proteins, lipids,
nucleic acids
• Plants & autotrophs:
– Intake: Absorb CO2 from atmosphere
• Create glucose & sugar via photosynthesis
– Output: Release CO2 during respiration
• Consumers
◦ Intake: Carbon moves up the food chain as 1 feeds on
another
◦ Output: Release CO2 during respiration

24. • Decomposers
–Input: Feed on dead organic matter
–Output: Release CO2 during respiration
–Output: Organic molecules returned to soil during
decomposition
• Human Industry
◦ Output: Release CO2 into atmosphere when fossil
fuels (coal, oil, natural gas) are burned

25. Carbon is required for building organic compounds
1. Reservoir – atmosphere (as CO2), fossil fuels (oil, coal),
durable organic materials (for example: cellulose).
2. Assimilation – plants use CO2 in photosynthesis; animals
consume plants.
3. Release – plants and animals release CO2 through
respiration and decomposition; CO2 is released as wood and
fossil fuels are burned.

26. Nitrogen cycle: key points
• Nitrogen is in the atmosphere as N2 (78%)
• N2 is an inert gas and cannot be used by plants or animals.
• N2 can be converted to a usable form via
◦ Lightening
◦ N2-fixing plants and cyanobacteria (BGA)
◦ Industrial process (energy intensive)
• Nitrogen limits plant growth.
• Nitrogen is easily lost from biological systems.

28. 1. Reservoir – atmosphere (as N2); soil (as ammonium, ammonia,
nitrite, nitrate
2. Assimilation – plants absorb nitrogen as either NH4+ or as N03-,
animals obtain nitrogen by eating plants and other animals.
3. Release – Denitrifying bacteria convert N03- back to N2; detrivorous
bacteria convert organic compounds back to NH4+; animals excrete
NH4+, urea, or uric acid.

29. Importance of phosphorous cycle
1.Phosphorous is an essential nutrient of both plants and animals.
2. It is part of DNA molecules which carry genetic information.
3. It is part of ATP and ADP that store chemical energy for use by
organisms in cellular respiration.
4. Forms phospholipids in cell membranes of plants and animal cells.
5. Forms bones, teeth, and shells of animals as calcium phosphate
compounds.
Phosphorous cycle

30. Phosphorus is required for the manufacture of ATP and all nucleic acids
1. Reservoir – erosion transfers phosphorus to water and soil;
sediments and rocks that accumulate on ocean floors return to the
surface as a result of uplifting by geological processes
2. Assimilation – plants absorb inorganic PO4
3- (phosphate) from soils;
animals obtain organic phosphorus when they eat plants and other
animals
3. Release – plants and animals release phosphorus when they
decompose; animals excrete phosphorus in their waste products

32. Sulphur cycle
Importance of Sulphur cycle
1.Sulphur is a component of most proteins and some vitamins.
2.Sulphate ions (SO4
2-) dissolved in water are common in plant
tissue. They are part of sulphur-containing amino acids that are the
building blocks for proteins.
3.Sulphur bonds give the three dimensional structure of amino acids.
4.Many animals, including humans, depend on plants for sulphur-
containing amino acids.

34. • The term was first given by Hult (1885).
• Community are never stable but keep on changing.
• This relatively definite sequence of communities over a period of time
in the same area is called ecological succession.
• Communities are never found permanently in complete balance with
their component species or with the physical environment.
• Succession is a universal process of directional change in community
composition, on an ecological time scale.
Succession

35. What is Ecological Succession?
Ecological succession is the observed process of change in the
species structure of an ecological community over a period of time
• Ecosystems are constantly changing.
• Ecological succession is a gradual process of change and replacement
of the types of species in a community.
• Each new community makes it harder for the previous community to
survive.

36. • Environment is always changing over a period of time due to
1) variations in climatic and physiographic factors, and
2) the activities of the species of the communities themselves.
• These influences bring about marked changes in the dominants
of the existing community, which sooner or later replaced by the
another community at the same place.
• Gradual replacement of simple organisms with more complex
organisms overtime
• Role of succession is to make an ecosystem more
sustainable/biodiverse
• Odum (1971) preferred to designate this orderly process as
ecosystem development rather than the ecological succession.

37. Process of Ecological Succession
The process of ecological succession can be explained in the following
steps.
1. Nudation: It is the development of a bare area without any life form
2. Invasion: It is the establishment of one or more species on a bare
area through migration followed by establishment.
a. Migration - Migration of seeds is brought about by wind, water
or birds.
b. Establishment - The seeds then germinate and grow on the
land and establishes their pioneer communities.

38. 3. Competition: As the number of individual species grows, there is a
competition with the same species and between different species for
space, water and nutrients.
4. Reaction: The living organisms take water, nutrients and grow and
modify the environment is known as reaction. This modification becomes
unsuitable for the existing species and favor some new species, which
replace the existing species this leads to seral communities.
5. Stabilizations: It leads to stable community, which is in equilibrium with
the environment

39. Types of Ecological Succession
There are two main types of Ecological Succession:
• Primary Succession: It is the process of creating life in an area
where no life existed earlier.
• An example of an area in which a community has never lived
before, would be a new lava or rock from a volcano that makes a
new island.

40. Hundreds of year

41. • Begins in a place without any soil, like:
* Sides of volcanoes
* Landslides
* Flooding
• Starts with the arrival of living things such as lichens that do
not need any soil to survive.
• They are called Pioneer Species

42. • When lichens die, they decompose, adding small amounts of
organic matter to the rock to make soil.
• Simple plants like mosses and ferns can grow on this new soil

43. • The simple plants die, adding more organic
material.
• The soil layer thickens, and grasses and
other plants begin to take over.
• These plants die, and they add more
nutrients to the soil.
• Shrubs and trees can survive now, on this
soil.

44. • Insects, small birds and mammals can now begin to move in.
• What was earlier only bare rock, now supports a variety of life

45. • Secondary succession follows a major disturbance, such as a fire
or a flood.
• The stages of secondary succession are similar to those of
primary succession; however, primary succession always begins
on a barren surface, whereas secondary succession begins in
environments that already possess soil.
• In addition, through a process called old-field succession,
farmland that has been abandoned may undergo secondary
succession.
Secondary Succession

49. Basis for
Comparison
Primary succession Secondary succession
Definition Primary succession is a type
of ecological succession
that takes place in an
environment that is recently
formed and lacks habitable
soil but then is colonized for
the first time by living
organisms.
Secondary succession is a
type of ecological
succession that occurs in
an environment with an
already established
ecosystem that gets
disruption due to some
events like fire or hurricane
and is then re-colonized by
other organisms.
Initial vegetation Primary succession occurs
in an area without any
initial vegetation.
Secondary succession
occurs in an area with
initial vegetation.
Initiation Primary succession is
initiated either due to a
biological factor or an
external agent.
An external factor initiates
secondary succession.

50. Soil Before the beginning of
the primary succession,
the surface soil is absent in
the area.
Secondary succession
occurs in an area
covered with surface soil.
Organic matter There is no organic matter
present in the environment
undergoing primary
succession.
Organic matter is present
in the environment
undergoing secondary
succession
Environment The environment during
primary succession is
unfavorable and is made
favorable as new species
continue to grow.
The environment is
favorable from the
beginning.
Pioneer species The pioneer species of
primary succession enter
the ecosystem from the
outside environment.
The pioneer species of
secondary succession are
the species already
present within the
previous ecosystem.
The pioneer species in
primary succession are
mostly lichens, followed
by algae and fungi.
The pioneer species in
secondary succession
are mostly grasses.

51. Intermediate
community
Numerous intermediate
communities are formed
during primary succession.
Fewer intermediate
communities are formed
during secondary
succession.
Previous
community
No previous community is
present in the environment
prior to primary succession.
Previous communities are
present in the environment
prior to secondary
succession.
Time Primary succession takes a
longer time to complete.
Secondary succession takes
a shorter time to complete.
Examples Some examples of primary
succession include the
formation of a new
ecosystem after a volcano,
glacier outbursts, or a
nuclear explosion.
Some examples of
secondary succession
include succession after fire,
harvesting, logging, or
abandonment of land or
the renewal after a disease
outbreak.

52. Types of Seres Explanation
Hydrosere
Succession in aquatic
habitat.
Xerosere
Succession in dry
habitat.
Lithosere
Succession on a bare
rock surface.
Psammosere
Succession initiating on
sandy areas.
Halosere
Succession starting in
saline soil or water.
Senile
Succession of
microorganism on dead
matter.
Eosere
Development of
vegetation in an era.

54. Hydrosere

55. Mesarch or Mesosere Succession

56. Lithosere Succession

57. Psammosere Succession

58. Halosere Succession

59. Autogenic and Allogenic Succession
• When succession is brought about by living inhabitants of that
community itself, the process is called autogenic succession, while
change brought about by outside forces is known as allogenic
succession.
• Autogenic succession is driven by the biotic components of an
ecosystem.
• Allogenic succession is driven by the abiotic components (fire,
flood) of the ecosystem.

61. Autotrophic Succession - The succession where initially the green
plants are much greater in quantity than the animals, is known as the
autotrophic succession. it begins in a predominantly inorganic
environment and the energy flow is maintained indefinitely. There is a
gradual increase in the organic matter content supported by energy flow.
• Heterotrophic Succession- It is characters iced by early dominance of
heterotrophs such as animals, fungi, bacteria, actinomycetes.
• It begins in a predominantly organic environment and there is a
progressive decrease in the energy content.
• Progressive Succession- When succession occur in direction of
simple community to complex community known as progressive
succession.
• Retrogressive Succession- when succession occur from complex
community to simple community.