2. Syllabus
Definition
Scope and Importance of ecosystem.
Classification, structure and function of an
ecosystem
Food chains, food webs and ecological pyramids.
Flow of energy
Biogeochemical cycles
Bioaccumulation
Biomagnifications
Ecosystem value, services and carrying capacity.
3. Environment is the physical and biotic habitant (living
place of organisms) which surrounds us; that which
we can see, hear, touch, smell and taste.
Environment = Physical Environment (Non-living
system which includes water, land, air) + biological
environment (which includes plants, animals and
microorganisms)
4. CONCEPT OF ECOSYSTEM
Eco:- Region of space where living things can exist
System:- Interacting organism in a particular habitat
(living place)
System resulting from the integration of all the living
and non-living factors of the environment.
Plants, animals and other organisms together with the
physical environment with which they interact constitute
ecosystem
Definition of Ecosystem
5. SCOPE AND IMPORTANCE OF ECOSYSTEM
Ecosystems are communities of organisms and
non-living matter that interact together.
Each part of the ecosystem is important because
ecosystems are interdependent.
Damaged or imbalanced ecosystems can cause
many problems.
6. Classification of ecosystem
Ecosystem can be classified based on size, nature and
duration
On the basis of nature
1.Natural: This ecosystem forms naturally without
interference of human. Example: pond, river, forest,
village, hill etc.
2. Artificial Ecosystem: This ecosystem is developed
and maintained by human. Example: flowerbed,
backyard, aquarium etc.
7. On the basis of duration
1. Temporary ecosystem: it is short lived and man made or
natural. Example include rain fed pond.
2. Permanent ecosystem: it is long lived and self supported
natural ecosystem for very long period. Eg: forest, river..
On the basis of size
1. Small: it is small and also known as microecosystem. It
can be temporary or permanent. Ex. Pond, flowerpot etc
2. Large: it is large in size and also known as
macroecosystem. It is always permanent and mostly
natural. For ex. Ocean, river, forest and desert.
8. COMPONENTS OF ECOSYSTEM
• Abiotic component:- Physical environment which
consists of light, heat, wind etc. and it provides
environment and raw materials for the synthesis of
organic food.
• Biotic environment:- the living autotrophic
bacteria and green plants (producers) are capable
of trapping solar radiations to form organic matter
by combining CO2, H2O and minerals. These
organism provide food directly or indirectly to all
9. STRUCTURE OF ECOSYSTEM
Structure:- description of the composition of biotic and
abiotic components in a particular habitat.
Abiotic component:- The term abiotic means without life.
Chemical abiotic component: Inorganic (C, CO2, H2O etc.)
and Organic (Fats, proteins etc.)
Physical abiotic component: Edaphic (relate to soil and act
as a solid medium for variety of organisms like bacteria
etc.), Climatic (Wind, water, temperature, light and rain),
10. Topography (Surface behaviour of earth like slope, altitude. Hills
etc.). Abiotic components are the physical environment which
consists of light, heat, wind etc. and it provides environment and
raw materials for the synthesis of organic food.
Biotic environment:- The living organisms (plants, animals,
microorganisms) constitute biotic components of the ecosystem.
From nutritional point of view biotic environment are classified
as:-
Autotrophic and heterotrophic components
11. Autotrophs or Producers: Producers are the base for
biotic community in an ecosystem. They are capable of
trapping solar radiations to form organic matter by
combining CO2, H2O and minerals. They are also termed
as autotrophs as they are capable of synthesizing their
own food. They are capable to change radiant energy
into chemical energy so they are also known as
transducers. These are two types- phototrophs and
chemotrophs
Phototrophs:- those which produce their food through
12. photosynthesis, eg: green plants,
6CO2 +6H2O C6H12O6 +6O2
Chemotrophs:- those which produce food through
chemosynthesis (exothermic oxidation of inorganic or
simple organic molecules without aid of light).
CO2 + 4H2S +O2 CH2O +4S + 3H2O
Heterotrophs or Consumers: organisms which depends
on autotrophs or primary producers. These are called
consumers because they consume the matter built up by
the producers. Producers provide food directly or
13. depending upon their food habits, they are classified
as
(a) Primary consumers or herbivores: Obtain food
directly from plants Eg: Cow, goat etc
(b) Secondary consumers:-these are carnivores and eat
flesh. Eg: Lion, birds etc.
(c) Tertiary consumers:-these are the top carnivores
feed both on primary and secondary consumers. Eg:
14. Omnivores: These are herbivores as well as carnivores
are those which eat both flesh and plant. Eg:- Man,
dogs etc.
Decomposers: those organisms which eat dead organic
matter. Eg:- bacteria, fungi etc.
15. FUNCTION OF ECOSYSTEM
Nutrient cycles – biogeochemical cycles
Energy cycle
Diversity/Interrelation – inter linkages
between organisms
Cybernetics
Food chain and food web
16. Nutrientcycling:-
Autotrophic plants obtain a number of
inorganic nutrients from the
environment, which become
components of organic matter. From
producers it goes into consumers and
then through decomposers it goes into
environment. Thus nutrient is circulating
between living and non-living organisms
by different biogeochemical cycles.
17. Flow of energy:- Autotrophic plant change radiant
energy into chemical energy through photosynthesis.
Part of this energy is consumed by autotrophs during
their respiration, growth and other metabolic reaction.
Other organism will get energy from autotrophs, where
organic compounds are used in body building and
energy is used for growth and maintenance. The flow of
energy in ecosystem is uni direction ie, from producers
to living organism and energy is losing when it transfer
from one organism to another.
18. With each trophic transfer, some usable energy is
degraded and lost to the environment as low quality
heat. Thus, only a small portion of what is eaten and
digested is actually converted into an organisms.
19. The first level
always has
autotrophs
The second level has
primary consumers –
heterotrophs,
herbivores.
The last level contains
secondary, tertiary consumers
– heterotrophs, carnivores,
omnivores
Energy is eventually lost as heat on the top of the pyramid
20. • Interrelation:- Different ecosystems exchange biotic and
abiotic materials. Eg: Plants provide O2, food, shelter to
animals and animals will supply CO2 to plants. Animals are
also interrelated in food web to become the food of another.
• Cybernetics:- Ecosystem maintain a functional balance
between various components. It is achieved by a number of
limitations, which is called cybernetics. Eg:- species control
depend on scarcity of resources, recycling of waste by
environment (self regulation), one living component can
control other through feed back system (when number of
zooplankton increases it decreases the number of
phytoplankton which result in reduction of zooplankton .
21. FOOD CHAIN
A food chain describes a
ingle pathway that energy and
utrients may follow in an
cosystem. They usually start
with a primary producer and end
with a top predator.
Food chains/webs show how matter and
energy move from one organism to another
through an ecosystem
22. 22
Types of food chains
1. Grazing food chain: It starts with green plants (primary producers)
and culminates in carnivores. Example :
• Grass —> Rabbit —> Fox
• Phytoplankton —> Zooplantkton —> Fish —> Man
2. Detritus food chain: It starts with dead organic matter which the
detritivores and decomposers consume. Partially decomposed dead
organic matter and even the decomposers are consumed by detrivores
and their predators. Example -Dead organic matter —> Detrivores —
>predators.
23. FOOD WEB
Some organisms eat a variety of other organisms,
then food chain become complex. A combination
of different food chains is called a food web.
24. ECOLOGICAL PYRAMIDS
An ecological pyramid is a diagram that shows the
number of organisms, energy relationships, and
biomass of an ecosystem.
Food chains and food webs do not give any information
about the numbers of organisms involved.
They are
1.Pyramid of Biomass
2.Pyramid of Energy
3.Pyramid of Numbers
25. Ecological Pyramid of Energy –
show the energy flow through an ecosystem
The energy pyramid will always be
upright because there is always gradual
decrease in the energy content at
successive trophic level from producers to
consumers because one part of energy is
used for metabolic process, growth etc..
Remaining part is transferred to other level.
At the producer level the
total energy will be
much greater than the
energy at the
successive higher
trophic level.
26. Ecological Pyramids of Biomass
The pyramid of biomass is two types. If a larger weight of
producers support a smaller weight of consumers, results an
upright pyramid (grass ecosystem) and if a smaller weight of
producers support a larger weight of consumers, an inverted
biomass pyramid results (aquatic ecosystem). In the example,
phytoplankton grow and reproduce so rapidly that they can
support a large population of zooplankton even though the
biomass of phytoplankton is smaller than that of the zooplankton.
29. Ecological Pyramids of Numbers
This shows the relationship among the number of producers and consumers. It
also show the number of individuals per unit area of each trophic level. The
structure and shape of pyramid will vary from one ecosystem to other.
Grass land ecosystem- Producers (grasses large in number), primary
consumers (rabbit, mice etc. less in number compared to plants), secondary
consumers are much lesser (lizard, snake etc..). Thus the pyramid is upright.
30. Aquatic ecosystem – Producers (algae large in number), primary
consumers (small fishes less in number compared to algae) and
secondary consumers (birds less in number etc..). This will also give
upright pyramid.
But in parasite food chain pyramid is inverted. Single large tree can
support many fruit eating birds. This each bird support the growth of
large number of parasites. Thus the number of organism gradually
increased from first trophic level to last.
31. Ecological Pyramids of Numbers
In grass land and aquatic ecosystem In parasite food chain
32. FLOW OF ENERGY
The cycle of energy is based on the flow of energy
through different trophic levels in an ecosystem. Our
ecosystem is maintained by the cycling energy and
nutrients obtained from different external sources.
At the first trophic level, primary producers use solar
energy to produce organic material through
photosynthesis. The herbivores at the second trophic
level, use the plants as food which gives them energy. A
large part of this energy is used up
33. for the metabolic functions of these animals such as
breathing, digesting food, supporting growth of
tissues, maintaining blood circulation and body
temperature.
The carnivores at the next trophic level, feed on the
herbivores and derive energy for their sustenance
and growth. If large predators are present, they
represent still higher trophic level and they feed on
carnivores to get energy.
34. Decomposers break down wastes and dead
organisms, and return the nutrients to the soil, which
is then taken up by the producers. Energy is not
recycled during decomposition, but it is released.
35. BIOGEOCHEMICAL CYCLES
Biogeochemical cycles refer to the flow of elements
and compounds between organisms and the physical
environment.
Chemicals taken in by organisms are passed through
the food chain and come back to the soil, air, and water
through mechanisms such as respiration, excretion, and
decomposition. Such cyclic exchange of material
between the living organisms and their non-living
environment is called Biogeochemical Cycle.
36. Following are some important biogeochemical
cycles −
Carbon Cycle
Nitrogen Cycle
Oxygen Cycle
Phosphorus Cycle
Sulphur Cycle
Hydrological cycle
37. CARBON CYCLE
Carbon used to constitute almost all organic
compounds of the cell such as carbohydrates, proteins,
lipids, enzymes, nucleic acids, hormones etc.
Together, photosynthesis and cellular respiration form
the basis of the carbon cycle.
Photosynthesis: in which algae, higher plants, and
photosynthetic bacteria use light energy to fix inorganic
carbon in a high-energy organic form:
38. In atmosphere and hydrosphere carbon content is
maintained because of its return through 2 major
processes
(1)Biological respiration and decomposition of organic
matter
(2) Non biological combustion of fuel that further
releases CO2 in the atmosphere.
In this way carbon is fixed on earth and returned to
atmosphere again.
39. Carbon cycle was almost a perfect cycle. But now
carbon has been added to the atmosphere faster
than producers can remove it. Also, deforestation
reduces the amount of carbon dioxide being used
in photosynthesis. Further, the use of land for
agriculture releases carbon dioxide into the
environment.
Plants in water need carbon dioxide to perform
photosynthesis and release oxygen. Fish use the
oxygen to breathe and the plants for food. Thus,
40. Atmospheric
carbon dioxide
Dead organic matter
Animals
Combustion
Coal, gas
Death and Excretion
Producers
(Green plants)
Photosynthesis
Respiration
D
ec
o
m
p
o
s
e
r
s
41. NITROGEN CYCLE
Nitrogen Cycle is a biogeochemical process which
transforms the inert nitrogen present in the
atmosphere to a more usable form for living
organisms.
Processes:
Nitrogen fixation
Ammonification
Nitrification
Denitrification
42. Nitrogen fixation
Atmospheric nitrogen is converted into useful
nitrate form by a process known as nitrogen fixation
(i)Biological (living) nitrogen fixation: It involves
the transformation of atmospheric nitrogen into
nitrites and nitrates by living organisms. It is brought
about by certain bacteria. Rhizobium associated with
nodules of legume family plants have ability to
convert atmospheric N2 into NH3 to synthesize
aminoacids, proteins in plant cells.
43. This usable nitrate form is transferred to herbivores
and carnivores through food chain
N2 → NH3 → Aminoacids → Proteins
(ii)Atmospheric (nonliving) nitogen fixation:
(a)Industrial fixation: Haber’s process- N2 and H2 are
reacted under high P and T in the presence of
catalyst to produce NH3 which may be used as
fertilizer
(b) Photochemical and electrochemical fixation:O2
combine with N to form nitrogen oxides (Nox).
44. These oxides dissolved in water to form nitrous acid and
nitric acid ormay be combine with salt to produce
nitrates.
Ammonification
It involves the decomposition of proteins of dead plants
and animals and nitrogenous waste into ammonia in
presence of ammonifying bacteria.
Proteins (dead plants and animals)→ Amino acids → Ammonia
Nitrification
It involves oxidation of ammonia to nitrates through
nitrites in presence of nitrifying bactria
45. NH3 →NO2
-
→NO3
-
Denitrification
It is a biological process in which ammonium
compounds are reduced to molecular nitrogen in
presence of denitrifying bacteria under anaerobic
conditions.
NO3
-
, NO2
-
, NO N2
This nitrogen is slowly released back to atmosphere
to maintain nitrogen concentration constant and the
cycle gets completed.
denitrifying bacteria
47. PHOSPHOROUS CYCLE
Phosphorous are essential nutrients for growth and
maintenance of animal bones and teeth while
organo-phosphates are required for cell division
involving the production of nuclear DNA and RNA
Sources:
Natural: Phosphate minerals are located in rock and
soil where phosphate exist in soluble and insoluble
forms.
Artificial: Human activities
48. Processes:
Phosphorous cycle contains terrestrial and aquatic
processes. Phosphorous containing rocks are broken
down by rock weathering, chemical reaction and
eroding action of wind and moving water. Some of
the part become dissolved in water as phosphate
and other particles become part of soil. Terrestrial
plants and bacteria absorb inorganic phosphate salt
from soil and convert these into organic phosphates.
49. Phosphorous moves from plants to animals of different
trophic levels in ecosystem through food chains. After
their death and decay, phosphorous present in plants
and animals (organic form) is returned to soil and water
(inorganic form) through decomposition dead remains
by microorganisms; to be reused by plants. In this way
phosphorous is recycled.
51. SULPHUR CYCLE
Sulphur is an essential part of protein and
aminoacids. It exist in nature as: elmental sulphur,
sulphides and sulphates.
Sources:
Atmosphere: SO2, H2S, SO3
Natural emission: sources that emit sulphur directly
into atmosphere such as volcanic eruption etc.
Artificial: Combustion of fuel
Hydrocarbons (containing S) → CO2 + H2O+ SOx
52. Processes:
Cycle begins with weathering of rocks, releasing
stored sulphur. This S comes in contact with air
where it is converted into sulphate in presence of
moisture. Sulphur in soluble form, mostly as sulphate
is absorbed through plants, where it is incorporated
into certain organic molecule such as aminoacids
and proteins. From the producers, the sulphur in
aminoacids transferred to the consumerswith excess
being excreted in faeces. Excretion and death carry
53. sulphur in living material back to soil where ythe
organic material acted upon by the bacteria of
dentritus food chain. Again sulphur produced that
can be reused by autotrophs and the cycle goes on.
55. OXYGEN CYCLE
Major component needed by the most plants,
animals and man for aerobic respiration or enzymatic
oxidation of organic food is oxygen.
Production of O2:
(a)Photosynthesis: CO2 + H2O → C6H12O6 + 6O2
(b)Photodissociation: High energy UV radiation break
down the atmospheric water and nitrogen oxide to
provide oxygen.
Sunlight
UV UV
56. Oxygen consumption:
(a)Respiration and natural decay: As a constituent of
CO2, it circulates freely throughout the biosphere
C6H12O6+ 6O2 → 6CO2 + 6H2O
(b) Combustion reaction: Burning of fossil fuel
C + O2 → CO2
(c) Oxidation weather process: O2 is consumed in
natural oxidation of some oxidative weathering
process of minerals in earth crust
4FeO + O2 → 2Fe2O3
57. It is again made available to the environment in
combination with carbon in the form of CO2 or with
hydrogen as H2O. Oxygen is also released as a part
of CO2 due to death and decay of organic matter. In
such a vital cycle, O2 is replenished and maintained
in the ecosystem.
59. HYDROLOGICAL CYCLE
Water or hydrological cycle involves, the circulation of
water and moisture among air, land, sea and living
organisms
Mainly 2 cycles
1)Larger global cycle: in which living organisms are not
involved. It include
Evaporation: Evaporation of water by solar energy
Cloud formation: Clouds are formed by cooling and
condensation of water vapours
Precipitation: Clouds get cooled and precipitated as
60. 2) Local or biological cycle: It involves entry of water
to the living organisms and its return to the
atmosphere. Large amount of rain water goes into
soil which is extracted by plants through their
roots. Another route for cloud formation is called
transpiration, in which water from plants get
converted into clouds. This combined process is
called evapotranspiration
61. Cloud
Evaporation
Water bodies
Eg: Ocean, river, lakes
Soil moisture
Plants
Transpiration Precipitation
Surface run-off
Infiltration for
ground water storage
Rainfall
62. BIOACCUMULATION
Accumulation of pollutants in an organism over its
life span
Can occur whenever the half-life of the pollutant is
greater than the life span of the organism
Seen at all levels of a food chain with continual
exposure to a chemical
Examples: atrazine in amphibians, most chemical
exposure in humans
63. Why it is important to study:
1.Enhance the persistence of industrial chemicals in the
ecosystem
2.Stored chemicals are not exposed to direct physical,
chemical, or biochemical degradation.
3.Stored chemicals can directly affect an individual's
health.
4.Predators of those organisms that have bio-
accumulated harmful substances may be endangered by
food chain effects.
64. BIOMAGNIFICATION
Biomagnification stands for Biological Magnification,
which means the increase of contaminated substances
or toxic chemicals that take place in the food chains.
accumulation of pesticides across trophic levels
(up a food chain)
observed mostly in top predators
Examples: lead in California Condors, mercury in
billfish, rodent killer in coyotes and mountain lions
65. When an animal consumes food having DDT residue,
the DDT accumulates in the tissue of the animal by a
process called bioaccumulation. The higher an animal is
on the food chain (e.g. tertiary consumer such as seals),
the greater the concentration of DDT in their body as a
result of a process called biomagnification.
Bioaccumulation is the
concentration of pollutant
from the environment which
occurs within a trophic level,
ie. One level of a food chain
Biomagnification is the
concentration of pollutant
across the food chain
66. ECOSYSTEM VALUES:
1. Direct value: Resources that people depend upon
directly
Consumptive use value: Non-market value of fruit etc.
that are used by people who collect them from their
surroundings
Productive use value: Commercial value of fish,
medicinal plants etc. that people collect for sale.
2. Indirect value: These are uses that do not have easy
ways to quantify them in therms of a clearly definable
67. Non-consumptive use value- bird watching,
scientific research, tourism etc.
Option value – maintaining options for the future,
so that by preserving them one could reap
economic benefits in the future
Existence value – ethical and emotional aspects of
the existence of wildlife and nature
68. ECOSYSTEM SERVICES:
1. Purification and Detoxification (of air, water and soils)
2. Cycling Processes: (nutrient cycling, nitrogen fixation,
carbon sequestration, soil formation)
3. Regulation and Stabilisation: pest and disease
control, climate regulation, mitigation of storms and
floods, erosion control, regulation of rainfall and water
supply;
4. Habitat Provision: refuge for animals and plants,
storehouse for genetic material;
69. 5. Regeneration and Production: production of biomass
providing raw materials and food, pollination and
seed dispersal; and
6 Information/Life-fulfilling: aesthetic, recreational,
cultural and spiritual role, education and research.
Some further examples of these services are
provided below.
70. CARRYING CAPACITY OF AN ECOSYSTEM
In ecological terms, the carrying capacity of an
ecosystem is the size of the population that can be
supported indefinitely upon the available resources and
services of that ecosystem.
It depends on many abiotic and biotic factors in the
ecosystem. For example, the availability of the basic
needs of organisms such as food, water and shelter
dictates how many individuals the ecosystem can
sustain. This process is self-regulating to some extent
71. because individuals will die when the carrying capacity is
exceeded.
Other factors that influence the carrying capacity of
an ecosystem include disease, predator-prey
interactions, the consumption rate of resources and the
number of populations in the ecosystem. However, there
are other factors that are hidden, less obvious and/or
disregarded which have a significant impact on
populations such as pollution, eradication of habitat and
climate change.
