ECOSYSTE

Presented By:
M
Ms. Margi Grewal
FSH Department
Poornima University

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 • Introduction
• Structure of Ecosystem
• Function of Ecosystem
CONTENTS
• Energy Flow
• Ecological Succession
• Biodiversity
• Conservation of
Biodiversity

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 INTRODUCTION

What is Ecosystem?
• All the organisms (from virus to man) are obligatorily dependent on other organisms and

environment for food, energy, water, oxygen, shelter and for other needs.

•The system resulting from the integration of all living and non-living factors of the

environment. It is a self-sustaining structural and functional interaction between living

and non-living components.

•Ecosystem refers to a system of living and non-living components interacting as a whole.

• The relationship and interaction between organisms and environment are highly complex. It

comprises both living (biotic) and non living (abiotic) components.

• The term ecosystem was first proposed by the British ecologist Sir Arthur. G. Tansley.
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Characterstics of an Ecosystem
a. The ecosystem is a major structural d. The relative amount of energy
and functional unit. needed to maintain an ecosystem
b. The structure of an ecosystem is depends on its structure. The more
related to its species diversity. The complex the structure, the lesser the
more complex systems have a high energy it needs to maintain itself.
species diversity. e. Ecosystem mature by passing from
c. The function of an ecosystem is the less complex to more complex
related to energy flow and material states.
cycling through and within the f. Both, the environment and the
system. energy fixation in any given
ecosystem, are limited and cannot
be exceeded without causing
serious undesirable effects.
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Types of Ecosystem
Ecosystem

Terrestrial Aquatic
Ecosyste Ecosyste
m m

Artificial or Man-Made
Natural Natural
Man-Made / Artificial

Desert Forest Grassland Mountain Marine Fresh

Space
Ecosyste Ecosyste Ecosyste Ecosyste Crop field Gardens Ecosyste water
ecosystem
m m m m m ecosystem

Warm Cold
Desert Desert

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 Aquatic
Ecosystem

Natural Artificial

Marine Fresh Water Aquarium Sewage

Coastal or
Ocean Coral Reefs Lotic(running Lentic((stagna
estuarine
Ecosystem ecosystem water) nt water)
ecosystem

River and Ponds, Lakes

Streams and Wetlands

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Structure
of
Ecosystem
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Components Of Ecosystem

Biotic Abiotic
Temperature
Producers Light
Soil
Consumers Water
Decomposers Air
Humidity
Precipitation
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 Decomposers/Detritivor
Producers Consumers
es
• They are Autotrophs • They are heterotophic • They feed dead decay organic
• They manufacture both food organisms which directly or matter of plants and animals.
and energy they require by indirectly depend on producers • They breakdown the complex
photosynthesis for energy. organic compound to simple
• They produce food by • Consumers have been divided inorganic matter.
converting inorganic material to in 3 categories: • They assist in returning the
organic compound with the • 1.Primary Consumers: nutrient back to the producers
help of sunlight. Herbivores, depend on green or autotrophs.
• Examples include: plants for food, e.g. cow, goat, • Detritivores essentialy refers to
• a.Photoautotrophs(planktons, rabbit, some insects, the small insects, earthworms,
algae,cyanobacteriaand all zooplanktons. bacteria and fungi.
green plants,phytoplanktons.) • 2.Secondary
• b.Chemoautotrophs Consumer:Carnivores that
(Sulfolobus,Thiobacillus and consume herbivores. E.g.
thiotrhix). snake, frog, small fishes.
• 3.Tertiary Consumers: these
are the top consumers; they kill
and eat 2 and 1 consumers.
E.g. lion, tiger, hawk, large
fishes etc.

Parasites are the organisms that derive their food and shelter at the expense of living hosts. E.g.
tapeworm, round worm and plasmodium. 9
Scavangers are animals that eat on dead animals. E.g.: termites, vultures ( Consumers)
Structure of Ecosystem Comprises:
Composition and arrangement of biotic community: this comprises species in the community, their
abundance, their biomass, life history, distribution in space etc.
Amount and allocation of non-living substances, such as different nutrients, water, etc.
Range or gradient of the factors of survival, such as temperature, sunlight, ph etc.

Structure
of
Ecosyste
m

Food Food Ecological

Chains Webs Pyramids

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 FOOD CHAINS
•In all the ecosystem food is the primary source of energy for all the animals and plants.

•The sun is the ultimate source of energy on earth. It provides the required energy for all plant life because green plants
alone are able to trap solar energy and convert it into chemical energy and stored as a food, this process known as
photosynthesis.

•The chemical energy is locked up in the various organic compounds, such as carbohydrates, proteins, fats etc. and this
is passed on through successive trophic levels.

•Trophic Levels: The successive levels of energy flow constituting the links of the food chain are called trophic levels. E.g.
first trophic level- Producers, second trophic level- 1 ̊ consumers, third trophic- 2 ̊ consumers

•Food Chain: The transfer of food energy from the source in plants through a series of organisms with repeated eating
and being eaten is referred to as food chain.

• In simple term it is a linked feeding series.

•The quantity of energy decreases readily in a long food chain, whereas in a short food chain, higher amount of energy is
available.
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Types of Food Chains
Mainly food chains are of two types:
(a.) Grazing food chain (b.) Detritus food chain
(a.) Grazing Food Chain: It starts from green plants and operates from herbivores to primary carnivores and so
on.
Examples of Grazing food chain in different ecosystem-
(i) Pond Ecosystem:
Phytoplanktons Aquatic insects (zooplanktons) Small Fishes Large Fishes

(ii) Marsh Community:

Green Plants Butterfly Dragon Fly Frog Snake Hawks

(iii) Forest Ecosystem:

Green Plants Deer Tiger

(iv) Grassland Ecosystem:

Grass Mouse Snake Hawks

(v) Agro-ecosystem:
Crop plants Aphids/insects Insectivores Hawks 12
(b.) Detritus Food Chains: It starts from dead organic matter to micro organisms and then to detritus feeding organisms (detrivores)
and their predators.

❑ The dead organic matter is decomposed into detritus by microorganisms like bacteria and fungi.

❑ The detritus food chain helps in solving inorganic nutrients.

❑ Detritus food chain includes sub soil species that can be macroscopic or microscopic in nature.

❑ Compared to other kinds of food chains, the detritus food chain has much larger energy flow in a terrestrial ecosystem.

❑ Detritus food chain has continuous energy flow compared to other food chains. For instance, in the grazing food chain, there is a
distinct transfer of energy flow between different trophic levels.

❑ The organisms that feed on dead organic matter or detritus, are known as detritivores or decomposers. These detritivores are later
eaten by predators. In the detritus food chain, the excreted products by one organism is utilized by another organism.

Example: In Mangrove ecosystem when the leaves of a red mangrove tree fall into a shallow water body, only about five percent of the leaves are eaten by
phytophagous insects before they fall. The parts of the leaves are eaten by smaller organisms like insect larvae, crabs, copepods, etc. Later these organisms are
consumed by fishes who are carnivores. Finally these fishes are eaten by larger fishes or fish-eating birds.

Mangrove leaves Detritus Crabs & Shrimps Small Fish Large Fish

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14
 Complex Nature of
Ecosystem
Interaction
Between
Biotic and Abiotic Components
 •Food web is a network of interconnected food chains.

• It comprises all the food chains within a single ecosystem.

FOOD WEB •It helps in understanding that plants lay the foundation of all the food
chains.

•There are a number of options of eating and being eaten at each

trophic levels.

•The food web become more complicated because of variation in taste

and preference, availability and compulsion and several circumstancial
factors.
Importance of Food Web
•Food web are quite important in maintaining the ecosystem
stability.
E.g. In a grassland if the population of rabbit decreases, the
number of alternative host such as mouse will increase.

•Food webs with alternative food chains do not let the imbalance
occur and in this way play a vital role in the maintenance of the
stability of the ecosystem.
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 Common Features of
Food Web
1. The mean proportion of top predators,
intermediate species and basal species
remains nearly constant in webs of
widely differing species diversity.
2. Linkage density is about constant for
webs with few species but can increase
with increase in species diversity.
3. The lengths of common food chains
for top predators are very commonly 2
or 3.
4. Species at higher trophic levels have
more prey and fewer predators than
those at lower levels.
5. Webs having small numbers of species
commonly have internal overlaps in the
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predators use of prey species.
Ecological Pyramids
Less Energy
• The concept of Ecological pyramids was given by ecologist

Charles Elton.

• Ecological pyramids are the graphical representation of the

trophic structure of ecosystem.
• It shows the relationship between the living organisms
present at different trophic levels.
• Trophic levels are the feeding position in a food chain such
as primary producers, consumers and decomposers.
• Most ecological pyramids are large at the base and narrow
More Energy
at the top.
• This is because every time that an organism is eaten by the
next trophic level, some of the energy is lost as heat.

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 Pyramid of
Number

Types of
Pyramid of
Ecological
Biomass
Pyramids

Pyramid of
Energy
 PYRAMID OF NUMBER PYRAMID OF BIOMASS PYRAMID OF ENERGY
• The number of organisms in each • This indicates the total amount of dry • Thepyramidofproductivity
trophic level is considered as a level in organic matter present at each trophic looksatthetotalamount of
the pyramid. level. energypresentateachtrophiclevel,aswe
• Inanuprightpyramidofnumber,thenu • Biomass= mass of each individual llasthelossof
mberoforganismsgenerallydecreasesfr x number of individual at each energybetweentrophiclevels.
omthebottom trophic level. (measured in grams, • Thispyramidshowsthat
totop.Thisgenerallyoccursingrassland kg etc) energyistransferredfrom lower trophic
andpondecosystemswheretheplants(u • Forinstance,apyramidofbiomassisade levelswithmoreamountofenergy(prod
sually the grasses)occupy piction of theamountoffood ucers)tohigherones(consumers)andco
thebaseofthepyramid.Thesucceedingl availableandhowmuchenergyisbeing nvertedinthebiomass.
evelsofthepyramidincludetheconsum passed on at each trophic level. • ThispyramidisbasedonLindeman’sTen
ers. • Mostthebiomassthatanimalsconsumei PercentLaw,whichstatesthatonly
• Aninvertedpyramidofnumber,ontheot susedtoprovidetheenergy,convertedto about10%
herhand, new tissues,orjust remainundigested. oftheenergyinatrophiclevelwillgotowa
isjusttheoppositeoftheformer.Itisusua rdscreatingbiomass.
lly observedintreeecosystemswith • Pyramid of energy always remain
thetreesas upright in all the ecosystems.
theproducersandtheinsectsasconsum
ers.

✔ The number and biomass of organisms at any trophic level depend on the rate at which food is being
produced. 20
PYRAMID OF NUMBER PYRAMID OF ENERGY

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PYRAMID OF BIOMASS

AQUATIC ECOSYSTEM GRASSLAND ECOSYSTEM

Presentation title 22
Functions
of
Ecosystem
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Functions of Ecosystem

•The functions of the ecosystem are as follows:

✔It regulates the essential ecological
processes, supports life systems and renders
stability.
✔It is also responsible for the cycling
of nutrients between biotic and abiotic
components.
✔It maintains a balance among the various
trophic levels in the ecosystem.
✔It cycles the minerals through the biosphere.
✔The abiotic components help in the synthesis
of organic components that involve the
exchange of energy.

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So the functional units of an ecosystem or functional components that work together in an
ecosystem are:

Productivity – It refers to the rate of biomass production.

The productivity of an ecosystem is the rate at which solar energy is fixed by the vegetation of
the ecosystem; it is further classified into primary productivity, secondary productivity and net
productivity.

Energy flow – It is the sequential process through which energy flows from one trophic level to
another. The energy captured from the sun flows from producers to consumers and then to
decomposers in a unidirectional manner and finally back to the environment.

Decomposition – It is the process of breakdown of dead organic material. The top-soil is the
major site for decomposition.

Nutrient cycling – In an ecosystem nutrients are consumed and recycled back in various forms
for the utilisation by various organisms.

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PRODUCTIVITY
Productivity is of the following types-
a) Primary Productivity: Green plants fix solar energy and accumulate it in the organic forms as chemical
energy. It is the first and the basic form of energy storage.
The rate at which the energy accumulate in the green plants is known as primary productivity.
It is expressed in terms of weight energy (kcal m^2).

b) Secondary Productivity: The rate at which heterotrophic organisms resynthesise the energy yielding
susbstances is called secondary secondary productivity.
Secondary productivity actually remains changing, i.e., keeps on moving from one organisms to another
organisms.

c) Net Productivity: It refers to the rate of storage of organic matter not used by consumers or heterotrophs
and is thus the rate of increased of biomass of the primary producers which has been left over by the
consumers.

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ENERGY FLOW
The energy flow in an ecosystem works on law of thermodynamics i.e.
• First law :- energy may be transformed from one form to another but it can neither
be created nor be destroyed.
• Accordingly, light is a form of energy and it can be transformed into heat, work or potential
energy of food depending upon the situation.

• Second law:- No process involving an energy transformation will occur spontaneously unless
there is a degradation of energy from a concentrated to a dispersed form.
• It explains that the energy flows from a region of high concentration to lower one and work is
performed through degradation of energy.
• It is this process that the living organisms use in metabolism.

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 The Ten Percent Law

• The concept was introduced by

Raymond Lindeman.

• According to this law, during the

transfer of energy from organic food
from one trophic 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.

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 DECOMPOSITION
The important steps in the process of decomposition are:

1. Fragmentation: Detritivores (e.g., earthworm) break down detritus into smaller particles. This process is
called fragmentation.

2. Leaching: Leaching is the normal mechanism by which water-soluble compounds from soil or waste are washed
out.

The fragmented particles may contain a lot of water-soluble nutrients which are inorganic in nature. These nutrients
get dissolved in the water and seep into the soil and get precipitated in the process of leaching.

4. Catabolism: Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is
carried out by various fungal and bacterial enzymes

5. Humification: It is the process of formation of a dark-coloured layer of amorphous substance on the soil called
humus. It cannot be decomposed easily as it is highly resistant to the action of microbes. The layer of humus is
very rich in nutrients as it provides high fertility to the soil.

6. Mineralization: It is the final step in the process. The humus is further degraded by some microbes and release of
inorganic nutrients occur by the process known as mineralisation.
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 ECOLOGICAL
SUCCESSION
“Ecological succession is a series of changes that occur
in an ecological community over time.”

The term coined by “Hult”.

❖Ecological succession is the steady and gradual change

in a species of a given area with respect to the changing
environment.

❖The ultimate aim of this process is to reach equilibrium in

the ecosystem.

❖It ends in a stabilized ecosystem in which maximum

biomass and symbiotic function between the organisms
are maintained
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 TYPES OF SUCCESSION
1. Primary Succession:
• Type of succession that occurs where there was no
• ecosystem before.
• Occurs on rocks, cliffs, and sand dunes.
• Primary succession is very slow.
• Begins where there is no soil.
• Takes several hundred years to produce fertile soil Lichen colonization

• naturally.
• First species to colonize bare rock would be bacteria and lichens.
2. Secondary Succession:
More commonly
• Occurs on a surface where an ecosystem has previously existed.
• Occurs on ecosystems that have been disturbed or disrupted by
humans, animals, or by natural processes such as storms, floods, 31
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GENERAL PROCESS OF ECOLOGICAL SUCCESSION

Pioneer Community

• Pioneer Community : The first SeralStage 1

development of community is called a
pioneer community.
SeralStage 2
• Sere : The whole series of communities
which develop in a given area is called
sere. SeralStage 3
• Climax Stage/ Community : The final
or last stage of succession is called as
SeralStage 4
climax community.
• The intermediate stages are known as
seral stages or pioneer stages . Climax Community
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 PROCESS OF ECOLOGICAL SUCCESSION
• Development of a bare
area (an area without
Nudation
any life form)
• Causes: Disaster, Biotic
• New species reaches
the newly created
Invasion bare area and then
try to establish there.

Migration: The transfer of survival of fit individuals

Competition
species from one area to a
new area by air, water and & Co-action
animals, is called migration • Comprises of modifications in the
environment through the influence
Ecesis: The adjustment followed by of living organism present on it.
the establishment of a migrated Reaction
• Reaction leads to the changes in soil,
species into the new area known as
water, light and temperature of the
ecesis.
area.
• This is the stable community called
Aggregation: Final stage of
Stabilization the climax community.
invasion. As a result of becomes
(Climax) • longer The final more or lesscommunity
or terminal stabilized for
reproduction number of period of time.
species increases and they • Climax community is determined 34 by
grow close to one another.
the climate of the region.
 CLASSIFICATION OF SUCCESSION
The primary and secondary succession are mainly of
following types:

1. Hydrosere: beginning in
the aquatic environment
• Hydrosere: beginning on
the fresh water
• Halosere: beginning on the
salty habitat.
• Originated in water body.
• Planktons will be pioneer
community
• Forest will be climax
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community
1. Xerosere : beginning in xeric or dry habitats.
• Lithosere : beginning on the rock surface.
• Psammosere : beginning on the sandy habitats.
• Plant succession which occurs in areas limited by water availability.

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 BIODIVERSITY
✔Biodiversity term was coined by E.O. Wilson
✔The Biological diversity term was coined by
Thomas Lovejoy.
✔Biodiversity defined as “the variability
among millions of species of plants,
animals and microorganisms; the gene
they contain and the intricate ecosystem
they help to build into the living
environment”.
✔Biodiversity is earth’s primary life support
system and is a precondition for human
survival.

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 Types of Biodiversity
1. Genetic Diversity: Genetic diversity refers to
the variation of genes that occur within the species,
may be in the genes or entire chromosomal
structure.

2. Species Diversity: Species diversity refers to

the diversity within the population or between
different species of a community or an ecosystem.

3. Ecosystem & Community Diversity:

Community or ecosystem diversity refers to the
number of ecological niche, various ecological
processes and variety of trophic levels that sustain
food chain, food webs and recycling of nutrients.

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Genetic Diversity
•It refers to the total genetic information
contained in the genes of individual of
plants, animals and microorganisms.

•The genes found in organisms can form

enormous number of combinations each
of which gives rise to some variability.

•When the genes within the same species

show different versions due to new
combinations, it is called genetic
variability.

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 Species Diversity
❑Species diversity is the diversity between
different species. The sum of varieties of
all living organisms at the species level is
known species diversity.

❑Species richness is the simplest measure

of biodiversity and is simply a count of
the number of different species in a
given area.

❖Plant Species: Apple, Mango, Wheat

❖Animal Species: Lion, Tiger, Elephant, Deer

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Community or
Ecosystem Diversity
•The diversity at the
ecological or habitat level
is known as ecosystem
diversity.

•A large region with

different ecosystem can
be considered as
ecosystem diversity.
•e.g., River Ecosystem,
Forest ecosystem 41
Threats to Biodiversity
Habitat loss
& Over Exotic
Fragmentatio Exploitation Species
n

Hunting
Climate
Pollution &
Change
Poaching

Diseases Man-Wildlife
Tourism
Outbreak Conflict
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Methods of Conservation
There are two methods of conservation of biodiversity.
(a.) In-situ conservation (within habitat)
(b.) Ex-situ conservation (outside habitats)

In-situ Conservation: In-situ conservation of biodiversity is the conservation of species within their
natural habitat.
In this method, the natural ecosystem is maintained and protected.
The in-situ conservation has several advantages.

Following are the important advantages of in-situ conservation:

1. It is a cost-effective and convenient method of conserving biodiversity.
2. A large number of living organisms can be conserved simultaneously.
3. Since the organisms are in a natural ecosystem, they can evolve better and can easily adjust to
different environmental conditions.
Certain protected areas where in-situ conservation takes place include national parks, wildlife
sanctuaries and biosphere reserves.

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Ex-situ Conservation: Ex-situ conservation of biodiversity involves the breeding and
maintenance of endangered species in artificial ecosystems such as zoos, nurseries, botanical
gardens, gene banks, etc.
There is less competition for food, water and space among the organisms.

Ex-situ conservation has the following advantages:

1. The animals are provided with a longer time and breeding activity.
2. The species bred in captivity can be reintroduced in the wild.
3. Genetic techniques can be used for the preservation of endangered species.

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 THANK YOU
MARGI GREWAL
margi.grewal@poornima.edu.in

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