NOTES

Ecosystem

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 Key Takeaways

Types of ecosystem 1

Based on location

Based on human
interference

2 Ecosystem components

Abiotic

Biotic

Ecosystem structure 3

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 Ecosystem functions 4

Productivity

Decomposition
5 Food chain
Nutrient cycling
Grazing food chain
Energy flow
Detritus food chain

Food Web 6

7 10% law

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 Ecological pyramids 8

Pyramid of numbers

Pyramid of biomass
9 Ecological successions
Pyramid of energy
Primary succession

Nutrient cycle 10 Secondary succession

Carbon cycle

Phosphorus cycle
11 Ecosystem services

Summary
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 Ecosystem
 Ecosystem is the functional unit of nature.
 The term was coined by A.G. Tansley.
 It is self-sustainable.
 Organisms interact and use available resources, such as
food, space, light, heat, water, air and shelter to survive.
 Each population of organisms and the individuals within
it interact in limited specific ways wherein they can
derive benefit from other organisms.
 Interactions between different organisms are numerous
and are described according to their positive
(beneficial), negative or neutral effect on each other.
 The interactions between living things and their non-
living counterparts in the environment make up a total
ecosystem.
 Entire biosphere (global ecosystem) = sum of all local
ecosystems.

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 Types of Ecosystem
 There are 2 types of ecosystem based on location:

Terrestrial

Land ecosystem
Aquatic

Water ecosystem

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 Types of Ecosystem

Man-made/Anthropogenic
Natural ecosystem
ecosystem

Develops in nature without Created and maintained by

human interference human beings
Terrestrial Aquatic

Forest Pond Aquarium Crop fields Garden

Desert

Grassland Ocean

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 Did You Know!

 Agriculture or agroecosystem is the first and largest

man-made ecosystem.
 It was formed for fulfilling the needs of the increasing
human population.

Agricultural crop fields

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 Components of Ecosystem
 Ecosystem is made up of biotic and abiotic components.

Biotic Abiotic
components Ecosystem components
All living Physical
organisms environment
of living
organisms

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 Components of Ecosystem

Temperature

Water

Abiotic factors

Light

Soil

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 Components of Ecosystem
Biotic factors

Producers Consumers Decomposers

Primary consumer/ Secondary consumer/ Tertiary consumer/

First order consumer Second order consumer Third order consumer
 Feeds directly on  Feed on herbivores  Feed on secondary
producers  Also called primary consumers
 Also called herbivores carnivores  Also called secondary
 Ex - grasshopper, cow,  Ex - spiders, lizards, carnivores
tadpoles, molluscs hydra, frog  Ex - snake, large fishes

Top carnivore
 Not eaten by any other organism
Note:  Can exist at any level
 E.g. - tiger, lion, panthers, peacock

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 Components of Ecosystem
Producers Decomposers
 Green photosynthetic plants  Saprophytic microorganisms
 Also called  Also called reducers as they are
autotrophs/transducers/con capable of decomposing dead
verters organisms
 Producers in terrestrial  Functions -
ecosystem - herbaceous, o Brings about cyclic exchange of
woody plants minerals between biotic and
 Producers in aquatic abiotic elements
ecosystem - phytoplankton, o Naturally replenishes soil with
algae, submerged plants minerals

Complex organic substrates Inorganic

compounds Process of
decomposition
Simple organic substrates

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 Components of Ecosystem
The interaction of biotic and abiotic components results in physical
structure that is characteristic for each type of ecosystem.

Abiotic factors

Biotic factors

Physical structure

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 Structure of Ecosystem

Species composition
Physical structure
of ecosystem
Stratification

 Physical structure of ecosystem includes species

composition and stratification.

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 Structure of Ecosystem
Species composition Stratification
 Identification and listing of  Vertical distribution of species at
plants and animals in an different levels
ecosystem.  E.g. - Following subdivision are
 Based on geography and present in a forest
climate – it differs from one o Top layer - Trees
ecosystem to another.
o Second layer - Shrubs
o Bottom layer - Grasses and
herbs

Coral reef Grassland

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 Function of Ecosystem Components

Productivity - Synthesis of organic matter by producers

Decomposition - Degradation of dead organic matter

Nutrient cycling - Cycling minerals and nutrients

Energy flow – Sequential process of movement of energy

through the ecosystem

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 Function of Ecosystem Components
Productivity
(Rate of biomass production)

Primary Secondary
productivity productivity

 Rate at which biomass is  Rate of formation of

produced by producers during new organic matter
photosynthesis per unit area by consumers
over a time period
 Expressed in terms of weight
as (gm/m2)/yr
 Expressed in terms of energy
as (kcal/m2)/yr

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 Productivity
Primary productivity is
divided into:

Gross primary Net primary

productivity (GPP) productivity (NPP)

 It is rate of production of  It is the organic matter

organic matter during available for consumption
photosynthesis. by the heterotrophs.
 Plants use some of the GPP in  GPP – R = NPP
respiration (R).  R = Respiratory loss

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 Productivity
Factors affecting primary
productivity

Photosynthetic Solar radiation

Soil moisture
capacity of producers available

Availability of
Temperature
nutrients

Reasons for low primary productivity of deep marine habitats

 Low light which decreases further with depth
 Limited nutrients - Most limiting nutrient of the marine
ecosystem is nitrogen

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 Productivity

Some important terms

 Community productivity = It is the rate of net synthesis and build up of organic

matter by a community per unit time and area
 Ecological efficiency = Energy converted into biomass at trophic level X 100
Energy present in biomass at lower trophic level
 Photosynthetic efficiency = Gross primary productivity X 100
Incident total solar radiation
 Net production efficiency = Net primary productivity X 100
Gross primary productivity

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 Did You Know?
Total biosphere productivity is
approximately 170 tons

Terrestrial Aquatic

Productivity is Productivity is
115 billion tons 55 billion tons

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 Decomposition

 The process of breaking down complex organic matter into

simpler compounds like nutrients, minerals, carbon dioxide and
water is known as decomposition.

 The complex materials are the dead plant remains such as leaves,
bark, flowers and dead remains of animals, including faecal matter.

 The complex materials constitute detritus, which is the raw

material for decomposition.

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 Decomposition - Fragmentation
 Decomposition occurs in a stepwise manner starting from fragmentation.

 The detritivores like earthworms, small insects etc., feed on the detritus
(dry leaves) and break them down into smaller particles. This process is
known as fragmentation.

Detritus
Earthworm

Fragmentation

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 Decomposition - Leaching
 Water soluble inorganic nutrients go down into the soil horizon and
get precipitated as unavailable salts. This process is called leaching.

Detritus

Fragmentation

Leaching

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 Decomposition - Catabolism
Fungal, bacterial enzymes act on the detritus to degrade it into
simple inorganic substances. This is catabolism.

Detritus

Fragmentation

These three
Leaching processes occur
simultaneously.

Catabolism

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 Decomposition - Humification
 During decomposition, accumulation of dark amorphous substance (as a thin
layer) is called humification. The dark substance formed is called humus.

Nutrient rich

Catabolism Colloidal in nature

Humus
Highly resistant to
Humification microbial action

Extremely slow rate of

decomposition

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 Decomposition - Mineralisation

 Humus is further degraded by action of microbes.

 It releases inorganic substances from humus.

Hence, this process is known as mineralisation.

Catabolism

Humification

Mineralisation
Mg N H2O
Cu
H2O Fe
Ca

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 Decomposition
Some are eaten by insects and
A tree grows in the soil other animals. Nutrients and
energy enter food web. Detritus

A green leaf falls Fragmentation

to the ground

Leaching
Leaves partially consumed Some nutrients
by decomposers such as leach into soil by
fungi and bacteria. They chemical action
begin to lose form and
become litter Catabolism

Further, Humification
decomposition by
earthworms,
bacteria, soil, mites,
fungi, etc. Mineralisation
Organic rich soil

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 Decomposition

Nutrient immobilisation

 Phenomenon in which inorganic nutrients in the soil are taken up by

microbes in soil and converted into organic form by incorporation of
nutrients in living microbes

 Immobilised nutrients become available again for solubilisation after

the death of microorganisms

 Immobilisation protects nutrients from being washed out and lost

from ecosystem

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 What Affects Decomposition?
1. Climatic condition: Temperature, moisture

Rate of decomposition is Rate of decomposition is

slower in cold and dry faster in warm and moist
conditions. conditions.

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 What Affects Decomposition?
2. Aerobic and anaerobic conditions

Rate of
decomposition is
faster in presence
of oxygen.

Rate of
decomposition is
slower in absence
of oxygen.

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 What Affects Decomposition?
3. Chemical composition of detritus

If chitin, lignin,
tannins and cellulose
are present in the
detritus, the rate of
decomposition is
O
OH slow.
NH
O HO
O H
HO O
HO O If water-soluble
NH substances like
O OH n sugars, nitrogenous
compounds etc., are
Chitin present in the detritus,
the rate of
decomposition is
quicker.

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 Nutrient Cycling

Movement of nutrient elements through

various components of an ecosystem is also Nutrient cycles are of
known as nutrient/ biogeochemical cycle. two types

Biogeochemical cycle
Gaseous cycle Sedimentary cycle

Have reservoir in Have reservoir in

the atmosphere the earth’s crust
Living Rocks, air Chemical E.g.- Carbon, oxygen E.g.- Phosphorous
organism and water processes and nitrogen cycles and sulphur cycles

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 Nutrient Cycling
The function of the reservoir is to meet the deficit which occurs due
to imbalance in the rate of influx and efflux of nutrients.

Reservoir
Factors affecting nutrient release

Efflux Influx

Soil Moisture pH Temperature

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 Energy Flow
 It is a sequential process of the movement of energy through a
series of organisms in an ecosystem.
 Sun is the only source of energy common to all ecosystems on
Earth, except for deep sea hydrothermal vents.

Incident solar radiation (100%)

Photosynthetically active radiation Absorbed by

(PAR) (Less than 50%) gases/water vapours; reflected by
clouds; scattered by dust particles
Energy loss (45-49%) (More than 50 %)

Captured in photosynthesis
(GPP) (1-5%)
Respiratory loss (0.2-1%)

NPP (0.8-4%)
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 Sun-Source of Energy
 50 per cent of all the sun’s radiation is Photosynthetically Active
Radiation (PAR)

2-10% of PAR

PAR

Only 2-10% of PAR is captured by

plants and photosynthetic bacteria

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 Energy Flow

 Energy from plants is transferred to other organisms.

 Energy flow in an ecosystem is always unidirectional.
 Herbs, shrubs and woody plants act as producers.
o Green plants of the ecosystem are producers.
o Examples:
▪ Forest ecosystem: Trees
▪ Aquatic Ecosystem: Phytoplanktons

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 Energy Flow
 All other organisms depend on plants (directly or indirectly) for their food needs.

 Hence, they are called consumers and heterotrophs.

o Herbivores are primary consumers.
▪ Animals that feed on producers
▪ Example:
Terrestrial system: Insects, birds, deer etc.
Aquatic system: molluscs, clams etc.
o Primary carnivores are secondary consumers.
▪ Animals that feed on herbivores (indirectly feed on plants).
▪ Example: Fox feeding on deer.
o Secondary carnivores are tertiary consumers.
▪ Animals that feed on primary carnivores (indirectly depend on plants).
▪ Example: Tiger feeding on fox.

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 Food Chain
 Chronological (organisms arranged order) series of organisms each
depending on other for food.
 Each level in a food chain where transfer of energy takes place is
called trophic level.
 Organisms of a trophic level depend on the organisms at the lower
trophic level for their energy demands.

Types of food chain

Grazing food chain/ Detritus food chain/ Parasitic food chain/

Predator food chain Saprophytic food chain Auxiliary food chain

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 Food Chain – Trophic levels

4th trophic Top carnivores

level (Tertiary consumers)

3rd trophic Carnivores

level (Secondary consumers)

2nd trophic Herbivores

level (Primary consumers)

1st trophic
level Producers

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 Food Chain – Trophic levels

1st trophic
level

Fresh weight Dry weight

 Biomass expressed in fresh or

dry weight
 Fresh weight is weight
recorded immediately
after the organism dies
or part of an organism is
Total biomass (mass of
harvested.
organic matter) of
producers in a unit area =  Dry weight is the weight
standing crop of producers of the organism or part of
the organism after it has
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 Food Chain – Trophic levels

Standing crop of 4th

trophic level

 Standing crop refers

to amount of living
Standing crop of 3rd matter present in
trophic level different trophic
levels at a given time
 Expressed in numbers
Standing crop of 2nd or biomass of
trophic level organisms per unit
area

Standing crop of 1st

trophic level

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 Grazing Food Chain

Primary Secondary  As an organism

consumer consumer consumes another
organism, the energy
produced by
Deer Fox producers is passed
on to next organism.
Grazing Food
Chain (GFC)  Energy is gained from
photosynthesis.
 Such a food chain is
Tertiary known as grazing
Producer consumer food chain.

Plants Tiger

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 Grazing Food Chain

Grazing food chain (GFC) examples:

 In aquatic ecosystem, GFC is major conduit of energy flow.

Primary Secondary Primary Secondary

consumer consumer consumer consumer

Rodent Snake Clams Fish

Tertiary Tertiary
Producer Producer
consumer consumer

Grains Hawk Phytoplankton Shark

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 Detritus Food Chain

 Food chain where

Bacteria energy is obtained from
and fungi Detritivores
dead organic matter
 Begins with dead
organic matter,
Decomposers Earthworm
followed by
Detritus food decomposers,
chain (DFC) detritivores and then
their predators
 In terrestrial
Dead
ecosystems, a much
organic Sparrow
larger fraction of energy
matter
flows through DFC than
through GFC.
Predators

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 Detritus Food Chain

1st 2nd 3rd 4th 5th 6th

trophic trophic trophic trophic trophic trophic
level level level level level level
 Energy is lost in DFC as
well.
Heat Heat Heat Heat Heat
 Example:
o Plants die without
being consumed by
20,000 kJ 2,000 kJ 200 kJ 20 kJ 2 kJ 0.2 kJ
animals.
o Their biomass is not
passed onto next
Heat Heat Heat Heat Heat Heat consumer.
o Decomposition of
waste/dead matter
leads to loss of energy
in the form of heat.

Decomposers

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 Detritus Food Chain

Decomposers

 Decomposers are heterotrophic.

 They are also known as saprotrophs
(sapro = to decompose).
 They meet their energy and Bacteria
nutrient requirements by degrading dead
organic matter.
 When an organism dies, decomposers Fungi
secrete digestive enzymes that
Earthworm
breakdown dead and waste materials
into simple, inorganic materials.
 They are subsequently absorbed by the
decomposers.

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 Detritus Food Chain

Decomposers

Earthworm (Detritivore)

The earthworm, which is a Earthworms are eaten by small

detritivore, feeds on such birds such as sparrows.
bacteria, fungi and further
decomposes detritus.

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 Food Web

 An animal may be
Bear eaten by different
animals and thus,
Hawk different food
chains get
interconnected,
Fox and one animal
may be a link in
Fish Snake more than one food
Rodent chain.
 Bear, fish,
deer, fungi etc., are
Clams such organisms
Deer Sparrow that lead
to interconnection
of food chains.

Fruits
Fungi Earthworm
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 Food Web
Food web is a network of food chain interconnected to each other.
 Food web is more real than food chain.

o E.g. - Jackals are both carnivores and scavengers

o E.g. - Sparrow is a primary consumer when it eats seeds but

secondary consumers when it eats insects and worms

 Food Web is essential for the stability of an ecosystem.

 Provides opportunity for the endangered prey to recover its number.

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 10% Law
 At every stage of organism's lifecycle, energy
is lost to environment.
 Example:
o Excretion
o Respiration
Heat
Heat

Energy flow in ecosystem follows

1st law of thermodynamics

It states that energy can neither be created nor

destroyed, only altered in form.

Energy is always conserved.

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 10% Law
 Energy flow in the ecosystem follows the 2nd law of thermodynamics.
o It states that whenever energy is converted from one form to
another, there is a tendency toward disorder (entropy) in the
system or some of the energy is lost to environment.
 Thus, energy is lost to environment when it moves from one trophic
level to other.

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 10% Law

20,000 kJ 2,000 kJ 200 kJ 2 kj 20 kJ 0.2 kJ

1st trophic 2nd trophic 3rd trophic 4th trophic 5th trophic 6th trophic
level level level level level level

10% Law

 10 percent of the energy is transferred to each

trophic level from the lower trophic level

 Proposed by Lindeman in 1942

 Consequently, an ecosystem can support only a

limited number of trophic level (3-5)
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 Ecological Pyramids
 It is the graphical representation of ecological parameters at
the successive trophic levels of a food chain.

Number of individuals

Biomass

Energy

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 Ecological Pyramids
 To constructs the ecological pyramids, all organisms
at that trophic level should be included.
 Trophic level represent functional levels.
 One organism can occupy more than one trophic
level simultaneously.

Sparrow as secondary consumer when it eats insect

Sparrow as primary consumer when it eats seed, fruit, etc

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 Ecological Pyramids

01
Pyramid of numbers

Pyramid of biomass
02

Pyramid of energy 03

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 Ecological Pyramids
Pyramid of numbers

Upright

Trophic levels Number of individuals

Tertiary consumers (TC) 3

Secondary consumers (SC) 354,000
Primary consumers (PC) 708,000
Producers (P) 5,842,000
Pyramid of number in grassland ecosystem

 The number of top carnivores is too small to support any other

trophic level and they do not act as prey for any other organism.

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 Ecological Pyramids
Pyramid of numbers

 There are exceptions to this

Trophic levels Upright generalization:

o If the number of insects

feeding on a big tree are
Large birds (TC) counted, then inverted
Small birds (SC) pyramid is obtained.

Insects (PC) o The number of small birds

depending on the insects are
One big tree (P) less and the number of larger
birds eating the smaller birds
Inverted are few, then upright
Pyramid of number on a pyramid is obtained.
big tree ecosystem

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 Ecological Pyramids
Pyramid of biomass

Upright

Trophic levels Dry weight (Kg m-2)

Tertiary consumers (TC) 1.5

Secondary consumers (SC) 11
Primary consumers (PC) 37
Producers (P) 809
Pyramid of biomass in forest ecosystem

 Pyramid of biomass in terrestrial ecosystems is usually upright.

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 Ecological Pyramids
Pyramid of biomass

 However, a different shape of

the pyramid of biomass can be
Inverted
Trophic levels seen in aquatic habitats

o The pyramid of biomass in

Large fishes (TC) sea is generally inverted
because the biomass of
Small fishes (SC)
fishes far exceeds that of
Zooplankton (PC) phytoplankton.

o The producers are very

Phytoplankton (P)
small and have limited
biomass, they also
Pyramid of biomass in aquatic ecosystem reproduce and die quickly.

o So, there is less biomass of

producers at any given time
compared to consumers.
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 Ecological Pyramids
Pyramid of energy

 Pyramid of energy is always upright, it can never be inverted,

because when energy flows from a particular trophic level to the next
trophic level some energy is always lost as heat at each step.

 Primary producers convert only 1% of the energy in the sunlight

available to them into NPP.

 Each bar in the energy pyramid indicates the amount of energy

present at each trophic level in a given time or annually per unit area.

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 Ecological Pyramids
Pyramid of energy

Always
Upright

Trophic levels Energy (J)

Tertiary consumers (TC) 10

Secondary consumers (SC) 100
Primary consumers (PC) 1000
Producers (P) 10,000
Pyramid of energy in any ecosystem

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 Limitations of Ecological Pyramids

1 2 3

Does not account

Does not No place in
for same species
accommodate ecological
belonging to more
food web; assumes pyramids for
than one trophic
simple food chain saprophytes
level

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 Ecological Succession
 It is the gradual and fairly predictable changes in the species
composition of a given area.
 This change is orderly and sequential.
 Succession and evolution are ideally parallel processes.

Based on area of origin

Primary succession Secondary succession

It occurs in an area It occurs in an area where

which has been bare natural biotic communities
from the beginning. have been destroyed.

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 Primary Succession
Succession starts in an area where there are few or no living organisms (barren area).
 Newly exposed sea floor
 Newly cooled lava sediments
 Newly created pond or reservoir
 Bare rock

Pioneer species is the first biotic community which develops in a bare area.
E.g. - Lichens on rocks, phytoplankton and zooplanktons in a new pond.

Bare area with Grasses and small Bigger plants

only rocks plants begin to begin to appear
appear
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 Primary Succession
Sere Seral stage/Community
 It is the entire sequence of  They are the individual transitional
communities that communities.
successively change in an  Following things occur during
area. E.g. bryophytes, herbs, different seral stages:
shrubs, on a bare rock.
o Diversification of species
o Increase in number of species
o Increase in total biomass

Bigger plants begin to appear Trees begin to appear

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 Climax Community

It is the last community that forms as a result of

ecological succession which is relatively stable and
is in near equilibrium with the environment.
E.g. : Forests

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 Secondary Succession

Secondary succession is recolonization of habitats (of plants and animals)

after major disturbances like:

Abandoned farmland Flooded land

Deforested land Forest fire

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 Secondary Succession
 After disturbances, all the vegetation is lost, only soil is left.
 Small plants like grasses slowly start growing here.
 Later, bigger plants like shrubs appear.
 With time, trees appear to reach the climax community.
o Example : Forest

Grasses and Bigger plants Climax

small plants begin to appear community
begin to appear

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 Ecosystem characteristics that
Change During Succession
• Change in diversity of species - Some species colonise an area and
their populations become more numerous, whereas populations of
other species decline and even disappear
• Little diversity to high degree of diversity - Increase in the number
of species
• Total biomass increases
• Increase in humus content of soil
• Aquatic or dry conditions to mesic conditions - Both hydrarch and
xerarch successions lead to medium water conditions (mesic),
neither too dry (xeric) nor too wet (hydric)
• Vegetational changes - This in turn affect food and shelter for
various types of animals.
• Thus, as succession proceeds, the number and types of animals and
decomposers also change

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 Xerarch Succession
Stage I - Lichen stage
 Lichen are symbiotic association of (algae)
photobionts and mycobionts (fungi).
 They are pioneer species.
 They can tolerate desiccation, excessive
heat and cold temperatures.
 They secrete acids to dissolve rock to form Bare rocks without water
soil. This process is called weathering.

Stage II - Moss stage

 Mosses help in further weathering as
their rhizoids can penetrate deeper.
 This leads to accumulation of more soil
and organic matter which can retain
more moisture. Growth of moss on rocks

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 Xerarch Succession
Stage III - Grass stage
 The roots of grasses penetrate the
rocks and contribute to weathering.
 They provide shade to small animals.
 Accumulates soil and moisture helps in
germination of seeds of annual grasses
and herbs
Growth of grass and shrubs
Stage IV - Shrub stage
 The roots of shrubs penetrate the
rocks and contribute to weathering.
 They provide shade for larger animals.

Stage V – Forest/Climax stage

 Trees begin to grow.
Forest
 The land can turn into coniferous,
deciduous or temperate forest.
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 Hydrarch Succession

Stage I - Plankton stage

 Phytoplanktons and zooplanktons are the
pioneer species.
 The death of these organisms provide
organic matter.

Stage II - Submerged plant stage Growth of phytoplanktons

 Submerged plants are rooted in the
bottom mud layer.
 The death of these organisms provide
organic matter.
 Water becomes shallower.

Submerged plants

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 Hydrarch Succession
Stage III - Submerged free-floating plant
stage
 Free floating plants provide minerals
and organic matter.
 The water becomes shallower on the
periphery.

Stage IV – Reed-swamp stage Submerged free-floating plants

 Amphibious plants start to grow.
 They transpire large amounts of water.
 They produce organic matter.
 Their tangled roots accumulate silt.

Amphibious plants

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 Hydrarch Succession

Stage V – Marsh-meadow stage

• Reed-swamp stage is invaded by marshy plants.
• Pond becomes shallower due to deposition
until it gets transformed into terrestrial habitat.

Stage VI - Scrub stage

 Shrubs can tolerate sunlight and water-logged Shrubs
conditions.
 They transpire large amounts of water.
 They add organic matters to bottom layer.

Stage VI - Forest stage

 This is the climax stage.
 Trees begin to grow.
 The land can turn into coniferous, deciduous or Forest
temperate forest.
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 Nutrients

 Organisms need a constant

supply of nutrients to grow,
reproduce and regulate various Nutrients
body functions. required to

 Numerous different nutrients

are needed to sustain life. Grow

 However, the most essential ones

are carbon, hydrogen, oxygen,
phosphorus and sulphur- in
H S O C
1 16 8 6
short also known as "CHNOPS“.
1.008 32.06 16.00 12.01
 Along with them there are Hydrogen Sulfur Oxygen Casrbon
other nutrients needed like
calcium, potassium, sodium, etc.
P N
15 15

30.97 14.01
Phosphorus Nitrogen

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 Standing State
The amount of nutrients such as carbon, nitrogen, phosphorous, calcium, etc.,
present in the soil at any given time, is referred to as standing state.
 The amount of nutrients vary in different kinds of ecosystem.
 The amount of nutrients vary on a seasonal basis.

Pond Grassland Desert

Ocean Forest
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 Gaseous Cycles
Carbon cycle

 Carbon is important element found in all the living beings.

 Carbon constitutes 49% dry weight of organisms.

 Carbon cycle occurs through Atmosphere

(Reservoir)
atmosphere, ocean and through
living and dead organisms.
 Atmosphere is the reservoir for Living organisms
gaseous nutrient cycle.
Ocean

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 Gaseous Cycles
Carbon cycle

 Carbon is present in atmosphere in the form of carbon dioxide.

 Only 1% of the global carbon is found in the atmosphere.
 71% of carbon is present in dissolved form in the ocean.
 Some of the remaining carbon dioxide is captured by plants.

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 Gaseous Cycles
Carbon cycle

 Carbon from atmosphere reaches plants in the form of carbon dioxide

which is converted to glucose by photosynthesis.
 Animals get the required carbon through plants.
o Primary consumers like deer feed on plants to get the carbon.
o Carnivores like tiger feed on deer.
 When these animals and plants die,
CO2 in atmosphere
decomposers release carbon.
 Decomposers act on decomposing Photosynthesis
Burning of forest fuelwood
and organic debris
(terrestrial food chain)
and decaying matter, further
contributing to the release of
carbon dioxide.
Detritus food chain Coal
 Carbon is released back as Carbon Oil and Gas

dioxide majorly through respiratory

Limestone and Dolomite
activities of producers and
consumers.
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 Gaseous Cycles
Carbon cycle

 In addition to the above, burning of wood, forest fire and combustion of organic
matter, fossil fuels, volcanic activity are other sources which release carbon
dioxide into the atmosphere.
 Carbon cycle’s part on land ends here. Carbon cycle occurs through oceans as well.

CO2 in atmosphere

Burning of forest, fuel, wood

Photosynthesis
and organic debris
(terrestrial food chain)

Burning wood Volcanic activity

and fossil fuels
Detritus food chain Coal
Oil and Gas

Limestone and Dolomite

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Forest fires
 Gaseous Cycles
71% of global carbon is
found dissolved in
Carbon cycle
oceans
 In oceans, carbon dioxide is captured by underwater plants,
seaweeds and phytoplankton.
 These producers are eaten by smaller fishes, which in turn
71% of
are eaten by larger fishes.
global
 Carbon is transferred from one organism to another when carbon
one feeds on the other.
 Some of the carbon dioxide is released back into the
atmosphere when these organisms respire.

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 Gaseous Cycles
Carbon cycle

 Further, when these organisms

die, decomposers present in the
ocean decompose them.
 Some of the carbon is released as
carbon dioxide
 Shells and skeleton of these
organisms get deposited in the deep
ocean to form calcareous sediments.
 Thus, some amount of the fixed carbon
is lost to sediments and removed from
circulation.

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 Gaseous Cycles
Complete carbon cycle

CO2 in atmosphere

Photosynthesis
(terrestrial food chain) Burning of forests, fuel,
wood and organic debris

Respiration and
decomposition

Plankton
photosynthesis
(aquatic food chains)
Coal
Detritus food chain
CO2 in water Organic Oil and Gas
sediments

Limestone and Dolomite

Decay
organism Calcareous
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sediments
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 Carbon Cycle

CO2
 Carbon cycle maintains and balances
total amount of global carbon.
 However, human activities have
significantly affected the carbon cycle.
 Human activities have increased the rate
of release of CO2, thereby causing Total amount of global carbon
increase in the global temperature.
 For example:
o Rapid deforestation
o Massive burning of fossil fuels for
energy and transport.

Increase in global temperature

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 Carbon Cycle
CO CO
Primary 2 2 Fossil fuel combustion and
production and industrial processes
respiration

Biotic and abiotic

components Ocean

CO2 release Changing

land-use
CO2 absorption

CO2 release due to

human activities
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rights reserved
All rights reserved
 Phosphorus Cycle

 Phosphorus is another
biologically important
element.
 It is a major constituent of ATP
different biological
membranes, ATP
P
15
molecules, nucleic acids. Cell membrane Nucleic acids
30.97
 They are also required Phosphorus

in large quantities to
make bones and teeth,
as well as shells in certain
animals.

Bones and teeth Shells of certain animals

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 Phosphorus Cycle

 Rocks are major natural reservoir of phosphorus.

 Minute amounts of phosphate is released into the
soil solution when rocks undergo weathering.

POP₄
POP₄
³⁻
³⁻
POP₄ POP₄
³⁻ ³⁻
POP₄
³⁻ POP₄
³⁻

POP₄ POP₄
³⁻ ³⁻ POP₄
POP₄ POP₄ ³⁻
³⁻ ³⁻
POP₄³
POP₄ POP₄
⁻ PO₄³⁻
³⁻ ³⁻
POP₄ POP₄
³⁻ ³⁻
POP₄ POP₄
PO₄³⁻
³⁻ POP₄ ³⁻
³⁻ POP₄
³⁻ POP₄
POP₄ ³⁻ PO₄³⁻ PO₄³⁻
³⁻

Phosphorus occurs as phosphate in rocks

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 Phosphorus Cycle

 The released phosphate gets  The dissolved phosphate present in

dissolved into the soil solution the soil is absorbed by the plants.
and also get leached into
surface water.

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 Phosphorus Cycle

 Herbivores and other animals  After the animals die, they along with
obtain phosphorus by consuming other waste products are
plants. decomposed by the phosphate-
solubilising bacteria in the soil.
 Phosphate-solubilising bacteria release
phosphorous again into the soil.

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 Phosphorus Cycle

Consumers
Weathering of rock
minerals
PO₄³⁻
PO₄³⁻ Producers
PO₄³⁻
PO₄³⁻

PO₄³⁻
PO₄³⁻ PO₄³⁻

PO₄³⁻
Phosphorus in soil PO₄³⁻ Runoff
PO₄³⁻ solution PO₄³⁻
PO₄³⁻

Phosphate solubilising
bacteria act on detritus
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 Phosphorus Cycle

Consumers Producers

Phosphate solubilising Litter fall

bacteria act on detritus

Uptake
Decomposition
Phosphorus in soil solution

Runoff
Weathering of
rock minerals

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 Ecosystem Services

They are the products of ecosystem processes which are beneficial to humans.

Ecosystem
services

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 Ecosystem Services
Among the products of ecosystem processes, soil formation is the most
beneficial ecosystem service to humans.

60

50

40
Percentage of

30
service

20

10

0
Soil formation Climate regulation Habitat for wildlife Recreation

Service

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 Summary
 Ecosystem - It is the functional unit of nature which is self - sustainable.

Types of ecosystems
(based on location)

Terrestrial Aquatic

Types of ecosystems (based on

presence/absence of human interference)

Natural Anthropogenic

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 Summary

Structure of ecosystem

Producers Temperature

Consumers Biotic factors

Water

Decomposers Abiotic factors

Light

Soil

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 Summary

Energy flow

Productivity
Functional aspects
of ecosystem
Decomposition

Nutrient cycling

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 Summary
Dead remains of plant and animal
Detritus
including faecal matter

Detritivores break detritus into

Fragmentation
small particles

Soluble inorganic nutrients go

Decomposition Leaching
down into soil as salts

Degradation of detritus by fungal

Catabolism
and bacterial enzymes

Accumulation of dark amorphous

Humification substance named humus

Mineralisation Degradation of humus by action of

microbes

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 Summary

Grazing food chain Detritus food chain

Dead organic
Producer - Plant
matter

Primary
Earthworm
consumer - Deer

Secondary
Sparrow
consumer - Fox

Tertiary
Hawk
consumer - Tiger

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 Summary

Ecological pyramid

Pyramid of numbers Pyramid of biomass Pyramid of energy

 In grassland
 In forest
ecosystem, it is
ecosystem, it is  It is always
upright.
upright. upright and can
 In a big tree never be
 In aquatic
ecosystem, it is inverted.
ecosystem, it is
upright and
inverted.
inverted.

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 Summary
Based on plant habitat

Based on area of origin Xerarch succession

Primary succession Ecological succession in dry areas.

 Lichen stage
It occurs in an area which Ecological succession  Moss stage
has been bare from the  Grass stage
beginning It is the gradual and  Scrub stage
 Forest stage
predictable change in the
species composition of a
Hydrarch succession
given area.
Ecological succession in wet areas.
Secondary succession  Plankton stage
 Submerged plant stage
 Submerged free-floating plant
It occurs in an area where
stage
natural biotic
 Reed swamp stage
communities have been
 Marsh meadow stage
destroyed.
 Scrub stage
 Forest stage
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 Summary
Primary v/s Secondary succession

Primary succession Secondary succession

Occurs where natural biotic

Occurs in barren area
communities have been destroyed

Soil is absent and is formed during Some soil and microbes are
the course of succession present

Pioneer communities (initial Pioneer communities (initial

species) are migrants species) are already present

Many seral communities Fewer seral communities

are formed are formed

Takes 1000 years or more Takes 50-200 years or more

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 Summary

Carbon cycle Phosphorus cycle

Gaseous type of cycle Sedimentary type of cycle

Involves respiratory release into the Doesn’t involve respiratory release

atmosphere into the atmosphere

Atmospheric inputs of Atmospheric inputs of

carbon are higher phosphorous are much lower

Involves gaseous exchange Absorbed by plants from soil

between organism and through roots and then passed on
environment to consumers

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