..

1. F1g. D.
5.12 ECO-SYSTEM
A biotic community lives in an environment, which provides material, energy
Tquirement and other living conditions to it. "An ecological system in which the
Community and the non-living environment function together is called Ecosystem."
Ihe term Ecosystem was introduced by Sir Arthur Tansely (1935). "An
ystem is a group of biotic communities ofspecies interacting with one another
w t h their non iiving environment exchangingenergy and matter. Now ecology
ET defined as "the study ofecosystems" in other words". An ecosystem
2De defind i.e. as a structural and functional unit ofbiosphereor segment of
Consisting ofcommunityof living beings and the physical
environment both
cting and exchanging
materials between them."
cach other. This relationship is called
" h o l o c e n o s i s " .
cCosystem the biotic
communities and abiotic
environment influence
CCOSystem is a natural grouping ofnutrients,
minerals, plants animals and
astes linked together by flow of food,
nutrients and energy
from on part
astes linked
OS
y stem to another part. Thus, the ecosystem
is the smallest units of
Te that has all the characteristic to sustain life. Pond stream, seas, deserts,
d s etc. are all examples of ecosysteim.
of the sy
wsphere
239

2. An ecosystem may be natural (e.q.
forest, grassland lake et
(eg. on aquaria, crop
field etc.) temparary
(rainted pond) or permar
forestetc.)or
terrestrial (e.g. grassland,
torest etc.). The aquatic.
be either fresh water (e.g. ponds,
lakes,
streams) or salt water
em
estuaries type) Fig.5.13
(1) Natural Ecosystem:
These systems perate by themselves un
natural eonditions without any major
interrererance Dy man. These aro e
divided into:
5.13 TYPES OF
ECOSYSTEM
or man made
nent (eg. lake
aquatic ecosyystem can
mar ne,
water (e.g. ma
under
rther
(i) Terrestrial ecosystem : which include forest, grassland and des.
(i) Aquatie ecosystem: may be further distinguished
(a) Fresh water: as which may be lotic (running water as spring
or rivers) or lentic (standing water as lake, pona, pools, ditch, pudd
swamp etc.).
(b) Marine water : such as ocean (deep bodies) or sea (shallow onesi
(2) Artificial (Man-made) Ecosystem : These are maintained artificial h
man where, by addition of energy and planned manipulations, natural
balance is destributed regularly. For e.g. croplands like maize, wheat, rice
fields etc. Where man tries to control the biotic community as well as the
physio-chemical environment, are man engineered ecosystem.
desertet
Ecosystem
Artificial ecosystem
(crop, urban industrial.
laboratory, space
Lentic(standingwater)
(lake, pond swamp)
Natural ecosystem
Terrestrial (Forest, grassland
deserl)
PFresh water-
>Aquatic
Lontic (running water)
(River, springstream
Marine (ocean, sea)
Fig. 5.13 :
Types of Ecosystem
ECOSYSTEM-STRUCTURE AND FUNCTION
5.14
The structure of an ecosystem is characterised by the physical org
a n i s a t e
of biotic and abiotic components. The major structural features or
are speciescompoSition, stratification, trophic organisation and nutric
1. Species composition. Each ecosytem has its own tyYpe A
Species
composition. 1Difierent ecosystems have different species compositto
240 BAsIc ENvIRONMENTAL ENGINEERIN

3. T
241
EcooGY

4. variety of species is found in forest
ecosystem,
whereas a few
a desert ecosystem.
2.
Stratification. The organisms
in each ecosystem form On.
or strata, each comprising
the population
kind of species. In son
species ocCurs
more layer
ecosystems
und vegeta
form different strata and are occupied by
different species. Onthe eta
Sumers s
the desert ecosystem
shows a low
discontinuous herb layer consicti. ha
ne
such as tropical rain forest, the crown of trees, bushes and orocOsy
other hand
of fewe
ous herb layer consistir
and extensive bare patches of soil.
3. Trophic organisation. Food relationship of producers and
another way to depict ecosystem
structure. Trophic (food) structure of
is based on the existence ofseveral trophic levels in the ecosystem. The
, and
(autotrophs) form the firsttrophic level or
T1, herbivores the second
Or T
There may be 2-3 levels ofcarnivores. The top carnivore belong to T.o
trophic levels. Decomposers form ultimate or detritus trophic level (Fio 141
carnivores constitute the third or Ta.
Parasites feed upon the organisms ofall trophic levels. Therefore, they
have a fixed trophic level. Similarly there is no fixed trophic level for omnivorou
donot
organism like man.
Secondary Top
Primary
carnivores carnivores
Producers Herbivores carnivores
T T2 T3 T4 Ts
Decomposers
Fig. 5.14: Trophic levels in an ecosystem
In an ecosystem there can be only 4-5 successive trophic levels, becau
(i) All the food available at one trophic level is not eaten by tneanimals
the next trophic level. Some of the food energy is lost in this mannn
i) All the food eaten by an animals is not useful, thus a gooddca
containing food is passed out as waste.
good deal ofeneie
() A large amount of energy is lost in respiration to deriv
metabolism, and thus, there is not much energy left to support e
levels.
Trophic structure may also be described in terms of the amo
material present in different trophic levels. The amount of the i
of
live
n a t e
242 DASIC ENVIRONMENTAL ENGINEERIM

5. ditierent tnophie levels at a given time is called standing crop. It is
as the number or biomass of organisms per unit area. n
monly enpressed as
of a species may be expressed in terms of either fresh or dry wcight.
i erally dry weight is prelerred so that the variations in weight
mass ot
But. g e n e r a l l y
due to
moisture differ
terenees in biomass can be avoided.
S Nutrients. In each ccosystem, the nutrients necessary for the growth of
4. N
i n t Organism are accumulated in the biomass and the abiotic components like
ingorganism
il. The anmoun
the
ail at any given time IS termed as standing state. Different ecosystems
Qunt of nutrients such as nitrogen phosphors and calcium present in
have different standing state of nutrients. The standing state of nutrients may vary
at ditterent time even in the same ccosystem.
15 FOOD CHAIN AND FOOD WEB
In the ecosystem various trophic levels connected through food chain. The
transfer of food energV from the source in plants through a series of organisms
with repeated eating and being eaten is referred to as a food chain. Or the
ransfer of energy from one trophic level (e.g. producers) to the next trophic
evel (e.g. consumers) is called food chain. AII types of ecosystems posses
wo types of food chain : grazing food chain and detritues food chain.
1. Grazing food chain. It extends from producers through herbivores to
carnivore. Producers are autotrophic organism which synthesis organic food from
simple inorganic raw materials through photosynthesis utilizing solar energy. A
part ofthefood systhesised by the producers is used in their body building, while
the rest is utilized in providing energy for various life activities.
The animals that feed on other organisms are called consumers. The consumers
which directly take their food plants are called herbivores or first consumers e.g
z0onplanktons, smalI fish, grass-hooper, field mouse, rabbit, deer, goat, elephant
A part of the plant food eaten by herbivores become constituentof their body,
ile major part is utilized by them in production of energy for various life
Ves. The herbivores are eaten by second order consumers or primary carnivore
Irog, some birds, fishes, wild cat, fox etc. A part of flesh or food obtained
nerbivores is used in body building by the primary consumers, while the rest
sumed in providing energy for various life activities. The larger carnivores
CoPo the primary carnivores are called tlhird order consumers or secondary
Conres. e.g. Snake (prey upon frog), wolf (prey upon fox). The lest order
Consumers are not
are not preyed upon by other animals. They are called
topcarnivores
ed top carnivores
&shark, crocodile, tiger, lion etc.
Ome common food chains are given below.
)Vegetation
(i) Vegetation
Shrew Hawk.
> Grasshopper
Fox >Wolf- > Tiger.
Rabbit
EcoLOGY
243

6. Peacock.
Snake
Frog
(ii) Vegetation
Frog Snake Hawk
(iv)Plant B u t t e r f l y
Trophic level
Quaternary
consumers
Tertiary
consumerrs
Secondary
consumerrs
Primary
consumerrs
Producers
A terrestrial food chain
An aquatic food chain
Fig. 5.15: Food chains and trophic levels in terrestrial anu aquatie
ecosystems
Aquatic Food Chains
() Phytoplankton Zooplankton SmallCrustacean
244 BASIC ENvIRONMENTAL ENGINEERING

7. ArLr ish Crosdile
Predator insects Small fish
Mrk/K.ing fisher
Zooplankton Smallfish aryer fish Shark
( i ) P h y t o p l a n
ankton> Zooplankton>
Fish Crane>Hawk.
ankton
P h y t o p l a n k t e
Detritus food chain. It starts with dead organic matter and passes
itus feeding organism in soil to organisms feeding on detritus feeders
throughdetritus fee
Mangrove
leaves
Fungi
hacteria
Phytoplakton protozoa
and
benthic algac
Hoingestionand
Croprophagy.
Harpacticoid copepod
Crabs
Bivalve
mollusc
Nematode
Grass
shrimp
) Sheephead
minnow
Detritus consumcrs
Small carnivores
(Minnow small game fish etc.)
Large top carnivores
(Game fish, fish cating birds)
Fig. 5.16 :
245

8. and their predators e.g.
decomposition
of
a c c u m u l a t e d 1litter i.
ecosystems
exhibiting
detritus
food chain are
thus less depen
in
forest. The
endent or
irect solar
energy.
These depend chiefly on the influx or organic
matter producedCtso
food chain A
good
system. In fact. detritus food chain is simply a
s u b - c o m p o n e n t ofanoth
A much larger
fraction of energy
flows through the detritus food c
matter producediin
another
another ecosystem
example of a
detritus food chain based on
mangrove
levels is descri," 800M
Small fishes Large fishes
is describe below
> Carbs and shrimns
Mangrove
l e v e s > D e t r i t u s
Micro organisms
are at
interconnected with one
another. 'A network of food chains wh:.e
interconected at various trophic levels, so as lo Jorm a number of fan
FOOD WWEB
ich are
In nature, the food chains are not isolated sequences but a.
ber of feeding
.
Fig. 5.17 : A food web shows the main food links and
infora
nau
of many food chains. An
organisms may form a food souree
i n t e r c o n n e c
other
organism, thus forming a web.
BASIC ENvVIRONMENTAL ENGINEER
246

9. amongst different organisms of a hiotic
community is called
Fi
ecti 3.6). A food web opens several alternate pathways for the flow
[t also allows an
organism to obtain its food from more than one
ONnections
mdweh
| energy. It also allows
pe forganismof
by
wild cat,a snake
of
tood
the lower trophic level. Thus, a field mouse may be eaten
at a snake or an owl.
Similarly. wild cat eats a
number of herbivores
ice. squirrels etc. A wolf or
jackal can eat both rabbit and deer
ike birds,
Gene
rally, a food web operates according to taste and food preferences of
orgar
isms at each
trophical level, yet availability of food source and other
eions are equally important. For
example, tiger normally do not eat fish or
the
npulsions are equa
oft in Sunderbans, they are forced to feed on them in absence or their
crabs. but in
natural prey
Decomposers or Reducers
These are saprophytic (rapro to
decompose) micro-organism such as bacteria
nd fungi. which obtain their food form dead bodies of producers (plants)
oOnsumers (animals) and their organic wastes
Decomposers are offer called micro consumers because of their small size.
They are also called reducers because they decompose and remove the dead
hodies of the organisms.
Decomposers secrete digestive enzymes in the surrounding medium to
digest
theorganic materia (extracelluardigestion).They absorb a
part of the decomposition
products for their own nourishment. The remaining substances add materials and
minerals to the substration. This process is called mineralization : The relased
mineralsare reutilized as nutrients by the bioduces
Secondary cosumers or
primary carnivores
The animals which feed or prey upon other animals. The carnivores which
Iecd upon herbivores are calted primary carnivores or second order consumers
cq frog, brids, fox, cat e.c.
C)
Tertiary consumers: Third orderconsumers
ECOndary consumers are prefed upon by some larger carnivores. They are
Caled
tertiary consumers and so on.
(d)Quaternary
They are the largest
not caten up
consumers or Fourth order consumers or omaivores.
5.16ECOLOGICAL PYRAMIDS
est carnivores which fuel on the tertiay consumers and are
other aninmals eg. lion and tiger.
by any
stem, starting with producers at the base and successive trophie
Graphic repre ientation of trophic structure aud function of an
levels forming
Pramids B the apex is knows as an ecological pyramid. Ecological
WTamids are of three ypes
Pyre o f nunmbers: It represents the number of indivIdual organisms at
EcoLoGY 247

10. each trophic level. We may
have upright or
inverted pyramid of numbers
5.18. A
grassland
ecosystem (Fig. 5.18 a) and a pond ecosystem show an upright
in a pondare
S
lepending
upon the type of ecosystem and food chain as shown in fig. 5.18 Pendine
pyramid of
phytoplanktons (algaeetc.),
which are
small in size and very large in nu are
number So
nd are insects while
and le
the producers from a broad base. The
herbivores in a grassland are ince S
tertiary
carnivores are hawks or other birds which are gradually less an
numbers. The producers in the grasslands
are grasses and that in
a
upright pyramid.
Similar is the case with the herbivores, carnivores
carnivores in pond which decrease in number at higher trophic levels
number and hence the pyramid apex
becomes gradually narrower foS
es and top
Top carnivores
Top ca Hawks, Lion, Tiger
other birds
Carnivores Frogs.birds
Insects
Herbivores
Carnivores Snakes, foxes lizards
Herbivores
Insects. birds
Producers Grasses T Trees
(b)
(a)
Fleas. microbes
Lice, bugs
Herbivores Birds
|Producers Trees
Hyper parasites
Parasites
(c)
Fig. 5.18: Pyramid of numbers (a) grassland (b) forest
(c) Parasitic food chain
In a forest ecosystem, big trees are the producers, which are less in nuu
and hence from a narrow base. A larger number of herbivores including ou
insects and several species ofanimals feed upon the trees (on leaves,
flowers, bark etc.) and form a much broder middle level. The secondary consu
hke fox, Snakes, lizards etc. are less in number than herbivores while topcanu d
like lion, tiger etc. are still smaler in number. So the pyramid is
narro
mivor
sides and broader in the middle (Fig. 5.18 b).
Parasitie food chain shows an inverted pyramid of number. 1he
pi
like a few bigtrees harbour fruit eating birds acting like herbivores ites
larger in number. A much higher number of lice, bugs etc. grow leas
these birds while a still greater number of hyperparasites like dugo
"asites
and
microbes fecd upon them, thus making an inverted pyramid (18 at
5.18 o
Pyramic of biomass: It is based upon the total biomass (dry T right
trophic level in a food chain. The pyramid of biomass can also Dc
(drymatter)
BAsIc NMENTAL ENGINEERIN
248

11. Fig. 19 (a, b) shows pyramids of biomass in a forest and an
aquatic
The pyramid of t
e
pyramid ofbiomass in a forest is
upright in contrast to its pyramid
seThis is because the
producers (trees) accumulate a
huge biomass
imered
mbers. This
mer's total biomass feeding on them declines at higher trophic
c o n s u m e r '
whle
the
resulting in broad base and
narrowing top.
Tertiary Carnivores
Snakes. frog. birds Big fish
Carnivores Small fish
Squirrel, rabbit, Herbivores Insects
Herbivores insects
Grasses,
Producers Phytoplanktons
herbs
(a) b)
Fig. 5.19 : Pyramid of biomass (a) Grassland (b) Pond
The pond ecosystem shows an inverted pyramid of biomass(Fig. 5.19 b). The
tal biomass of producers (phytoplanktons) is much less as compared to herbivores
20oplanktons, insects), Carnivores (small fish) and tertiary carnivores (big fish).
Thus the pyramid takes an inverted shape with narrow base and borad apex.
Pyramid of Energy: The amount of energy present at each trophic level is
considered for this type of pyramid. Pyramid ofenergy gives the best representation
07 the trophic relationships and it is always upright.
very successive trophic level, there is a huge loss ofenergy (about 90%)
orm ofheat, respiration etc. Thus, at each next higher level only 10% of
e
passes on. Hence, there is a sharp decline in energy level
ofeach
the rophic level as we move from producers to top carnivores. Therefore,
e
pyramid of energy is always upright as shown in Fig. 5.20.
College o
Top carnivores
Carnivores
LIBRARY
Herbivores
S17 MAJOR ECOSYSTEMS
Producers
nt
interacting systems in the biosphere.
The major
ecosystems
with their
30202
Fig. 5.20 Pyramid ofenerg
Different ecosystems like a pond, a lake, a river, a stream, a spring, an
y, the sea, a Cst, grassland, a desert, and a cropland are operating as self-
249
Kukae.a
ueyoy

12. malaria, is obtained from Chinchonaledgeriana, and (i) Taxol, an
drug is obtained from the bark ofthe yew tree (Taxus baccata andT nticance
f plants
Most of the traditional drugs over the world are prepared from plants. Aho
bout 2
of the pharmaceutical drugs are derived from a mere 120 species
Several plant species are used for the manufacture of innumerahlePan
products. Such plant based synthetic products are called botanochemi
synt
icak,
aesthetio
3. Aesthetic and cultural benefits. Biodiversity also has great a
bird watching
value. It provides a good deal offun and recreation. Ecotourism, bird
rewardsof
wild lie, pet keeping gardening, etc. are some examples of aesthetic rewa
biodiversity
ts and
Biodiversity is also related to out cultural and religious beliefs. Plants
ritage
animals are considered to be the symbols of national pride and cultural herita
Many plants like Ocimum samctunm (Tulsi), Ficus religiosa (Pipal), Pros
cineraria (Khejri), etc. are considered sacred and worshiped by the people
majority of Indian villages and towns. Several birds, animals and even snakesa
considered sacred and worshipped.
4. Ecosystem services. Biodiversity is essential to keep natural cycle
going and make the ecosystem self sustaining unit. It is esseential for the
maintenance and sustainable utilization of good and services from ecological
systems as well as from individual species. Some of these forests are:Ro
maintenance of gaseous composition of the atmosphere, (ii) climate control by
orests and oceanic systems, (ii) natural pest control, (iv) formation and protection
of soil, (v) conservation and purification of water, and (vi) nutrient eyeling, etc.
It is estimated that the value of ecosystem services is in the range of 16 to S4
trillion (10) US dollars per years.
5. Unknown benefits. It is unpredictable that which species may become
useful in future. If Penicillium and cinchona tree of Peru had become extinet
before the Penicillin.
5.6 ENERGY FLOW
To maintain life activites, energy in required living organisnms are operated oy
means of energy, which is derived from the environment. As we known the su
Energy
is the main source of energy in an ecosystem. The plant make use of the ra
materials from the environmental in the form of water salts and CO to prepa
food, namely strach. This synthesis is aided by the energy the derivetro
a r e
the
sunlight trapped by the chlorophyll. Thus, energy from the sun enters the Iivmg
to
words through photosynthetic organism and passes on from one organis
BASIc ENVIRONMENTAL ENGINEERING
224

13. another in the form of food.
l.at energy flows through AN ecosystem is unidirectonal and non
another
W e s a w
ayflow of energy 1s governed by laws ofthermodynamics hich
e l h c .
his one way
state
t h a t
Energy is neithe
is neither created nor destroyed but may be transferred from one
rm
to
a n o t h e r ,
and
(b)
During energytransfe there is degradations of energy froma cncentrates
f o r m ( m e c h a n ,
CH,O
carbohydrate Oxygen
hanical, chemical or electrical etc.) to a disperssed form (heat)
+ O2 CO HO
Carbondioxide Water
Respiration equation
Thils, there is a continious loss of energy within each tropic level from
groducer to consumer Within ecosystem.
This is accounted for largely by the energy dissipated asheatduring metabolism
of the organism present in the food chain.
It also indicates that shorten the food chain, greats would be the available
food energy and with an increase in the length of the food chain, there is a
corresponding theorem in loss of energy.
Routes of usage
In an ecosystem energy's usage takes places in following ways
Ihe
sunshine provides the necessary heat to maintain the required range in
Which proper physical end chemical processes can take place.
me bacteria obatin useful energy by oxidation ofcertain elements such as
sulphur and iron.
s is very limited because most oftheiron and sulphur on earth surface
is already oxidized.
in photosysnthesis
Potosysnthesis, plants use chlorophyll to transform sunlight in to chemical
which is stored in chemical compounds (foods). These compounds
ergy enters c c o s y s t e m
from the solarradiations
and is
convertedint
Cner
ansterred from organism to organism and utilized as a source of
energy
nergy flow in Ecosystem
The f
Oning ecosystem depends on the flow of energy through matter.
EcoLOGY
225

14. chemical form by the producers.
The plants
make use of the ra
the environment in the form of water, salts and carbondioxide t
namely starch.
naterials
to prepare f
raw
The flow of energy in the ecosystem is governed by t
thermodynamics i.e.
It law ofTheromodynamics : state that energy can neither
bedestroved but it can be transformed from one form to another
from one component to another.
Imd law of thermodynamics:
slats that during energy transf
degradation ofenergy form a concentrated from (mechanical, chemical e
etc.) to a dispessed form (heat)
As energy tlows through the food chain, there occures dissipations
at every tropic level
The loss ofenergy takes place through respiration,los of energy in locomes
running. hunting and other activities.
At every level then is about 90% loss of energy and the energy transe
wo
basic la
be created
transfeme
sfer here
chemical or eleat
f enen
omotin
from one tropic level to the other is only 10%.
These are two aspects with respect to energy flow in ecosystem.
G)There is unidirectional or one way flow of energy in the ecosystemie.fin
producers through herbivore to carnivores. The energy can not betransfem
in the reverse direction i.e. the energy that is captures by theautotrophs
is capature by the autotrophs does not revert back to solar input: or
energy which passes to the herbivores does not pass back to the
autotrtgs
(in) The amount
ofenergy flow decreases with successive trophic levels.Proga
captures only small fraction of solar energy (1-15% oftotal radiation)ands
bulk of utilization energy is dissipated mostely as heat. Part energy capu
in gross production of producers gross primary production (GPP) 13
maintenance
oftheir standing crop (respiration) and for provi1dng
herbivores.
sedir
The Natural Cycles of the Environment or
Biogeochem
(Material cycles) or Nutrient eycles
The biosphere in its widest sence consists of the earth's crust, tne
and various species oflife which exist in the zone 600 meters abov
meters below sea level. The biosphere is very large and comp
divided into smaller units called
ecosystems.
andlu
hen
226
BASIC ENvIRONMENTAL ENGINEER

15. he earth is like an energy or entropy pump that revejves enerey frm sun
he
it power and drive the eyoles of water, nutrients and otherelements,
INO as biogechemienl-eyeles
L a n s
sof thermodynamies dictate that all the natural processes eu
accompained by an inereases in entropy or randomens
y N m t a n e v n u s
uarh does not cireulate in nature. It is used only once by an organiem and
rted into heat which in lost to the ecosystem 1hu, these ia ething
i s t h e n c o n v e r t e
The materials i.e,chemiealelementsincludingall the esentia
ike energy Cele.
tend to cinculate in the biosphere in characteristic paths from the environmert
e k m e n t s
of protpplasm ike water, carbon, nitrogen, phosphorus ett, hepwever
These paths are generany knoWn as biogeochemieal-eyeles.
Riogeochemical cycles in the cnvironment are the cyclid pathways in which
a regular andcontinuustransistionof elements occur Irom
theenvironmentsnto
the organism and from organism into the environment
"The word bio represents living organisms, geo denotes soil environment while
chemical means elements such as carbon, phosphorus, Nítrogen and wulphur
which undergo transition regularly.
Biogeochemical cycles There are two basic types of biogeochemical
cycles
Types of biogeochemical eyeles
Sedimentary type
PS. iodine
Gaseous Type
e.g
Carbon and nitrogen cycle
(a)Gaseous Type:
In
thisgroup of biogeochemicalcycles, the atmosphere
constitutes the major
v O i r of the element that exist there in gascous phase. Such cycles show ittle
O permanent change in the distribution and abundance if the element. The
oxEC carbon and nitrogen cycles are good examnples of biogeochemnIcal cycle
with a prominent gaseous phase.
(6)Sedimentary Types
Sedimentary type ofcycle, the major
reservoir is the lithosphere,
from
Ch the elements are released by weatherng
cycles
The sedimen 1ypes arebest examplilied by phosphorus,
sulphurandiodine
p e s ofcycles involve biotic and abiotic agents.
Both are driven by
flow of energ
cycles. Both type
Cnergy and both are tied to the waler or hydrological cycle.
EcoLOGY
227

16. BASICS OF ENVIRONMENT
1 Water Cycle or HydrologicalCycle:
IPITATION
RECIPITATION
PREC
ON
CLOUDS
EVAPORATION
RAIN
RAIN FALL
PLANTS
WATER BODIES
SOIL MOISTURE
WMTERCCAE
1 Water Cycle: The circulation of water b/w living organisms & their environment is
called water cycle. This cycleincludes:
The evaporation of water takes place from lakes. seas, etc. The transpiration from
plants also increases water vapors in atmosphere.
The water vapor rises up in the skywhere it condensed to form clouds.
Water from clouds comes down in the form of rain, which fills the rivers & sea.
The rain water penetrates deep inside the earth crust & form ground water source.
2. Oxygen Cycle: Oxygen important component of life as it essential for aerobic
respiration in plants & animals which is released in atmosphere by plants in
photosynthetic process. The atmosphere contains 20.99% of O2
The 02 Cycle involves circulation of O2 b/w living organisms å environment
16
NOLLVLaSNVa

17. BASICS OF ENVIRONMENT
pote
ATMOSPHERIC OXYGEN
ORGANIC
COMPOUNDS
PHOTSYNTHESIS IN
RESPIRATION IN
PLANTS
PLANTS&ANIMALS
CARBON-DIOXIDE
WATER
OXGEN GCLG
The cycle includes:-
The main source of Oz is photosynthetic process in plants in which it absorbed
CO2& H2O in the presence of light & Chlorophyll produce CsH1206&O2.
hv
6CO2+6H20
C6Hi206+6 O2
The other source of O2 is the photolysis reaction of H2O & N20 occurring in the
atmosphere in the presence of UV-rays
2 H20 +4H+O2
2NO 4N +OO2
Oxygen is mainly consumes in respiration in plants & animals & natural
decay in which consumption of O2 takes place & produce CO2.
respiration
CoHi206 + 6 Oz 6CO2+ 6H20
Carbon Cycle:
17

18. BASICS OF ENVIRONMENT
pHOTOSYNTHESTS
ATMOSPHERIC CO
COAL GAS
PRODUCERS
VOLCANIC
(GREEN PLANTS)
ERUPTIONS
DEAD ORGANIC
MATTER
ANIMALS
cARBONCYELE
Carbon is an important
constituent of all organic compounds. About 49% of dry wt. of
organism is made up of Carbon. Atmosphere
contain 0.03% CO2 gas.
The Carbon cycle involves:-
CO2 from atmosphere is absorbed by plants for the production of food in photosynthetic
process in presence of sunlight & chlorophyll
hv
6CO2+6H20
CoHi20s+6 Oz
The carbon moves along food chain through
consumers at different tropic level.
Carbon returns to atmosphere through respiration, decay of dead animals & plants,
combustion of fossil fuels & volcanic eruption.
Nitrogen Cycle:
18
RESPIRATIoN

19. BASICS OF ENVIRONMENT
Nitrogen is an important constituent of all organisms because it forms the structural
part of proteins, nucleic acid &chlorophyll molecules.
Earth atmosphere contains 79% of N2 but it can not be used by living organisms as such,
it has to be combined with other elements like C, H, O to make itusable.
The nitrogen cycle involves:-
Fixation of Nitrogen in atmosphere: The nitrogen in atmosphere is fixed by three
ways
I. Atmospheric Fixation:_N2 in atmosphere combines with Oz in the presence of
thunder lightening forms nitrogen oxides like NO,NO2 ,
NO3 etc. These oxides
dissolve in rain to form nitrates.
II. Industrial fixation:_N2 & H2 combines in presence of catalyst to form NH; in
industries which is used in manufacturing of urea &fertilizers
III. Biological fixation: it involves conversion of free Na in to organic nitrogen by
symbiotic bacteria ( present in roots leguminous plants) & free bacteria
Rhizobium
N2 NO2 NOg
Bacteria
Nitrobacter
Azotobacter
+NH3
Nitrosomonas
NO2 NO3
Bacteria Bacteria
Bacteria
Release of Nitrogen in atmosphere: Nitrogen in the atmosphere comes by
denitrification process carried out by bacteria like pseudomonas & colestridium which
convert nitrate back into nitrogen gas.
19

20. BASICS OF ENVIRONMENT
NIN
ATMOSPHER E|
E N I T R I F Y T N s
ACTERT
PROTETN
SYNTHESTS
NITROGEN
PLANT BODY PROTEIN
NITRATE FIXATION BY
PROTOPLASM
BACTERIA,
ALGAE ETC.
ANIMALS
E ORGANIC
DEAD ORGANIC
NITROGEN
MATTER
NITRITE
DECOMPOSER
TTRITE
&ACTERIA AMMONIA
Niroged Cyee
Sulphur Cycle:
Sulphur is one of the important component of protein, vitamins, & hormones. It plays a
crucial role in health of plants & animals. The sulphur cycle involves:-
Sulphur enters in atmosphere in the form of H2S, SO2 through human & natural
activities like industrial, automobile emission, volcanic eruption, decay of dead organic
materials.
In atmosphere S02 react with O2 to form SO3 which get dissolved in water & produce
H2504 which comes down on the earth with fog & rain where it is absorbed by plants in
the form of sulphates for the synthesis of proteins
From plants it transferred to animals through food chain.
After the death of animals bacteria decomposed the animal & produce H:S gas which is
absorbed by the plants.
20

21. BASICS OF ENVIRONMENT
HS, SO
Oxidation
So3
H20
Nere
HSOA
FOG PRECIPITATION INDUSTRIAL
OCEAN EARTH PROCESS
i n e r a l
SULPHATE
VOLCANIC
ERRUPTION
PLANTS
Protein &
Amino Acids
ANIMALS
Death
Decay
ANAEROBIC
AEROBIC
DECAY
DECAY
SULPHATES
HS
SOIL
SOLRHOR CCLE
Phosphorous Cycle:
It is sedimentary cycle because it does not enter into atmosphere. It can be found on
earth in water, soil & sediments. So, it is the cycle which describes the movement of
phosphorous through lithosphere, hydrosphere & biosphere.it involves:-
21

22. BASICS OF ENVIRONMENT
PLANTS
Protiens,Nucleic acids ANIMALS
DEAD PLANTS,
ANIMALS
EXCreia
of
Arimals
BONES,
TEETH
Decomposition by
Phosphate
Bacteria
PHOSPHATES DISSOLVED Lnler i
PHOSPHATE
VelC
p h e
WATER
BODIES
(ehli3e
s
PHYOPLANKTONS
ZOOPLANKTONS
FOSSIL FOSSILS
ROCKS
Phosphorous Cyele
I t is an important nutrient for plants & animals in the forn of P04°".It is the building
block of parts of human & animals body like bones, teeth etc
After decomposition of plants & animals P come back to soil & ocean in the form of
POA
P in the form of PO4 salt come into soil through weathering process of rocks.
22

23. BASICS OF ENVIRONMENT
Pfrom the soil is absorbed bythe plants where it is converted into organic phosphate
wnich is transferred to animals through food chain.
Energy flowinanEcosystemn:
The capacity to do the work is known as energy. In an ecosystem the ener9y flows
fhrough one organism to another in the form of food & it is unidirectional & flows laws of
ollos
thermodynamics-
"Energy can neither be created nor be destroyed". (1s" law of thermodyrnamics) &
"When energy is changed from one form to another it accompanied with loss energy in
the form of heat". (2"d law of thermodynamics).
The mair source of energy is sun. The solar energy is trapped & stored by producers in the
form of chemical energy which passed to primary consumer, secondary & tertiary consumer
through food chain.
Green plants absorbed < 5% of solar energy & rest of the energy is lost in the form of
pavau Cev
heat. Some of this energy is used by plants in respiration & rest is used in production of food
which is ecten by herbivores. Only 10 % of this energy is absorbed by herbivores & rest is lost
in the form of heat. 10% of energy is absorbed by carnivores from herbivores. The net energy
keeps on decreasing with increase of tropic level.
ww
Sun 5%Energy 10% of Ener Herbivores
Producers
w Phorasyihesis
N 10% of Energy
10% of Energy
Decomposers Carnivores
Energy flow in an Ecasystem
w.t