Carbon cycle:
• All living things are made of carbon. Carbon is also a part of the ocean, air, soil and
even rocks.
• In the atmosphere, carbon is present in form of a gas called carbon dioxide and
methane. Trace amount of carbon monoxide is also present.
•
Plants use carbon dioxide and sunlight to make their own food and grow. The
carbon becomes part of the plant and it moves further in other trophic level
through food chain.
• Plants that die and are buried may turn into fossil fuels made of carbon like coal
and oil over millions of years. These fossil fuels are important source of energy for
human being.
• When humans burn fossil fuels, most of the carbon quickly enters the atmosphere
as carbon dioxide. Carbon dioxide acts as green house gas so its increase
concentration in atmosphere results into increase earth surface temperature a
phenomenon known as global warming.
•
Ocean is most important sink of atmospheric CO2 followed by plant biomass.
Oxygen Cycle:
The oxygen cycle is the biogeochemical cycle that describes the movement of oxygen
within and between its three main reservoirs: the atmosphere (air), the biosphere
(living things), and the lithosphere (Earth's crust).
By far the largest reservoir of Earths oxygen is within the silicate and oxide minerals of
the crust and mantle (99.5%). Only a small portion has been released as free oxygen to
the biosphere (0.01%) and atmosphere (0.36%).
The main source of atmospheric oxygen is photosynthesis, which produces sugars and
oxygen from carbon dioxide and water:
6CO2 + 6H2O + energy → C6H12O6 + 6O2
An additional source of atmospheric oxygen comes from photolysis, whereby high
energy ultraviolet radiation breaks down atmospheric water and nitrous oxides into
component atoms.
2H2O + energy → 4H + O2
2N2O + energy → 4N + O2
The main way oxygen is lost from the atmosphere is via respiration and decay, process
in which animal life and bacteria consume oxygen and release carbon dioxide.
Chemical weathering of exposed rocks also consumes oxygen.
4FeO + O2 → 2Fe2O3
Primary Production: The rate at which radiant energy is converted into organic
substances by photosynthesis or chemo-synthesis by the primary producer. It is also
known as gross primary production (GPP).
Net Primary Production( NPP) : Some part of the organic matter produce during
photosynthesis get used during respiration process to produce energy for the
sustenance of the primary producer, so the amount of remaining organic matter left
is known as Net primary production (NPP).
GPP = NPP + R
Secondary Production: The plant energy is used up for producing organic matter of
the herbivores which, in turn is used up by carnivores. The amount of energy stored
by the herbivores or carnivores( in excess of respiratory loss) is known as secondary
production.
In other word we can say that energy stored at consumer level for use by the next
trophic level is known as secondary production.
Wet tropical forest and Estuarine ecosystem are highly productive ecosystem and
needed to conserve.
Ecological Succession: Ecosystems are dynamic in nature and often changes its
structure and function due to change in the physical environment or change in the
biotic composition. Some of these changes are very orderly and can be
predicted.
During this change process one type of a biotic community is totally replaced by
another type of community over a period of time and this transition continue till a
stabilized biotic community sets up. This transition process is known as Ecological
Succession.
Ecological succession is defined as an orderly process of changes in community
structure and function with time mediated through modifications in the physical
environment and ultimately culminating in a stabilized ecosystem known as
climax.
Type of succession:
1) Primary Succession: It start from the primitive substratum, where their was no
living matter present before. It is a slow process due to lack of any build up
substratum.
Secondary succession: It starts from previously built up substrata where their was
presence of living matter before. Due to external factor existing community
disappear . These processes are fast.
Succession can be autogenic (induced by community itself) or allogenic( due to
external factors).
Some Definitions:
1) Pioneer community: The first group of organism established in a particular area is
known as pioneer community.
2) Seral stages or sere: The whole sequence of communities which are transitory
between from Pioneer to climax community are known as Seral stages.
3) Climax community: It is the stabilized community formed in the end of succession
process which is in equilibrium with the environment.
Ecological Succession type: Based on the substrata type :
1) Hydrarch or Hydrosere: It start in watery area like, pond, swamp,bog.
2) Mesarch: starting in the area of adequate moisture.
3) Xerarch or Xerosere: Starting in dry area with little moisture. It can be of following
type:
a) Lithosere: starting on a bare rock
b) Psammosere: starting on sand
c) Halosere: starting on saline soil.
Process of succession: Succession take place in a systematic order of sequential steps:
1) Nudation: It is development of bare area without any life form. This formation can
be due to landslide, volcanic eruption (topographic factor), or due to drought,
glaciers ( climatic factor) or due to overgrazing, disease outbreak ( biological
factor).
2) Invasion: This is successful establishment of a species in a bare area. It start with
migration or dispersal process where seeds, spores reach the bare area through
air, water etc.
After migration successful establishment of the species( adjustment with the
prevailing condition) is know as ecesis.
After ecesis , number of species increase in number due to reproduction and come
closer to each other a process know as aggregation.
3) Competition and Coaction: As the number of individuals grows there is
competition, both inter-specific( between different species) and intra-specific (
within the same species) for space, food and water. Individuals of species affects
each other life in various ways and this is known as coaction.
4) Reaction: once the number of species increases, they have a strong influence on
the physical environment. The mechanism of the modification of the environment
through the influence of living organism in it, is known as reaction. Most of the
changes occurs in soil, water, light condition etc.
5) Stabilization: It is the final stage of succession process, where more or less stable
community called climax formed which is in equilibrium with the environment.
Example of Ecological Succession:
1) Hydrosere (Hydrarch): This type of succession start in a water bodies like pond and
culminates in a climax community which is forest. It has following stages:
a) Phytoplankton stage: These are the pioneer community. Mainly blue green algae,
green algae, diatoms and bacteria etc.
b) Rooted submerged stage: Due to death and decomposition of phytoplankton
organic matter start accumulating on the pond subsurface. This new environment
is favorable for the growth of rooted submerged hydrophytes like Hydrilla, Elodea
etc.
Hydrosere: different stage of plant growth
3) Rooted submerged stage: Now the depth of lake reduces to 2-5 feet, favoring the
growth of rooted hydrophytes with their large leaves floating on the water surface.
Example: Nelumbo, Trapa, Azolla etc.
4) Reed-swamp stage: also known as amphibious stage as the plants of community
are rooted but most of it part is in air. Example: Scirpus, Sagittaria etc.
5) Sedge-meadow stage: They form mat like vegetation, results into higher loss of
water through evapotranspiration process. The marsh like condition in the previous
stage is removed and area with soil moisture left. Example: carex,cyperus etc.
6) Woodland stage: As the marsh land disappear soil become more dry and give rise
to vegetation like shrubs( Salix, cornus) and trees ( populus, Alnus).
7) Forest stage: This is climax community. It can developed as tropical rain forest or
mixed forest depending upon the climate of the region. Example: Ulmus, Acer and
Quercus.
2) Lithosere: A Xerosere on Rock: It start with bare rock and culminate into a forest
stage. Different stages of Lithosere are as follows:
a) Crustose lichen stage: The lichen are the pioneer community. The substratum is
very poor in moisture and organic matter, subjected with extreme of temperature.
Examples: Rhizocarpon, Rinodina etc.
b) Foliose lichens stage: They can absorb more water and retain more water and are
able to accumulate dust particle which further help in build up of substratum.
Examples: Parmelia, Dermatocapron.
c) Moss stage : Xerophytic mosses such as Tortula, Grimmia appears after lichens
stage.
d) Herbs stage: due to growth of mosses there is more accumulation of soil.This stage
is constituted by shallow rooted grasses such as Aristida,Festuca etc which further
replaced by shrubs.
e) Shrub stage: Species like Rhus, Phytocarpus start growing in the area, which over
compete the herbaceous species.
Crustose lichen
Foliose lichens
Moss
f) Forest stage: This is the climax community for this type of ecological succession.
Starting with Xerophytic tree species it changes into mesophytic type and finally into
forest type.
Forest Ecosystem
• Forests are formed by a community of plants which is predominantly structurally
defined by its trees, shrubs, climbers and ground cover.
• Natural vegetation looks vastly different from a group of planted trees, which are in
orderly rows. The most ‘natural’ undisturbed forests are located mainly in our
National Parks and Wildlife Sanctuaries.
• Each forest type forms a habitat for a specific community of animals that are
adapted to live in it.
Forest ecosystem has two component:
a) abiotic aspects: Include soil type, rainfall pattern in the forest are, light pattern,
water amount, temperature condition.
b) biotic aspects: The plants and animals form communities that are specific to each
forest type.
Plants include the trees, shrubs, climbers, grasses, and herbs in the forest.
Animal include the species of mammals, birds, reptiles, amphibians, fish, insects and
other invertebrates and a variety of microscopic animals.
Forest types in India
They can also be classified according to the nature of their tree species – evergreen,
deciduous, xerophytic or thorn trees, mangroves, etc.
They can also be classified according to the most abundant species of trees such as Sal
or Teak forests.
In many cases a forest is named after the first three or four most abundant tree
species.
Coniferous forest:
• grow in the Himalayan mountain region, where the temperatures are low.
These forests have tall trees with needlelike leaves and downward sloping branches
so that the snow can slip off the branches.
•have cones instead of seeds
•Trees- Pine, deodar
•Animals- Wild goats and sheep, Snow leopard, Himalayan black bear,
Evergreen forests:
High rainfall areas of the Western Ghats, North Eastern India and the Andaman and
Nicobar Islands.
There is no dry leafless phase as in a deciduous forest. An evergreen forest looks
green throughout the year. Thus very little light penetrates down to forest floor. The
forest abounds in animal life and is most rich in insect life.
Trees- Jamun, Ficus, Dipterocarpus
Animals- Tiger, Leopard, Sambar
Deciduous forests:
• are found in regions with a moderate amount of seasonal
• Rainfall. Teak tree is one of the dominant tree species in these type of forest
• The deciduous trees shed their leaves during the winter and hot summer months.
In March or April they regain their fresh leaves just before the monsoon, when they
grow vigorously in response to the rains.
• Thus there are periods of leaf fall and canopy regrowth. The forest frequently has
a thick undergrowth as light can penetrate easily onto the forest floor.
Trees- Teak, Sal
Animals- Tiger, Chital, Deer,
Thorn forests:
• Thorn forests are found in the semi- arid regions of India.
• The trees, which are sparsely distributed, are surrounded by open grassy
areas.
• Thorn forest trees have long or fibrous roots to reach water at great depths.
These have thorns to reduce water loss through evapotranspiration.
• Trees- Babul, Ber, Neem Animals - Blackbuck, Chinkara, Wolf,
Mangrove forests
• grow along the coast especially in the river deltas.
• These plants are able to grow in a mix of saline and fresh water.
• The mangrove trees have breathing roots that emerge from the
mudbanks.
Trees- Avicenia, Rhizophora
Animals- Crocodile, fish, shorebirds – sandpipers
Importance of Forests resource:
1) Consumptive value
2) Environmental services
3) Aesthetic and cultural values.
Problem associated with the forest resource and its conservation.
Grassland Ecosystems
• rainfall is usually low and/or the soil depth and quality is poor.
• The low rainfall prevents the growth of a large number of trees and shrubs, but
is sufficient to support the growth of grass cover during the monsoon.
• Grassland shows seasonal variation with low productivity during summer
and high productivity during rainy
• A variety of grasses, herbs, and several species of insects, birds and mammals
have evolved so that they are adapted to these wide-open grass covered areas.
These animals are able to live in conditions where food is plentiful after the
rains, so that they can store this as fat that they use during the dry period
when there is very little to eat.
• Man began to use these grasslands as pastures to feed his livestock
Grassland Types in India:
The Himalayan pasture belt extends up to the snowline. The grasslands at a lower
level form patches along with coniferous or broadleaved forests
•The animals migrate up into the high altitude grasslands in summer and move down
into the forest in winter when the snow covers the grassland.
•These Himalayan pastures have a large variety of grasses and herbs. Himalayan hill
slopes are covered with thousands of colorful flowering plants. There are also a large
number of medicinal plants.
Terai:
• Extends as a belt south of the Himalayan foothills
• Terai consists of patches of tall grasslands interspersed with a Sal forest
ecosystem.
• The patches of tall elephant grass, which grows to a height of about 5m,
are located in low-lying waterlogged areas.
Scrublands of the Deccan Plateau:
• Semi-arid plains of Western India, Central India and the Deccan - covered by
grassland tracts with patches of thorn forest.
• Several mammals such as the wolf, the blackbuck, the chinkara, and birds such as
floricans are adapted to these arid conditions.
• The Scrublands of the Deccan Plateau are covered with seasonal grasses and herbs
on which its fauna is dependent.
Shola grasslands:
• The Shola grasslands consist of patches on hillslopes along with the Shola
forests on the Western Ghats, Nilgiri and Annamalai ranges.
• This forms a patchwork of grassland on the slopes and forest habitats along the
streams and low-lying areas.
Grasslands are not restricted only to low rainfall areas. Certain grassland
types form when clearings are made in different forest types.
• The grasslands are related to repeated fires that do not permit the forest to grow.
• Some grass and herb species are more sensitive to excessive grazing and are
suppressed if the area is over grazed.
• Others are destroyed by repeated fires and cannot regenerate. Thus overused or
frequently burnt grasslands are degraded and are poor in plant species diversity.
Important of Grassland:
1) Pasture land
4) habitat for diverse species of insects.
2) Fodder source
3) Grass is also used to thatch houses and farm sheds.
Threats to grassland ecosystem:
• Over utilization and changes in land use of the ‘common grazing lands’ of rural
communities has lead to their degradation. Extinction of their species- Cheetah,
Wolf
• A major threat to natural grasslands is the conversion of grasslands into irrigated
farmlands. In the Deccan, grasslands have been altered to irrigated farms and are
now mainly used to grow sugarcane.
How can grassland ecosystems be conserved?
• Grasslands should not be overgrazed and areas of the grasslands should be either
closed for grazing or rotational grazing pattern is established.
• Fires must be prevented and rapidly controlled. In hilly areas soil and water
management in each micro-catchments helps grasslands to return to a natural
highly productive ecosystem.
• To protect the most natural undisturbed grassland ecosystems, Sanctuaries and
National Parks must be created. Their management should focus on preserving all
their unique species of plants and animals.
Desert ecosystem
• Desert and semi arid lands are highly specialised and sensitive
ecosystems that are easily destroyed by human activities.
• The species of these dry areas can live only in this specialised habitat.
Desert ecosystem in India:
• Deserts and semi arid areas are located in Western India and the Deccan Plateau.
The climate in these vast tracts is extremely dry. There are also cold deserts such as in
Ladakh, which are located in the high plateaus of the Himalayas.
•The most typical desert landscape that is seen in Rajasthan is in the Thar Desert. This
has sand dunes. There are also areas covered with sparse grasses and a few shrubs,
which grow if it rains.
In most areas of the Thar, the rainfall is scanty and sporadic. In an area it may rain
only once every few years.
In the adjoining semi arid tract the vegetation consists of a few shrubs and thorny
trees such as kher and babul
• The Great and Little Rann of Kutch are highly specialized arid ecosystems. In the
summers they are similar to a desert landscape.
• However as these are low-lying areas near the sea, they get converted to salt
marshes during the monsoons.
• During this period they attract an high number of aquatic birds such as ducks,
geese, cranes, storks, etc.
• Desert and semi arid regions have a number of highly specialized insects and
reptiles. The rare animals include the Indian wolf, desert cat, desert fox and birds
such as The Great Indian Bustard and the Florican.
• Some of the commoner birds include partridges, quails and sandgrouse.
How are desert and semi-arid ecosystems used?
• Areas of scanty vegetation with semi-arid scrubland have been used for camel, cattle
and goat grazing in Rajasthan and Gujarat.
• Areas that have a little moisture, have been used for growing crops such as jowar,
and bajra.
• The natural grasses and local varieties of crops have adapted to growing at very low
moisture levels. These can be used for genetic engineering and developing arid land
crops for the future.
What are the threats to desert ecosystems?
• Conversion of these lands through extensive irrigation systems has changed several
of the natural characteristics of this region. The canal water evaporates rapidly
bringing the salts to the surface. The region becomes highly unproductive as it
becomes saline. Example: The Indira Gandhi Canal
• Pulling excessive groundwater from tube wells lowers the water table creating an
even drier environment.
How can desert ecosystems be conserved?
• Desert ecosystems are extremely sensitive. Their ecological balance that forms a
habitat for their plants and animals is easily disturbed.
• Desert people have traditionally protected their little water resources. The Bishnois
in Rajasthan are known to have protected their Khejdi trees and the blackbuck
antelope for several generations.
•There is an urgent need to protect residual patches of this ecosystem within
National Parks and Wildlife Sanctuaries in desert and semi arid areas.
Aquatic ecosystems
The Pond ecosystem
• The pond is the simplest aquatic ecosystem to observe.
• There are differences in a pond that is temporary and has water only in the
monsoon, and a lake that is an aquatic ecosystem throughout the year.
• Most ponds become dry after the rains are over and are covered by
terrestrial plants for the rest of the year.
• When a pond begins to fill during the rains, its life forms such as the algae and
microscopic animals, aquatic insects, snails, and worms come out of the floor
of the pond where they have remained dormant in the dry phase.
•
Gradually more complex animals such as crabs frogs and fish return to the
pond. The vegetation in the water consists of floating weeds and rooted
vegetation on the periphery which grow on the muddy floor under water and
emerge out of the surface of the water.
• As the pond fills in the monsoon a large number of food chains are
formed.
• Algae is eaten by microscopic animals, which are in turn eaten
by small fish on which larger carnivorous fish depend. These are in turn
eaten by birds such as kingfishers, herons and birds of prey.
• Aquatic insects, worms and snails feed on the waste material excreted by
animals and the dead or decaying plant and animal matter.
• The temporary ponds begin to dry after the rains and the surrounding
grasses and terrestrial plants spread into the moist mud that is exposed.
Animals such as frogs, snails and worms remain dormant in the mud,
awaiting the next monsoon.
Lake Ecosystem:
Euphotic zone
( High productivity)
Aphotic zone
(little productivity)
Lakes are big fresh water bodies with standing water. They are divided into shallow
water zone called Littoral zone, an open water zone where effective penetration of
solar light takes place called Limnetic zone and deep profundal zone with no
penetration of light.
Lakes shows thermal stratification during the summer period: Epilimnion( warm
surface layer) and Hypolimnion ( Cold, bottom layer). In between there is
thermocline( region of sharp drop in temperature).
Lakes can be Oligotrophic (low nutrient concentration), mesotrophic and eutrophic(
high nutrient concentration especially nitrogen and phosphate)
River ecosystem: It’s a lotic ecosystem, where water flow downward from mountain
highland and flowing through the plain fall in the sea. River ecosystem have two type
of production: autochthonous( production within the stream) and allochthonous( supplied
from terrestrial sources).
Ocean ecosystem:
Ocean have two major life zone:
1) Costal zone: relatively warm, nutrient rich shallow water. Due to ample sunlight it is
zone of high productivity.
Open sea: It is deeper part of ocean away from the continental shelf. It is vertically
divided into three parts:
a) Euphotic zone: receive abundant sunlight and shows high photosynthetic activity.
b) Bathyal zone: receive dim light and is zone of geological activity.
c) Abyssal zone: is the dark zone( 2000 to 5000 meter deep), however it support
world’s largest ecological unit.
Estuary ecosystem: It is partially enclosed coastal area at the mouth of river where
fresh water and salty sea water meet. Therefore organism present in in estuaries
shows wide range of tolerance for temperature and salinity. Such organism are known
as eurythermal and euryhaline.
Estuaries have a rich biodiversity and many of the species are endemic.
How are aquatic ecosystems used?
• clean freshwater on which his life is completely dependent and for other
domestic uses.
• Water is essential for agriculture
• Marshes and wetlands are of great economic importance for people who
live on their fish, crustacea, reeds, grasses and other produce.
What are the threats to aquatic ecosystems?
• Water pollution occurs from sewage and poorly managed solid waste in urban
areas when it enters the aquatic ecosystem of lakes and rivers.
• Sewage leads to a process called eutrophication, which destroys life in the water as
the oxygen content is severely reduced.
• Beside domestic waste addition of industrial waste results into metal pollution,
which is dangerous for both aquatic biota and human life.
How can aquatic ecosystems be conserved?
• Water pollution must be prevented.
• Aquatic ecosystems, especially wetlands, need protection by including
them in Sanctuaries or National Parks in the same way in which we protect
natural forests.
• Construction of dam and barrage should be avoided to maintain the
natural flow of river system.