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Ecosystem

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					Compiled and edited by Dr. Biswanath Mahanty
Ecosystem
An ecosystem is defined as a dynamic entity composed of a biological community and its
associated abiotic environment linked in numerous and complex dynamic interactions and
identifiable on its bio-geographical features. Ecosystems always undergo alterations to their
biotic and abiotic components where change in one component cascades and sometimes amplifies
into other components. The stability of an ecosystem are controlled by abiotic components such
as geographical climatic conditions, soil characteristics as well as the biotic components of
various plants, animals and microbes. Interactions of biotic and abiotic components are essential
feature for any dynamic ecosystem. The ecosystem may be considered as large as our planet or as
small as an aquarium. The boundary of any ecosystem is completely imaginary that we make to
understand it in a simpler way.
To have a complete profile of any given ecosystem, we must know what variants of ecosystem is
it (the broad classification on bio-geographical basis e.g. aquatic, desert, pond or grass land),
what are the biotic components present in it, how the animal or plant species interact one with
other. Additionally the study should include knowledge about its possible threats, dynamic
nature, stability and versatility.


Major Classification of ecosystem
Ecosystem can broadly be classified into terrestrial or aquatic based on their location. Climate
differences from place to place largely determine the types of ecosystems we see. How terrestrial
ecosystems appear to us is influenced mainly by the dominant vegetation which in turn largely
depends on climatic condition such as temperature, rain fall, humidity and geological properties
such as soil type, altitude etc. The terrestrial ecosystem based on its bio-geographical nature can
be classified into (i) forest ecosystem, (ii) grass land ecosystem (iii) desert ecosystem. On the
other hand aquatic ecosystems are also classified either into pond, river and marine ecosystem.


Major components of an ecosystem
Each ecosystem whether natural or artificial must have two sets of components viz. the living or
biotic and non-living or abiotic such as soil, atmosphere, solar radiation, water and living
organisms




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Compiled and edited by Dr. Biswanath Mahanty
    Soils are complex mixture of weathered rock fragments, mineral particles, organic matter,
       and living organisms. It provides nutrients, water, and a structural growing medium for
       organisms.
    The atmosphere provides organisms found within ecosystems with carbon dioxide for
       photosynthesis and oxygen for respiration.
    Solar radiation is used in ecosystems to heat the atmosphere and to evaporate and
       transpire water into the atmosphere. Sunlight is also necessary for photosynthesis which
       provides the energy for plant growth, metabolism and the organic food for other forms of
       life.
    Living tissue is composed of a very high percentage of water which is deemed essential
       for survival. Water is the medium by which mineral nutrients enter and are translocated in
       plants. It is also necessary for photosynthetic chemical reactions.
Variety of living organisms in an ecosystem can be classified as:
    Producers - are organisms that can manufacture the organic compounds they use as
       sources of energy and nutrients. Most producers are green plants that can manufacture
       their food through photosynthesis
    Consumers which get their energy and nutrients by feeding directly or indirectly on
       producers can be of herbivores - eating plants for their energy and nutrients or carnivores
       - consuming herbivores other carnivores.
    Decomposers utilize dead tissue of plants and animals and there by converting back the
       organic matter into inorganic nutrients in the soil, which can again be used by plants for
       the production of organic compounds in a cyclic way


Energy flow through ecosystem
Energy flow through an ecosystem is unidirectional. Energy obtained is used for various body
activities where much amount of energy gets dissipated as heat.
The energy flow begins with the Sun, where through photosynthesis reaction green plants utilize
water and carbon dioxide to make glucose as energy store acting as producer. The energy moves
through primary consumers or herbivore which takes up plant as energy source. Most of the
energy the primary consumer gets from the producer is used up for its own activity and the
remaining energy can be available to secondary consumer. The secondary consumer may be a
carnivore or herbivore.


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Compiled and edited by Dr. Biswanath Mahanty
The representation transfer of energy from sun to producer to primary consumer to secondary
consumer to tertiary consumer is known as food chain. That the amount of available energy
decreases down the food chain, where a large number of producers are required to support a small
number of primary consumers and similarly a large number of primary consumers to support a
small number of secondary consumers. When represented in food pyramid, the photosynthetic
animals forms the first tropic level and the herbivores are presented in second tropic level. In
apex, only small numbers of carnivores are there. In Ecosystem, large number of interlinked food
chains creates food web, where one consumer can take up two distinct species from two
otherwise different food chains or any member of a food chain can serve two distinct predators at
two food chains.


Ecological Succession
Ecological succession is predictable and orderly changes in the composition or structure of an
ecological community from an un-occupied habitat or during recovery from a disaster. This is the
gradual replacement of one community by another through natural processes over time.
Succession that begins in areas where no soil is initially present is called primary succession such
as in volcanoes sides, land-slides etc.
    Starts with the arrival of living things such as lichens that do not need soil to survive
    Lichens and the forces of weather and erosion breaks down rocks into smaller pieces
       starting soil formation
    Simple plants like mosses and ferns can grow in the new soil. When they die, adds more
       organic material
    The soil layer thickens, and grasses, wildflowers, and other plants begin to take over.
    These plants die, and they add more nutrients to the soil so that shrubs and tress can
       survive
    Insects and birds, animals starts moving in new ecosystem


Succession that begins in areas where soil is already present is called secondary succession.


Forest ecosystem in India
A forest ecosystem is natural woodland consisting of all plants, animals and microorganisms with
all abiotic factors functioning together in a given environment. Forests sometimes contain many
tree species within a small area or relatively few species over large areas. In India major forest
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based ecosystems are primarily classified based on the leaf structure either as broadleaf forest or
coniferous forests and further classified on the climatic condition, predominant plant species, and
canopy structure. Apart from coniferous forest major other four variants are of important types.


    The evergreen forests usually occur in areas receiving more than 200 cm of rainfall and
       having a temperature of 15 to 30°C. These forests are dense and multi-layered harbors
       many types of plants and animals. The trees are tall, hardwood and evergreen as there is
       no period of drought. Leaves are broad and give out excess water through transpiration. In
       India, evergreen forests are found in the western slopes of the Western Ghats in States
       such in Kerala, in Khasi and Jaintia hills of Meghalaya and NE India. Some of the trees
       found are rosewood, mahagony and ebony. Trees like Ablus, Mahogany, ebony,
       rosewood, sisham (Dalbergia Sissoo), Sandalwood (Santalum album) grow in these
       forests. The trees are tall and form a dense canopy overhead.
    The deciduous forests are found in areas receiving annual rainfall of 100 to 200 cms in
       India, with a distinct dry and rainy seasons and a small range of temperature. They occur
       on the western side of the Deccan Plateau, the north-eastern part of the Deccan Plateau
       and the lower slopes of the Himalayas covering parts of Chhattisgarh, Orissa, Bihar,
       Jharkhand, Andhra Pradesh, Karnataka, Kerala and Tamil Nadu. The principal trees of
       these forests are teak, sal, sandalwood, mahua, khair, mango, jackfruit, sisasm,
       myrobalan, arjun and the banyan tree. Species belonging to these forests drop leaves in
       autumn.
    The thorn and scrub forests are confined to areas with a rainfall of less than 75cms. It
       spreads over north-western part of the country in Rajasthan, Punjab, Uttar Pradesh,
       Madhya Pradesh, Haryana and also in parts of south India. Kikar, babul, khair, acacia,
       munj and sawai grass are found in these forests. These forest areas are being converted
       into residential areas due to population pressure. Thorn and cactus are found in western
       Punjab and western Rajasthan where the rainfall is less than 50 cms.
    Mangrove forest are found in the tidal areas along the coast of India particularly the
       lowlands and river-mouths of the eastern coast. Mangrove trees can survive both in fresh
       and saline water- the major characteristic of the tidal areas as Sundarban vast tidal
       mangrove forests of the Ganga-Brahmaputra delta in West Bengal.




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Grassland Ecosystem
Grassland is an area where the annual rainfall is insufficient to support growth of trees, but is still
high enough to inhibit desert formation Grasslands are not restricted to low rainfall areas rather
several grassland types form either clearings in different forest types or are located on hill slopes
with patches of forests. Grassland ecosystems form Himalayan pastures, the terai grassland of the
foothills, semi-arid grasslands of Western and Central India, in scrublands of the Deccan Plateau
and in the Shola forests of the Western Ghats, Nilgiri ranges are of predominant classification.
    Himalayan pastures in the Himalayas extend up to the snowline. These grasslands at the
       lower level are found along with coniferous or broad-leaved forests. The Himalayan
       wildlife requires both the forest and the grassland ecosystem. Several wild sheep and goat
       such as the Goral are found here.
    Terai grasslands at the foothills of the Himalayas consist of tall elephant grass along with
       Sal forest. The largest herbivore of the Terai is the elephant. It requires an enormous
       amount of tall grass to feed on. The Terai grasslands form the habitat of the Swamp deer,
       Wild buffalo and the Rhinoceros.
    Semi-arid grasslands of the Western and Central India are interspersed with thorn forests.
       Some of the very important Indian animals such as the blackbuck, chinkara and
       endangered birds like the Great Indian Bustard are found here. The apex predator of this
       ecosystem was the cheetah which is now extinct in India.
    The Shola grasslands are found in high rainfall areas in Southern India located on hill
       slopes with patches of forest. The highly endangered Nilgiri Thar is found only in these
       grasslands.




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