Ecosystem
(Term by A.G. Transley, 1935)
Eco = implies the
environment, “System” = implies an interacting, interdependent complex
- The natural conceived as single, giant ecosystem –
The BIOSPHERE
- The overall view of this type of approach is that
living organism and their non-living environment are is separable
interrelated and interact with each other.
- The term ecosystem was proposed by A.G. Transley in
1935, who defined it as ‘the system resulting from the integration of all
the living and non-living factors of the environment’.
- The vast ecosystem –biosphere – subdivided into
smaller units of smaller ecosystem (terrestrial-forest, desert, grass
land, man – engineered as cropland, aquatic-freshwater, marine etc.) of
different size.
TYPES OF ECOSYSTEM
Ecosystem component or structure
An ecosystem
consists of two types of components –biotic and abiotic. This biotic components
include all types of living beings. They are often distinguished into
autotrophs and heterotrophs.
(I) Biotic (living) components:
This is indeed
the trophic structure of any ecosystem where living organism are distinguished
on the basis of their nutrition relationship. From this trophic (nutritional)
stand point, on ecosystem has two components:
(1) Autotrophic components (= self nourishing =
Producers)
·
These are mainly green plants, including
photosynthetic bacteria.
·
Members of the autotrophic component are known
as producers
·
These are prepare organic compounds from
inorganic raw materials with the help of sunlight through the process of
photosynthesis.
(2) Heterotrophic (= other feeding) or
consumers or phagotrophs (Phago = to eat)
·
They consume the matter built up by the
producers (autotrophs)
·
Consumers are of two types:
(i)
Herbivores:
Feed directly on plant. They are also called first order consumer or primary
consumer. Ex- Grasshopper – deer - rabbit - goat etc. Elton (1927) called primary consumers as “key industry animals”
because they convert the pant material into animal material.
(ii)
Carnivores:
·
They are animals which feed or prey upon other
animals. The carnivores which feed upon herbivores are called secondary
consumers or primary carnivores e.g. Frog, bird, fox, cat etc.
·
The animal which feed upon the primary carnivores
are called secondary carnivores or third order consumer or tertiary consumer
e.g.Owl, peacock, tiger, lion etc.
·
Which can not be preyed upon further occupy top
position in the food chain are called top carnivores
(iii) Decomposers:
- These are saprophytic (sapro = to decomposer) micro
organism such as bacteria and fungi, which obtain their food from dead
bodies of producers (plant) and consumers (animals) and their organic wastes.
- Decomposers are often called micro-consumers because
of their smaller size. They are also called reducers.
- Decomposers secrete digestive enzymes in surrounding
medium to digest the organic material (ex. Extra- cellular digestion)
- They absorb a part of the decomposition products for
their own nourishment
- The remaining substances add materials and minerals
to the substratum. This is called mineralization.
(II) Abiotic or Non-living components:
- It includes (i) the amount of inorganic substrances
as P, S, C, N, H etc. involved in material cycles. The amount of these
inorganic substances, present at any given time in an ecosystem, is designated
as standing state or standing quality.
- Amount and distribution of inorganic chemicals, such
as chlorophylls etc. and of organic materials as protein, carbohydrate,
lipid etc present either in the biomass or in the environment.
- The climate of the given region
Functions of an ecosystem:
- It allows flow of biological energy i.e., control the
rate of production and respiration of the consumer
- It controls the rate of nutrient cycle i.e.,
production and consumption of minerals.
- It regulates both ways i.e., the environment by
organism and the organism by environment for ex. The nitrogen fixing and
photoperiodism is the process of organism nutrient by environment.
-->