· This is an integrated approach in which all organisms (Plants and Animals) along with their environment and studied as one unit. Materials and energies pass in and out of the components.
Odum has defined ecosystems as “The basic fundamental unit of organisms and their environment interacting with each other and within their own components.”
· Study of an ecosystem may be carried out in various sizes.
· It may be the edge of a pond, a lake, a patch of forests land or even an aquarium.
· Odum has recognized the following components of an ecosystem:-
(a) Abiotic substances
These are the non-living constituents like:
CO2, O2, H2O, Ca, N,P,K. etc.
These are the autotrophs which are able to produce food from inorganic compounds. Main autotrophs are green plants and some forms of bacteria.
· They are those constituents of the ecosystem which consume the food which has been produced by the producers or autotrophs.
· The herbivores which depend upon green plants for their food requirements are the primary consumers e.g. Insects, Rodents etc.
· The primary consumers are fed upon by primary carnivore such as Frogs.
· The primary carnivores are fed by Secondary Carnivores such as Snakes.
· The Top carnivores include Lion, Tiger, Leopard, Vulture etc.
The function of these decomposers is to break down the dead cells, tissues etc. into simple substances to be reused by producers e.g.
i. Bacteria (Bacillus, Clostridium) etc.
ii. Fungi (Agarious, Mucor) etc.
· Different types of ecosystem support different types of food chains, each consisting of all three levels.
· There is a proportionate relationship between the number, biomass or amount of energy flow at producer, primary, secondary and tertiary consumers level of a food chain.
· All these kinds of relationship can be represented characteristically in the form of pyramids called ecological pyramids.
· These are the following types:-
i. Pyramid of Numbers
ii. Pyramid of Biomass
iii. Pyramid of Energy
i. During the process of Photosynthesis solar energy is trapped by producers and converted into chemical energy.
ii. This energy flow in the food chain from the producers to the top carnivore, decreasing at successive trophic levels.
iii. This can be depicted by the pyramid where the base showing energy utilization at the producer level and apex showing energy utilization by the top carnivores.
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