Ecosystem : Structure and function
Organisms interact with each other and also with the physical conditions that are present in their habitats. 'The organisms and the physical features of the habitat form an ecosystem' - Clarke (1954). The concept of ecosystem was first put forth by A.G.Tansley(1935). Ecosystem is the major ecological unit. It has both structure and function. The structure is related to species diversity.
According to E.P.Odum, the ecosystem is the basic functional unit of organism and their environment interacting with each other. The function of ecosystem is related to the energy flow, decomposition, nutrient cycling and major biomes.
Generally ecosystems consist of two basic components.
1. Abiotic component.
2. Biotic component.
1. Abiotic components
It includes basic in-organic (soil, water, oxygen, calcium carbonates, phosphates etc.) and organic compounds. It also includes physical factors such as moisture, wind currents and solar radiation. Radiant energy of sun is the only significant energy source for any ecosystem.
2. Biotic components
Include producers, consumers and decomposers.
Producer : These are the autotrophic, chlorophyll-bearing organisms, which produce their own food.
Consumers : A consumer which gets nutrition by eating plants is called Primary consumers (herbivore) (eg) Rabbit, deer and cow.
The Secondary Consumer: (carnivores) is an animal that eats the flesh of herbivores (eg) cats and dogs.
Tertiary Consumers: are the type of carnivores, which prey upon other carnivores. (eg) Lion, tiger and vulture.
Decomposers attack the dead remains of producers and consumers and degrade the complex organic substances into simpler compounds to derive their nutrients. The decomposers play very important role in maintaining the dynamic nature of ecosystem.
An ecosystem is a functional and life sustaining environmental system. The environmental system consists of biotic and abiotic components. Biotic components include living organisms and abiotic components includes in organic matter and energy.
In an ecosystem there are three functional components.
1. Inorganic constituents
3. Energy input
These three components interact with each other to form an environmental system. The primary producers convert inorganic constituents into organic components by photosynthesis using the energy from the solar radiations. The herbivores make use of the energy from the producers and they themselves serve as a food for the carnivores. Animals of different types accumulate organic matter in their body which is taken as food. They are known as secondary producers. The dead organic matters of plants and animals are decomposed by bacteria and fungi which break the complex molecules and liberate inorganic components. These are known as decomposers. During this process some amount of energy is released in the form of heat. The ecosystem of different habitats are interrelated with one another.
Productivity refers to the amount of organic matter accumulated in any unit time. It is of following types.
1. Primary productivity
Green plants absorb solar energy and store it in organic form as chemical energy. This forms the first and basic form of energy storage and is known as primary productivity. It is the rate at which the organic material is formed by photosynthesis per unit area of surface per unit time.
2. Secondary productivity
It refers to consumers or heterotrophs. The consumers utilize the food materials during the process of respiration. The rate at which the food energy is assimilated is called secondary productivity.
3. Net productivity
This refers to the rate of storage of organic matter which is not used by heterotrophs. These may be equivalent to the net primary production minus consumption by the heterotrophs.