An ecosystem consists of two biotic components, the autotrophic components and the heterotrophic components.
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1. Autotrophic Components:
(Autotrophs: auto – self, troph = nourishing)
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These are self nourishing components in the fixation of light energy, use of simple inorganic substances and manufacture of complex materials predominates.
2. Heterotrophic Components:
(Heterotrophs; Hetero = other, troph = nourishing)
These are other nourishing components and consume the products of the autotrophs. They also attack the dead bodies of the organisms.
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The interaction of autotrophic and heterotrophic components is a universal feature of all ecosystems, whether they are located on land, in fresh water or in the ocean. From structural view point three biotic components have been recognized.
(i) Producers:
These are autotrophic organisms like photosynthetic and chemo synthetic bacteria, blue green algae, algae and. other green plants. In a ecosystem producers capture energy from non-organic sources, especially light, and store some of the energy in the form of chemical bonds, for later use.
Various types of algae are the most important producers of aquatic ecosystems, although in marshes and estuaries, grasses may be producers. In terrestrial ecosystems tree, shrubs, herbs, grasses and mosses that contribute with varying importance to the production of ecosystem.
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The amount of energy that the producers capture sets the limit on the availability of energy for the ecosystem. Thus when a green plant captures a certain amount of energy from sunlight, it is said to produce the energy for the ecosystem. Heterotrophic organisms depend on nutrition. Based on size of producers, they are of two types:
(i) Micro producers (microscopic) : Algae, phytoplankton etc smaller size)
(ii) Macro producers (Macroscopic): Green plants, grasses, crops etc. larger in size.
(ii) Consumers
Consumers are heterotrophic organisms (Primarily animals) in the ecosystem, which eat other living creatures. These are herbivores, which eat plants, and carnivores, which eat other animals. Sometimes herbivores are known as primary macro consumers and carnivores are called secondary macro consumers.
Based on dependency, they are classified into three major groups:
(i) Primary consumers: depend on producers (Plant)
(ii) Secondary consumers: dependent on primary consumers.
(iii) Tertiary consumers: dependent on both primary and secondary consumer.
(iii) Decomposers or reducers
The decomposers are the heterotrophic organisms. They feed on dead protoplasm breaking down its complex organic components of cells from dead producers and consumers organisms either into small organic molecules, which the utilize themselves as saprophytes or into inorganic substance that can be used as raw materials by green plants.
Fungi Agaricus, Mucor, Aspergillus and certain bacteria (Clostridium, Pseudomonas) axe the prime representation of this category. Decomposer, decompose the complex materials in dead organisms, rendering them simple enough for use by the producers for their own growth, thus completing the cycle. No ecosystem could function alone without decomposers. Dead organism would pile up without rotting, as would paste products.
The decomposer takes the energy and matter that they have harvest during this feeling process for their own metabolism. Heat is liberated in each chemical conversion along the metabolic pathway.
Examples of Ecosystem
Small lake or pond is a classic example of Ecosystem. Ponds are not stratified as the force of wind keeps the entire mass of water in circulation. It results in uniform distribution of oxygen C02 and temperature. The different components are:
Abiotic components:
Non living parts of a fresh water pond include the water, dissolved oxygen, CO-, inorganic salts such as phosphate, nitrates and chloride of sodium, potassium and calcium and organic compounds such as amino acids humic acids. Producers take them in a small amount in soluble form and most of them remain inside the bodies of animals.
Biotic components:
The living parts of the freshwater pond is related to function of organisms i.e. contribution towards keeping ecosystem operating and interacting.
(i) Producers:
The aquatic green plants might be submerged, floating and amphibians the two types of producers are larger plants along with shore or floating in shallow water and microscopic floating plants e.g. Algae, distributed through the deep water as light is there.
These tiny plants are referred as phytoplankton. Phytoplankton’s have more significance as food producers for the freshwater pond ecosystem than larger plants.
(ii) Consumers:
The macro consumers include insect larvae, insects, fish-crustacean, and mollusks. Macroconsumers are also known as photographs. Primary consumers or herbivores remain dependent upon the living green plants or the plants remains.
The herbivores comprise two category Primary consumers such as 200 plankton (animal’s phytoplankton) found near the surface of water and benthos (bottom forms) is the plant eater (herbivores).
The secondary consumers (carnivores) are the carnivores that eat the primary consumers e.g. Fish, frogs, insect. There might be tertiary consumers that eat the carnivores (secondary consumers).
(iii) Decomposers:
Bacteria, flagellate Protozoan’s and fungi, which break down the organic compounds of dead producer and consumers into inorganic substances that can be used by green plants.
In pond ecosystem we observed all four basic components-abiotic, producers, consumers and decomposers.
Types of Ecosystem – Ellenbery (1973)
1. Biosphere is the largest ecosystem
2. Megaecosystem is:-
(a) Marine ecosystems: (Saline water, ocean, lake)
(b) Limnic ecosystem: fresh water
(c) Semi terrestrial: Wet soil and air.
(d) Terrestrial ecosystem: Aerial soil and air.
(e) Urban industrial ecosystem: manmade e.g. Cropland, city.
3. Macro ecosystems: forests.
4. Meso ecosystems: Cold deciduous broad leaf forest and fauna. Two types:
(a) Micro ecosystems: Low lands, mountains, subalpine cold deciduous broad leaf forest and fauna.
(b) Nano ecosystems: small ecosystem of individual.