An ecosystem referred to as a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life. Ecosystems contain biotic or living, parts, as well as abiotic factors, or non-living parts.
Generally ecosystems consist of two basic components.
The components of the ecosystem are seen to function as a unit when you consider the following aspects:
(i) Productivity
(ii) Decomposition
(iii) Energy flow and
(iv) Nutrient cycling
Productivity refers to the amount of organic matter accumulated in any unit time. It is of following types.
Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts.
Energy flow is the amount of energy that moves through a food chain. The energy input, or energy that enters the ecosystem, is measured in Joules or calories. Accordingly, the energy flow is also called calorific flow.
Except for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth. Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR).
Plants capture only 2-10 per cent of the PAR and this small amount of energy sustains the entire living world.
The energy flow takes place via the food chain and food web. During the process of energy flow in the ecosystem, plants being the producers absorb sunlight with the help of the chloroplasts and a part of it is transformed into chemical energy in the process of photosynthesis.
This energy is stored in various organic products in the plants and passed on to the primary consumers in the food chain when the herbivores consume (primary consumers) the plants as food. Then conversion of chemical energy stored in plant products into kinetic energy occurs, degradation of energy will occur through its conversion into heat.
Then followed by the secondary consumers. When these herbivores are ingested by carnivores of the first order (secondary consumers) further degradation will occur. Finally, when tertiary consumers consume the carnivores, energy will again be degraded. Thus, the energy flow is unidirectional in nature.
Moreover, in a food chain, the energy flow follows the 10 percent law. According to this law, only 10 percent of energy is transferred from one trophic level to the other; rest is lost into the atmosphere. This is clearly explained in the following figure and is represented as an energy pyramid.
The ecological pyramids represent the trophic structure and also trophic function of the ecosystem. Each bar of the pyramid represents a different trophic level. The different types of ecological pyramids include:
Pyramid of Numbers: This represents the number of organisms in each trophic level, irrespective of their size.
Pyramid of Biomass: This represents the total mass of organisms at each trophic level.
Pyramid of Productivity: It is the total amount of energy present at each trophic level and the total energy lost between each trophic level.
Ecological succession, the process by which the structure of a biological community evolves over time. Two different types of succession—primary and secondary—have been distinguished. The final stage of succession is a climax community, which is a very stable stage that can endure for hundreds of years.
The process of plant succession consists of nine steps. The nine steps are: (1) Nudation (2) Migration (3) Germination (4) Ecesis (5) Colonisation and Aggregation (6) Competition and Co-action (7) Invasion (8) Reaction and (9) Stabilisation.
Plant succession may be of two kinds:
The nutrient cycle is a system where energy and matter are transferred between living organisms and non-living parts of the environment. This occurs as animals and plants consume nutrients found in the soil, and these nutrients are then released back into the environment via death and decomposition. Mineral cycles include the carbon cycle, sulfur cycle, nitrogen cycle, water cycle, phosphorus cycle, oxygen cycle, among others that continually recycle along with other mineral nutrients into productive ecological nutrition.
The carbon cycle describes the process in which carbon atoms continually travel from the atmosphere to the Earth and then back into the atmosphere. Since our planet and its atmosphere form a closed environment, the amount of carbon in this system does not change.
Fossil fuel also represent a reservoir of carbon. Carbon cycling occurs through atmosphere, ocean and through living and dead organisms.
According to one estimate 4 × 1013 kg of carbon is fixed annually in the biosphere through photosynthesis. A considerable amount of carbon returns to the atmosphere as CO2 through respiratory activities of the producers and consumers.
The phosphorus cycle is the process by which phosphorus moves through the lithosphere, hydrosphere, and biosphere. Phosphorus is essential for plant and animal growth, as well as the health of microbes inhabiting the soil, but is gradually depleted from the soil over time.
Phosphorus is a major constituent of biological membranes, nucleic acids and cellular energy transfer systems. Many animals also need large quantities of this element to make shells, bones and teeth. The natural reservoir of phosphorus is rock, which contains phosphorus in the form of phosphates.
Ecosystem services are the many and varied benefits to humans provided by the natural environment and from healthy ecosystems.
These ecosystems, functioning in healthy relationship, offer such things like natural pollination of crops, clean air, extreme weather mitigation, human mental and physical well-being.
Robert Constanza and his colleagues have very recently tried to put price tags on nature’s life-support services. Researchers have put an average price tag of US $ 33 trillion a year on these fundamental ecosystems services, which are largely taken for granted because they are free. This is nearly twice the value of the global gross national product GNP which is (US $ 18 trillion).
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