Structure and Functions of an Ecosystem
* An ecosystem is a stable and functional unit where all living organisms interact among themselves and the surrounding physical environment, leading to a flow of energy and nutrients.
* Typically, an ecosystem has two major components-abiotic and biotic.
* The structure of an ecosystem involves:
• The composition of a biological community in terms of number, biomass, life history, population and distribution of species.
• Availability and distribution of several non-living factors such as the distribution of nutrients, water and climatic and physical conditions.
* In an ecosystem, the energy flow is unidirectional while nutrients keep moving in a cyclic manner.
Decomposition in an Ecosystem
* The natural process in which decomposers break down complex organic matter and convert them into simple, inorganic substances like water, carbon dioxide and nutrients in known as decomposition.
* The raw material for decomposition is detritus comprising dead and decaying plant and animal remains.
* The important steps involved in the process of decomposition are fragmentation, leaching, catabolism, humification and mineralisation.
* The rate of decomposition depends on the chemical composition of the detritus and climatic factors like soil moisture and temperature.
* Warm temperature and a moist environment result in a faster rate of decomposition whereas low temperature and anaerobiosis slow the process of decomposition.
Productivity of an Ecosystem
* Biomass is the mass of living organisms or the organic matter present in a unit area of an ecosystem at a given tie.
* Primary productivity si the amount of biomass produced per unit area and per unit time by plants during photosynthesis.
* Gross primary productivity is the total energy fixed by primary producers through photosynthetic activity per unit area per unit time.
* Net primary productivity is the net biomass available for consumption by heterotrophs.
* Secondary productivity is the rate of formation of biomass per unit area and time by consumers
Ecological Pyramids
* An ecological pyramid is a graphic representation of an ecological parameter such as number of individuals , amount of biomass or amount of energy present at different trophic levels in an ecosystem.
* Ecological pyramids are of three types: pyramid of numbers, pyramid of biomass and pyramid of energy based on the types of parameters used.
* A pyramid of numbers is a graphic representation of the number of individuals per unit area present at various trophic levels in an ecosystem.
* A pyramis of biomass is a graphic representation of biomass present per unit area at each trophic level in an ecosystem.
* A pyramid of energy is a graphic representation of the amount of energy trapped per unit time and unit area at different trophic levels of a food chain.
Ecological Succession
* The gradual and fairly predictable change in composition of different species in a given area is known as ecological succession.
* All communities undergo constant changes in a sequential and orderly manner, leading to a climax community, which is in near equilibrium with the environment.
* The sequence of communities that replace one another in the process of ecological succession in a given area is known as a sere or seres.
* Primary succession takes place in areas where no life previously existed.
* Secondary succession takes place in areas that once has an existing biotic community, which was wiped out due to reasons like earthquakes, landslides or fire.
Energy Flow in Ecosystems
* Photosynthetic Active Radiation or PAR is the spectral range of solar radiation that can be used by green plants for photosynthesis.
* In nature, there are two types of food chains- Grazing Food Chain and Detritus Food Chain.
* All organisms in a food chain occupy a specific place depending their source of food and nutrition, which is known as their trophic level.
* Standing crop is the mass of living material at a particular time at each trophic level.
* The transfer of energy follows a ten-percent law, that is, o average only ten-percent of energy is transferred from one trophic level to another.
Nutrient Cycling and Ecosystem Services
* The cyclic movement of nutrient elements between organisms and the environment is known as nutrient cycling or biogeochemical cycles.
* The amount of nutrients in soil at any given time is known as standing state.
* The atmosphere is the main reservoir of nutrients in gaseous cycles.
* Soil, rocks and minerals in the earth’s crust are the main reservoir of nutrients in sedimentary cycles.
* Nitrogen, oxygen, carbon and water are some important gaseous cycles while phosphorous , calcium and iron are some important sedimentary cycles.
* Ecosystem services are a range of products and services that human beings receive from functioning ecosystems.