? The term ecosystem was first coined by A.G.Tansely. ? Ecosystem consists of two Words : Eco Environment System Interaction Ecosystem2. According to E.P.Odum, an American ecologist, the ecosystem is the basic functional unit of organism and their environment interacting with each other and with their own components. ? e.g. Grassland, Forest, Aquarium, Pond, Lake, River and Ocean. ? Grassland Ecosystem Forest Ecosystem Ocean Ecosystem3. Ecosystem Terrestrial Aquatic Eg.Forest, Grassland and Desert Eg. Pond, Lake, Wetland, River and Estuary4. Abiotic non-living Eg. soil, water, light, inorganic nutrients and weather Ecosystem Biotic living Eg. producers and consumers5. ? From nutrition point of view, the biotic components of ecosystem can be grouped into three categories: Biotic components of Ecosystem Producers Consumers Decomposers6. ? The vertical distribution of different species occupying different levels is called stratification. ? Eg. Trees occupy top vertical strata or layer of a forest, shrubs the second, herbs and grasses occupy the bottom layers.7. The components of the ecosystem are seen to function as a unit when we consider the following aspects: ? Productivity ? Decomposition ? Energy flow ? Nutrient cycling8. PRODUCTIVITY Productivity – The rate of biomass production is called productivity. Units: g–2 yr –1 or (kcal m–2) yr–1 ? Gross primary productivity – The rate of production of organic matter during photosynthesis is called gross primary productivity. Gross PP (GPP) = total energy fixed Net PP (NPP) = GPP – respiration ? Secondary productivity – The rate of formation of new organic matter by consumers is called secondary productivity . ?9. ? The breakdown of complex organic matter into inorganic substances like carbon dioxide, water and nutrients and the process is called decomposition. Steps in decomposition Fragmentation Leaching Catabolism Humification Mineralization10. Decomposition cycle in a Terrestrial Ecosystem11. ? The flow of energy is one way direction from producer to consumers, and ends in decomposition process. ? However, a part of the energy is lost as heat and agrees with the phenomenon of second law of Thermodynamics.12. Man (Secondary consumer) Goat (Primary Consumer) Grass (Producer)13. Detritus Food Chain Detritus is non-living particulate organic material includes the bodies or fragments of dead organisms as well as fecal material. ? Decomposers are heterotrophic organisms also called saprotrophs. Eg. Fungi and Bacteria. ?14. ?A food web depicts various feeding connections in an ecological community. ? Natural interconnected food chains make a food web.