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Concept of an Ecosystem

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Concept of an Ecosystem CONCEPT OF AN ECO SYSTEM Dr.R.Priscilla, HoD of Physics, ADM. College for Women, Nagapattinam. Eco System The various communities of living organisms interact among themselves As well as with their physical environment like soil, air and water. This functional unit or ‘system’ made up of living and non-living components is called an ‘ecosystem’. This term ‘ecosystem’ was coined by Tansley in 1935. The interaction is through energy flow and cycling of materials. *This makes the ecosystem to sustain life continuously. *An eco system may be of any size. i.e, the whole world may be considered as an ecosystem called biosphere. *They are natural but some man made and none of the eco system is independent but all of them are interdependent. Structure and function of an ecosystem Two major components 1. The abiotic component which includes the physical environment. 2. The biotic component comprising of all the living organisms. ABIOTIC COMPONENTS BIOTIC COMPONENTS Sunlight Primary producers Temperature Herbivores Precipitation Carnivores Water or moisture Omnivores Soil or water chemistry (e.g., P, NH4+) Detritivores etc. etc. Abiotic component consists of 1. the solid mineral matter of the earth(lithosphere) 2. the water in the oceans, lakes, rivers and ice caps etc.(hydrosphere). 3.the gaseous mixture in the air(atmosphere) and 4. the radiant solar energy. The environment created and maintained by the interactions of the common environmental factors, function as a whole unit. Any of these factors cannot be removed or altered without affecting the other factors. Therefore, the environment is called HOLISTIC. Producers, consumers and decomposers Biotic Component – the organisms of ecosystems are divided into two classes. 1. The producers: autotrophs (green plants & certain bacteria) – produce their own food. Since these organisms produce food for all the other organisms they are also known as producers. 2. consumers: Heterotrops – depends on the producers for the food. Depends directly or indirectly upon the autotrophs for their food. Consumers Decomposers. Consumers are of three kinds. They are 1. Primary consumers 2. Secondary consumers 3. tertiary consumers. Primary consumers - a herbivore is a primary consumer. - it derives its nutrition directly from plants Secondary consumers - a carnivore is a secondary consumer. - it derives its energy from the producers (plants) Tertiary consumers - they are Carnivores that feed on other carnivores. Omnivores are consumers that derive their energy from both producers and herbivores. Decomposers - consists of bacteria and fungi. - produce enzyme within their bodies. - act on dead plant & animal material and some of the degraded and digested products and then absorbed. - perform an invaluable service to the ecosystem by the mineralization of organic matter and made available for reuse. The process of eating and being eaten forms a chain. Producer herbivore carnivore carnivore – back to producers. The position of the organism in the food chain is indicated by tropic levels. Tropic level may be defined as the no. of links by which it is separated from the producer. Grass -» Grasshopper -» Lizard -» Snakes -» Hawks. Grass -» Mice -» Snakes -» Hawks Grass -» Rabbits -» Dogs -» Tigers/Lions. Trees -» Deer/Goats -» Foxes -» Tigers/Lions. Trees -» Birds -» Snakes -» Hawks. Phytoplankton -» Larvae -» Fishes -» Whales. First Tropic Level – producers 2nd Tropic Level – herbivores 3rd Tropic Level – carnivores The same organism may operate in the ecosystem at more than one tropic level,i.e, deriving food from more than one source. An organism may be eaten by several organisms of a higher tropic level or an organism at a lower tropic level may feed upon several different organisms. Thus we obtain several food chains linked together and intersecting each other to form a network known as FOOD WEB Energy flow in a Eco system Energy flow : In any eco system, for their structural development and functioning obtain energy from a group of organisms that are already present in a particular system. 1.Energy travels only through single way 2.There is reduction of energy in each tropic level * Energy level is const. for every ecosystem * One cannot increase or decrease the energy level * Can be converted into one state to another state * A portion of energy remains unused during the conversion of energy * After conversion its reaction capacity gets reduced. * Because of this, there is flow of energy from higher tropic level to the lower tropic level. * A part of the radiant energy of the sunlight is converted into chemical energy by the producers and is stored in the organic compounds * The rest of the radiant energy is converted into heat energy. Food Chains, Food Webs and Ecological Pyramids. Food Chains : The transfer of food energy from producers (plants) through a series of organisms, i.e, Herbivores Carnivores Top carnivores Decomposers with repeated eating and being eaten is known as a food chain. It is also called as trophic level. Example : In grassland ecosystem, the food chain starts from grasses and goes through the grasshopper, calotes, snake and the eagle or hawk in an orderly sequence. Food webs Though many food chains can be traced in an ecosystem they never operate as isolated sequences. But they are interconnected with each other forming some interlocking pattern. This is known as food web. Ecological Pyramids The interrelation between numbers, biomass and energy contents of consumersof the first order, second order and upto the top carnivores in any ecosystem is represented in diagrammtic ways. They are called as ecological pyramids. They are of three Ecologicaltypes, viz., Pyramids Pyramid of Pyramid of Pyramid of numbers biomass energy 1. Pyramid of numbers : The relationship between the number of producers and the primary, secondary and tertiary consumers constitutes the pyramid of numbers. Tiger or lion(Top carnivores) Fox (Sec.carnivores) Rabbit(Pri.consumer) Grasses(Pri. Producer) Grassland ecosystem shows upright pyramid In the grassland ecosystem the wide base of the pyramid represents the large number of primary producers. The primary consumers like the rabbit and the grasshopper form the second large number. The top carnivores like the tiger is present in the least number and occupy the peak of the pyramid. So in this way the numbers are represented in a diagramatic way and an upright pyramid is formed. Pyramid of Biomass Biomass is the amount of living organisms and living matter present in a particular ecosystem Tiger In grassland ecosysytem, the Biomass of the producers is the Fox highest of all the trophic levels. Grasses Pyramid of Biomass in Grassland Ecosystem Here, not only the number decreases but the biomass also continue to decrease from primary producers to the top carnivores. The relationship between the biomass of producers and the consumers of the ecosystem can again be represented in the form of upright pyramids. Pyramid of energy _______Carnivores(Tertiary consumers) _________Carnivores(Sec.consumers) ________Herbivores (Pri.consumers) ________Producers In an ecosystem the primary producers trap the sunlight energy and convert into chemical energy through Photosynthesis. The energy traped in the food materials flow in the food chain from the producers to the herbivores and then to carnivores and finally to top carnivores. Here the energy flow is always unidirectional and at successive trophic levels it decreases. Therefore the pyramid of energy is always vertical. The components of a forest ecosystem are Abiotic components – organic and inorganic matter present in the land and atmosphere. Biotic components – living flora and fauna are the living cpts. of a forest. They are recognized as Producers consumers Decomposers Producers: * trees are the primary producers. * Vines and epiphytes are the two characteristics of evergreen forest. * In India tropical evergreen forest are found along the West Ghats and the NEFA Consumers: *The macro consumers (animals) in different forests are well adapted for the conditions prevailing there. *Foliage arthropods such as ants, flies, beetles, leaf hoppers, bugs and spiders are found. *Moles, squirrels, fruit bats, mongooses are also present. Decomposers: The soil organisms found in the forest are protozoan, flat worms, nematodes, annelids, snails, millipedes, centipedes, spiders, spring tails, termites, trips and ants. Some of the soil organisms and soil bacteria play the role of decomposers. Productivity: *Different types of forest vary in gross productivity *The plants and other autotrophic organisms store some dry matter by their photosynthetic activity. The rate at which this dry matter is stored in the ecosystem is called the primary productivity. *The productivity is the highest due to the stable environment, large availability of water and high constant temperature. Pond Ecosystem : Ponds are small bodies of shallow standing water. They are characterized by relatively quite waters and abundant vegetation. A pond serves as a good example for a fresh water ecosystem. It consists of both abiotic and biotic components. The chief components of abiotic components are heat, light, pH value, organic and inorganic compounds namely carbon di oxide, oxygen, calcium, nitrogen, phosphates, amino acids, humic acids, etc. The amount of these components are estimated for biomass determination. The various organisms of the biotic components
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