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STD : 9TH (1ST UNIT TEST ), SUB : -SCIENCE, LESSON : - 7 ENERGY FLOW IN AN ECOSYSTEM, Q.1. Complete the following table (carefully study the carbon , oxygen and nitrogen cycle ), Q . 2. Correct and rewrite the following statement and justify your correction :, Carnivores occupy the second trophic level in the food chain ., Ans : Correction : Carnivores occupy the third trophic level ., Autotrophic producers constitute the first trophic level . Herbivorous animal obtain their nutrient from them . They occupy second tropic level . carnivorous animal feed upon these Herbivorous animals ,therefore they occupy the third trophic level in the food chain ., The flow of nutrient in an ecosystem is considered to be a one way transport ., Ans : Correction : The flow of nutrient in an ecosystem is considered to be cyclic ., The green plants are producers . by photosynthesis they convert minerals and in organic compound in to glucose This food is transferred along with food from producers –primary consumers –secondary consumers The decomposers of the ecosystem .decompose all the dead and decaying organism and return these nutrients back to the ecosystem . Thus the flow of nutrients in cyclic and not one way transport ., Plants in an ecosystem are called Primary consumers ., Ans : Correction : Plants in an ecosystem are producers ., Green plants are called producers as they carry out photosynthesis with the help of solar, Energy . The food which they produce it utilized by the herbivores . Therefore , they are called, Producers . Herbivores are primary consumers ., Q . 3. Give reasons., Energy flow through an ecosystem is ‘one way ‘, Ans : i) Sun is ultimate source of energy ., ii) In all ecosystem producers ( Green plants ) store the solar energy in the form of food., iii) This energy is passed on from one trophic level to the other trophic level ., iv) owing to decomposition some part of this energy is released in the form of heat ., v) However no part of energy returns to the sun . Therefore , energy flow through an, ecosystem is one way ., Equilibrium is necessary in the various bio-geochemical cycle ., Ans : i) In nature , the various bio-geochemical cycle operate simultaneously and there is an, Equilibrium between them ., ii) During these cycles , the inorganic compounds that are released from organic compound, are released back to the nature ., iii) Soil bacteria and other decomposers’ play a vital role in these cycles ., iv) If bio-geochemical cycle are Imbalanced then they bring about the imbalance in the, ecosystem as a result of which the ecosystem is destroyed . This shows the equilibrium is, necessary in the various bio-geochemical cycles., Flow of nutrients through an ecosystem is cyclic ., Ans : i) Producers obtain nutrients from the soil , and CO2 from the atmosphere and synthesis, Food from them with the help of photosynthesis ., ii) During this process , the inorganic substance are converted in to organic substance ., iii) Consumers consume the food produced by producers . The energy in the form of food is, thus passed from one trophic level to other tropic level ., iv) Both producers and consumers after their death undergo decomposition and after, decomposition the nutrients released from them mix with the soil . In the same way ,the, excreta of animals undergo decomposition and released nutrients to the environments., Thus , we see that the flow of nutrients in the ecosystem follows the cyclic path ., Q . 4. Explain the following cycles in your own words with suitable diagram ., Carbon cycle, Nitrogen cycle, Oxygen cycle, Ans : (1) Carbon cycle : -, From the atmosphere , carbon in the form of carbon dioxide reaches the green plants ., From green plants carbon in the form of food is carried to plants and from plants to the animals .From both plants and animals , carbon reaches the atmosphere following a cyclic path . This cyclic path of carbon from plants to animals and from both these to the atmosphere is called carbon cycle ., In the atmosphere and water bodies , carbon dioxide is the main source of carbon . Green plants synthesize carbohydrate from carbon dioxide of the atmosphere as shown below :-, Light, 6CO2 +12 H2 O >>>>>>>>>>>>>>>>>>C6H12O6 + 6H2O +6O2, Carbon water Chlorophyll Glucose water Oxygen, Dioxide, The carbohydrates (glucose ) in the form of food chain reaches the plants , from plants to herbivorous animal and from herbivorous animal to carnivorous animals . In this ways , the carbon moves from one living being to another living being ., During the process of respiration , both plant and animals oxidize carbohydrates and libret energy along with the evolution of CO2 ., C6H12O6 +6O2 ……………6CO2 +6H2O +Energy, During the process of fermentation and anaerobic respiration microorganisms produce carbon dioxide ., Carbon compound undergo decomposition through micro- organisms. During this process also carbon dioxide is produced which mix with the atmosphere ., During combustion ,the organic carbon undergo oxidation and produced energy and carbon dioxide ., In this way , carbon in the form of carbon dioxide from the atmosphere reached the food chain through plants. Processes like respiration , combustion ,fermentations , decomposition , etc. released carbon dioxide which reaches the atmosphere again and in this way there is a cyclic movement of carbon ., (2) Oxygen cycle :, The air (atmosphere ) contain about 21% of oxygen .The atmospherics oxygen is slightly soluble in water ., Terrestrial plant and animals obtain oxygen from the air while aquatic plant and animal use oxygen dissolve in water for respiration ., During the process of respiration carbohydrates are oxidized and carbon dioxide is released along with the release of energy ., Coal , wood , petrol ,etc .need oxygen during combustion .during the process of combustion also along with carbon dioxide , energy is also released., Both respiration and combustion take oxygen from the atmosphere and release carbon dioxide to the atmosphere, Green plant during the process of photosynthesis use carbon dioxide of the atmosphere and release oxygen to the atmosphere . oxygen mixes with the air and the cycle is completed ., Nitrogen cycle :, The atmospheric nitrogen move from atmosphere to the soil , from the soil to the plants , from plant to the animals and from all living beings to the soil and back to the atmosphere from the soil .This cycle journey of the nitrogen is called nitrogen cycle ., Source of nitrogen : Plant can not take the atmospheric nitrogen as it is . Therefore they take up, Various compound of the nitrogen that are available in the soil . for the plants nitrogen compound in the soil is the only source of nitrogen ., Nitrogen fixation : Nitrogen fixation is the process in which nitrogen is converted in to compound, Viz ., Physical fixation :, Further divided in to atmospherics fixation and industrial fixation and biological fixation ., Physical Fixation : The lightning in the sky bring about oxidation of atmospheric nitrogen, And converts it in to nitrogen oxide ( NO2) . Nitrogen oxide dissolve in rain water and forms nitrous and nitric acid .These acid seep in the soil with the rain water . They undergo with chemical reactions with other element in soil and form different compound of nitrogen ., Atmospheric nitrogen lightning ……….Nitrogen Oxide, Nitrogen Oxide + Rain water …….. Nitrous acid and nitric acid ., (b)Biological fixation :, i) The symbiotic bacteria Rhizobium living in the root nodules of leguminous plant carry, out the function of biological nitrogen fixation ., Azotobacter and Clostridium are free living bacteria in the soil . They also bring about, Biological nitrogen fixation ., The blue- green aquatic algae Nostoc and Anabaena also perform biological nitrogen fixation ., Utilization of nitrogen compound by the living organisms :, Plants take up nitrates and nitrites from the soil . They synthesis protein and nitrogenous compound from the absorbed nitrates and nitrites ,, Herbivorous animals consume plants and fulfil their protein requirement ., Protein are broken down to amino acid during the metabolism . In the bodies of animals the amino acid are ones again assembled to form required protein ., In addition to nitrogen fixation there are other three processes which are important in nitrogen cycle ., Ammonification : Release of ammonia through decomposition of dead bodies and excretory, Wastes of organisms., Nitrification : conversion of ammonia in to nitrite and then nitrate., Denitrification : Conversion of nitrogen compound into gaseous nitrogen ., Q . 5. What would you do to help maintain the equilibrium in the various bio-geo-chemical cycles ? Explain in brief ., Ans : For maintaining the balance in the bio-geo-chemical cycles , following measures have to be taken :, We have to conserve plants like trees , creepers and the entire available flora . for this , we have to at ones stop felling on the trees . If plants are destroyed , the productivity of the ecosystem is hampered . Therefore the flora has to be well maintained., We should not kill and poach carnivorous wild animals . This disturbance in the ecological balanced . In order to protect the equilibrium we should conserve the food chains ., Under any condition , apex consumer should not be killed . The hunting makes the valuable species to becomes extinct . Moreover , the population of herbivorous animals will not be under control if carnivorous are killed . by exterminating the apex consumers , the interrelationship between food chain and food web will suffer, Anthropogenic activities such as pollution , deforestation , construction in wild habitat, over consumption of natural resources should be immediately kept under control ., Q . 6. Explain in detail the inter-relationship between food chain and food web ?, Ans :, In every ecosystem , interaction go on continuously between producers , consumers and saprophytes., These interaction follow a definite sequence called the food chain ., Each food chain consist of four , five or more links ., An ecosystem consisting of interconnected food chains at various level constitute a food web. e. g. Insects (primary consumer) . Frog (secondary consumer) feed on insects . This is a straight food chain . Insects are also eaten by sparrow . sparrow becomes food for owl . Owl also kill snakes . snakes ( tertiary consumer ) feed on frog . Apex carnivore , hawk feeds on sparrow , snake or frog too. IN this way ,smaller food chains are interconnected in a web from constituting the food web., Thus , there is an interrelation between food chain and food web ., Q .7 . State the different type of bio- geo-chemical cycle and explain the importance of those cycles ., Ans :, The bio-geo-chemical cycle are are of two types , viz ; gaseous cycle and sedimentary cycle ., The gaseous cycle include cyclic transformation of carbon dioxide , oxygen , nitrogen , water vapour etc. while sedimentary cycle include cyclic movement of calcium , phosphorus , iron etc .that are present in soil ., In an ecosystem producers produce food by making use of solsr energy . while doing so , air and water . In gaseous biogeochemical cycle , the nutrient are in air while in sedimentary cycle they are in soil ., Consumers that feed on producers also pass nutrients to their bodies ., Importance of bio-geochemical cycle :, Plant require water ,CO2, phosphorous , Potassium , nitrogen ,etc . as nutrient while animal require carbohydrates , proteins , fats ,etc . as nutrients ., Producers and consumers after their death undergo decomposition and release element which mix with the soil ., The cyclic movement of nutrients is possible through bio-geochemical cycle ., The cyclic movement of element like carbon , nitrogen , phosphorous ,etc . continuously occur on the earth ., Q . 8. Explain the following with suitable examples :, What types of changes occur in the amount of energy during its transfer from plant to apex consumers ?, Ans :, Green plants of the ecosystem store large amount of energy in the carbohydrates and proteins ., Before reaching the decomposers , this energy passed through different trophic level like primary consumers , secondary consumers , tertiary consumers , etc ., The level of energy goes on decreasing while moving through one trophic level to other because some amount of energy is liberated in the form of heat ., The apex consumers receives the least amount of energy ., What are the difference between flow of matter and of energy in an ecosystem ? why ?