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Energy Flow inan Ecosystem Points to Remember: According to mode of nutrition, organisms are classified as producers, consumers. saprotrophs (saprophytes) and decomposers. Primary consumers are directly dependent on autotrophs (producers). e.g.: Grasshopper, squirrel, elephant) Secondary consum...

Energy Flow inan Ecosystem Points to Remember: According to mode of nutrition, organisms are classified as producers, consumers. saprotrophs (saprophytes) and decomposers. Primary consumers are directly dependent on autotrophs (producers). e.g.: Grasshopper, squirrel, elephant) Secondary consumers use herbivores as their food. e.g.: Frog, owl, fox, etc. Apex or top consumers use herbivores and carnivores as their food. No animals feed on top consumers. e.g.: Tiger, lion, etc. Omnivores feed on herbivores and carnivores. e.g.: Humans, bear, etc. Continuous interactions between producers, consumers and decomposers in a definite sequence is called as food chain. Many food chains interconnected at various levels is called as food web. Each level in the food chain is called a trophic level. Atrophic level is the step at which the organism obtains its food in the chain. The initial quantity of energy goes on decreasing at every level of energy exchange. Similarly, the number of organisms also decreases from the lowest level to the highest level. This patern of energy exchange in an ecosystem is called a Pyramid of Energy'. After the death of apex consumers, their energy becomes available to the decomposers. Energy is passed on from one trophic level to the other. Decomposers dissipate some amount of energy in the form of heat. However, no part of the energy ever returns to the Sun. Hence, such passage of energy is referred to as 'one way' transport. The cyclical flow of nutrients within an ecosystem is called the bio-geo-chemical cycle. Nutrients, necessary for the growth of organisms are continuously transferred from abiotic to biotic factors within an ecosystem. This cycle operates continuously through the medium of the biosphere formed by the lithosphere, atmosphere and hydrosphere. There are two types of bio-geo-chemical cycles - Gaseous cycle and sedimentary cycle. Gaseous cycle includes nitrogen, oxygen, carbon dioxide, water vapour, etc. Sedimentary cycle includes soil components like iron, calium, phosphorus etc. The circulation and recycling of carbon from the atmosphere to living organisms and after their death back to the atmosphere is called the carbon cycle. Abiotic carbon atoms are circulated and recycled into biotic form mainly through photosynthesis and respiration. The circulation and recycling of oxygen within the biosphere is called the oxygen cycle. Oxygen is released in the process of photosynthesis and used up in the processes like respiration, combustion, decomposition, corrosion, rusting, etc. (112)  113 Floyinan EnTgy Ecosystem The circulation and recyeling of nitrogen gas into the form of different compounds throug various biotic and abiotic processes in nature is called the nitrogen cycle. Important processes of nitrogen cycle are: Nitrogen fixation: Conversion of nitrogen into nitrates and nitrites through atmosphenG, industrial and biological processes. Ammonification: Release of ammonia through decomposition of dead bodies and excretory wasters of organisms. Nitrification: Conversion of ammonia intoanitrite and then nitrate. Denitrification: Conversion of nitrogen compounds into gaseous nitrogen. between biotic Can you recall? *(5) How do interactions take place (Textbook and abioticfactors of an ecosystem ? 1) What is meant by nitrogen fixation? (Textbook Page no. 81) Page No. 86) Ans. Ans. The process of conversion of Nitrogen into (i) Abiotic factors include non-living factors such include all nitrates and nitrites is called Nitrogen fixation. as soil, water etc. and biotic factors L:/9) Which microbes bring about the process of living organisms. nitrogen fixation? (Textbook Page No. 86) (ii) Both these abiotic and biotic ecosystems are Ans. Rhizobium present in the root nodules of the connected through various bio-geo-chemical leguminous plant bring about the process of cycles. nitrogen fixation. (iii). These connections/interactions are important (3) What is meant by 'ecosystem'? (Textbook Page for the flow of matter and flow of energy. n0. 81) Ans. An ecosystem includes all of the living things MASTER KEY QUESTION SET - 7 like plants, animals and other organisms in agiven area, interacting with each other and Q.1. (A) 1. Fill in the blanks and rewrite the also with non-living environmental factors complete statements: like weather, earth, sun, soil, climate and (1) in 1942 studied the food chain and atmosphere. energy flow through it. 14) Which are different types of ecosystems? (2) After the death of apex consumners, energy (Textbook Page no. 81) becomes available to Ans. ECOSYSTEMS (3) Green plants of the ecosystem store in the form of food. (4) Plants convert carbon dioxide into by the process of photosynthesis. Natural EcosystemManmade/Artificial Ecosystem (5) Carnivores feed upon (6) is used up in the processes like respiration, combustion, decomposition, Terrestrial Ecosystem Aquatic Ecosystem corrosion, rusting, etc. (7) Nitrogen forms %of the atmosphere. (8) Most organisms cannot use the free form of Forest Grassland Desert Marine Fresh water water  114 Master Key Science and Techrology (St4. (9) irst proposed the concept of (5) Burming of fossil fuels, forest fire, respirzs Ecological Pyramid in 1927. volcanic activity. (10) Ecological Pyramid is called (11) Ans. Respiration. It is a biotic process of releai isproduced from carbon dioxide, whereas the others are abir various atmospheric processes.oxygen through processes of releasing carbon dioxáde. (12) Interactions between producers, consumers (6) Photosynthesis, combustion, decompositg and saprophytes in a definite sequence is called corrosion. Ans. Photosynthesis. It is a process that relez (13) Many food hains oxygen whereas the others use up oxygen. levels is called interconnected at various Q.1. (A)3. Complete the analogy: (14) Decomposers dissipate some amournt of energy (1) Grasshopper : Primary consumer Tig in the form of (15) The flow of nutrients in an (2) Owl : Secondary consumer : Squir ecosystem is (16) The cyclical flow of nutrients within an (3) Flow of energy :One way: Flow of nutrients ecosystem is called (17) isan accumulation of themain abiotic (4) Plants : Producers : Bacteria and Fung gaseous nutrient materials found in the earth's atmosphere. (5) NitrOgen : Gaseous yde Phosphong (18) Oxyvgen is released into the atmosphere by the process of. (6) Oxygen: 21% :: Nitrogen: (19) Charles Elton studied the of the Beer (7) Photosynthesis:Carbon cyde::Ammonificatia islands in England. Ans. (1) Lindeman (2) deconiposers (3) solar energy (8) Respiration : Oxvgen cycde : Nitrification (4) carboydrates (5) herbiores (6) Orygen (7)78(8) nitrogen (9) Charles Elton (10) Eltonian (9) Respiration : Biotic process : Combustion Pyramid (11)Ozone (12) food chain (13) food oeb (14) heat (15) cyclical (16) bio-geo-chemical cycle (10) Microbes using oxygen: Aerobes : Mirobes (17) Gaseous cycle (18) photosynthesis (19) Tundra not using oxygen : Ecosystem Ans. (1)Apex consumer (2) Primary consumer (3) Cvit (4) Decommposers (5) Sedimentary cycle (6) 78% Q.1. (A) 2. Find the odd man out: (7)Nitrogencycle(8) Nitrogencycle(9) Abioticprozs (1) Frog, Owl, Squirel, Fox. (10) Anaerobes Ans. Squirrel. It is a primary consumer, whereas the Q.1. (A) 4.Match the columns: rest are secondary consumers. (1) Column 'A Column B (2) Grasshopper, squirrel, elephant, lion. Ans. Lion. It is an apex consumer, the others are (1) Flow of nutrients (a) Sedimentary yd primary consumers (herbivores). (2) Flow of energy (b) One way (3) Nitrogen cyce, oxygen cyde, carbon cycle, (3) Carbon (c) Gaseous cyde phosphorus cyde. (9) Phosphorus (d) Cyclical Ans. Phosphorus cyde. It is a sedimentary cycde, Ans. (1 - d) (2 - b) (3 - c) (4 - a) whereas the others are gaseous cycdes. (2 Column A' Column B (4) Photosynthesis, Nitriffcation, Ammonification, (1) Producers (a) 2nd trophic level Denitrifcation. Ans. Photosvnthesis. It is a process in carbon and (2) Herbivores (b) 3r trophic level oxygen cycde whereas the others are processes (3) Carnivores (c) 1* trophic level in nitrogen cyde. Ans. (1 - c) (2- a) (3 - b)  115 Flowi1 an Ecosystem Energy dioxide gases is (A)5. State whether the following statements equilibrium of oxygen and carbon The conversion O.1 re true or false. Correct the false statements: maintained by plants. (14) False. then nitrate is nitrite and Herbivores occupy the third trophic level in a of amnonia into a Conversion of (15) False. called nitrifcation. 1) food chain. gaseous nitrogen is called nitrogen compounds into cyclic flow denitrification. (16) True (17) False. The bio-geo Apex Consumers use herbivores and carnivores 2) as their food. is called of nutrients within an ecosystem Humarns are apex consumers. chemical cycle. G) Omnivores feed only on carnivores. 4) Afood chain has two links. Q.1. (A) 6. Name the following: Theanimals that feed on herbivores. 5) The number of consumers in afood web is (1) 6) Ans. Carnivores. fixed. herbivores and The amount of matter and energy goes on (2) Organisms that feed on carnivores. increasing atevery levelin a food chain. Ans. Omnivores. Robert Brown first proposed the concept of (8) Ecological Pyramid. (3) Two examples of primary consumers. After the death of apex consumers, the energy Ans. Grasshopper, squirrel. 9) Two examples of secondary consumers. becomes available to decomposers. (4) n0 The gaseous cycle is a speedier cycle than the Ans. Frog, owl. sedimentary cycle. (5) Two examples of Apex consumers. 11) Climatic changes and human activities Ans. Lion, tiger. seriously affect the speed, intensity and (6) Levels in the food chain. equilibrium of bio-geo-chemical cycles. Ans. Trophic level. (12) Carbon dioxide is released in the atmosphere (7) Organisms that decómpose the dead bodies through photosynthesis. of plants and animals. 13) The equilibrium of oxygen and carbon dioxide gases is maintained by decomposers. Ans. Decomposers. 14) The conversion of ammonia into a nitrite and (8) Process which releases oxygen. then nitrate is called nitrogen fixation. Ans. Photosynthesis. (15) Conversion of nitrogen compounds into (9) Release of ammonia through decomposition gaseous nitrogen is called nitrogen fixation. of dead bodies and excretory wastes of (16) Release of ammonia through decomposition of organisms. dead plantsand excretory wastes of organismns Ans. Ammonification. is called ammonification. (10) Conversion of nitrogen into nitrates and (17) The cyclic flow of nutrients within an nitrites through atmospheric, industrial and ecosystem is called Energy Pyramid. biological processes. Ans. (1) False. herbivores occupy the second trophic level Ans. Nitrogen fixation. in a food chain as they, are directly dependent on *Q.1. (A) 7. Correct and rewrite the following producers. (2) True (3) True (4) False. Omnivores statements and justify your corrections: feed on both herbivores and carnivores. (5) False. A (a) Carnivores occupy the second trophic level in food chain consists offour,fiveor more links. (6) False. the food chain. Afood web can have many consumers. (7)False. The amount of matter and energy goes on decreasing at Ans. Correct Statement: Producers form the first cvery level in afood chain. (8) False. Charles Elton trophic level in the food chain. Herbivores first proposed the concept of Ecological Pyramid. depend directly on producers. (9) True (10) True (11) True (12) False. Carbon Justification: So herbivores form the second dioxide is released in the atmosphere through trophic level, whereas carnivores depend on respiration, burning of fossil fuels and wood, herbivores, so they form the third trophic level forest fires and volcanic activity. (13) False. The in the food chain. 116 Muster Key Science and Teclhnology (Sta.n (b) The flow of nutrients in an ecosystem is (9) is an important component considered to be a 'one way' transport. proteins and nucleic acids. Ans. Correct Statement: The flow of nutrients in an (a) Carbon (b Nitrogen ecosystem is cyclic. (c) Phosphorus (d) Oxygen Justification: The nutrients are circulated and (10) Amount of matter and energy recycled frOm the biosphere to living organisms the lowest level to the highest level. from and after their death back to the biosphere. (ay decreases (b) increases (c) Plants in an ecosystem are called primary (c) remains the same (d) multiplies consumers. (11) is the most important source Ans. Correct Statement: Plants in an ecosystem are energy in any ecosystem. called autotrophs. (a) The Sun (b) The Moon Justification: They produce their own food by (c) Producers (d) Decomposers the process of photosynthesis. All animals in (12) Flow of energy in an ecosystem is an ecosystem directly or indirectly depend on plants for food. (a) cyclical (b) two way transport Q.1. (B) Choose and write the correct option: (c) one way transport (d)to and fro transpon (13) The Indian Institute of Ecology and (1) An intricate network of food chains is called Environment, Delhi, has published (a) Invasive species in a changing Environment (a) Biosphere (byFood web (b) Encyclopaedia of Ecology and Environment () Energy pyramid (d) Ecosystem (2) Fungi and other microbes are called () Environment and Ecology Magazine (a) Producers (b) Consumers (d) Biodiversity and Disaster Management (14) Oxygen is released in the process of (c) Decomposers (d) Omnivores Oxygen forms (a) Respiration (b)Decomposition (3).of the atmosphere. (a) 78% (b) 21% (c) 10% (d) 90% (c) Combustion (d) Photosynthesis (4) Microbes which do not need oxygen are called (15) cycle is a gaseous cycle. (a)Carbon (b) Phosphorus (c) Calcium (d) Iron (a) Producers (b) Aerobes (9Anaerobes (d) Decomposers (16) is a sedimentary cycle. (a) Carbon (b) Nitrogen (5) The pattern of energy exchange in an ecosystem is called a (c) Oxygen (d) Calcium (a) Food chain (b) Food web Based on Practicals (c) Pyramid of energy (d) Trophic levels (6) Carbon atoms are circulated and recycled (17)....i.s a primary consumer. through (á) Elephant (b) Frog (a) Nitrification and denitrification (c) Owl (d) Tiger (b) Photosynthesis and respiration (18) is a secondary consumer. (c) Respiration and nitrification (a) Grasshopper (b) Elephant (d) Photosynthesis and ammonification (c) Frog (d) Human Conversion of ammonia into a nitrite and then (19) Tiger is a /an (7) nitrate is called (a) Producer (b) Primary consumer (a) Nitrogen fixation (b) Denitrification (c) Apex consumer (d) Secondary consumer (c) Nitrification (d) Ammonification (20) Carbon dioxide is released into the atmosphett (8) Conversion of nitrogen compounds into through gaseous nitrogen iscalled (a) burning of fossil fuels (a) Nitrogen fixation (b) Denitrification (b) volcanic activity (c) Ammonification (d) Nitrification (c) respiration (d) all of these  117 in an Ecosystenn (7)(b) food wel (2) (c) deconposers (3) (b) 21% (ii) step at which the organism Atrophic level is thethe Ans. naerobes (5) (c) Pyramid of chain. pylotosynthesis and energy (6) (b) obtains its food in respiration (7) (c) nitrification matter and energy gradually (üi) The amount ofproducers S)(0) denitrification (9) (b) Nitrogen (10) (a) decreases from at the lowest level to decreases(11)(a) The Sun (12) (c) one way highest level. transport ECyclopaedia of Ecologyand Environment the top consumers at the (14)(a) plhotosynthesis (15) (a) Carbon (16) (d).: (2) Food web. Calcium (17) (a) Elephant (18) (c) Frog (19) (e) Ans. Consumer (20) (d) all of these of many food chains () An ecosystem consists at various levels. This Definethe following: that are interconnected ) Q21. Foodchain is called food web. for many other Ans. Interactions betweern producers, consumers (i) An organism may be the prey d decomposers in a definite sequence is organisms. of called as a food chain. feeds upon leaves (iii) For example, an insect the prey 2) Foodweb various plants but the same insect is birds etc. lizards, Ans. The interconnection among different food for different animals like wall instead of a linear chains in an ecOsystem at various levels is (iv) This forms an intricate web network is called called as a food web. food chain. Such an intricate B) Trophiclevel as food web. Ans. Atrophic leevel is the step at which the orgarnism (v) Generally food webs are formed everywhere in obtains its food in the chain.. nature. 9 Pyramid of energy (3) Energy Pyramid. Ans. The pattern of energy exchange in an ecosystem is called a Pyramid of energy'. 6) Bio-geo-chemical cycle 10 kcal Ans. The cyclical flow of nutrients within an Humans ecosystenm is called bio-geo-chemical cycle. 100 kcal (6) Carbon cycle Fishes/ Inserts Ans. The circulation and recycling of carbon from 1000 kcal the atmosphere to living organisms and after Zooplanktons their death back to the atmosphere is called the carbon cycle. 10,000 kcal () Oxygen cycle Phytoplanktons Ans. The circulation and recycling of oxygen within the biosphere is called as oxygen cycle. Fig. 7.1 : Energy Pyramid in an ecosystem Ans. (9) Nitrogen cycle Ans. The circulation and recycling of nitrogen gas (1) Each level in the food chain is called a trophic into the form of different compounds through level. various biotic and abiotic processes in nature is (ii) The amount of matter and energy gradually called the nitrogen cycle. decreases from producers at the lowest level to 9 Nitrogen fixation the top consumers at the highest level. ARs. The process of conversion of free nitrogen gas (iüi) The initial quantity of energy goes on Or the atmosphere into nitrogen compounds is decreasing at every level of energy exchange. called of nitrogen fixation. (iv) Similarly, the number of organisms also 022. Write short notes on: decreases from the lowest level to the highest 0) Trophic level. level. Ans. (v) This pattern of energy exchange in an ecosystem () Each level in the food chain is called atrophic is called aPyramid of energy. level. 118 Master Key Science and Technology (Sta *Q.2.3. Complete the following table: Bio-geo-chemical cycles (1) Carbon cycle Biotic Processes Abiotic Processes Photosynthesis, Respiration, Burning of fossil fuels, forest fre Decomposition. volcanic activity. (2) Oxygen cycle Photosynthesis, Respiration, Combustion, Corrosion, rusting Decomposition. formation of ozone (0,). (3) Nitrogen cycle Biological nitrogen fixation, Atmospheric nitrogen fixation, ammonification, nitrification, industrial nitrogen fixation. denitrification. Q.2.4. Distinguish between: (1 Gaseous Cycle and Sedimentary Cycle. Ans. Gaseous Cycle Sedimentary Cycle ) It is an accumulation of the main abiotic (6) It is an accumulation of the main abiok, gaseous nutrient materials found in the earth's nutrient materials found in the soil, sedimen atmosphere. and sedimentary rocks, etc. of the earth. (1) It includes ritrogen, oxygen, carbon dioxide, (ii) It includes soil components like iron, calcium, water vapour etc. phosphorus etc. (2) Carbon Cycde and Nitrogen Cycle. Ans. Carbon Cycle Nitrogen Cycle (i) The circulation and recycling of carbon from (i) The circulation and recycling of nitrogen into the atmosphere to living organisms and after the form of different compounds through their death back to the atmosphere is called various bioticand abiotic processes in nature is carbon cycle. called the nitrogen cycle. (ii) Main processes involved in carbon cycle are (ii) Main processes involved in nitrogen cycle are photosynthesis and respiration. nitrogen fixation, ammonification, nitrification and denitrification. (iüi) Carbon in the form of carbon dioxide is directly (ii) Nitrogen gas cannot be directly absorbed by absorbed by plants for photosynthesis. plants. So nitrogen is fixed by the process of nitrogen fixation and then absorbed from the soil. *(3) Flow of matter and Flow of energy. Ans. Flow of matter Flow of energy (i) Itinvolves circulation and recycling of nutrients (i) It involves the flow of energy from one trophic in a cyclic manner within the biosphere. level to another in unidirectional or non-cyci manner. (iü) There is no dissipation of matter at any level. (ii) There is dissipation of energy at every level. (ii) Biosphere is the source of nutrients. (iii)The Sun is the most important source of energy. Q.2.5. Give scientific reasons: (ii) Green plants of the ecosystem (store some "(1) Energy flow through an ecosystem is 'one amount of solar energy in the form of food. way'. (iii) Before reaching the decomposers, this energ Ans. ispassed on from one trophic level to the next (i) The Sun is the most important source of energy (iv),Decomposers dissipate some amount of energ in the form of heat. in any ecosystem.  119 in,an Flow Ecosystem Eury from the harmful ultraviolet of However, no part the energY ever returns layer protects us rays of the Sun. take the Sun. Hence, energy flow through an nitrogen fixation? How does it PCOSysterm is ´one way', (2) What is Equilibriumis necessary in the various bio- place? gas geo-chemicalcycles. process of conversion of free nitrogen Ans. The atmnosphere into nitrogen compounds is of the nitrogen fixation. Ans. Thecycliiccflowr of nutrients within an ecosystem called as following ways: is called bio-geo-chemical cycles. It takes place in Atmospheric nitrogen fixation: Nutrients, necessary for the growth of (a) in a reaction between organisms are continuously transferred from Lightning results () present in the air to abiotic to biotic tactors and biotic to abioic nitrogen and oxygen factors within an ecosystem. produce oxides of nitrogen. rainwater forming Anyimbalancein the cycles will break the link (i) These oxides dissolve in (üi) dilute nitricacid. botween the biotic and abiotic factors. of the reacts with the alkalis Therefore, equilibrium is necessary between (ii) This nitric acid turn into nitrates. bio-geo-chemical cycles. soil (like limestone) to ia Elow of nutrients through an ecosystem is Biological nitrogen fixation: (b) of atmospheric nitrogen cyclic. () It is the conversion organisms. Ans. into nitrogen compounds by livingrhizobium are bacteria, called All organisms need nutrients for their growth. (ü) Nitrogen fixing nodules of the leguminous found in the root (i) The nutrients carbon, oxygen, nitrogen, iron, calcium etc. are circulated and recycled from plants. nitrogen into nitrates. the biosphere to living organisms and after (ii) They can fix atmospheric What is ammonification? their death back to the biosphere. (3) (i) Nutrients are taken up by plants and then Ans. remains passed on to the consumers. () When plants and animalls die, their ammonium (iv) Eventually, after their death, all types of are converted into ammonia and consumers, are decomposed by decomposers compounds by decay bacteria and fungi like bacteria and fungi and the nutrients are (decomposers) present in the soil. again released into the biosphere and are, used release of ammonia (ii) This process of again by living organisms. through decomposition of dead bodies and Therefore, flow of nutrients through an excretory wastes of organisms is called as ecosystem is cyclic. ammonification. (4) What is nitrification? 0.2.6. Answer the following: (1) What is the importance of oxygen? Ans. Ans. () Ammonia is converted first into a nitrite and then nitrate. 0) Oxygen forms 21% of the atmosphere. This conversion of ammonia into a nitrite and (i) ) It is also present in hydrosphere and then a nitrate is called as nitrification. lithosphere. (5) What is denitrification? of ) Oxygen is required for the process respiration, combustion, decomposition, Ans. (1) Nitrogen compounds in the soil are corrosion, rusting etc. of ") Oxygen is important for the synthesis converted into free gaseous nitrogen by the proteins,carbohydrates and fats. denitrifying bacteria present in the soil. ltis also used in various chemical reaction. (ü) This process of conversion of nitroger () Ozone (0) is produced from oxygen through compounds into gaseous nitrogen is called a ozone denitrification. Yarious atmospheric processes. This  120 Master Key Science andI Technology(Std. (6) Write the balanced chemical Pictures of various organisms are given bel, Ans. photosynthesis and respiration.equations for (b) Construct a food web from these pictures Ans. Food web (i) Photosynthesis: 6C0,+ 12HO Sunlight -CH,0, +6H,0+60,1 (i) Chlorophyll Respiration: Mitochondria CH,0,+ 60, + 6C0%‘ +6H,0 + Energy (7) The cycle of gases and the sedimentary cycle cannot be completely separated from each other. Give two examples to support this statement. Ans. (i) Nitrogen is presernt in the form of agas in the atmosphere and in the form of compounds like Fig. 7.2: Food Web nitrogen oxide in the soil and sediments. (i) Similarly, carbon, occurs in abiotic form mainly Open ended questions in coal, granite, diamond, limestone, etc. in *Q.3.1. Answer the following questions: the earth's crust and in form of carbon dioxide gas *(1) Why is balance or equilibrium necessary in a in the atmosphere. food web? (Use your brain power; Textbook. Page (iüi) Therefore, the cycle of gases and the No. 82) Ans. sedimentary cycle cannot be completely separated from one another. (i) It is necessary to maintain the balance or (8) How does interaction take place between equilibrium in a food web as the survival of biotic and abiotic factors of an ecosystem? consumer is dependent on another. Ans. (ii) For example, the carnivorous animals will starve and their number will dwindle due (i) All living organisms depend upon abiotic to starvation if the primary consumers are factors. removed from the food web. (i) Plants use the abiotic factors like carbon (iii) On the other side, if secondary consumers are dioxide, water and energy from the Sun to rèmoved from the food web the population of produce food by photosynthesis. primary consumers would remain unchecked and that will directly affect the producers. (ii) Also, the type of soil and the climatic (iv) Therefore, removing any one of the consumers conditions determine the type of flora and from the food web would affect the whole food fauna in that region. web in general. (iv) Thus, the biotic and abiotic factors interact *(2) Explain the food chain of various ecosystems with each other through biogeochemicalcycles. which you have studied last year. (9) la) Make a list of the various consumers of (Use your brain power; Textbook Page No. 81) the ecosystem around you and classify them Ans. according to mode of nutrition. (Use your brain (a) Food chain in a forest ecosystem: power; Textbook. Page No. 82) Ans. Primary Secondary Apex Mixed Consumers Consumers Consumers Consumers Rabbit, deer, Frog, owl, Tiger, lion, Human, monkey, fox, lizard crocodile, bear, crow Grass Deer Tiger zebra, birds leopard Fig. 7.3: Food chain in aforest ecosystem  121 in an Ecosystem levels, the amount Therefore, after a few trophic In a forest ecosystem, grass is eaten by a deer, (ii) of energy in the food chain cannot support a which in turn is eaten by a tiger. higher trophic level. The grass, deer and tiger form a food chain. of tertiary consumers is In this food chain, energy flows from the grass (ii) Therefore, the numberconsumers. less than that of other (producer) to the deer (primary consumer) to consumers in a food web the tiger (secondary consumer). *(2) Is the number of power; Textbook Page No. fixed? (Use your brain Food chain in an aquatic ecosystem (Pond): 82) consumers in a food web is Ans. No. The number of not fixed. ecosystem if *(3) What will be the effect on an organism in it forms the only one type ofdifferent consumers in that food for several Page Insects Small fsh Big ish Fish eating bird ecosystem?(Use your brain power; Textbook Algae No. 82) Fic. 74:Food chain in an aquatic ecosystem (Pond) Ans. In a aquatic ecosystem algae are eaten by organism forms the food insects. 1) If only one type of there Insects are eaten by small fish, small fish are for several consumers in an ecosystem, among i) in turn eaten by big fish. will be competition for that food organisms. ) And the big fish are eaten by fish eating birds. (iü Slowly the organism that is the prey will go of In this food chain, energy flows from the algae on declining and other organisms will die (producer) to the insects (primary consumers) imbalance in the starvation. This will lead to an to the small fish (secondary consumers) to the ecosystem. big fish (tertiary consumer) and to the fish eating birds (apex consumer). *(4) What would happen if the energy remains trapped in the body of apex consumers even (3) The carbon cycle is very effective in the after their death? What will happen if there temperate region. Why is it so? were no decomposers like microbes and fungi (Thiuk about it; Textbook Page No. 85) in nature? (Use your brain power; Textbook Page Ans. No. 83) ) Temperate regions are rich in forests. Forests Ans. play a major role in carbon cycle. (i) After the death of apex consumers, their i) Trees absorb carbondioxide and convert it energy becomes available to the decomposers. into food (chemical energy) by a process of Ifenergy remains trapped in the body of apex photosynthesis. consumers, then energy will not be available ) Thus, carbon cycle is very effective in for decomposers and they will not survive, temperate regions. thus disturbing the balance of the ecosystem. (ii) Decomposers like microbes and fungi break Open ended questions down the bodies of dead plarnts and animals and () Why are the number of tertiary consumers convert them into simple carborn compounds. (apex carnivores) always less than those (iii) These substances easily mix with air, water of other consumers? (Use your brain power; and soil from where they are again absorbed Textbook Page No. 83) by the plants and incorporated into the food Ans. chain. In a food chain, at each trophic level some (iv) If there were no decomposers, decomposition will not happen and the nutrients will be amount of energy is used by the organism for lts own life processes and some amount of trapped in the bodies of plants and animals and this will disturb the food chain, food web energy is lost to the surroundings in the form and the equilibrium in the ecosystem. of heat energy. 122 Master Key Science and Technology (Std.I, "(5) What happens to the energy during its transfer from producers to apex consumers? (iii) We should avoid deforestation as trees play, Does it remain trapped in apex important role in maintaining the balance Does it remain in the body of apexconsumers? (iv) We should avoid overuse of fertilizers. N till its death? consumer fertilizerS get washed away in the near. water bodies disrupting the balance. (Think about it: Textbook Page No. 83) Ans. (v) Avoid burning of fossil fuels as these fu release a large amount of carbon in the fom. (i) When energy is transferred from producers carbondioxide, thus disrupting the balance to apex consumers, some amount of energy (vi) Vehicular emissions is another contributor is used by the organisms for their own life the disruption in balance of the various cyde processes at every trophic level and some These emissions release oxides of nitrogen an amount of energy is lost to the surroundings carbon and other hazardous air pollutants.S as heat energy we must use better quality fuel like CNG (ii) No, the energy does not remain trapped in apex ethanol to reduce vehicular emissions. consumer, it is passed on to the decomposers. *(2) Explain in detail the inter-relationshin (iü) Yes, it does remain in the body of apex between the food chain and food web. consumer till its death. Only after its death, the Ans. energy is passed on to the next consumer. (i) Interaction go on continuously between "(6) Even though the carbon content on the earth producers, consumers and decomposers. is constant, why is there a rise in temperature due to carbon dioxide? (ii) There is a definite sequence in these interactions which is called the food chain. (Think about it; Textbook Page No. 85) (ii) Each chain consists of four, five or more links Ans. Carbon content on earth is constant but the burning of wood, and fossil fuels release CO, (iv) An ecosystem consists of many food chains into the atmosphere which is a greenhouse that are interconnected at various levels. Thus a food web is formed. gas and causes more heat to be trapped on the earth's surface leading to increase in (v) An organism may be the prey for many other temperature. organisms. *(7) Identify the relationship between carbon (vi) For example, an insect feeds upon leaves of in the air and the rise in atmospheric various plants but the same insect is the prey for different animals like frog, wall lizard, temperature. birds, etc. (Think about it; Textbook Page No. 85) (vii) Thus, many food chains interconnected Ans. There is a direct relationship between carbon together form an intricate web called as food in air and rise in atmospheric temperature. web. More the level of carbon dioxide, more the heat *(3) State the different types of bio-geo-chemical trapped and hence higher rise in temperature. cycles and explain the importance of these Q.4. Ans wer in detail: cycles. *(1) What would you do to help maintain the Ans. equilibrium in the various bio-geo-chemical (i) The different types of bio-geo-chemical cydes cycles? Explain in brief. are nitrogen, oxygen, carbon, water vapout, Ans. iron, calcium, phosphorus, etc. (i) Bio-geo-chemical cycles always involve the (ii) Nutrients, necessary for the growth of the achievement of equilibrium, i.e., a balance organisms are continuously transferred from in the cycling of the nutrients between the abiotic to biotic factors and biotic to abiotic spheres. factors within an ecosystem. (ii) Human activities that are known to be (ii) These cycles operate continuously through environmentally unfriendly can disrupt this the medium of the biosphere formed by the balance. lithosphere, atmosphere and hydrosphere.  in an Ecosystemn 12.3 of with suitable The recycling biological, Explain the following questions 2y an chemical sOurces of nutrientsgeological and (6) diagrammatic representation: through these cycles. takes place Nutrients from the biosphere enter the *la) Carbon cycle. The of plants and animals. Eventually, after bodies death, Ans. arby all types of consumers are decomposed by Sunlight CO, from factories decomposers like bacteria and uels fungi and areagain released into the biosphere and they are mof usedagain by living organisms. Respiration in plants rto Therefore, these cycles help in maintaining |Biotic cafRespiration in animala the floww of nutrients and energy through les. ecosystem and andSo the ecosystem. maintairing the equilibrium in Explainthe,following with suitable examples. Biotic wWhat type of changes occur in the amount of decompositions Absorption in water energy during its transfer from plants to apex Consumers? Fossil fuels Ans. Fig. 7.5: The carbon cycle The circulation and recycling of carbon from en Plants of the ecosystem store some of the solar (i) energy in the form of food. the atmosphere to living organisms and after Se () Before reaching the decomposers, this energy their death back to the atmosphere is called the is passed on from one trophic level to the nex. carbon cycle. and (i) At every trophic level, some amount of (ii) Abiotic carbon atoms are circulated energy is used by the organism for its own life recycled into biotic form mainly through processes and some amount of energy is lost to photosynthesis and respiration. Hence, the the surroundings. carbon cycle is one of the important bio-geo iv) Decomposers dissipate some amount of energy chemical cycles. in the form of heat. (iii) Plants convert carbon dioxide into carbohydrates by the process of photosynthesis. () However, no part of the energy ever returns to the Sun. Hence, such passage of energy is (iv) Similarly, they produce carbon compounds referred to as ´one way' transport. like proteins and fats, too. (vi) Therefore, energy is maximum at the base (v) Carnivores feed upon herbivores. In this way, of the pyramid and is least at the apex, e.g. biotic carbon is transported from plants to phytoplanktons which form the base of the herbivores, from herbivores to carnivores and pyramid have 10,000 kcal of energy while from carnivores to apex consurmers. humans at apex have 10 kcal of energy. (vi) Main processes in the carbon cycle 6) Write the important processes of nitrogen 6CO, +12H,0 Sunlight GH,0,+ 6H,0 +60,t cycde. Chlorophyll Ans. Mitochondria CH,0, +60, 6CO,f +6H,0 +Energy 0 Nitrogen fixation: Conversion of nitrogen into nitrates and nitrites through atmospheric, (vii) Everntually, after death, all types of consumers, industrial and biological processes. are decomposed by decomposers like bacteria (ü) Ammonification: Release of ammonia through and fungi and carbon dioxide is released again decomposition of dead bodies and excretory into the atmosphere and is used again by living organisms. wastes of organisms. i) Nitrification: Conversion of ammonia into a (vi) In this way, carbon is continuously passed on nitrite and then nitrate. from one living organism to another. After the death of living organisms, carbon goes to the iv) Denitrification: Conversion of nitrogen atmosphere and is again taken up by living components into gaseous nitrogen. organisms. 124 Master Key Science andI Technology (Std. *(b) Nitrogen cycle. Nitrification: Conversion of ammonia i Ans. (c) nitrite and then nitrate. (d) Dernitrification: Conversion of nitrog Nitrogen gas compounds into gaseous nitrogen. *lc) Oxygen cycle. Denitrification Nitrogen fixation Ans. (Conversion of nitrogen (Formation of nitrates and nitrites) compounds into NITROGEN gaseous nitrogen) CYCLE Plants producé oxýgen Plants absorb CO, and Ammonification produce food Nitrification (Release of ammonia) material (Conversion of Animalsbreathe in ammonia into a nitrite oxygen and thern nitrate) Animals give out Fig. 7.6 :The nitrogen cycle CO, Breakdown of sugar molecules by animáls (i) Nitrogen forms 78% i.e. the maximum portion of the atmosphere. It is necessary for the Fig. 7.7 : The oxygen cycle maintenance of the cycle of nature. () Oxygen forms 21% of the atmosphere. It is alk (i) The circulation and recycling of nitrogen gas into the form of different compounds present in the hydrosphere and lithosphere through Circulation and recycling of oxygen within th: various biotic and abiotic processes in nature is biosphere is called the oxygen cycle. called the nitrogen cycle. (ii) This cycle, includes both the biotic and abiot: (iii) All organisms participate in the nitrogen cycle. components. Oxygen is continuously produci It is an important component of proteins and as well as used up in the atmosphere. nucleic acids. (ii) Oxygen is highly reactive and it readily react (iv) As compared to other elements, it is inactive with other elements and compounds. and does not easily combine with other (iv) As oxygen is found in various forms like elements. Most organismns cannot use the free molecular oxygen (0,), water (H,0), carbon form of nitrogen. dioxide (CO,), inorganic compounds etc, h: (v) Important processes of nitrogen cycle: oxygen cycle of the biosphere is extremel; (a) Nitrogen fixation: Conversion of nitrogen complex. into nitrates and nitrites through atmosphere, (v) Oxygen is released in the process ol industrial and biological processes. photosynthesis, whereas it is used up in (b) Ammonification: Release of ammonia through processes like respiration, combustion decomposition of dead bodies and excretory decomposition, corrosion, rusting, etc. wastes of organisms.