(ii) [(Session 10.1)] Write a short note on pH of soil. 9. Answer the following questions in 3-4 sentences. (i) [(Session 10.3)] Why recycling and recovery of materials is considered as one of the best methods to reduce soil pollution? CHAPTER 10. SOIL POLLUTION 49
(ii) [(Session 10.3)] Write a short note of pyrolysis. 10. Answer the following questions in 3-4 sentences. (i) [(Session 10.2)] What do you mean by decomposition? (ii) [(Session 10.2)] Distinguish between biodegradable waste and non–biodegradable waste with suitable examples. CHAPTER 10. SOIL POLLUTION 50
AS2-Asking questions and making hypothesis Short Answer Type Questions 11. Answer the following questions in 3-4 sentences. (i) [(Session 10.1)] Waheeda’s teacher taught about the components of soil in the class. You are Waheeda. Write any two important points from the class. (ii) [(Session 10.1)] What questions would you like to ask your teacher about soil? CHAPTER 10. SOIL POLLUTION 51
12. Answer the following questions in 3-4 sentences. (i) [(Session 10.3)] Now–a–days farmers are not interested in soil waste management. What does soil waste management involve? (ii) [(Session 10.3)] What are the effects of soil pollution in urban areas? AS6-Appreciation and aesthetic sense, Values 52 Long Answer Type Questions 13. Answer the following questions in 6-8 sentences. CHAPTER 10. SOIL POLLUTION
(i) [(Session 10.3)] How do you appreciate the Prime Minister’s Swach Bharath program? Is it helpful in controlling land pollution to some extent? AS7-Application to daily life, concern to bio diversity Short Answer Type Questions 14. Answer the following questions in 3-4 sentences. (i) [(Session 10.1)] If you are given some organic forms of elements, how can you liberate carbon dioxide from them without using any chemicals? CHAPTER 10. SOIL POLLUTION 53
(ii) [(Session 10.1)] What may happen if we remove top soil from one acre of land? 15. Answer the following questions in 3-4 sentences. (i) [(Session 10.3)] Why should we not throw wastes wherever we want? CHAPTER 10. SOIL POLLUTION 54
(ii) [(Session 10.3)] What are the different methods which we can use for soil conserva- tion? Long Answer Type Questions 16. Answer the following questions in 6-8 sentences. (i) [(Session 10.3)] Release of polluted water near agricultural fields can affect fertility of soil and also the crop. Is it true? Explain. CHAPTER 10. SOIL POLLUTION 55
(ii) [(Session 10.3)] We often come across the words ‘biodegradable’ and ‘recyclable’. Do you think if we can reuse vegetable waste for electricity production? 17. Answer the following questions in 6-8 sentences. (i) [(Session 10.2)] ’ Hospital waste generated during diagnosis and treatment causes land pollution’. What are the steps to be taken here to rectify this? CHAPTER 10. SOIL POLLUTION 56
Objective Questions AS1-Conceptual Understanding 18. Choose the correct answer. (i) Which of the following resource has 45% mineral particles in it? (A) Air (B) Water (C) Soil (D)All of the above (ii) Land pollution occurs massively during (A) Earthquakes (B) Land slides (C) Floods (D)All of the above (iii) Which of the following is not a physical property of the soil? (A) Colour (B) Texture (C) pH (D) Porosity (iv) This method helps in the percolation of water into the soil. (A) No–till farming (B) Contour ploughing (C)Crop rotation (D)Planting trees CHAPTER 10. SOIL POLLUTION 57
(v) Major part of soil microbial biomass is composed of (A) Virus (B) Fungi (C) Algae (D) Protozoa (vi) Burning of fossil fuel adds (B) CO2 , SO2 , NO2 gases in air (A) Only CO, SO2 gases in air (D) None (C)Both A and B (vii) Life supporting zone of the earth is (A) Biosphere (B) Lithosphere (C) Hydrosphere (D) Atmosphere (viii) The gas present in gobar gas is (A) Ethane (B) Methane (C) Propane (D) Methylene (ix) The layer of the soil which is the foundation for life on the earth is (A) Middle layer (B) Bottom layer (C)Top layer (D)None of the above (x) Which of the following terms is used for combustion in the absence of air? (A) Reduction (B) Deoxygenation (C) Combustion (D) Pyrolysis (xi) Which of the following constitute the highest percentage in the composition of soil? (A) Air (B) Water (C)Mineral Particles (D)Organic matter CHAPTER 10. SOIL POLLUTION 58
(xii) Organic soil is the one which consists of % of organic matter. (A) 30 or more (B) less than 30 (C)10 or more (D)less than 10 (xiii) The best range of pH for a good soil is: (A) Below pH 7 (B) Above pH 7 (C)Between pH 5.5 –7.5 (D)Both A and B (xiv) Mycorrhiza is the symbiotic association of which of the following? (A) Soil bacteria and plant roots (B) Soil fungi and plant roots (C)Soil bacteria and soil fungi (D)Both A and B (xv) e–waste is an example of: (A) Biodegradable waste (B) Non–biodegradable waste (C)Infectious solid waste (D)Re–usable waste (xvi) What is meant by Pyrolysis? (A) Combustion in the absence of oxygen (B) Combustion in the presence of oxygen (C)Using plants for cleaning contamination (D)Both A and C (xvii) Earthworms increase soil fertility by: (A) Increasing soil porosity (B) Enhancing availability of macronutrients in soil (C)Killing harmful insects and microbes in soil CHAPTER 10. SOIL POLLUTION 59
(D)Both A and B (xviii) The three R’s for control of soil pollution stands for: (A) Reduce, Reuse and Recycle (B) Return, Reuse and Recover (C)Reuse, Recycle and Reprocess (D)Reuse, Recycle and Reclaim (xix) Which of the following chemicals present in polluted underground water is not dangerous for human life? (A) Cadmium (B) Arsenic (C) Lead (D) Potassium (xx) Which of the following waste is biodegradable? (A) DDT (B) Aluminium cans (C) Hay (D)Plastic materials CHAPTER 10. SOIL POLLUTION 60
11. BIOGEOCHEMICAL CYCLES SESSION 1 INTRODUCTION AND THE WATER CYCLE 1.1 Mind Map 1.2 Terminology i. Water cycle/hydrologic cycle – The whole process in which water evaporates and comes back to the surface of the earth as rain and other forms of precipitation includ- ing its flow from land into the sea/oceans via several routes like rivers, ground water channels etc. is known as the water–cycle. ii. Ground water – Groundwater is the water present beneath earth’s surface in soil porespaces and in the fractures of rock formations. iii. Condensation – Condensation is the process of change of water from its gaseous form (water vapour) into liquid water. iv. Acid rain – Acid rain describes any form of precipitation with high levels of nitric and sulphuric acids. SESSION 1. INTRODUCTION AND THE WATER CYCLE 61
1.3 Key Concepts i. Living things within an ecosystem interact with each other and also with their non–living environment to form an ecological unit. ii. Resources in the ecosystem have to be regenerated. iii. The cycles that involve the flow of nutrients (elements essential for the living cell) from environment to organisms and back through certain pathways are known as biogeochemical cycles. iv. There is a constant interaction between biotic and abiotic components in the ecosys- tem. These interactions consist of transfer of matter and energy between the different components of the biosphere. v. Water is constantly recycled in a process known as the hydrological cycle or water cycle. 97% of all the water on the earth is in the oceans, and so only about 3% is fresh water. About 2% of this fresh water is permanently frozen in glaciers and in the polar ice caps. vi. There is only about 1% is available fresh water. About 1/4 of this 1% of it is present as groundwater. Only about 0.009% of water on earth is in the rivers and lakes. vii. Human body has about 70% of water. viii. The whole process in which water evaporates and comes back to the surface of the earth as rain and other forms of precipitation including its flow from land into the sea/oceans via several routes like rivers, ground water channels etc. is known as the water–cycle. ix. Water provides hydrogen and oxygen that form integral part of basic organic com- pounds of life. x. Dissolution of some harmful substances like gases like SO2 and oxides of nitrogen in rain water leads to acid rain. 1.4 Conceptual Understanding Q1. What is the importance of different biogeochemical cycles in the nature? [Refer to TB page 182 Q1] SESSION 1. INTRODUCTION AND THE WATER CYCLE 62
A. 1. Biogeochemical pathways determine the path of transfer of matter on earth. The name itself it includes biological, geological and chemical or physiochemical pathways. This means the reservoir or pool of nutrients on earth may contain some chemicals of biological origin while others may be purely inorganic in nature, some may also be geochemical (obtained from rocks and soil) in origin. 2. A constant interaction between the biotic and abiotic components of the biosphere makes it a dynamic and a stable system. 3. These interactions consist of transfer of matter and energy between the different components of the biosphere. 4. Biogeochemical cycles are important to understand how nature is maintaining itself and the impacts of human activities on this self–contained ecological unit, e.g.water cycle, nitrogen cycle etc. Q2. Why could we say that biogeochemical cycles are in “balance”? [Refer to TB page 182 Q3] A. We can certainly say that biogeochemical cycles are in “balance” as they satisfy the following: i. The biogeochemical cycles are the key to the movement of nutrients through an ecosystem. ii. Living things need these nutrients to survive and grow, and when they die, the materials are recycled through the system. iii. Nitrogen is used in nucleic acids, to form proteins in all living organisms. iv. Carbon is the core element for almost all living things. v. Biogeochemical cycles link living organisms with other living organisms, living organisms with the non–living organisms and non–living organisms with other non–living organisms. Biogeochemical cycles regulate the flow of substances. vi. Matter is continually recycled among living and abiotic elements on earth. vii. Biogeochemical cycles facilitate the transfer of matter from one form to another and from one location to another on earth. viii. Additionally, biogeochemical cycles are sometimes called nutrient cycles because they involve the transfer of compounds that provide nutritional support to living organisms. SESSION 1. INTRODUCTION AND THE WATER CYCLE 63
1.5 Asking Questions and Making Hypothesis Q1. If all the vegetation in the pond died, what effects would it have on the animals? Why? [Refer to TB page 182 Q4] A. i. All the organisms on earth are interdependent. ii. They form a part of one or more food chains and in turn are present in the food web. iii. If all the vegetation in the pond died, the life in the pond would come to a halt. iv. Carnivores in a pond feed on herbivores, herbivores feed on plants, and plants in turn depend on sunlight, water and carbon dioxide. v. So, when plants (vegetation) die, all life would slowly die after starvation due to lack of food. 1.6 Information Skills and Projects Q1. Go to a nearby pond. Observe organisms living in the pond and bio degradable sub- stance mixing in water. How do they affect those organisms? Write your observation. [Refer to TB page 182 Q6] A. i. The term biodegradable is used to describe materials that decompose through the actions of bacteria, fungi, and other living organisms. ii. Bio degradable substances present in the ponds does not adversely affect the organisms living in the ponds. iii. Bio degradable substances in the pond are broken down in to simpler substances that do not harm the organisms surviving in the pond. 1.7 Application to Daily Life, Concern to Bio Diversity Q1. How do human activities cause an imbalance in biogeochemical cycles? [Refer to TB page 182 Q11] A. 1. Human activities cause an imbalance in biogeochemical cycles. For e.g., humans have altered the biological carbon cycle, increasing atmospheric CO2 levels through forest clearing and land use. SESSION 1. INTRODUCTION AND THE WATER CYCLE 64
2. Trees store large amounts of carbon; when they die and decompose, much of this stored carbon is released as CO2 . 3. However, when humans clear large expanses of forest, primarily through the use of fire, the levels of atmospheric carbon are affected in two ways. 4. First, during combustion, stored carbon is released directly into the air as CO2 , and second, the clearing of land takes away a key mechanism for removing excess carbon dioxide from the atmosphere (via photosynthesis). 5. Since carbon dioxide is a primary greenhouse gas, the increase in atmospheric CO2 due to human activities has resulted in an enhanced greenhouse effect resulting in higher global temperatures. Q2. List three ways we, as humans, have affected the water cycle. [Refer to TB page 182 Q12] A. i. By cutting down trees;which cools the atmosphere to bring rains into the water cycle. ii. By releasing pollutants and harmful chemicals into the nearby rivers and oceans; ocean water dissolves the chemicals and evaporates. This mixes with gases when coming down as rain and thus forms acid rains. iii. By using chemical fertilizers which get mixed up with water and seep into the ground and pollutes the underground water, which is a part of water cycle. SESSION 1. INTRODUCTION AND THE WATER CYCLE 65
SESSION 2 NITROGEN CYCLE 2.1 Mind Map 2.2 Terminology i. Nitrogen cycle – Nitrogen cycle is a complex biological cycle in which nitrogen is con- verted from its inert atmospheric molecular form into a form that is useful in biological process. ii. Nitrogen fixation –Atmospheric nitrogen is converted into a form that can be used by plants is the process called nitrogen fixation. iii. Nitrification –Nitrification is the biological oxidation of ammonia or ammonium to ni- trite followed by the oxidation of the nitrite to nitrates. iv. Assimilation – Assimilation is the process in which nitrates or ammonium ions are taken up from the soil by plants and then used in the formation of plants proteins and animals eat these plants, animal proteins are synthesized. SESSION 2. NITROGEN CYCLE 66
2.3 Key Concepts i. The nitrogen cycle is a complex biogeochemical cycle in which nitrogen is converted from its inert atmospheric molecular form ( N2 ) into a form that is useful in biological processes. ii. Atmospheric nitrogen is converted into a form that can be used by plants is the pro- cess called nitrogen fixation. iii. Rhizobium and Nitrosomonas are biological forms able to fix atmospheric nitrogen. iv. Production of ammonia ( NH3 ) from nitrates and other nitrogenous compounds called as ammonification. v. Nitrate ( NO3 ) is converted back to gaseous nitrogen ( N2 ) in the process of denitrification. 2.4 Communication Through Drawing and Model Making Q1. Describe interdependence of biotic and abiotic components by taking nitrogen cycle as an example. [Refer to TB page 182 Q7] A. i. A constant interaction between the biotic and abiotic components of the biosphere makes it a dynamic, but a stable system. These interactions consist of transfer of matter and energy between the different components of the biosphere. ii. E.g. Nitrogen is the most abundant element in the atmosphere and a building block of proteins and nucleic acids. The nitrogen cycle is a complex biogeochemical cycle in which nitrogen is converted from its inert atmospheric molecular form ( N 2 ) into a form that is useful in biological processes. iii. The element nitrogen is constantly moving in a giant circle from the air, through the soil, into the bodies of plants and animals, and eventually back to the air by the process of nitrogen cycle. iv. The atmospheric nitrogen is thus converted into certain compounds that plants may take up from the soil by some biochemical (caused by certain bacteria like Rhizobium, Nitrosomonas etc.) and physico–chemical (caused by lightning) pro- cesses. Animals get the required amount of nitrogen from plants either directly (herbivores) or indirectly (carnivores). SESSION 2. NITROGEN CYCLE 67
The nitrogen cycle is as follows: 1. Nitrogen fixation: Most atmospheric nitrogen is ‘fixed’ through biological processes. Rhizobium and Nitrosomonas convert atmospheric nitrogen into the organic nitrogen for their own cells. As they die, this nitrogen, now present in the soil as compounds be- come available to plants. In leguminous plants like pea, beans etc. there is a symbiotic relationship of the nitrogen fixing bacteria with the plant. Nitrogen can also be fixed as nitrates by lightening. This reaches soil and water through precipitation that follows. Nitrates are taken up by plants to form proteins and nucleic acids. 2. Nitrification: Nitrates can also be converted to ammonia by the nitrifying bacteria in the soil. The nitrifying bacteria may then use this ammonia to synthesize compounds for their own cell and it is eventually converted to proteins, nucleic acids, nitrites and nitrates. Nitrites are produced mainly by Nitrosomonas, and nitrates by Nitrobacters. These are capable of utilizing nitrites and converting them to nitrates. Death of the microorganisms adds the nitrogenous compounds to the soil. Plants take up nitrates as well as ammonium ions from the soil to convert them to proteins and nucleic acids. 3. Assimilation: Nitrogen compounds mainly as nitrates or ammonium ions ( NH4- ) are taken up from soils by plants which are then used in the formation of plant proteins and as animals eat these plants, animal proteins are also synthesised. SESSION 2. NITROGEN CYCLE 68
4. Ammonification: Production of ammonia (NH3 ) from nitrates and other nitrogenous compounds is called as ammonification. Ammonification also occurs when plants and animals die, or when animals emit wastes, the nitrogen in the organic matter enters the soil and water bodies where it is broken down by other microorganisms, known as decomposers. This decomposition produces ammonia which is then available for other biological processes. 5. Denitrification: Nitrogen makes its way back into the atmosphere through a process called denitrification, in which solid nitrate ( NO3 ) is converted back to gaseous nitrogen. SESSION 2. NITROGEN CYCLE 69
SESSION 3 THE CARBON CYCLE 3.1 Mind Map 3.2 Terminology i. Carbon cycle –It is the process in which carbon travels from the atmosphere into organisms and the earth and then back into the atmosphere. ii. Greenhouse Effect – The warming of the earth’s atmosphere and surface by the at- mospheric greenhouse gases such as carbon dioxide, methane and water vapours is called greenhouse effect. SESSION 3. THE CARBON CYCLE 70
iii. Global warming –Phenomenon of increase in the earth’s temperature is called global warming. iv. Combustion –Combustion is a chemical process in which a substance reacts rapidly with oxygen and gives off heat. 3.3 Key Concepts i. Carbon occurs in the elemental form as soot, diamond and graphite. In the com- bined state, it is found as the gases –carbon dioxide and carbon monoxide in the atmosphere ii. Carbon dioxide ( CO2 ) makes up about 0.04% by volume of air. Animals and humans return carbon to the atmosphere as CO2 through respiration. Plants accept CO2 in the process of photosynthesis. iii. Phenomenon of increase in the earth’s temperature is called global warming. iv. Release of carbon dioxide and other gases into the atmosphere has depleted the ozone layer and that leads to greenhouse effect. 3.4 Experimentation and Field Investigation Q1. Write an experiment to prove Green house effect on temperature. [Refer to TB page 182 Q5] A. Aim: Test the effect of a greenhouse on temperature. Materials Required: Plastic bottle, nail, 2 thermometers, notebook and pencil. Procedure: i. Make a hole on top of the plastic bottle with a nail. ii. Insert the first thermometer into the hole. iii. Place the second thermometer next to the bottle. Make sure the same amount of sunlight reaches both the thermometers. iv. Note the temperature values for both the thermometers after 10 minutes. v. Record the values in a notebook. vi. Take the temperature record again after 10 minutes and repeat it for 2–3 times. Observation: The temperature values for both the thermometers are different. Conclusion: Greenhouse gases increase the atmospheric temperature. SESSION 3. THE CARBON CYCLE 71
3.5 Appreciation and Aesthetic Sense, Values Q1. Burning of fossil fuels a concern for scientists and environmentalists. Why? [Refer to TB page 182 Q9] A. i. Coal, petrol and natural gas are called fossil fuels. They are so called as they are formed due to the decomposition of dead plants and animals from several thousands of years. They are drilled from the layers of earth and made useful. They are non–renewable resources. ii. Human beings tap into the geological carbon cycle by extracting oil and coal, which are both hydrocarbons (formed of carbon and hydrogen),used in automobiles and power plants. The by products of combustion of these hydrocarbons are CO2 and CO gases. Carbon dioxide levels in the atmosphere have increased measur- ably, mostly as a result of human use of fossil fuels. iii. Burning any of these fossil fuels would release carbon dioxide. Carbon dioxide is a greenhouse gas. It is responsible for depletion of ozone layer and thus leads to global warming. Global warming is an alarming factor as it can cause droughts, famines or floods. This would create a great threat to life of organisms. Hence scientists and environmentalists are concerned about burning fossil fuels. 3.6 Application to Daily Life, Concern to Bio Diversity Q1. 'Carbon dioxide play a vital role in plant life processes'. Comment. [Refer to TB page 182 Q10] A. Carbon is incorporated into life through various processes. It plays a major role in plant life processes as it helps in photosynthesis. Photosynthesis is a life process in which carbohydrates are produced by plants with the help of water, sunlight and carbon diox- ide. i. Photosynthesis : The first step in the biological carbon cycle is the conversion of inorganic atmospheric carbon into a biological form. ii. This ‘fixing’ of carbon in biological form takes place within plants and other organ- isms known as producers a process called photosynthesis, by which energy from sunlight is converted into chemical form. SESSION 3. THE CARBON CYCLE 72
iii. In photosynthesis, light energy helps to combine carbon dioxide and water to cre- ate the simplest of sugars, the carbohydrate molecules known as glucose (C6 H12 O6). In oceans, photosynthesis is carried out by microscopic aquatic plants called phytoplankton. iv. The carbohydrates then become the source of chemical energy that fuel living cells in all plants and animals. In plants, some carbon remains as simple glucose for short–term energy use, while some are converted to large complex molecules such as starch for longer term energy storage. SESSION 3. THE CARBON CYCLE 73
SESSION 4 OXYGEN CYCLE 4.1 Mind Map 4.2 Terminology i. Oxygen cycle –The oxygen cycle is the biogeochemical cycle that describes the move- ment of oxygen within its three main reservoirs: the atmosphere (air), the total con- tent of biological matter within the biosphere (the global sum of all ecosystems), and the lithosphere (Earth’s crust). ii. Ozone Depletion –Destruction of the ozone layer which shields the earth from ultra- violet radiation. iii. BOD – The content of the biodegradable substance in water is expressed by a special index called Biological Oxygen Demand (BOD). SESSION 4. OXYGEN CYCLE 74
iv. CFCs –CFCs (Chloro Fluoro Carbons) are the chemicals which contain carbon, chlo- rine, and fluorine, used in air conditioners and refrigerators which cause a destruction of ozone layer present in the stratosphere of the atmosphere. 4.3 Key Concepts i. Earth’s atmosphere is divided into troposphere and stratosphere. ii. Ozone is a molecule containing three oxygen atoms. It is blue in colour and has a strong odour. iii. Montreal protocol is associated with ozone depletion and greenhouse gases. iv. The ozone layer absorbs a portion of the radiation from the sun, preventing it from reaching the planet’s surface. 4.4 Conceptual Understanding Q1. What emissions from human activities lead to ozone depletion? And what are the prin- cipal steps in stratospheric ozone depletion caused by human activities? [Refer to TB page 182 Q2] A. i. Chlorofluorocarbons and carbon dioxide and other gases emitted from vehicles, industries etc. lead to the ozone layer depletion. ii. Certain industrial processes and consumer products result in the emission of ozone–depleting substances to the atmosphere. iii. These gases bring chlorine and bromine atoms to the stratosphere, where they destroy ozone in chemical reactions. iv. Important examples are the chlorofluorocarbons (CFCs) used in almost all refrig- eration and air conditioning systems. v. Most of these gases accumulate in the lower atmosphere because they are unre- active and do not dissolve readily in rain or snow. vi. Natural air motions transport these accumulated gases to the stratosphere, where they are converted to more reactive gases. vii. Some of these gases then participate in reactions that destroy ozone. viii. The ozone hole is not really a hole, but it was observed that there is less ozone in Antarctica than in the arctic region. SESSION 4. OXYGEN CYCLE 75
4.5 Communication Through Drawing and Model Making Q1. Draw oxygen, water and nitrogen Cycles. [Refer to TB page 182, Q15] A. Students' Activity 4.6 Appreciation and Aesthetic Sense, Values Q1. What do you understand by ozone layer? Write an essay to participate in elocution competition on the importance of ozone layer. [Refer to TB page 182 Q8] A. The Earth’s atmosphere is divided into several layers. The lowest region, the tropo- sphere, extends from the Earth’s surface up to about 10 kilometres (km) in altitude. The next layer, the stratosphere, continues from 10 km to about 50 km. Most atmospheric ozone is concentrated in a layer in the stratosphere, about 15–30 kilometres above the Earth’s surface. The student can make use of following points and create a add–on for writing the essay. i. Ozone is a molecule containing three oxygen atoms. It is blue in colour and has a strong odour. Normal oxygen, which we breathe, has two oxygen atoms and is colourless and odourless. ii. Ozone is much less common than normal oxygen. iii. Out of each 10 million air molecules, about 2 million are normal oxygen, but only 3 out of 10 millions are ozone. iv. However, even the small amount of ozone plays a key role in the atmosphere. The ozone layer absorbs a portion of the radiation from the sun, preventing it from reaching the earth’s surface. Most important of all it absorbs the portion of ultraviolet light which causes many harmful effects, including various types of skin cancer and harm to some crops, certain materials, and some forms of marine life. 4.6 Application to Daily Life, Concern to Bio Diversity Q1. Prepare an article for newspaper on the item “How human activities effects the environ- ment” [Refer to TB page 182 Q13] A. It’s interesting to note that modern humans have been around for a very long time and lived for much of it without causing much irreparable damage to the environment. How- ever, over exploitation and pollution have started affecting the environment negatively over the last few centuries. Negative Impacts Caused by Humans SESSION 4. OXYGEN CYCLE 76
Unfortunately, humans are the most polluting species. Earth is very good at recycling waste, but we are generating far more than earth can cope with. Pollution occurs at different levels and it doesn’t just impact our planet; it impacts all species, including mankind, who dwell on it. Soil pollution: Pesticides, herbicides, large landfills, waste from food processing industries, and nuclear waste generated from nuclear reactors and weapons deplete our soil of its nutrients and make it virtually lifeless. According to the Environmental Protection Agency, ”Usually, contaminants in the soil are physically or chemically attached to soil particles, or, if they are not attached, are trapped in the small spaces between soil particles.” Water Pollution: Effluence from industries, fertilizer run off, and oils spills all damage fragile ecosystems. According to the Water Project, “Nearly a billion people do not have access to clean and safe water in our world.” Worldwatch Institute says, “The 450 million kilograms of pesticides U.S. farmers use every year have now contaminated almost all of the nation’s streams and rivers, and the fish living in them, with chemicals that cause cancer and birth defects.” Air Pollution: Burning of fossil fuels and toxic gases produced in factories causes pollution. Air pollu- tion infects the environment and threatens the health of all who inhabit the earth. Ac- cording to the United Nations, “The estimations we have now tell us there are 3.5 million premature deaths every year caused by household air pollution, and 3.3 million deaths every year caused by outdoor air pollution.” Global Warming and Ozone Layer Depletion: Carbon footprint is the measure of direct or indirect CO2 . Greenhouse gases like CO2 and methane are believed to lead to global warming. Chlorofluorocarbons (CFCs), used in refrigeration, and aerosols destroy the ozone layer that shields the earth from UV rays. Q2. Prepare slogans on greenhouse effect and read the out in school assembly. [Refer to TB page 182, Q14] A. Students' Activity SESSION 4. OXYGEN CYCLE 77
—— CCE Based Practice Questions —— AS1-Conceptual Understanding Very Short Answer Type Questions 1. State true or false. [Refer to Session 11.1 ] (i) Water is constantly recycled in a process known as the hydrological or water cycle. [] (ii) Water is considered as a biogeochemical cycle by most ecologists. ] [ (iii) Water is a universal solvent and essential for various reactions to take place in a living cell. [] (iv) Fresh water available is about 10%. [] (v) Water participates in many biogeochemical metabolisms. [ ] 2. Fill in the blanks. [Refer to Session 11.1 ] (vi) Water is constantly recycled in a process known as the . (vii) Water is a and essential for various to take place within a living cell. (viii) Nearly % of all the water on the earth is in the oceans. (ix) All living organisms together constitute only of water on earth. (x) determine the path of transfer of matter on earth. CHAPTER 11. BIOGEOCHEMICAL CYCLES 78
(xi) Dissolution of some harmful substances like SO2 and oxides of nitrogen in rain water leads to . (xii) The human body is composed of about % of water. (xiii) Biogeochemical cycles, from name itself, include , and pathways. (xiv) Water provides and that form an integral part ofbasic organic compounds of life. (xv) Water is the precursor of major elements viz and . 3. Match the following. Column B [(Session 11.2)] a. NH3 Column A b. Legumes i. Rhizobium ii. Nitrosomonas iii. Ammonification c. Nitrogen fixation iv. Assimilation d. N2 e. NH4+ v. Denitrification 4. Fill in the blanks. [Refer to Session 11.3 ] (xvi) Graphite consists of element. (xvii) By products of combustion of hydrocarbons are and gases. (xviii) In photosynthesis, energy from sunlight is converted into energy. (xix) Carbon dioxide level in the atmosphere has increased significantly as a result of human use of . CHAPTER 11. BIOGEOCHEMICAL CYCLES 79
(xx) Carbon buried under the ocean floor might take million years to return to the atmosphere. (xxi) A is a small house made of glass that is used to grow plants. (xxii) change waste material in to H2 S and other poisonous and foul smelling substances. (xxiii) and act as natural greenhouse gases. (xxiv) is a primary greenhouse gas. (xxv) affects the weather patterns on earth and causes climate change. 5. Match the following. Column B [(Session 11.4)] a. 0.04% in air Column A i. Nitrogen ii. Oxygen b. 97% of water on earth iii. Carbon dioxide c. 78% in air iv. Fresh water d. 21% in air v. Salt water e. 3% of water on earth 6. Fill in the blanks. [Refer to Session 11.4 ] (xxvi) Most atmospheric is concentrated in a layer in the stratosphere. (xxvii) The ozone layer is present about above the earth’s surface. (xxviii)Ultraviolet rays cause in living organisms. CHAPTER 11. BIOGEOCHEMICAL CYCLES 80
(xxix) is a substance used in refrigerators and air conditioners that destroys the ozone layer. (xxx) There is in Antarctica than in the Arctic region. Short Answer Type Questions 7. Answer the following questions in 3-4 sentences. (i) [(Session 11.1)] What are biogeochemical pathways ? (ii) [(Session 11.1)] What trouble do you encounter with water cycle? CHAPTER 11. BIOGEOCHEMICAL CYCLES 81
8. Answer the following questions in 3-4 sentences. (i) [(Session 11.4)] Write any two points on Biological Oxygen Demand. (ii) [(Session 11.4)] What are the uses of oxygen? AS2-Asking questions and making hypothesis 82 Short Answer Type Questions 9. Answer the following questions in 3-4 sentences. CHAPTER 11. BIOGEOCHEMICAL CYCLES
(i) [(Session 11.1)] Abhishek said that water is found in different states during water cycle. Name the different states of water giving examples for each from the water cycle. (ii) [(Session 11.1)] Prepare a questionnaire on water cycle. AS4-Information skills and projects Long Answer Type Questions 10. Answer the following questions in 6-8 sentences. (i) [(Session 11.1)] Collect details of statistical data about the presence of water on earth. Deduce what percentage of water is available as fresh water. CHAPTER 11. BIOGEOCHEMICAL CYCLES 83
AS5-Communication through drawing and model making Long Answer Type Questions 11. Answer the following questions in 6-8 sentences. (i) [(Session 11.2)] Sketch a flow chart which describes the process of nitrogen fixation. CHAPTER 11. BIOGEOCHEMICAL CYCLES 84
AS6-Appreciation and aesthetic sense, Values Short Answer Type Questions 12. Answer the following questions in 3-4 sentences. (i) [(Session 11.4)] What has caused holes in the ozone layer? Are they good for us? (ii) [(Session 11.4)] Write a short note on ozone layer. How can we protect it ? Long Answer Type Questions 13. Answer the following questions in 6-8 sentences. (i) [(Session 11.3)] How would you appreciate carbon as the “central element of life”? CHAPTER 11. BIOGEOCHEMICAL CYCLES 85
14. Answer the following questions in 6-8 sentences. (i) [(Session 11.4)] What are the causes of ozone depletion? How would you appreciate the emergence of Montreal protocol towards ozone depletion? CHAPTER 11. BIOGEOCHEMICAL CYCLES 86
AS7-Application to daily life, concern to bio diversity Short Answer Type Questions 15. Answer the following questions in 3-4 sentences. (i) [(Session 11.3)] State in brief the roles of photosynthesis and respiration in carbon cycle in nature. (ii) [(Session 11.3)] We know that an increase in the carbon dioxide level causes an adverse effect on biodiversity in nature. State the reason behind the increasing levels of carbon dioxide in the atmosphere. Long Answer Type Questions 87 16. Answer the following questions in 6-8 sentences. CHAPTER 11. BIOGEOCHEMICAL CYCLES
(i) [(Session 11.1)] Explain how human involvement has affected the water cycle. 17. Answer the following questions in 6-8 sentences. (i) [(Session 11.3)] Explain how human intervention has affected carbon cycle and has caused increased carbon dioxide levels. What are the effects of increased carbon dioxide levels on earth? CHAPTER 11. BIOGEOCHEMICAL CYCLES 88
Objective Questions AS1-Conceptual Understanding 18. Choose the correct answer. (i) Which of the following is responsible for maintaining the earth as a greenhouse with temperature conditions suitable for life? (A) Oxygen (B) CO2 (C) Hydrogen (D) Nitrogen (ii) Proteins contain (A) Carbon (B) Nitrogen (C) Oxygen (D)All of these (iii) The main reservoirs of carbon are (A) Sedimentary rocks (B) Fossil fuels (C) Oceans (D)All the above (iv) Oxygen is returned to the atmosphere mainly by (A) Respiration (B) Photosynthesis (C)Burning of wood (D) Fungi (v) Excessive amount of carbon dioxide and other green houses are emitted to the environment due to (A) Burning of fossil fuels, deforestation (B) Burning of fossil fuels, industrialization (C)Deforestation, industrialization (D)Burning of fossil fuels, deforestation, industrialisation CHAPTER 11. BIOGEOCHEMICAL CYCLES 89
(vi) Ozone layer is getting depleted because of (A) Industrial units (B) Automobiles (C) CFCs (D) None (vii) exists in the biosphere as the central element of life. (A) Carbon (B) Nitrogen (C) Oxygen (D) Water (viii) Which of the following gas protects the earth from ultraviolet radiations? (A) Nitrogen (B) Oxygen (C) Ozone (D) Hydrogen (ix) Carbon dioxide now makes up about by volume of air. (A) 0.05% (B) 0.04% (C) 0.1% (D) 1% (x) To protect ozone layer, the protocol emerged was (A) Washington protocol (B) Montreal protocol (C)Vancover protocol (D)Geneva protocol (xi) In biogeochemical cycles, there is a constant interaction between: (A) Biotic and Abiotic components of biosphere (B) Flora and Fauna in the biosphere (C)Biological, Geological, Chemical and Physiological components of biosphere (D)Both A and C (xii) Which cycle is also known as hydrological cycle? CHAPTER 11. BIOGEOCHEMICAL CYCLES 90
(A) Water cycle (B) Nitrogen cycle (C)Carbon cycle (D)Oxygen cycle (xiii) Which of the following is not a green house gas? (A) Carbon dioxide (B) Methane (C)Carbon monoxide (D) Nitrogen (xiv) Denitrification refers to conversion of to . (A) Nitrate to Ammonia (B) Solid nitrate to gaseous nitrogen (C)Nitrate to Nitrite (D)All of the above (xv) The process of converting atmospheric nitrogen into more available organic forms is called as: (A) Nitrogen assimilation (B) Ammonification (C)Nitrogen fixation (D) Denitrification (xvi) Which of the following element is referred as the central element of life? (A) Hydrogen (B) Oxygen (C) Carbon (D) Nitrogen (xvii) In the process of photosynthesis, carbon dioxide and water combine in the pres- ence of light energy to produce molecules. (A) Starch (B) Sucrose (C) Glucose (D) Fructose (xviii) Which gases are produced as a by product of combustion of hydrocarbons? (A) CO2 and CO (B) NO2 and CO2 (C)CO2 and SO2 (D)CO2 and O2 CHAPTER 11. BIOGEOCHEMICAL CYCLES 91
(xix) The phenomenon of naturally warming of earth leading to increase in global temperature is known as: (A) Green–house effect (B) Global warming (C)Global climate change (D)All of the above (xx) Most atmospheric ozone which protects the earth from harmful ultraviolet radia- tions of the Sun is present in which layer of the atmosphere? (A) Troposphere (B) Stratosphere (C) Ionosphere (D) Exosphere CHAPTER 11. BIOGEOCHEMICAL CYCLES 92
PROJECT BASED QUESTIONS —— Project Based Questions —— (i) Visit a nearby soil testing center and collect the information from the scien- tist/technician on methods and techniques used for soil testing. Also write a note on different metals present in the contaminated soil. (ii) With the help of your books/internet from the library, collect the information of various plants and animals in different ecosystem around the world. Provide the information in a tabulated form. (iii) You are asked to give a seminar on “Soil pollution–Cause, Effects, and Control mea- sure”. How would you prepare for the topic? What points would you include? Write a synopsis about the topic. (iv) Nitrogen cycle is a complex biogeochemical cycle. Take the help of internet or library book to make a collage with pictures which shows the detailed explanation of Nitrogen cycle. Project Based Questions 93
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