Bio - Geo - Chemical Cycles

Q1. Give the balanced chemical equation:1. Green plants form carbohydrates during photosynthesis. (or) Carbon dioxide reacts with water in presence of chlorophyll and sunlight. Ans. During photosynthesis, green plants synthesize carbohydrate from carbon dioxide and water in the presence of sunlight. The overall chemical reactions involved during the process can be represented by the following equations.

2. Oxidation of carbohydrate during the aerobic respiration in a cell. Ans. During aerobic respiration in a cell, the carbohydrate undergoes oxidation and forms CO2 and H2O with the release of energy. The overall chemical reactions involved during the process can be represented by the following equation.

3. Dehydration synthesis in a plant cell. Ans. Removal of water molecule is called dehydration. During dehydration synthesis in a plant cell, small molecules get linked together to form large molecules by the elimination of water as shown below.

4. Fermentation of glucose solution Ans. During fermentation sugar such as glucose is converted into alcohol and carbon dioxide and energy is released. The overall changes involved during fermentation can be represented by the following equations.

Q2. Give scientific reasons. 1. Oxygen is called a life supporting gas. Ans. Oxygen is called a life supporting gas because. 1. The atmosphere contains about 20% of oxygen. 2. All organisms require oxygen for respiration process during which food is oxidized in order to release energy. 3. The energy obtained from respiration process is utilized for performing various metabolic activities with out which life activity of an organism comes to an end. 2. Bacteria like nitrosomonas and nitrobacter are called denitrifying bacteria.

Ans. Bacteria like nitrosomonas and nitrobacter are called denitrifying bacteria because 1. The conversion of ammonia into nitrites and nitrates is called nitrification. 2. Nitrosomonas bring the conversion of ammonia into nitrites. 3. Nitrites are converted into nitrates by nitrobacter. 4. These bacteria help in nitrification. 3. Coal, petroleum and natural gas are called fossil fuels. Ans. Coal, petroleum and natural gas are called fossil fuels because 1. They are the dead remains of plants and animals of the remote past. 2. They are free from water and are rich in hydrocarbons. 3. They have been formed by the process of fossilization over a period of millions years. Q3. Define 1. Bio – geo chemical cycles:-The circular flow of nutrients from the environment to the living organisms back to the environment in a cyclic manner is called bio – geo chemical cycles. 2. Nutrients:- All kinds of ions and molecules taken up by the living organisms are called nutrients. 3. Anaerobes:- Microbes that do not require oxygen for their respiration are called anaerobes. 4. Aerobes:- Microbes that require oxygen for their respiration are called aerobes. 5. Fermentation:- Fermentation means conversion of the complex organic compounds into simpler organic ones by the activity of micro – organisms. 6. Ammonification :- The process in which nitrogenous compounds are converted into ammonia by the activity of micro – organisms is called ammonification. 7. Nitrification :- The process in which the ammonia gets converted to nitrites and then to nitrates is called nitrification. 8. De – nitrification :- Conversion of nitrates to molecular nitrogen by the activity of de – nitrifying bacteria is called de – nitrification. 9. Nitrogen fixation :- Conversion of atmospheric nitrogen into compounds is called nitrogen fixation. Q4. Write short notes on 1. Fossil Fuels:Ans. 1. Fossils are formed due to burial of plants and animals remains. 2. These animals and plants existed on the earth in the remote past. 3. Their remains accumulated slowly under the cover of sediments. 4. They got locked up and count not get decomposed, as oxygen was not available due to over lying sediments.

5. The pressure of the sediments squeezed out water. 6. These remains are carbon rich fossil fuels. 7. Fossilized forests have resulted in the formation of coal bed. Ex. Coal, petroleum and natural gas are fossil fuels. 2. Carbon in food. Ans. 1. Carbon forms the most important constituent of food. 2. Carbohydrates, proteins, lipids are all carbon compounds. 3. They are used as the source of energy by all living organisms. 4. During respiration, food gets oxidized and energy is released. Ex. Glucose is oxidized during respiration. 3. Methods of Nitrogen fixation :- Nitrogen fixation occurs in two methods:1. The physical process:- During lightening, nitrogen in the atmosphere is oxidized to nitrogen oxide. It then gets dissolved in rainwater to form nitrous and nitric acid and is added to the soil. In the soil, they react with each other elements to forms nitrogen compounds. This process is called physical process of nitrogen fixation. 2. The biological process:- The conversion of molecular nitrogen to its compounds is carried out by prokaryotes, namely some bacterial and some blue green algae present in the soil. This process is called biological nitrogen fixation. 4. Global water cycle or Hydrological cycle:1. In global water cycle, the atmosphere contains water vapour due to evaporation mainly over the oceans. 2. This leads to cloud formation, which results in precipitation, which rains on the oceans as well as on the land. 3. The excess of precipitations results in the formation of surface and ground water system. 4. This water flows back to the sea. 5. This water cycle does not involve life forms and therefore it is called as global water cycle. 5. Mineral cycle:1. Minerals such as phosphorus, magnesium, calcium, potassium, iron are important for the life of the organisms. They are called nutrients. Nutrients are needed for the growth and development. 2. Minerals are present in the soil is dissolved state and also found in water. 3. They are absorbed by the plants and are incorporated in their body. 4. From plants, they are passed over to the body of animals through food chain and food web. 5. Minerals return to the soil or water through waste matter or dead bodies and animals.

6. Decomposition of dead bodies of plants or animals is carried out by bacterial and fungi. 7. They release enzymes that degrade organic matter back to inorganic compounds. 8. Thus minerals are released to the surroundings and are available for racing. 9. All the minerals thus eventually make their way back to the environment. 6. Flow of energy (or) Energy flow Ans. 1. Solar energy is captured by the green plants during photosynthesis. It is stored in the form of organic molecules that is food molecules. 2. In the food chain food molecules pass from plants to animals. 3. During, respiration, food molecules are oxidized to release stored solar energy. Much of the energy stored in the food molecules is simply lost as heat energy. 4. It escapes to the surrounding. This energy cannot be recaptured and reused by plants or animals. 5. It cannot return to the sun. Thus the flow of energy becomes unidirectional. This means energy cannot be recycled. Q5. Answer the following briefly: 1. Give graphic representation of oxygen cycle and describe.

Ans. The cyclic journey of oxygen from the atmosphere to living organisms and from living organisms back to the atmosphere is called oxygen cycle. 1. The atmosphere contains 20% oxygen. Aquatic plants and animals obtain oxygen from water. 2. Both plants and animals require oxygen for respiration. During respiration carbohydrates are oxidized with the help of atmospheric oxygen and energy is released.

3. Carbon dioxide, which is a bi – product released in this reaction, is used by plants for synthesis of food during the process of photosynthesis. 4. During the process of photosynthesis carbon dioxide is taken in and oxygen is given out. Thus photosynthesis is the only process by which oxygen is returned to the atmosphere. 2. Give graphic representation of carbon cycle and describe.

Ans. The cyclic journey of carbon from the atmosphere to green plants from green plants to animals and from both these back to the atmosphere is called carbon cycle. 1. Carbon dioxide of the atmosphere is the main sources of carbon cycle. 2. Green plants during photosynthesis fix carbon dioxide from the atmosphere and convert it into carbohydrates. 3. Herbivorous use green plants as their food and which in turn are consumed by carnivorous. 4. Thus carbon passes from one organism to the other in the food chain. 5. Respiration of both, the green plants and animals bring about oxidation of carbohydrates, which gives carbon dioxide, and it returns to the atmospheres. 6. The decomposition of organic matter is carried out by the micro – organisms which release carbon dioxide and it also returns to the atmosphere. 7. Burning of wood, fuels like coal, petroleum and natural gasses and during the process of fermentation carbon dioxide is released to the atmosphere.

3. Give graphic representation of Nitrogen cycle and describe. Ans.

The cyclic journey of nitrogen from the atmosphere to soil, from soil to plants, from plants to animals and from both these back to the atmosphere is called nitrogen cycle. The nitrogen cycle is complete in the following phases:1. Nitrogen fixation:- Nitrogen fixation occurs in two methods:a. The physical process:- During lightening, nitrogen in the atmosphere is oxidized to nitrogen oxide. It then gets dissolved in rain water to form nitrous and nitric acid and is added to the soil. In the soil, they react with each other elements to forms nitrogenous compounds. This process is called physical process of nitrogen fixation. b. The biological process:- The conversion of molecular nitrogen to its compounds is carried out by prokaryotes, namely some bacteria and some blue green algae present in the soil. This process is called biological fixation. 2. Utilization of Nitrogenous compound by plants and animals:- Plants take up nitrogen compounds like nitrites and nitrates form the soil. They build up organic nitrogenous compounds like proteins and their derivatives. Herbivorous takes up proteins from the plant to form amino acids. From these amino acids, they build up their own body proteins. Carnivorous take up proteins from herbivorous. 3. Conversion of organic nitrogenous compounds into inorganic state:- Excretory products of animals and dead bodies of plants and animals are added to the soil. A variety of micro – organisms act upon these nitrogenous compounds and

convert them to inorganic state. Organic nitrogenous compounds at first are converted into ammonia. This process is called as ammonification. Ammonia thus formed gets converted into nitrite by nitrosomonas and nitrosococcus bacteria. The nitrite thus formed is finally converted into nitrate by nitrobacter by the process known as nitrification. The nitrates are finally converted into molecular nitrogen (N2 ) by denitrifying bacteria. This process is called de = nitrification. 4. Describe fermentation:Fermentation means enzymatic conversion of the complex organic compounds into simpler organic ones by the activity of micro – organisms. Fermentation is anaerobic respiration by which micro – organisms obtain energy required for their life processes. Baker’s yeast in the common fermenting microbe. It brings about the following reaction:

Carbon dioxide released during the process returns to the atmosphere. 5. What will happen to nitrogen cycle if all the bacterial disappear? Ans. Nitrogen cycle will not occur in nature because bacteria play a very important role in nitrogen cycle. 1. Nitrogen fixation:- Symbiotic bacteria like rhizobium and free living bacterial like azatobacter and clostridium fix atmospheric nitrogen and convert it into nitrites and nitrates. 2. Ammonification:- Certain bacterial decompose dead organic matter to release ammonia. 3. Nitrification:- Certain bacterial such as nitrosomonas and nitrosococcus convert ammonia into nitrites. Nitrobacter convert nitrites into nitrates. 4. Denitrification:- Denitrifying bacteria convert nitrates into molecular nitrogen. 6. Explain what happens, when solar energy is not available to bio – geo chemical cycle? Ans. 1. All biogeochemical cycles are regulated through solar energy. 2. Green plants play a key role in the entire process. 3. With the help of solar energy the green plants synthesize organic molecules. i.e. carbohydrates. 4. Herbivorous animals use green plants as their source of food, carnivorous animal consumes herbivorous animals. 5. Dead bodies of plants and animals are used as the source of energy by decomposers. 6. If there is no solar energy, there will be no green plants.

7. If there are no green plants there will be no animals and even there will be no decomposers. 7. Describe water cycle.

Ans. The cycle journey of water from soil to plants, from plants to atmosphere and from atmosphere back to the soil is called water cycle. Global water cycle:1. In global water cycle, the atmosphere contains water vapour due to evaporation mainly over the oceans. 2. This leads to cloud formation, which results in precipitation, which rains on the oceans as well as on the land. 3. The excess of precipitation results in the formation of surface and ground water system. 4. This water flows back to the sea. 5. This water cycle does not involve life forms and therefore it is called as global water cycle. Water cycle including living organism:1. Plants absorb water from the soil. 2. They use it for photosynthesis and other life processes. 3. During transpiration, water evaporates from the aerial parts of the body and returns to the atmosphere. 4. Animals use water directly for drinking and indirectly through food molecules. 5. Through excretion, perspiration and respiration, water returns back to the surroundings.

6. During decomposition of dead organic matter, water is produced as the bi – product, which passes to the surrounding. 8. How biogeochemical cycle is regulated? Ans. 1. All biogeochemical cycles are regulated through solar energy. 2. Green plants play a key role in the entire process. They absorb water and minerals from the soil. Carbon is taken from the atmosphere. 3. With the help of solar energy the green plants synthesize organic molecules. i.e. Carbohydrates. Thus inorganic molecules are converted to organic ones by using solar energy. 4. Herbivorous animals use green plants as their source of food, carnivorous animal consumes herbivorous animals. Energy in form of food thus passes from one organism to the other. 5. Dead bodies of plants and animals are used as the source of energy by decomposers. Because of the decomposers, the organic matter is converted back to inorganic compounds. 9. Explain role of water in living organisms. Ans. Water play vital role in the life of organisms as follows:1. Life originated in water 2. Water is the medium in which a large number of plants and animals spend their life. These organisms are called as aquatic organisms. 3. Nearly 90% of the production of the cell is made up of water. As such it is the most important constituent of the living organisms. 4. It is the universal solvent, may substances get

dissolved in water readily. 5. It is used as transporting medium in both, plants and animals. 6. Water is one of the raw material for photosynthesis and is a product of respiration. 7. In the cell, small molecules get linked together to form complex compounds. During such reaction water molecules are removed. This process is called dehydration synthesis. 8. Larger molecules split into their smaller units by the addition of water molecules. The reaction is called hydrolysis. Q6. Distinguish between nitrification and denitrification. Ans.

Nitrification 1. The process in which the ammonia gets converted to nitrites and then to nitrates is called nitrification. 2. In this, nitrogen is taken from the atmosphere.

Denitrification 1. The conversion of nitrates to molecular nitrogen by the activity of de – nitrifying bacteria is called de – nitrification. 2. In this, nitrogen is returned to the atmosphere.

Q7. Give graphic representation of the following: 1. Mineral Cycle

2. Construct carbon cycle with the help of the following: Photosynthesis, Respiration, Animals, Decomposers, Atmosphere, Combustion.