Some important questions of chemistry CBSE 10TH Class
Some important questions of chemistry CBSE 10TH Class
Saturday, January 26, 2019
Wednesday, August 15, 2018
Sources of Energy
Sources of Energy
Sources of Energy: 10 Class Q/A
Sources of Energy all Problem answer
Problem 1: What is a good source of energy?
Answer: A good source of energy fulfills the following criteria:
(I) It produces a lot of heat per unit mass.
(II) It does a huge amount of work per unit mass.
(III) It is easily accessible.
(IV) It is easy to store and transport.
(V) It is economical.
(VI) It produces less amount of smoke.
Problem 2: What is a good fuel?
Answer: A good fuel produces a huge amount of heat on burning, does not produce a lot of smoke, and is easily available.
Problem 3: If you could use any source of energy for heating your food, which one would you use and why?
Answer: Natural gas can be used for heating and cooking food because it is a clean source of energy. It does not produce a huge amount of smoke on burning. Although it is highly inflammable, it is easy to use, transport, and it produces a huge amount of heat on burning.
Problem 4: What are the disadvantages of fossil fuels?
Answer: The disadvantages of fossil fuels are as follows:
(a) The burning of coal and petroleum produces a lot of pollutants causing air pollution.
(b) Fossil fuels release oxides of carbon, nitrogen, sulfur, etc. that cause acid rain, which affects the soil fertility and potable water.
(c) The burning of fossil fuels produce gases such as carbon dioxide that causes global warming.
Problem 5: Why are we looking at alternate sources of energy?
Answer: Fossil fuels, which have been traditionally used by human beings as an energy source, are non-renewable sources of energy. These sources of energy are limited and cannot replenish on their own. They are being consumed at a large rate. If this rate of consumption continues, then the fossil fuels would be exhausted from the Earth. Therefore, we have to conserve the energy sources. Hence, we should look for alternate sources of energy.
Problem 3: How has the traditional use of wind and water energy been modified for our convenience?
Answer: Traditionally, waterfalls were used as a source of potential energy which was converted into electricity with the help of turbines. Since waterfalls are few in number, water dams have been constructed in large numbers. Nowadays, hydro-dams are used in order to harness the potential energy of stored water. In water dams, water falls from a height on the turbine, which produces electricity.
Earlier, the windmills were used to harness wind energy to do mechanical work such as lifting/drawing water from a well. Today, windmills are used to generate electricity. In windmills, the kinetic energy of the wind is harnessed and converted into electricity. The rotatory motion of the blades turns the turbine of the electric generator to generate electricity.
Problem 4: What kind of mirror − concave, convex or plain − would be best suited for use in a solar cooker? Why?
Answer: A solar cooker uses the heat of the sunlight to cook and heat food. A mirror is used in order to reflect and focus sunlight at a point. A concave mirror is used in a solar cooker for this purpose. The mirror focuses all the incident sunlight at a point. The temperature at that point increases, thereby cooking and heating the food placed at that point.
Problem 5: What are the limitations of the energy that can be obtained from the oceans?
Answer: The forms of energy that can be obtained from the ocean are tidal energy, wave energy, and ocean thermal energy. There are several limitations in order to harness these energies.
(i) Tidal energy depends on the relative positioning of the Earth, moon, and the Sun.
(ii) High dams are required to be built to convert tidal energy into electricity.
(iii) Very strong waves are required to obtain electricity from wave energy.
(iv) To harness ocean thermal energy efficiently, the difference in the temperature of surface water (hot) and the water at depth (cold) must be 20ºC or more.
Problem 6: What is geothermal energy?
Answer: Geothermal power plants use the heat of the Earth to generate electricity. This heat energy of the Earth is known as geothermal energy.
When there are geological changes, the molten rocks present in the core of the earth are pushed to the earth’s crust. This forms regions of the hot spot. Steam is generated when the underground water comes in contact with these hot spots forming hot springs. This trapped steam is used to generate electricity in the geothermal power plants.
Problem 7: What are the advantages of nuclear energy?
Answer: The advantages of nuclear energy are as follows:
(a) A large amount of energy is produced per unit mass.
(b) It does not produce smoke. It is a clean energy.
(c) Fission of one atom of uranium produces 10 million times the energy released by burning of
one atom of carbon
(d) Fusion of four hydrogen atoms produces the huge amount of energy approximately equal to 27
MeV.
Problem 8: Can any source of energy be pollution-free? Why or why not?
Answer: No source of energy can be pollution-free. It is considered that solar cells are pollution-free. However, even there making causes environmental damage indirectly.
Also, in the case of nuclear energy, there is no waste produced after the fusion reactions. However, it is not totally pollution-free. To start the fusion reactions, approximately 107 K temperature is required, which is provided by fission reactions. The wastes released from fission reactions are very hazardous. Hence, no source of energy is pollution-free.
Problem 9: Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Answer: Hydrogen gas is cleaner than CNG. CNG contains hydrocarbons. Therefore, it has carbon contents. Carbon is a form of pollutant present in CNG. On the other hand, hydrogen is waste-free. The fusion of hydrogen does not produce any waste. Hence, hydrogen is cleaner than CNG.
Problem 10: Name two energy sources that you would consider to be renewable. Give reasons for your choices. ?
Answer: Two renewable sources of energy are as follows:
(a) Sun: The energy derived from the Sun is known as solar energy. Solar energy is produced by the fusion of hydrogen into helium, the fusion of helium into other heavy elements, and so on. A large amount of hydrogen and helium is present in the Sun. Therefore, solar energy can replenish on its own. The Sun has 5 billion years more to burn. Hence, solar energy is a renewable source of energy.
(b) Wind: Wind energy is derived from the air blowing at high speed. Wind energy is harnessed by windmills in order to generate electricity. Air blows because of the uneven heating of the Earth. Since the heating of the Earth will continue forever, wind energy will also be available forever.
Problem 11: Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer: Two exhaustible energy sources are as follows:
(a) Coal: It is produced from dead remains of plants and animals that remain buried under the earth’s crust for millions of years. It takes millions of years to produce coal. Industrialization has increased the demand for coal. However, coal cannot replenish within a short period of time. Hence, it is a non-renewable or exhaustible source of energy.
(b) Wood: It is obtained from forests. Deforestation at a faster rate has caused a reduction in the number of forests on the Earth. It takes hundreds of years to grow a forest. If deforestation is continued at this rate, then there would be no wood left on the Earth. Hence, wood is an exhaustible source of energy.
Problem 13: A solar water heater cannot be used to get hot water on
(a) a sunny day (b) a cloudy day
(c) a hot day (d) a windy day
Answer: (b) A solar water heater uses solar energy to heat water. It requires bright and intense sunlight to function properly. On a cloudy day, the sunlight reflects back in the sky from the clouds and is unable to reach the ground. Therefore, solar energy is not available for the solar heater to work properly. Hence, the solar water heater does not function on a cloudy day.
Problem 14: Which of the following is not an example of a biomass energy source?
(a) wood (b) gobar gas
(c) nuclear energy(d) coal
Answer: (c) Bio-mass is a source of energy that is obtained from plant materials and animal wastes. Nuclear energy is released during nuclear fission and fusion. In nuclear fission, uranium atom is bombarded with low-energy neutrons. Hence, the uranium atom splits into two relatively lighter nuclei. This reaction produces the huge amount of energy. In the nuclear fusion reaction, lighter nuclei are fused together to form a relatively heavier nucleus. This reaction produces the tremendous amount of energy. Hence, nuclear energy is not an example of a biomass energy source.
Wood is a plant material, gobar gas is formed from animal dung, and coal is a fossil fuel obtained from the buried remains of plants and animals. Hence, these are bio-mass products.
Problem 15: Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Sun’s energy?
(a) Geothermal energy
(b) Wind energy
(c) Nuclear energy
(d) Bio-mass
Answer: (c) Nuclear energy is released during nuclear fission and fusion. In nuclear fission, uranium atom is bombarded with low-energy neutrons. Hence, the uranium atom splits into two relatively lighter nuclei. This reaction produces the huge amount of energy. In the nuclear fusion reaction, lighter nuclei are fused together to form a relatively heavier nucleus. The energy required to fuse the lighter nuclei is provided by fission reactions. This reaction produces the tremendous amount of energy. These reactions can be carried out in the absence or presence of sunlight. There is no effect of sunlight on these reactions. Hence, nuclear energy is not ultimately derived from Sun’s energy.
Geothermal energy, wind energy, and biomass are all ultimately derived from solar energy.
Geothermal energy is stored deep inside the earth’s crust in the form of heat energy. The heating is caused by the absorption of atmospheric and oceanic heat. It is the sunlight that heats the atmosphere and oceans.
Wind energy is harnessed from the blowing of winds. The uneven heating of the earth’s surface by the Sun causes wind.
Bio-mass is derived from dead plants and animal wastes. Chemical changes occur in these dead plants and animal wastes in the presence of water and sunlight. Hence, biomass is indirectly related to sunlight.
Problem 16: Compare and contrast fossil fuels and the Sun as direct sources of energy.
Answer: Fossil fuels are energy sources, such as coal and petroleum, obtained from underneath the Earth’s crust. They are directly available to human beings for use. Hence, fossil fuels are the direct source of energy. These are limited in amount. These are non-renewable sources of energy because these cannot be replenished in nature. Fossil fuels take millions of years after their formation. If the present fossil fuel of the Earth gets exhausted, its formation will take several years. Fossil fuels are also very costly.
On the other hand, solar energy is a renewable and direct source of energy. The Sun has been shining for several years and will do so for the next five billion years. Solar energy is available free of cost to all in unlimited amount. It replenishes in the Sun itself.
Problem 17: Compare and contrast bio-mass and hydroelectricity as sources of energy.
Answer: Bio-mass and hydro-electricity both are renewable sources of energy. Bio-mass is derived from dead plants and animal wastes. Hence, it is naturally replenished. It is the result of natural processes. Wood, gobar gas, etc. are some of the examples of biomass.
Hydro-electricity, on the other hand, is obtained from the potential energy stored in water at a height. Energy from it can be produced again and again. It is harnessed from water and obtained from mechanical processes.
Problem 18: What are the limitations of extracting energy from −
(a) the wind? (b) waves? (c) tides?
Answer: (a) Wind energy is harnessed by windmills. One of the limitations of extracting energy from wind is that a windmill requires wind of speed more than 15 km/h to generate electricity. Also, a large number of windmills are required, which covers a huge area.
(b) Very strong ocean waves are required in order to extract energy from waves.
(c) Very high tides are required in order to extract energy from tides. Also, the occurrence of tides depends on the relative positions of the Sun, moon, and the Earth.
Problem 19: On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Are the options are given in (a) and (b) the same?
Answer: (a) The source of energy that replenishes in nature is known as the renewable source of energy. Sun, wind, moving water, biomass, etc. are some of the examples of renewable sources of energy.
The source of energy that does not replenish in nature is known as the non-renewable source of energy. Coal, petroleum, natural gas, etc. are some of the examples of non-renewable sources of energy.
(b) Exhaustible sources are those sources of energy, which will deplete and exhaust after a few hundred years. Coal, petroleum, etc. are the exhaustible sources of energy.
Inexhaustible resources of energy are those sources, which will not exhaust in future. These are unlimited. Bio-mass is one of the inexhaustible sources of energy.
Yes. The options are given in (a) and (b) are the same.
Problem 20: What are the qualities of an ideal source of energy?
An ideal source of energy must be:
I. Economical
II. Easily accessible
III. Smoke/pollution free
IV. Easy to store and transport
V. Able to produce the huge amount of heat and energy on burning
Problem 21: What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Answer: Solar cooker uses Sun’s energy to heat and cook food. It is inexhaustible and clean renewable source of energy. It is free for all and available in unlimited amount. Hence, operating a solar cooker is not expensive.
The disadvantage of a solar cooker is that it is very expensive. It does not work without sunlight. Hence, on a cloudy day, it becomes useless.
The places where the days are too short or places with cloud covers around the year have limited utility for the solar cooker.
Problem 22: What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Answer: Industrialization increases the demand for energy. Fossil fuels are easily accessible sources of energy that fulfill this demand. The increased use of fossil fuels has a harsh effect on the environment. Too much exploitation of fossil fuels increases the level of greenhouse gas content in the atmosphere, resulting in global warming and a rise in the sea level.
It is not possible to completely reduce the consumption of fossil fuels. However, some measures can be taken such as using electrical appliances wisely and not wasting electricity. Unnecessary usage of water should be avoided. The public transport system with mass transit must be adopted on a large scale. These small steps may help in reducing the consumption of natural resources and conserving them.
By ARUN KUMAR with the help of ncert
Categories:
cbse science solution
ncert solution
Sources of Energy
Life Processes
Life Processes
Life Processes:10 Class NCERT Q/A
Life Processes all Problem answer
Problem 1: Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
Answer: Multicellular organisms such as humans possess complex body designs. They have specialized cells and tissues for performing various necessary functions of the body such as the intake of food and oxygen. Unlike unicellular organisms, multicellular cells are not in direct contact with the outside environment. Therefore, diffusion cannot meet their oxygen requirements.
Problem 2: What criteria do we use to decide whether something is alive?
Answer: Any visible movement such as walking, breathing, or growing is generally used to decide whether something is alive or not. However, a living organism can also have movements, which are not visible to the naked eye. Therefore, the presence of life processes is a fundamental criterion that can be used to decide whether something is alive or not.
Problem 3: What is outside raw materials used by an organism?
Answer: An organism uses outside raw materials mostly in the form of food and oxygen. The raw materials required by an organism can be quite varied depending on the complexity of the organism and its environment.
Problem 4: What processes would you consider essential for maintaining life?
Answer: Life processes such as nutrition, respiration, transportation, excretion, etc. are essential for maintaining life.
Problem 5: What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer:
Autotrophic nutrition
|
Heterotrophic nutrition
|
(i) Food is synthesized from simple inorganic raw materials such as CO2and water.
|
(i) Food is obtained directly or indirectly from autotrophs. This food is broken down with the help of enzymes.
|
(ii) Presence of green pigment (chlorophyll) is necessary.
|
(ii) No pigment is required in this type of nutrition.
|
(iii)Food is generally prepared during the daytime.
|
(iii)Food can be prepared at all times.
|
(iv)All green plants and some bacteria have (iv)All animals and fungi have this type of this type of nutrition. nutrition.
Problem 6: Where do plants get each of the raw materials required for photosynthesis?
Answer: The following raw materials are required for photosynthesis:
• The raw material CO2 enters from the atmosphere through stomata.
• Water is absorbed from the soil by the plant roots.
• Sunlight, an important component to manufacture food, is absorbed by the chlorophyll and other green parts of the plants.
Problem 7: What is the role of the acid in our stomach?
Answer: The hydrochloric acid present in our stomach dissolves bits of food and creates an acidic medium. In this acidic medium, enzyme pepsinogen is converted to pepsin, which is a protein-digesting enzyme.
Problem 8: What is the function of digestive enzymes?
Answer: Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. help in the breaking down of complex food particles into simple ones. These simple particles can be easily absorbed by the blood and thus transported to all the cells of the body.
Problem 9: How is the small intestine designed to absorb digested food?
Answer: The small intestine has millions of tiny finger-like projections called villi These villi increase the surface area for more efficient food absorption. Within these villi, many blood vessels are present that absorb the digested food and carry it to the bloodstream. From the bloodstream, the absorbed food is delivered to each and every cell of the body.
The enlarged view of a villus
Problem 10: What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Answer: Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals need to utilize oxygen present in the water. Air contains more O2 as compared to water. Since the content of O2 in the air is high, the terrestrial animals do not have to breathe faster to get more oxygen. Therefore, unlike aquatic animals, terrestrial animals do not have to show various adaptations for better gaseous exchange.
Problem 11: What are the different ways in which glucose is oxidized to provide energy for various organisms?
Answer: Glucose is first broken down in the cell cytoplasm into a three carbon molecule called pyruvate. Pyruvate is further broken down by different ways to provide energy. The breakdown of glucose by different pathways can be illustrated as follows.
In yeast and human muscle cells, the breakdown of pyruvate occurs in the absence of oxygen whereas, in mitochondria, the breakdown of pyruvate occurs in the presence of oxygen.
Problem 12: How is oxygen and carbon dioxide transported in human beings?
Answer: Haemoglobin transports oxygen molecule to all the body cells for cellular respiration. The hemoglobin pigment present in the blood gets attached to four O2 molecules that are obtained from breathing. It thus forms oxyhemoglobin and the blood becomes oxygenated. This oxygenated blood is then distributed to all the body cells by the heart. After giving away O2 to the body cells, blood takes away CO2 which is the end product of cellular respiration. Now the blood becomes de-oxygenated.
Since hemoglobin pigment has less affinity for CO2, CO2 is mainly transported in the dissolved form. This de-oxygenated blood gives CO2 to lung alveoli and takes O2 in return.
Transportation of O2 and CO2 in blood
Problem 13: How are the lungs designed in human beings to maximize the area for exchange of gases?
Answer: The exchange of gases takes place between the blood of the capillaries that surround the alveoli and the gases present in the alveoli. Thus, alveoli are the site for exchange of gases. The lungs get filled up with air during the process of inhalation as ribs are lifted up and the diaphragm is flattened. The air that is rushed inside the lungs fills the numerous alveoli present in the lungs.
Each lung contains 300-350 million alveoli. These numerous alveoli increase the surface area for gaseous exchange making the process of respiration more efficient.
Problem 14: What are the components of the transport system in human beings? What are the functions of these components?
Answer: The main components of the transport system in human beings are the heart, blood, and blood vessels.
The heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from the various body parts and sends this impure blood to the lungs for oxygenation.
Being a fluid connective tissue, blood helps in the transport of oxygen, nutrients, CO2, and nitrogenous wastes.
The blood vessels (arteries, veins, and capillaries) carry blood either away from the heart to various organs or from various organs back to the heart.
Problem 15: Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Answer: Warm-blooded animals such as birds and mammals maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. Hence, these animals require more oxygen (O2) for more cellular respiration so that they can produce more energy to maintain their body temperature.
Thus, it is necessary for them to separate oxygenated and de-oxygenated blood, so that their circulatory system is more efficient and can maintain their constant body temperature.
Problem 16: What are the components of the transport system in highly organized plants?
Answer: In highly organized plants, there are two different types of conducting tissues − xylem and phloem. Xylem conducts water and minerals obtained from the soil (via roots) to the rest of the plant. Phloem transports food materials from the leaves to different parts of the plant body.
Problem 17: How are water and minerals transported in plants?
Answer: The components of xylem tissue (tracheids and vessels) of roots, stems, and leaves are interconnected to form a continuous system of water-conducting channels that reaches all parts of the plant. Transpiration creates a suction pressure, as a result of which water is forced into the xylem cells of the roots. Then there is a steady movement of water from the root xylem to all the plant parts through the interconnected water-conducting channels.
Components of xylem tissue
Problem 18: How is the food transported in plants?
Phloem transports food materials from the leaves to different parts of the plant body. The transportation of food in phloem is achieved by utilizing energy from ATP. As a result of this, the osmotic pressure in the tissue increases causing water to move into it. This pressure moves the material in the phloem to the tissues which have less pressure. This is helpful in moving materials according to the needs of the plant. For example, the food material, such as sucrose, is transported into the phloem tissue using ATP energy.
Components of phloem tissue
Problem 19: Describe the structure and functioning of nephrons.
Answer: Nephrons are the basic filtering units of kidneys. Each kidney possesses a large number of nephrons, approximately 1-1.5 million. The main components of the nephron are glomerulus, Bowman’s capsule, and along renal tubule.
Structure of a nephron
Functioning of a nephron:
The blood enters the kidney through the renal artery, which branches into many capillaries associated with glomerulus.
The water and solute are transferred to the nephron at Bowman’s capsule. In the proximal tubule, some substances such as amino acids, glucose, and salts are selectively reabsorbed and unwanted molecules are added in the urine.
The filtrate then moves down into the loop of Henle, where more water is absorbed.
From here, the filtrate moves upwards into the distal tubule and finally to the collecting duct.
Collecting duct collects urine from many nephrons.
The urine formed in each kidney enters a long tube called ureter. From ureter, it gets transported to the urinary bladder and then into the urethra.
Problem 20: What are the methods used by plants to get rid of excretory products?
Answer: Plants can get rid of the excess of water by transpiration. Waste materials may be stored in the cell vacuoles or as gum and resin, especially in old xylem. It is also stored in the leaves that later fall off.
Problem 21: How is the amount of urine produced regulated?
Answer: The amount of urine produced depends on the amount of excess water and dissolved wastes present in the body. Some other factors such as habitat of an organism and hormone such as Anti-diuretic hormone (ADH) also regulates the amount of urine produced.
Problem 22: The kidneys in human beings are a part of the system for
(a) nutrition.
(b) respiration.
(c) excretion.
(d) transportation.
(c) In human beings, the kidneys are a part of the system for excretion.
Problem 24: The autotrophic mode of nutrition requires
(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
Answer: (d) The autotrophic mode of nutrition requires carbon dioxide, water, chlorophyll, and sunlight.
Problem 23: The xylem in plants are responsible for
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.
(a) In a plant, the xylem is responsible for transport of water.
Problem 25: The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.
Answer: (b) The breakdown of pyruvate to give carbon dioxide, water and energy takes place in mitochondria.
Problem 26: How are fats digested in our bodies? Where does this process take place?
Answer: Fats are present in the form of large globules in the small intestine. The small intestine gets the secretions in the form of bile juice and pancreatic juice respectively from the liver and the pancreas. The bile salts (from the liver) break down the large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This is referred to as emulsification of fats. It takes place in the small intestine.
Problem 27: What are the necessary conditions for autotrophic nutrition and what are its by-products?
Answer: Autotrophic nutrition takes place through the process of photosynthesis. Carbon dioxide, water, chlorophyll pigment, and sunlight are the necessary conditions required for autotrophic nutrition. Carbohydrates (food) and O2 are the by-products of photosynthesis.
Problem 28: What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Answer:
Aerobic respiration
|
Anaerobic respiration
|
1. It occurs in the presence of O2.
|
1. It occurs in the absence of O2.
|
2. It involves the exchange of gases between the organism and the outside environment.
|
2. Exchange of gases is absent.
|
3. It occurs in the cytoplasm and mitochondria.
|
3. It occurs only in the cytoplasm.
|
4. It always releases CO2 and H2O.
|
4. End products vary.
|
5. It yields 36 ATPs.
|
5. It yields only 2 ATPs.
|
Anaerobic respiration occurs in the roots of some waterlogged plants, some parasitic worms, animal muscles, and some micro-organisms such as yeasts.
Problem 29: How are the alveoli designed to maximize the exchange of gases?
Answer: The alveoli are the small balloon-like structures present in the lungs. The walls of the alveoli consist of the extensive network of blood vessels. Each lung contains 300−350 million alveoli, making it a total of approximately 700 million in both the lungs. The alveolar surface when spread out covers about 80 m2area. This large surface area makes the gaseous exchange more efficient.
Alveoli and capillaries
Problem 30: What would be the consequences of a deficiency of hemoglobin in our bodies?
Answer: Haemoglobin is the respiratory pigment that transports oxygen to the body cells for cellular respiration. Therefore, deficiency of hemoglobin in the blood can affect the oxygen supplying capacity of blood. This can lead to the deficiency of oxygen in the body cells. It can also lead to a disease called anemia.
Problem 31: Describe double circulation in human beings. Why is it necessary?
Answer: The human heart is divided into four chambers − the right atrium, the right ventricle, the left atrium, and the left ventricle.
The flow of blood in the heart:
The heart has superior and inferior vena cava, which carries de-oxygenated blood from the upper and lower regions of the body respectively and supplies this de-oxygenated blood to the right atrium of the heart.
The flow of blood in the human heart
The right atrium then contracts and passes the de-oxygenated blood to the right ventricle, through an auriculo-ventricular aperture.
Then the right ventricle contracts and passes the de-oxygenated blood into the two pulmonary arteries, which pumps it to the lungs where the blood becomes oxygenated. From the lungs, the pulmonary veins transport the oxygenated blood to the left atrium of the heart. Then the left atrium contracts and through the auriculo-ventricular aperture, the oxygenated blood enters the left ventricle.
The blood passes to aorta from the left ventricle. The aorta gives rise to many arteries that distribute the oxygenated blood to all the regions of the body.
Schematic diagram of blood circulation in humans
Therefore, the blood goes twice through the heart. This is known as double circulation.
Importance of double circulation:
The separation of oxygenated and de-oxygenated blood allows a more efficient supply of oxygen to the body cells. This efficient system of oxygen supply is very useful in warm-blooded animals such as human beings.
As we know, warm-blooded animals have to maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. Hence, they require more O2 for more respiration so that they can produce more energy to maintain their body temperature. Thus, the circulatory system of humans is more efficient because of the double circulatory heart.
Problem 32: What are the differences between the transport of materials in xylem and phloem? Answer:
Transport of materials in xylem
|
Transport of materials in phloem
|
(i) Xylem tissue helps in the transport of water and minerals.
|
(i) Phloem tissue helps in the transport of food.
|
(ii)Water is transported upwards from roots to all other plant parts.
|
(ii)Food is transported in both upward and downward directions.
|
(iii)Transport in xylem occurs with the help of simple physical forces such as transpiration pull.
|
(iii)Transport of food in phloem requires energy in the form of ATP.
|
by ARUN KUMAR with the help of ncert
Categories:
Acids
cbse science solution
codecademy c++
Life Processes
