CBSE Class 10 Biology Our Environment Management Of Natural Resources Worksheet Set B

Read and download free pdf of CBSE Class 10 Biology Our Environment Management Of Natural Resources Worksheet Set B. Students and teachers of Class 10 Science can get free printable Worksheets for Class 10 Science Chapter 15 Our Environment in PDF format prepared as per the latest syllabus and examination pattern in your schools. Class 10 students should practice questions and answers given here for Science in Class 10 which will help them to improve your knowledge of all important chapters and its topics. Students should also download free pdf of Class 10 Science Worksheets prepared by school teachers as per the latest NCERT, CBSE, KVS books and syllabus issued this academic year and solve important problems with solutions on daily basis to get more score in school exams and tests

Worksheet for Class 10 Science Chapter 15 Our Environment

Class 10 Science students should refer to the following printable worksheet in Pdf for Chapter 15 Our Environment in Class 10. This test paper with questions and answers for Class 10 will be very useful for exams and help you to score good marks

Class 10 Science Worksheet for Chapter 15 Our Environment

Objective Questions

Question : Accumulation of non- biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as:
(a) Eutrophication
(b) Pollution
(c) Biomagnification
(d) Accumulation
Answer :  C

Question : A food chain always starts with: 
(a) Respiration
(b) Decomposition
(c) Photosynthesis
(d) Nitrogen fixation
Answer : C
Explanation: A food chain in an ecosystem always starts with photosynthesis.
The autotrophs or the producers are at the first trophic level. They fix up the solar energy and make it available for heterotrophs or the consumers.
 
Question : In a given food chain, suppose the amount of energy available at the third trophic level is 50 KJ. What will be the energy available at the producer level? 
(a) 5000 KJ
(b) 50 KJ
(c) 5 KJ
(d) 500 KJ
Answer : A
Explanation: According to 10% law, the energy available to each successive trophic level is 10% of the previous trophic level.
Given, energy available at the third trophic level = 50 KJ
Energy available at second trophic level = 50 KJ x 10 = 500 KJ
Therefore, energy available at the producer level (first trophic level) = 500 KJ x 10 = 5000 KJ
 
Question : Vultures in an ecosystem are
(a) predators
(b) scavengers
(c) consumers
(d) top carnivores
Answer :  B
 
Question : In which of the following trophic levels in any ecosystem the maximum energy is stored ?
(a) Producers
(b) Herbivores
(c) Carnivores
(d) Top carnivores
Answer :  A

Question : Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer : B

Question. Choose one term from the following which include all others : coal, natural gas, fossil fuels, petroleum
Answer : Fossil fuels

Question. Why is the process of ‘reuse’ better than that of ‘recycling’ ?
Answer : Reusing is better than recycling because it saves the energy that comes with having to dismantle and re-manufacture products. It also significantly reduces waste and pollution because it reduces the need for raw materials, saving both forests and water supplies.

Question. Name a clean gaseous fuel other than LPG and natural gas.
Answer : Apart from LPG and natural gas, biogas is a clean gaseous fuel.

Question. Fill in the following blanks with suitable words :
(a) LPG is a ............... fuel but biogas is not a...............fuel.
(b) Glaciers are a source of .....................
(c) One of the main aim of management of forests and wildlife is to conserve the ................... which we have inherited.
(d) Khadin is a traditional ..................... harvesting system in Rajasthan.
(e) When a fuel burns in an insufficient supply of air, then some poisonous gas called ................ is also produced.
Answer : (a) fossil ; fossil (b) water (c) biodiversity (d) water (e) carbon monoxide

Case Study Questions

Food chains are very important for the survival of most species.

""CBSE-Class-10-Biology-Our-Environment-Management-Of-Natural-Resources-Worksheet-Set-B

Question : If 10,000 J solar energy falls on green plants in a terrestrial ecosystem, what percentage of solar energy will be converted into food energy?
(a) 10,000 J
(b) 100 J
(c) 1000 J
(d) It will depend on the type of the terrestrial plant.
Answer : B

Question : Matter and energy are two fundamental inputs of an ecosystem. Movement of
(a) Energy is bidirectional and matter is repeatedly circulating.
(b) Energy is repeatedly circulation and matter is unidirectional.
(c) Energy is unidirectional and matter is repeatedly circulating.
(d) Energy is multidirectional and matter is bidirectional.
Answer : C

Question : The decomposers are not included in the food chain.The correct reason for the same is because decomposers:
(a) Act at every trophic level of the food chain
(b) Do not breakdown organic compounds
(c) Convert organic material to inorganic forms
(d) Release enzymes outside their body to convert organic material to inorganic forms
Answer : A

Question : Which of the following limits the number of trophic levels in a food chain?
(a) Decrease in energy at higher trophic levels
(b) Less availability of food
(c) Polluted air
(d) Water
Answer : A

Question : If Ravi is consuming curd/yogurt for lunch , which trophic level in a food chain he should be considered as occupying ?
(a) First trophic level
(b) Second trophic level
(c) Third trophic level
(d) Fourth trophic level
Answer : C

Very Short Answers

Question : Name the radiations absorbed by ozone layer. Give any one cause of the depletion of the ozone layer. Name a disease likely to be caused due to depletion. 
Answer : Ozone layer absorbs the harmful ultraviolet radiations from sun.
One cause of the depletion of the ozone layer is the use of Chlorofluorocarbons (CFCs) in various objects such as refrigerators. Ozone layer depletion may lead to skin cancer in human beings.

Question : Write the mode of nutrition in fungi.
Answer :  Saprophytic mode.

Question : What is the physical environment of an ecosystem called? Give one example.
Answer :  Physical environment of an ecosystem is called the abiotic or non-living component of an ecosystem. This includes factors like air, water. Temperature etc.

Question : What is ozone? Name the chemicals that damage the ozone layer. 
Answer :  Ozone is a molecule formed by three atoms of oxygen.
Synthetic chemicals such as chlorofluoro- carbons (CFC) and aerosols are the chemicals that damage the ozone layer in the atmosphere.

Question : What are two main components of ecosystem?
Answer : An ecosystem has two types of components, biotic component and abiotic component. 

Question : Explain the flow of energy between various components of the environment.
Answer :  
(i) Green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls on their leaves.
(ii) The loss of energy at each step is so great that very little usable energy remains after four trophic levels.
(iii) In a food chain, the greatest number of individuals are at lower trophic level of an ecosystem, the greatest number is of the producers.

Question. Why are green plants called producers?
Answer : 
Green plants are called producers because green plants synthesize their own food during photosynthesis by taking raw materials from the earth and energy from the Sun.

Question. What is the important function of presence of ozone in earth’s atmosphere?
Answer : 
Ozone layer absorbs the harmful UV radiations of the sunlight, so this layer is very important for the survival and existence of life on earth

Question. What is the significance of ozone layer?
Answer : 
The ozone layer is found in the upper regions of the stratosphere where it protects the earth from the harmful ultraviolet rays of the sun. These radiations can cause skin cancer in humans.

Question. What does a trophic level represent in a food chain? State the position of autotrophs and herbivores in a food chain.
Answer : 
The position of organisms in a food chain or an ecological pyramid is called as a trophic level. Autotrophs are in first trophic level and herbivores are in second trophic level

Question. State one harmful effect of depletion of ozone layer on the living organisms of the ecosystem.
Answer : 
If the ozone layer in the atmosphere depletes then the extremely harmful ultraviolet radiations coming from the Sun would reach the earth. These uv-radiations would cause skin cancer and other ailments in men, animals and plants.

Question. In a food chain of frog, grass, insect and snake, assign trophic level of frog.
Answer : 
Food chain. Grass → insect → frog → snake
∴ Frog belongs to 3rd trophic level.

Question. What is an ecosystem?
Answer : 
Ecosystem is a unit of biosphere where interaction between biotic community and abiotic factors of an area or place takes place with each other

Question. Which of the following are always at the second trophic level of food chains? Carnivores, Autotrophs, Herbivores
Answer : 
Herbivores are always at the second trophic level of food chains.

Question. Depletion of ozone in the ozone layer is a cause for our worry. Why?
Answer : 
Depletion of ozone in the ozone layer is a cause for our worry because if the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiation coming from the Sun would reach the earth. These ultraviolet radiations would cause skin cancer and other ailments in men and animals, and also damage the plants.

Question. In the following food chain, 100 J of energy is available to the lion. How much energy was available to the producer? Plants → Deer → Lion
Answer : 
10,00,000 Joules.

Question. In the following food chain, 20,000 J of energy was available to the plants. How much energy will be available to man in this chain?
Plants → Sheep → Man
Answer : Plants have 20,000 J of energy available to them. Sheep will get 10% of 20000 J
20000 × 10/100 = 2000 J
Humans will get 10% of 2000 J.
2000 × 10/100 = 200 J

Question. Why are green plants called producers?
Answer : Green plants prepare their own food by photosynthesis with the help of CO2, H2O, sunlight and chlorophyll.

Question. Give one protective function of forests.
Answer : Forests help to reduce air pollution

Question. What is the functional unit of environment?
Answer : Ecosystem is the functional unit of environment.

Question. Which of the following are always at second trophic level of food chains?
Carnivores, Autotrophs, Herbivores.
Answer : Herbivores will always be at second trophic level.

Question. The following organisms form a food chain. Which of these will have the highest concentration of nonbiodegradable chemicals? Name the phenomenon. 
Insects, Hawk, Grass, Snake, Frog.
Answer : Hawk is a decomposer and have maximum concentration of non-biodegradable chemicals.
The phenomenon is called Biomagnification.

Short Answers

Question : What will happen if we kill all the organisms in one trophic level?
Answer : If all the organisms in one trophic level are killed then all the organisms of next trophic level which are dependent on these are killed. Next trophic levels will not get food to eat and the entire food chain gets disturbed. At the same time the organisms at the lower trophic level will reproduce and the population will increase in abundance there by disturbing the ecosystem.

Question : What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer : The pesticides and chemicals are absorbed by plants from the soil and enter the food chain. Being non-biodegradable they accumulate progressively at each trophic level.
As human occupy the top level of any food chain, the maximum concentration of chemicals is found in our bodies. This is called biological magnification.
The level of magnification will be different at different trophic levels, the maximum concentrations will be at the highest trophic level and the chemical will be less at lower trophic levels.

Question : If all the waste we generate is bio-degradable, will this have no impact on the environment?
Answer : If all the waste we generate is bio-degradable and is managed in such a way that it
is allowed to decompose then it will have no impact on the environment.

Question :  mention three harmful effects of using polythene bags on the environment. Suggest an effective alternative to these bags.
Answer :  Harmful effects of using polythene bags on the environment are listed below:
(1) Plastic causes land pollution and water pollution as it is a non-biodegradable substance.
(2) Burning of plastic releases toxic gases and causes air pollution.
(3) Plastic bags cause harm to the life of animals when they consume it along with food.
(4) Plastic bags can cause blocking in sewage line.
(5) The surfaces of tiny fragments of plastic may carry disease-causing organisms and act as a vector for diseases in the environment.

Question :  Give any two ways in which biodegradable substances would affect the environment. 
Answer : Accumulation of biodegradable waste leads to the following problems.
a. They will serve as breeding ground for flies and mosquitoes which are carriers of disease like cholera, malaria etc.
b. Open decomposition of biodegradable waste produces mehane gas which is a green house gas & has a foul smell, thus causing air pollution. 

Question : List four problems caused by non-biode gradable wastes. 
Answer :  Lot of Problems are caused by non- biodegrad- able wastes. Four Problems are as follow:
(1) Soil Pollution
(2) Water Pollution
(3) Ecological imbalance
(4) Biomagnification

Question : What are the by-products of fertilizer industries? How do they affect the environment?
Answer :  The harmful by-products are gases such as SO2 and NO. They cause extensive air pollution and are responsible for acid rain. The harmful by-products of the fertilizer industries are:
(1) Gases  SO2, NO, CO, CO2, and H2S.
(2) Solids - Pyrite ashes, calcium carbonate, sand and plastic bag. Effect on environment: The majority of the gaseous by-products like carbon dioxide, and methane are green house gases which contribute to global warming. The rest of the gases like sulphur dioxide and nitrous oxide are air pollutants and lead to acid rain. These gaseous by-products cause breathing and respiratory problems. The solid waste and waste water discharges into the water body. When these wastes are discharged into the water body, they increase the nutrient content of the water and cause algal bloom (increase in the number of algae). Due to algal bloom, algae form a layer on the surface of the water and hence, the oxygen does not reach the water body. Thus affecting the aquatic life. Also, these wastes are non-biodegradable, so they get accumulated at each trophic level by entering the food chain at the producer level and in the process of the transfer of food through food chains, these harmful chemicals such as pesticides , industrial effluents, heavy metals and radioactive substances get concentrated at each trophic level. This is called bio- magnification.

Question : List two causes of depletion of ozone layer. Mention any two harmful effects of depletion of this layer.
Answer :  Two causes of depletion of ozone layer are as follows:
(a) Use of CFCs
(b) Use of Halons
Harmful effects of ozone depletion:
(i) Due to depletion of ozone UV radiation reaches the earth. This UV radiation causes skin cancer, damage to eyes and immune system.
(ii) Ozone depletion may also lead to variation in global rainfall, ecological disturbances and dwindling of global food supplies.

Question : State any three ways of effective Garbage disposal so that pollution caused by it can be minimized.
Answer :  Pollution caused by garbage can be controlled by
(a) Recycling of certain wastes products like plastic and paper.
(b) Maximizing the use of biodegradable products like that of paper, cloth bags etc.
(c) Producing biogas from the organic wastes.
(d) Separation of biodegradable and non-bio-degradable waste during disposal.
(e) Making the compost of biodegradable wastes by decomposing them under the layers of soil. 
 

Question. What is ten per cent law ? Explain with an example.
Answer : Ten PerCent Law – According to ten per cent law only 10 per cent of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level. Example – Suppose 1000 Joules of light energy emitted by the sun falls on the plants.

Question. Write the full form of CFC. Give its one harmful effect.
Answer : The full form of CFC is chlorofluorocarbon.
Chlorofluorocarbons react with the ozone in the upper atmosphere and destroy the ozone layer, making the layer thinner and allowing ultraviolet (UV) radiation to pass through it and fall on the earth's surface. This UV radiation can cause skin cancer and other ailments in humans and also affect plants and animals.

Question. Explain how, harmful ultraviolet radiations of sunlight are prevented from reaching the earth’s surface.
Answer : Harmful radiations of sunlight are prevented from reaching the earth's surface by the ozone layer in the upper atmosphere, which absorbs them.

Question. What are the causes of depletion of ozone layer ? Which diseases are likely to be caused if the ozone layer will become thinner ?
Answer : If the ozone layer becomes thinner, harmful ultraviolet radiations will enter the earth and may cause skin cancer and other ailments in humans and also affect plants and animals.

Question. Explain how harmful chemicals enter our bodies.
Answer : As you use or come into contact with chemicals, be aware that they can enter your body through four major routes.
Inhalation – gases and airborne particulate can be breathed in through your nose or mouth.
Absorption – chemicals, including dust, smoke or vapors, can enter your body through your skin or eyes.
Ingestion – chemicals can enter your body through your mouth.
Injection – chemicals can enter your body through an accidental impact, cut or puncture to your skin.
Here's how these chemicals can enter your body, and what preventive measures are available:
Inhalation involves airborne contaminants that can be inhaled directly into the lungs through the nose or mouth. These contaminants include dusts, mists, fumes, vapors and gas.
Inhalation is the most common route of entry a chemical can take to enter the body.
Prevention - Personal protective equipment that provides protection from airborne contaminants includes respirators or masks appropriate for the specific contaminant.
Absorption involves hazardous chemicals that are absorbed through direct contact with the skin or eyes. These chemicals can include particulates (dust, smoke), liquids, gases and vapors.
Prevention - Absorption through the skin and eyes can be prevented with the use of appropriately selected gowns, gloves, work clothing, personal protective equipment that covers the eyes, such as full face masks, safety glasses with side shields, and face shields, appropriate for the specific contaminants. In some instances a hazard suit with full head mask is appropriate.

Question. ‘If we excessively use pesticides to protect the crops from diseases, then it may cause long-term damage to mankind’. Justify this statement.
Answer : Chemical substances such as pesticides are sprayed over crop plants to protect them from pests and diseases. Pesticides are non-biodegradable, so they get accumulated at each trophic level.
When herbivorous animals eat plants, these poisonous chemical pesticides go into their bodies. Man, being an omnivore, eats plant food as well as the meat of herbivores. Thus, the pesticides present in plant food and herbivores get transferred to man's body through food. Since humans occupy the top level in any food chain, the maximum amount of harmful chemical pesticides gets accumulated in our bodies, damaging our health gradually.
Hence the statement 'excessive use of pesticides to protect crops from diseases may cause long-term damage to mankind' is justified.

Question. What is meant by biological magnification ? With the help of a food chain, explain how biological magnification of harmful chemicals can occur.
Answer : The increase in the concentration of harmful substances, such as pesticides, in the body of living organisms at each level of a food chain is called biological magnification.
Chemical substances such as pesticides are sprayed over crop plants to protect them from pests and diseases.

Question. What is meant by bioconcentration of pesticides ? Which common pesticide has accumulated in human body in considerable amounts ?
Answer : The increase in the concentration of harmful chemical substances, such as pesticides, in the body of living organisms at each trophic level of a food chain is called the bioconcentration of pesticides.
The common pesticide that has accumulated in the human body in considerable amounts is DDT.

Question. What is garbage ? What does garbage consist of ?
Answer : Household waste or rubbish is called garbage. Garbage consists of leftover food, fruit, vegetable peels, fallen leaves of potted plants, waste paper, unwanted plastic objects, glass articles, metal objects, old wooden objects, rags, discarded shoes, sewage, etc.

Question. Name the various modes of waste disposal.
Answer : The various modes of waste disposal are as follows.
1) Recycling
2) Preparation of compost
3) Incineration
4) Landfill
5) Sewage treatment

Question. How can the wastes such as paper, plastic and metal objects be disposed of ?
Answer : Wastes such as paper, plastic and metal objects can be disposed of through recycling. This is done in the following ways.
1) Waste paper is sent to paper mills, where it is reprocessed to make new paper once again.
2) Broken plastic articles, such as plastic bags, buckets, bowls, cups and plates, are sent to plastic-processing factories, where they are melted and remoulded to make new articles.
3) Waste metal articles are sent to metal industries, where they are melted into solid metal and recycled for various purposes.

Question. Give a method for the disposal of household wastes such as left-over food, fruit and vegetable peels, and leaves of potted plants.
Answer : Leftover food, fruit and vegetable peels, and leaves of potted plants can be converted into compost by burying them in a pit dug in the ground. The compost thus prepared can be used as manure. In this way, household wastes can be disposed of.

Question. What is meant by incineration ? For what purpose is it used ?
Answer : Incineration means reducing something to ashes. In this method, waste material is burnt and converted to ashes. It is used to destroy household waste, chemical waste and biological waste (hospital wastes).

Question. How are most of the solid wastes in urban areas disposed of ?
Answer : Most of the solid wastes in urban areas are disposed of by dumping them in low-lying sites. These sites are then covered with earth to level the uneven ground. This process is called landfill.

Question. State two advantages of using disposable paper cups over disposable plastic cups.
Answer : Two advantages of using disposable paper cups over disposable plastic cups are as follows.
(a) Disposable paper cups decay naturally and become harmless after some time, but disposable plastic cups do not.
(b) Disposable paper cups usually do not pollute the environment, but disposable plastic cups pollute the environment.

Question. What is sewage ? How is sewage disposed of ?
Answer : The dirty drain water containing urine and faeces that is carried from our homes by underground pipes (called sewers) is called sewage. It is disposed of by treating it at a sewage treatment plant.

Question. Write the harmful effects of ozone depletion.
Answer : The following are the harmful effects of ozone depletion.
It causes UV rays to reach the earth and it causes harm to living organisms.
It can lead to skin cancer in humans.
It can lead to cataracts in humans.
It can lead to damage to our immune system by lowering the body's resistance to diseases.
It can lead to many diseases in animals.
It can lead to damage to plants.
The ultraviolet rays from the sun will damage the DNA and lead to mutation.

Question. What would happen if the ozone layer in the atmosphere completely disappears ?
Answer : If the ozone layer in the atmosphere completely disappears, then the harmful ultraviolet radiations from the sun would enter the earth's surface and cause skin cancer and many other ailments in humans and animals, and may also damage plants.

Question. What is meant by “sustainable development” ?
Answer : What is sustainable development? Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

Question. What is silviculture ? What are its advantages ?
Answer : Silviculture is a program started to replenish depleting forests due to deforestation. Advantages: It produces a large quantity of raw materials for timber and paper industries. It increases the area of earth under forests which is helpful in the conservation of wildlife.

Question. Write a short note on ‘Chipko Andolan’ (Hug the Trees Movement).
Answer : Chipko Movement, started in 1970's, was a non violent movement aimed at protection and conservation of trees and forests from being destroyed. The name of the Chipko moment originated from the word 'embrace' as the villagers used to hug the trees and protect them from wood cutters from cutting them. In 1731, the king of Jodhpur in Rajasthan asked one of his ministers to arrange wood for constructing a new palace. The minister and workers went to a forest near a village, inhabited by Bishnois, to cut down trees. A Bishnoi woman Amrita Devi showed exemplary courage by hugging a tree and daring king’s men to cut her first before cutting the tree. The tree mattered much more to her than her own life. Sadly, the king’s men did not heed to her pleas, and cut down the tree along with Amrita Devi. Her three daughters and hundreds of other Bishnois followed her, and thus lost their lives saving trees. The incident inspired the several other rural women, who launched such similar movements in different parts of India. The Chipko Movement gained momentum under Sunderlal Bahuguna, an activist, who spent his whole life persuading and educating the villagers, to protest against the destruction of the forests and the Himalayan mountains by the government. The chipko protests achieved a major victory in 1980 with a 15 years ban on tree felling in the Himalayan forests of the state by the order of Mrs. Indira Gandhi.

Question. Why should we conserve forests and wildlife ?
Answer : It sustains life on the planet, provides clean air and shelter. Also, forests help conserve biodiversity. Forests provide many resources such as food, medicine, fabric, and raw materials.

Question. Describe briefly the ‘khadin’ system of rainwater harvesting practised in Rajasthan.
Answer : A Khadin, also called a Dhora, is an ingenious construction designed to harvest surface runoff water for agriculture. Its main feature is a very long (100-300 m) earthen embankment built across the lower hill slopes lying below gravelly uplands. Sluices and spillways allow excess water to drain off.

Question. What measures would you take to conserve electricity in your house ?
Answer : The following are some steps we can take to save electricity in our homes:
Switch off all unnecessary lights.
Turn off fans when they aren't needed.
Make use of natural light whenever possible.
Make the best use of solar radiation.
Unplug any unused electronics.

Question. Although coal and petroleum are produced by the degradation of biomass, even then we need to conserve them. Why ?
Answer : Coal and petroleum are fossil fuels formed by the degradation of biomass buried deep inside the earth's crust over thousands of years. Hence, if the reservoirs of fossil fuel get depleted they will not be available to us in near future. Thus, we need to conserve them.

Question. Is water conservation necessary ? Give reasons.
Answer : Yes, water conservation is critical. Water is necessary for all living things. Water accounts for approximately 75% of our body weight. We cannot survive without water because it is necessary for all biological processes in our bodies.

Question. Name the products of combustion of fossil fuels like coal and petroleum products. How do they affect us and our environment ?
Answer : Effects of the products of combustion of fossil fuels on humans and the environment: Increased concentration of carbon dioxide causes greenhouse effects. When a high concentration of sulphur dioxide and nitrogen oxide reacts with rain, it causes acid rain. Greenhouse effects can lead to global warming.

Question. Why should fossil fuels like coal and petroleum be used judiciously ?
Answer : Coal and petroleum are fossil fuels that require millions of years to be formed. They are natural resources and are limited in supply. Once exhausted, they cannot be formed again in a short time. Therefore, fossil fuels like coal and petroleum should be used judiciously.

Question. What are the three R’s to save the environment ? Explain with one example of each.
Answer : The three Rs are reduce, recycle and reuse.
The term 'reduce' aims at lowering the usage of natural resources to avoid wastage. For example, using less electricity.
The term 'recycle' aims at using the discarded items by recycling them. For example, recycling paper and plastic and sending them to the respective industries for the formation of new paper and plastic.
The term 'reuse' means using the same thing again and again. For example, using a paper bag over and over again.

Question. What are the main uses of coal and petroleum products ?
Answer : Following are the main uses of coal and petroleum products:
Coal is used in homes and industries as a fuel. It is also used to generate electricity in power plants.
Petroleum products (such as petrol and diesel) are used as fuels in vehicles. Other products (like kerosene and LPG) are used as domestic fuels for cooking.

Question. State any five steps to reduce the consumption of coal and petroleum products.
Answer : Use of solar cookers, solar water heaters, solar panels should be used. Cleaner fuels like LPG and CNG should be used. Use of biofuels such as ethanol or biodiesel should be encouraged. Use of mass transportation (public transport) should be adopted.

Question. Explain why, despite good rains, we are not able to meet the demand for water of all the people in our country.
Answer : Despite good rains, we are not able to meet the demands for water of all the people in our country. This is because our population is increasing at a fast pace. Also, a high yielding variety of crops require more water for irrigation, in urban areas people consume more water and the industrial waste and untreated sewage is discarded into rivers making it contaminated. All these things need a large amount of water; hence, causing water scarcity.

Question. Give one example to show how the participation of local people can lead to the efficient management of forests.
Answer : Chipko Andolan was started by the common people in a remote village named Reni, in Garhwal.
They treated the forest like the sacred groves and they wanted to stop the felling of trees in their locality.
In this movement, when the workers came to cut the trees in the absence of the men of the village and all the women clasped the tree trunks with their arms, in order to save the trees.
Thus movement clearly shows the participation of local people to efficiently manage the forest and maintain the forest.

Question. Explain briefly, how rainwater harvesting is done from open spaces around the buildings in city areas.
Answer : For rainwater harvesting from open spaces around the buildings in city areas, percolation pits are constructed and covered with concrete slabs having holes in it. They are connected to a recharge well via a pipe. The rainwater goes into the percolation pit through the holes of the slab cover. It gets filtered in the pit and enters the recharge well via an outlet pipe and then, slowly, seeps into the soil.

Long Answers

Question : What are the two main components of an ecosystem? Describe the physical factors which affect the distribution of organisms in different habitats.
Answer :  Abiotic (physical) and biotic components are the two main components of an ecosystem.
Abiotic components or physical environment.
i. Temperature. The physiological and behavioral adaptations of most animals depend upon the changes in the environmental temperature. The rates of photosynthesis and respiration in plants also fluctuate depending upon the change in temperature.
ii. Water. The extent to which an organism is dependant on an abundant water supply depends on its requirements and its ability to conserve it in adverse conditions. Organisms living in dry habitats generally have good water conservation such as in cacti, camels.
iii. Light. This is essential for all green plants and photosynthetic bacteria, and for all the animals dependant on the plants.
iv. Humidity. This is important because it can affect the rate at which water evaporates from the surface of an organism, which in turn influence its ability to withstand drought.
v. Wind and air currents. This particularly applies to plants. Only plants with strong root systems and tough stems can live in exposed places where winds are fierce. Wind is also instrumental in the dispersal of spores and seeds.
vi. pH. This influences the distribution of plants in soil and fresh water ponds. Some plants thrive in acidic conditions others in neutral or alkaline conditions. Most are highly sensitive to changes in pH.
vii. Soil nutrients. These particularly affect the distribution of plants in the soil.
viii. Water currents. Particularly in rivers and streams. Only organisms capable of swimming or avoiding strong currents can survive.
ix. Topography. Minor topographical differences may be just as important in influencing the distribution of organisms as wide geographical separation.
x. Background. The distribution of organisms whose shape or colouration are such that they are camouflaged when viewed against a particular background is related to the general texture and pattern of the environment. 

Question : “Our food grains such as wheat and rice, the vegetables and fruits and even meat are found to contain varying amounts of pesticide residues.” State the reason to explain how and why it happens.
Answer : 
Pesticides are poisonous chemical substances which are sprayed over crop plants to protect them from pests and diseases. These chemical pesticides mix up with soil and water. From soil and water, these pesticides are absorbed by the growing plants along with water and other minerals. When herbivorous animals feed on these plants the poisonous pesticides enter their bodies through the food chain. Similarly, when the carnivorous animals eat these herbivores, the pesticides get transferred to their bodies. Therefore, the plant products such as food grains, vegetables and fruits as well as meat of animals contain varying amounts of pesticide residues in them depending upon the trophic level they occupy in a food chain.
• ways Abiotic components – Non-living components of ecosystem, e.g., soil, water, air, light, etc.
• Biotic components – Living components of ecosystem, e.g., plants, animals and microbes.

Question : In the following food chain, plants provide 500 J of energy to rats. How much energy will be available to hawks from snakes?
Plants → Rats → Snakes → Hawks
Answer : 
In an ecosystem, only 10% of energy is transferred from one trophic level to next, i.e. 10 percent law and rest is dissipated into the environment. Therefore, if plants (being producers- 1st trophic level)-transfer 500 J of energy to rats (2nd trophic level) then rats would transfer 50 J of energy to snakes (3rd trophic level) which in turn will transfer only 5 J of energy to hawks (4th or last trophic level) in a food chain.
Plants → Rats → Snakes → Hawks
5000 J 500 J 50 J 5J 

Question : Why is Government of India imposing a ban on the use of polythene bags? Suggest two alternatives to these bags and explain how this ban is likely to improve the environment.
Answer : Government of India is imposing a ban on the use of polythene hags because these are non-biodegradable substances which are not acted upon by the microbes. So, they cannot be decomposed and therefore persist in the environment for a long time thereby causing harm to the ecosystem. Such bags choke drains which results in water logging, that allows breeding of mosquitoes and hence leads to various diseases like malaria, dengue, etc. Jute bags and cloth bags are the alternatives to the polythene bags.

Question : Define an ecosystem. Draw a block diagram to show the flow of energy in an ecosystem.
Answer : An ecosyslcm is defined as a structural and functional unil of ihe biosphere. It comprises of living organisms and their non-living environment that interact by means of food chains and biogeo-chemical cycles resulting in energy-flow, biotic diversity and material cycling to form stable self-supporting system.
Green plants capture about 1% of the solar energy incident on the earth to carry out the process of photosynthesis. A part of this trapped energy is used by plants in performing their metabolic activities and some energy is released as heat into the atmosphere. The remaining energy is chemical energy stored in the plants as photosynthetic products. When these green plants are eaten up by herbivores, the chemical energy stored in the plants is transferred to
these animals. These animals (herbivores) utilise some of this energy for metabolic activities and some energy is released as heat while the remaining energy is stored in their body. This process of energy transfer is repeated till top carnivores. In an ecosystem, transfer of energy follows 10 percent law, i.e,, only 10 percent of the energy is transferred to each trophic level from the lower trophic level. Nearly 90 percent of energy is lost when it moves from one trophic level to the next.The given block diagram shows unidirectional flow of energy at different trophic levels in a freshwater ecosystem.

Question : (a) From the following group of organisms create a food chain which is most advantageous for human beings in terms of energy.
Hawk, Rat, Cereal plant, Goat, Snake, Human being
(b) State the possible disadvantage if the cereal plant is growing in soil rich in pesticides.
(c) Construct a food web using the organisms mentioned above.
Answer : (a) A food chain which is most advantageous for human beings in terms of energy is: Cereal plant → Human being
(b) If the cereal plant is growing in soil rich in pesticides, these pesticides are absorbed by growing plants along with water and minerals, when animals eat these cereal plants, these poisonous chemical pesticides go into their bodies through food. This increase in concentration of harmful pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification. Pesticides are lethal to non-target species also. The extensive use of pesticides in agriculture can change the community of microorganisms living in soil.

Question : (a) Construct a terrestrial food chain comprising four trophic levels.
(b) What will happen if we kill all organisms in one trophic level?
(c) Calculate the amount of energy available to the organisms at the fourth trophic level. If the energy available to the organisms at the second trophic level is 2000 J.
Answer : (a) A terrestrial food chain with four trophic levels is :
Grass → Insect → Frog → Eagle
(b) Removal of the organisms of any trophic level will always adversely affect the ecosystem, e.g., the removal of lions and tigers (top carnivores) will cause rapid increase in deer population, which leads to rapid consumption of vegetation resulting in scarcity of vegetation and population crash of deer.
(c) According to ten percent law, only 10% of the energy is received by the next trophic level.
Producers → Primary → Secondary → Tertiary
consumer consumer consumer
T1 T2  T3 T4
20000 J 2000 J 200 J 20 J
If the energy available at second trophic level (T2) is 2000 J, so the 20 J of energy will be at fourth trophic level (T4).

Question : “Industrialisation has adversely deteriorated the environment.” Give four reasons in support of this statement.
Answer : 
Industrialisation has deteriorated our environment in the following:
Rapid industrialisation has increased the demand of more land area for setting up of new factories. This demand is being fulfilled by clearing up of forest area. Deforestation is one of the major causes of ecological imbalance, biodiversity loss and ecosystem unstability.
• Industries release various harmful gases in the environment which pollute the air. These gases when inhaled by people around, cause various respiratory diseases in them.
• A lot ol effluent and liquid waste is discharged from various industries which is mostly dumped into nearby water bodies. This causes water pollution. Polluted water causes death of various aquatic organisms and consumption of this polluted water causes various diseases in humans.
• The solid waste released from factories is dumped on open land and not treated properly to ensure their proper decomposition. Ibis leads to land pollution that degrades quality of soil and also causes various kinds of diseases in humans and animals.

Question : We often observe domestic waste decomposing in the bylanes of residential colonies.
Suggest ways to make the residents realise that the improper disposal of their waste is harmful to the environment.
Answer : Some of the ways to make people realise that the improper disposal of waste is harmful to the environment includes making people aware of negative impacts of waste disposal. They can be made aware by:
(i) Conducting seminars about the negative effects of the wastes on environment.
(ii) Usage of pamphlets and posters for providing information.
(iii) Forming an eco-club in the society for spreading awareness about the ill effects of waste on the surroundings such as :
• Improper disposal of waste will release harmful gases in the environment that make it unclean and unhygienic for the living organisms.
• The waste will flow to water bodies along with rain water and become a threat to aquatic life and pollute the water bodies.
• It provides space for breeding of the mosquitoes and which results in spread of malaria, filariasis, dengue, etc.
• Hazardous chemicals from wastes get into the soil and can harm the plants when they take up the contamination through their roots. This will affect the health of other animals and humans and will have negative impact on environment.

Question : Producers are autotrophs. They manufacture organic food from inorganic raw material. For this they pick up energy from sun and raw materials from the environment. Solar energy is absorbed by chlorophyll and changed into chemical energy. The chemical energy is stored in organic food formed by photosynthesis. Photosynthesis is performed by plants, algae, phytoplankton, blue green algae and some bacteria. Producers are also called transducers or converts as they change solar energy to chemical energy. Food manufactured by producers is used by all organisms including themselves. Producers have also a global impact of keeping the balance of CO2 Oconstant. They absorb CO2 and release O2.
(a) Why are photoautotrophs called producers?
(b) Why are environmentalist stressing for growing more trees?
(c) What is the source of energy in the biosphere?
(d) Why are heterotrophs called consumers?
Answer :  (a) Photoautotrophs are chlorophyll containing organisms which manufacture organic food that is made available to all other organisms.
(b) Plantation of more trees will reduce the rising concentration of CO2 being produced because of higher combustion of fossil fuels.
(c) Sunlight
(d) Heterotrophs are organisms which obtain readymade food from outside sources. They are therefore called Consumers.

Question : Good quantity of ozone occurs in upper atmosphere or stratosphere at a height of 11-16 Km over poles reaching 23-25 km above equator. This region is called ozone layer or Ozonosphere. It is highly protective to life on earth as it destroys very harmful short waves ultraviolet radiations of 100-320 nm wavelength. Longer wave ultraviolet radiations (320-390 nm) are allowed to pass through and reach the earth. It was found in 1980s that thickness of ozone layer is decreasing rapidly. On searching for the reason, it was noted that certain man-made chemicals like chlorofluorocarbons and halons are bringing about destruction of ozone. They are called ozone depleting substances (ODS). With great international efforts starting from Montreal Protocol (1987) to Kigali conference (2016), it was decided to eliminate the use of ODS and replace them with safer chemicals.
(a) Where is ozone found in plenty in the atmosphere?
(b) What is the function of stratospheric ozone?
(c) Name an ozone depleting substance?
(d) Name an international effort to check damage to ozone layer.
Answer :  (a) Ozonosphere/Ozone layer in upper atmosphere.
(b) Ozone destroys harmful ultraviolet radiations so that they do not reach the earth.
(c) chlorofluorocarbons
(d) Montreal Protocol (1987) for limiting chlorofluorocarbons production level. 

Question. Why are some substances biodegradable and some non-biodegradable ?
Answer : The micro-organisms like bacteria and other decomposer organisms (called saprophytes) present in our environment are ‘specific’ in their action. They break down the natural substances or products made from natural substances (like dead remains of plants and animals, and their waste products, paper, etc.) but do not break down man-made substances such as plastics, metals and glass objects, etc. So, it is due to the property of decomposer organisms of being specific in their action that some waste substances are biodegradable whereas some are non-biodegradable.

Question. Give any two ways in which biodegradable substances would affect the environment.
Answer : (i) The rotting biodegradable wastes (like rotting plant and animal wastes) act as breeding grounds for flies and cockroaches. These flies and cockroaches carry germs and spread various diseases to people living in that area. (ii) The rotting biodegradable wastes emit foul smell in the environment which makes the life of people in the area miserable.

Question. Give any two ways in which non-biodegradable substances would affect the environment.
Answer : (i) Some of the non-biodegradable wastes (such as pesticides like DDT and metals like mercury) enter the food chain of humans These non-biodegradable wastes get concentrated in human beings and damage their health in the long run. (ii) The excessive use of non-biodegradable fertilisers in agriculture makes the soil either too much acidic or too much alkaline. When the soil becomes too acidic or too alkaline, the crop yield is reduced. (iii) The dumping of non-biodegradable wastes like plastic, glass and metal objects here and there acts as an eyesore and spoils the environment.

Question. What are trophic levels ? Give an example of a food chain and state the different trophic levels in it.
Answer : A food chain represents the flow of food (or energy) in a given set of organisms or living beings. The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels. In fact, in a food chain, each step representing an organism forms a trophic level. Consider a food chain operating in a grassland which consists of four organisms : Grass → Insects → Frog → Birds In this food chain, grass is the producer and represents the first trophic level. Insects are the herbivores (which eat grass) and represent second trophic level. Frog is the carnivore (which eats insects) and represents third trophic level. And birds are the top carnivores (which eat frogs) and represent fourth trophic level.

Question. What is the role of decomposers in the ecosystem ?
Answer : The decomposers help in decomposing the dead bodies of plants and animals, and hence act as cleansing agents of environment. The decomposers also help in putting back the various elements of which the dead plants and animals are made, back into the soil, air and water for re-use by the producers like crop-plants. This maintains the fertility of soil and the soil would continue to support crops again and again. For example, the decomposers like putrefying bacteria and fungi decompose the dead plants and animal bodies into ammonia (and other simpler substances). This ammonia is converted into nitrates by the nitrifying bacteria present in soil. These nitrates act as fertilizer in the soil and are again absorbed by the plants for their growth.

Question. What is ozone and how does it affect any ecosystem ?
Answer : Ozone is a gas made up of three atoms of oxygen joined together. The molecular formula of ozone is O3. Ozone is formed high up in the atmosphere by the action of ultraviolet radiations (coming from the sun) on the oxygen gas. The ozone layer present high up in the atmosphere protects all forms of life on earth by absorbing harmful ultraviolet radiations coming from the sun. Certain chemicals like chlorofluorocarbons (CFCs) which are widely used in refrigeration, fire extinguishers and aerosol sprayers reach the upper atmosphere and react with ozone gas present in ozone layer and destroy it gradually. Due to this the ozone layer in the upper atmosphere is becoming thinner, allowing more harmful ultraviolet rays to pass through it and reach the earth. Thus, due to the depletion of ozone layer caused by chlorofluorocarbons, more ultraviolet rays reach the earth. These ultraviolet rays can cause skin cancer, cataract in the eyes and damage immune system of human beings. They also harm animals and plants.

Question. How can you help in reducing the problem of waste disposal ? Give any two methods.
Answer : The two methods which can help in reducing the problem of waste disposal are : recycling, and preparation of compost. These are described below. (i) The solid wastes like paper, plastics, glass and metals, etc., are recycled. For example, waste paper is sent to paper mills where it is reprocessed to form new paper once again. The broken plastic articles like plastic bags, buckets, bowls, cups, plates, etc., are sent to plastic processing factories where they are melted and remoulded to make new articles. Similarly, waste metal articles are sent to metal industries where they are melted and recycled as solid metal for various purposes. (ii) Biodegradable domestic wastes such as left-over food, fruit and vegetable peels, and leaves of potted plants, etc., can be converted into compost by burying in a pit dug into ground, and used as manure.

Question. Which of the following groups contain only biodegradable items ?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit peels, cake and lime juice
(d) Cake, wood and grass
Answer : (a), (c) and (d).

Question. Which of the following constitute a food chain ?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer : (b) Grass, goat and human

Question. Which of the following are environment-friendly practices ?
(a) Carrying cloth bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
Answer : (d) All of the above.

Question. What will happen if we kill all the organisms in one trophic level ?
Answer : If we kill all the organisms in one trophic level, then transfer of food (and energy) to the next trophic level will stop due to which the organisms of next trophic level will starve and die or migrate to other areas. The killing of all the organisms in one trophic level will also lead to the overpopulation of organisms in the previous trophic level. These effects will cause an imbalance in the ecosystem. For example, if we kill all the herbivorous animals like deer, rabbits, etc., in a forest, then the carnivorous animals like lions, tigers, etc., will not get food. Due to this, the lions and tigers, etc., will starve and die or migrate from forest and go towards human settlements and attack people. Moreover, in the absence of herbivores like deer, rabbits, etc., the population of the previous trophic level ‘plants’ (or vegetation) will increase too much (because there are no deer or rabbits to eat them). All these effects will create an imbalance in the ecosystem.

Question. Will the impact of removing all the organisms in a trophic level be different for different trophic levels ? Can the organisms of any trophic level be removed without causing any damage to the ecosystem ?
Answer : (a) Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. For example, in the food chain : Grass ⎯⎯→ Deer ⎯⎯→ Lion : (i) If we remove all the lions at the third trophic level, then the number of deer will increase too much. All these deer will eat up all the grass and other plants turning the forest into a desert. (ii) If we remove all the deer at the second trophic level, then lions will not get sufficient food, they will starve and die. Deer eat grass and other green plants, so the amount of grass and other green plants will increase too much. (b) No, all the organisms of any trophic level cannot be removed without causing any damage to the ecosystem.

Question. What is biological magnification ? Will the level of this magnification be different at different levels of the ecosystem ?
Answer : (a) The harmful chemicals like pesticides enter the food chain at the producer level (plant level) and in the process of transfer of food through food chains these harmful chemicals get concentrated at each trophic level. The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification. Pesticides are nonbiodegradable chemicals, so they get accumulated at each trophic level. (b) Yes, the level of biological magnification is different for different trophic levels of an ecosystem. For example, in the food chain : Plants → Goat → Man, the harmful chemicals enter into plants from soil and water. When goat eats these plants, the chemicals enter into goat’s body. And ultimately when a non-vegetarian man eats the goat meat, the harmful chemicals are transferred to his body. The level or concentration of the harmful chemicals increases with increasing trophic level. In the above given food chain, the concentration of harmful chemicals is minimum in the plants, higher in the goat and maximum in man.

Question. What are the problems caused by the non-biodegradable wastes that we generate ?
Answer : The non-biodegradable wastes cannot be made less toxic easily, so they cause a lot of problems for us as well as the environment. For example : (i) Some of the non-biodegradable wastes (such as pesticides like DDT and metals like mercury) enter the food chain of humans These non-biodegradable wastes get concentrated in human beings and damage their health in the long run. (ii) The excessive use of non-biodegradable fertilisers in agriculture makes the soil either too much acidic or too much alkaline. When the soil becomes too acidic or too alkaline, the crop yields is reduced.

Question. If all the waste we generate is biodegradable, will this have no impact on the environment ?
Answer : Even if all the waste we generate is biodegradable, it will have an impact on the environment. This is because too much biodegradable waste cannot be broken down into harmless simpler substances by the decomposers like micro-organisms at the right time. Due to this, the biodegradable wastes will go on accumulating in the environment and act as pollutants resulting in harmful effects on the environment. For example, the rotting biodegradable wastes act as breeding grounds for flies and cockroaches, etc., which spread diseases. Moreover, the rotting biodegradable wastes emit foul smell in the environment which makes the life of people miserable.

Question. Why is the damage to the ozone layer a cause for concern ? What steps are being taken to limit this damage ?
Answer : The ozone gas layer high up in the atmosphere is very important for the existence of life on earth because it absorbs most of the harmful ultraviolet radiations coming from the sun and prevents them from reaching the earth. The damage to the ozone layer is a cause for concern because damage to ozone layer will make it thinner which will allow much more harmful ultraviolet radiations (coming from the sun) to reach the earth. These ultraviolet radiations can then cause skin cancer in humans They can also damage the eyes by causing an eye disease called cataract. Ultraviolet rays damage immune system by lowering the body’s resistance to diseases. They also damage crop plants. In fact, if too much damage occurs to the ozone layer and it disappears completely, then all the life on the earth would be destroyed gradually. The depletion of ozone layer is due to the use of chemicals called chlorofluorocarbons (CFCs) in refrigeration, fire extinguishers and aerosol sprayers. So, in 1987, in an attempt to protect ozone layer, the United Nations Environment Programme (UNEP) forged an agreement among its member countries to freeze CFC production at 1986 levels. The chlorofluorocarbons (CFCs) are now being replaced by hydroflurorocarbons (HFCs) which do not damage the ozone layer.

Question. (a) What is a natural resource ? Name three important natural resources.
(b) Why do we need to manage our natural resources ?
Answer : (a) Natural resources are the things present in the environment that can be used by humans. Three important natural resources are water, fossil fuels, like coal and petroleum, and forest and wildlife.
(b) We need to manage our natural resources. The reasons for this are given below:
They are limited in amount. We need to manage them so that they can fulfil the need of the present as well that of the coming generations.
This will prevent their exploitation for short term gain.
This will ensure equal distribution of natural resources so that everyone can benefit from their development.
This will also minimise the damage to the environment, which is caused during the extraction and usage of natural resources.

Question. (a) State the advantages of constructing dams across the rivers.
(b) Describe some of the problems associated with the construction of dams.
Answer : (a) Following are the advantages of constructing dams across the rivers:
They can store excess water, thereby preventing floods.
Water from the dams can be used for the irrigation of crops via a network of canals.
After a suitable treatment, people of towns and cities get dam water through pipelines, for usage.
Water falling from the dams is used to generate electricity in hydropower plants.
(b) Following problems are associated with building dams:
Social problems: It makes many people homeless, by submerging large areas of human- settlements, thereby causing a social issue.
Environmental problems: It causes deforestation and loss of biodiversity by submerging large varieties of plants and animals. This creates an ecological imbalance.
Economic problems: This is an issue raised by many people who consider that the construction of dams needs a large amount of public money and there are no proportionate benefits.

Question. (a) Name any five sources of water (other than rivers)
(b) Describe how, the water of river Ganga has been highly polluted.
Answer : (a) Five sources of water are lakes, rains, ponds, wells and glaciers. (b) The water of river Ganga has been highly polluted with industrial discharges and untreated sewage disposal.

Question. (a) Name the major industries which are based on forest produce.
(b) State the main aim of the management of forests and wildlife.
(c) Name the four main stakeholders in the management of forest resources.
Answer : a The various industries which are based on forest produce are; timber industry paper manufacturing industry 'lac' industry and sports equipment industry. b The main aim of the management of forests and wild life is to conserve the biodiversity which we have inherited.

Question. (a) What is meant by rainwater harvesting ? Name some of the ancient structures used for rainwater harvesting by the rural people.
(b) What are the various advantages of water stored in ground ?
Answer : (a) Rainwater harvesting is the method of collecting rainwater so that it can percolate in the soil more efficiently. The ancient structures used for rainwater harvesting by the rural people are Khadin in Rajasthan, Bandharas and Tals in Maharashtra and Ahars in Bihar.
(b) Following are the various advantages of water stored under the ground:
It does not evaporate.
It spreads out to recharge wells and provides moisture to the crops.
It does not promote the breeding of mosquitoes.
It is not contaminated by human and animal wastes.
It can be utilised by the local population.

Questions Based on High Order Thinking Skills (HOTS)

Question. In a village, farmers started cultivating crops all around a lake which was always filled with water. They added lot of materials W to the soil in their fields to increase the yield of crops. Soon they found that the whole surface of water in the lake was covered with a green layer made up of tiny organisms X. After some time, the fish present in the lake started dying in large numbers because they could not get sufficient Y due to a process Z which had occurred in lake water and drained out all the Y present in the water of lake.
(a) What do you think materials W are ?
(b) Name (i) X, and (ii) Y.
(c) What is the process Z known as ?
(d) What happens during the process Z which uses up all the Y present in lake water ?
(e) What does this example tell us about the use of materials like W ?
Answer : (a) Fertilisers (b) (i) Algae (ii) Oxygen (c) Eutrophication (d) When algae die, bacteria use all the oxygen dissolved in water to decompose dead algae (e) Excessive use of fertilisers in fields is not good for the environment

Question. There were lot of organisms A in the crop fields in an area. These organisms used to feed on organisms B also present in the crop fields but which damaged the standing crops. One day some people arrived in the fields and killed all the organisms A so that they could remove their C for making fancy items which were in great demand. Due to large scale killing of A, the population of B increased too much damaging all the crops in the area and causing a famine-like situation. Apart from A, there is another organism D which can also kill and eat B. Name A, B, C and D.
Answer : A : Snakes ; B : Rats ; C : Skin ; D : Cat

Question. There are two important fuels A and B both of which are extracted from deep inside the earth. Fuel A is a thick, dark, foul smelling liquid whereas fuel B is a black solid. Combustion of both the fuels produces products, C, D, E and F. The product C makes the rainwater only slightly acidic but it is mainly responsible for causing global warming. The product D is neither acidic nor basic. It is harmless and does not affect the environment in any way. Both E and F attack breathing system of humans and are mainly responsible for causing acid rain. In addition to combustion of fuels A and B, the product F is also formed when lightning occurs in the sky.
(a) What are (i) fuel A, and (ii) fuel B ?
(b) Name (i) C (ii) D (iii) E, and (iv) F
(c) What is the process of formation of F during lightning known as ?
(d) Which fuel is supposed to be exhausted sooner : A or B ?
(e) Which fuel is mostly used for generating electricity at thermal power plants ?
Answer : (a) (i) Petroleum (ii) Coal (b) (i) Carbon dioxide (ii) Water (iii) Sulphur dioxide (iv) Nitrogen oxides (c) Natural fixation of nitrogen (d) A (Petroleum) (e) B (Coal)

Question. A man bought a device X which could cook pulses, vegetables and rice without using any fuel like wood, coal, kerosene or LPG, etc. This device did not work at night. It also took a lot of time for cooking.
(a) Name the device X.
(b) What is the source of energy which cooks food in this device ?
(c) What is the name of the process which traps energy in this device ?
(d) State one advantage (other than saving on fuel) of using such a device for cooking food.
Answer : (a) Solar cooker (b) Sun (c) Greenhouse effect (d) It does not cause air pollution

Question. A person buys two electrical devices P and Q for lighting purposes in his house. The device P consumes only 5 units of electricity in a month but device Q consumes 15 units of electricity in a month when used for the same number of hours daily. The device Q wastes a lot of electricity by radiating energy C but P does not do so.
(a) What type of device is (i) P, and (ii) Q ?
(b) Name one component which is present in Q but not in P.
(c) Name the energy C.
(d) Which device is more energy efficient : P or Q ?
(e) Which fossil fuel is most likely to be conserved if all of us switch over to devices like P ?
Answer : (a) (i) Compact Fluorescent Lamp (CFL)(ii) Filament type bulb (or lamp) (b) Filament (c) Heat energy (d) P (e) Coal

Chapter 16 Sustainable Management of Natural Resources
CBSE Class 10 Science Sustainable Management of Natural Resources Worksheet

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How can I improve my scores by solving questions given in Printable worksheets in Class 10 Science Chapter 15 Our Environment

Regular revision of practice worksheets given on studiestoday for Class 10 subject Science Chapter 15 Our Environment can help you to score better marks in exams

Are there any websites that offer free test sheets for Class 10 Science Chapter 15 Our Environment

Yes, studiestoday.com provides all latest NCERT Chapter 15 Our Environment Class 10 Science test sheets with answers based on the latest books for the current academic session

Can test papers for Class 10 Science Chapter 15 Our Environment be accessed on mobile devices

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Are worksheets for Chapter 15 Our Environment Class 10 Science available in multiple languages

Yes, worksheets for Chapter 15 Our Environment Class 10 Science are available in multiple languages, including English, Hindi