ICSE Living Science Biology for Class 8 Solutions Chapter 5 Conservation of Resources and Pollution
Check Your Progress
Fill in the blanks.
Question 1.
The process in which rich top soil is lost or carried away either by wind or water is called soil ……………..
Answer:
The process in which rich top soil is lost or carried away either by wind or water is called soil erosion.
Question 2.
………… is the practice of growing different crops in a given area each season.
Answer:
Crop rotation is the practice of growing different crops in a given area each season.
Question 3.
The depth of the soil below which soil spaces are filled with water only is called ……………. table.
Answer:
The depth of the soil below which soil spaces are filled with water only is called water table.
Question 4.
An …………. is a species that is in danger of becoming extinct as their number has reduced drastically.
Answer:
An endangered Species is a species that is in danger of becoming extinct as their number has reduced drastically.
Question 5.
In India hunting of tigers is banned under ………………….. tiger which was initiated after the population of tigers declined sharply.
Answer:
In India hunting of tigers is banned under project tiger which was initiated after the population of tigers declined sharply.
Check Your Progress 2
Write True or False.
Question 1.
A pollutant is a material that saves the environment.
Answer:
False. A pollutant is a material that contaminates the environment.
Question 2.
The discharge of hot water by power plants into the lakes and rivers causes thermal pollution.
Answer:
True
Question 3.
The unit used to measure loudness of sound is called decibel.
Answer:
True
Question 4.
Solar panels are very cheap to make.
Answer:
False. Solar panels are very expensive to make.
Question 5.
Wastes which cannot be broken down into non-toxic substances by the action of microogranisms are called biodegradable wastes.
Answer:
False. Wastes which cannot be broken down into non-toxic substances by the action of microogranisms are called non biodegradable wastes.
A. Tick the most appropriate answer.
Question 1.
Which of the following is a renewable natural resource ?
a. Petroleum
c. Coal
Answer:
b. Water
Question 2.
Soil conservation can be done by
a. crop rotation
b. deforestation
c. by growing same crop year after year & ovegrazing Ans. a. crop rotation
Question 3.
Which of the following is not a leguminous crop ?
a. Peas
b. Grams
Answer:
d. Rice
Question 4.
Which of the following is not a cause of lowering of water table ?
a. Deforestation
b. Destruction of vegetation by overgrazing
c. Honking unnecessarily
d. Excessive construction of buildings
Answer:
c. Honking unnecessarily
Question 5.
Which of these methods do not result in conservation of water ?
a. Using drip irrigation
b. Recycling of water
c. Deforestation
d. Afforestation
Answer:
c. Deforestation
Question 6.
The practice of renewing a forest by large scale planting of seedlings or small trees is called
a. deforestation
b. afforestation
c. depletion
d. degradation
Answer:
b. afforestation
Question 7.
DDT is a
a. pesticide
b. man-made fertilizer
c. manure
d. fungicide
Answer:
a. pesticide
Question 8.
Which of the following is not a pollutant unless present in excess ?
a. Sulphur dioxide
b. Carbon dioxide
c. Carbon monoxide
d. Nitrogen dioxide
Answer:
b. Carbon dioxide
Question 9.
Which of the following corrodes metals and damages marbles ?
a. Acid rain
b. Open chulihas
c. Eutrophication
d. Sunlight
Answer:
a. Acid rain
Question 10.
Energy from the sun is called
a. nuclear energy
b. Solar energy
c. hydel energy
d. wind energy
Answer:
b. Solar energy
B. Fill in the blanks.
1. ………….. are resources that can be replaced by quick recycling through natural cycles.
Answer:
Renewable resources are resources that can be replaced by quick recycling through natural cycles.
2. Fossil fuels like coal …………. and natural gas are non-renewable resources.
Answer:
Fossil fuels like coal, petroleum and natural gas are non-renewable resources.
3. Growing the same crop year after year in the same soil results in …………. of fertility of the soil.
Answer:
Growing the same crop year after year in the same soil results in decrease of fertility of the soil.
4. …………. are low-lying areas where water table is very close to the surface.
Answer:
Wetlands are low-lying areas where water table is very close to the surface.
5. ………….. is plant or animal material that can be changed into fuel.
Answer:
Fossil is plant or animal material that can be changed into fuel.
6. ………….. is a device used for cooking food with the help of solar energy.
Answer:
Solar cooker is a device used for cooking food with the help of solar energy.
7. ………….. are the best sources of electric power in satellites.
Answer:
Solar Panels are the best sources of electric power in satellites.
8. The flowing water of rivers is constantly replenished by the ………….
Answer:
The flowing water of rivers is constantly replenished by the water cycle. ‘
9. Nuclear fission produces wastes that are ……………
Answer:
Nuclear fission produces wastes that are radioactive.
10. The waste which cannot be broken down into non¬toxic substances by the action of microorganisms is called …………. waste.
Answer:
The waste which cannot be broken down into non-toxic substances by the action of microorganisms, is called non-renewable waste.
C. Give reasons for the following :
Question 1.
Water is a renewable resource.
Answer:
Water is a renewable resource as it get replaced by -quick recycling through natural cycles. The flowing water in the rivers is replenished by the water cycle.
Question 2.
Fossil fuels are considered to be non-renewable sources of energy,
Answer:
Fossil fuels are considered as non-renewable sources of energy as these resources once used cannot be replaced within a reasonable time span.
Question 3.
Nuclear energy is an alternate source of energy.
Answer:
Nuclear energy is the energy stored in the nucleus of an atom. When the nucleus of certain atoms like uranium and plutonium splits, it releases large amount of energy, which is used to generate electricity in a nuclear power plant. So it is called alternate source of energy.
Question 4.
Plastic, glass bottles and polythene bags are non- biodegradable wastes.
Answer:
Plastic, glass bottles, and polythene bags are non- biodegradable wastes as they cannot be broken down in – to non-toxic ubstances by the action of microorganisms.
D. Differentiate between
Question 1.
renewable resources and non-renewable resources.
Answer:
Renewable resources :
- The resources that get replaced by recycling through natural cycles are called renewable resources.
- These are produced continuously in nature
- Air, water, solar energy, wind energy air some of the renewables resources.
Non-renewable resources :
- The resources that once used cannot be replaced within a reasonable time span are called non-renewable resources.
- These have been accumulated in nature over a very long time.
- Coal, natural gas, petroleum are some of the non-renewable resources.
Question 2.
afforestation and deforestation
Answer:
Afforestation :
- It is the practice of renewing a forest by large scale planting of seedlings or small plants in place of cut down trees.
more land for cultivation, - Afforestation helps to reduce soil erosion.
- Afforestation helps to maintain carbon dioxide-oxygen balance in nature.
Deforestation :
- It is the practice of cutting down of the trees to obtain housing, construction of roads raw materials for paper etc.
- Soil erosion increases due to deforestation.
- Deforestation disturbs carbon dioxide oxygen balance in nature.
Question 3.
solar energy and nuclear energy.
Answer:
Solar energy :
- Energy from the sun is called solar energy.
- No radioactive waste is produced.
- It is free of cost available to everybody.
Nuclear energy :
- Energy from the splitting nucleus of certain atoms is nuclear energy.
- Splitting of nucleus produces radioactive wastes which effects the environment.
- The process of releasing energy is very costly.
Question 4.
biodegradable wastes and non-biodegradable wastes.
Answer:
Biodegradable wastes :
1. Those waste materials which can be broken down to non-poisonous substances in nature by the action of micro-poisonous substances organisms are called biodegradable wastes.
Non-biodegradable wastes :
1. Those materials which cannot be broken docon to non-poisonous substances in nature are called non-biodegradable wastes.
E. Write short answers.
Question 1.
What is drip irrigation ?
Answer:
The method of supplying water to the roots of plant drop by drop instead of filling whole field with water is called drip irrigation.
Question 2.
Write names of two animals that have become extinct in recent years.
Answer:
The mountain quail of Western Himalyas, pink-hued duck and sikkim stag are some of the animals that have become extinct in recent years.
Question 3.
Name two organizations working towards conservation of wildlife.
Answer:
Worldwide fund for nature (WWF) and International Union for conservation of nature and natural resources (IUCN) are the two organisations that are working towards conservation of wildlife.
Question 4.
What is acid rain ?
Answer:
Oxides of sulphur and nitrogen when combines with oxygen and water in the air form sulphuric acid and nitric acids. The mixture of acid and rain water that falls on the earth is called acid rain.
Question 5.
What do you mean by SPM ?
Answer:
Minute solid particles suspended in air are known as suspended particulate matter or SPM. SPM are unburnt carbon particles during burning of fuels, exhaust of vehicles and soon. They also cause air pollution.
Question 6.
Define Geothermal energy.
Answer:
Energy that comes from heat beneath the earth’s surface is called geothermal energy. The temperature deep inside the earth is very high. Due to this water gets heated up ‘ and forms steam, which pushes the hot water to shoot out of the grounds through the opening. Geothermal energy is available only in certain areas, it is considered c as renewable source of energy.
Question 7.
Name the two divisions into which the natural resources are divided.
Answer:
Natural resources are divided in to two categories.
(i) Renewable resources : These are resources that can be replaced by quick recycling through natural cycles. For example soil, water, air and forests.
(ii) Non- renewable resources : These resources are in limited amount and cannot be replaced within a reasonable time span. Fossil fuels like petroleum, coal, metals are non-renewable resources.
Question 8.
List three alternate sources of energy.
Answer:
Alternate sources of energy are renewable sources which can be used effectively.
These are :
- Biomass Energy : Biomass energy is plant or animal material that can be changed into fuel.
- Solar Energy : Energy from the sun is called solar Energy.
- Hydel Energy : The kinetic energy of flowing water used by human as a source of energy is called Hydel Energy.
F. Answer in detail.
Question 1.
Define the term ‘natural resources’ with examples. Ans. Substances and sources of energy found in the nature (lithosphere, hydrosphere and atmosphere) that are used by human for supporting life, are called natural resources. Soil, air and water are some of our natural resources. Natural resources are classified into two categories.
(i) Renewable resources
(ii) Non-renewable resources
Renewable resources – These are resources that have the capacity to get replaced by quick recycling through natural cycles. Oxygen in the air is a renewable resource, because it is replaced by plants during photosynthesis. Soil, water, wildlife and forests are the main renewable resources. However, these resources might exhaust if used too rapidly due to improper management and to not get enough time for renewal.
Non-renewable resources : These are resources available in limited amounts. These resources once used cannot be replaced within a reasonable time span. Fossil fuels like coal, petroleum, metals, minerals and natural gas are non-renewable resources. Similarly, top soil takes hundreds of years to form Most of these resources once used are lost forever. Some non-renewable resources, such as metals can be used again and again since they can be recycled.
Question 2.
What is a renewable nature resource ?
Answer:
Those sources of energy which are being produced continuously in nature and are inexhaustible are called renewable resources of energy geothermal power, solar energy, wind energy, tidal energy. Oxygen in the air is a renewable resource because it is replaced by plants during photosynthesis. However, these resources might
exhaust if used too rapidly due to improper management and do not get enough time for renewal.
Question 3.
Oxygen in the air is a renewable natural resource. Explain why ?
Answer:
All living beings need oxygen to survive. We all respire oxygen and give out carbon dioxide. The plants take in this carbon dioxide and release oxygen during photosynthesis. So oxygen is replenished in nature by the plants. Therefore oxygen is a renewable resources as it is used and produced at the same time. We should plant more trees for the continuous supply of oxygen.
Question 4.
What do you mean by conservation of natural resources.
Answer:
Natural resources are depleting at a faster rate than ever due to overpopulation and selfish attitude of human beings having a short-sighted approach to life. Human beings have overused the natural resources without thinking of its impact on their own life over a period of time. But it is never too late. Even now if these resources are wisely used, they can continue to contribute to human welfare for all times to come.
The wise and careful use of natural resources is called conservation. Literally it means ‘to save’. Conservation includes not only wise use of resources but also maintaining their quality. Some of our natural resources and their conservation methods are discussed here. At many places, rich top soil is lost or is carried away either by wind or water. This process is called soil erosion.
Question 5.
What is soil erosion ? List two causes of soil erosion.
Answer:
At many places, rich top soil is lost or is carried away either by wind or water. This process is called soil
erosion. It normally takes places in areas where the land is without vegetable as the roots of plants hold the soil. Fine particles are also washed away by rain often on hilly slopes.
Causes of Soil Erosion :
1. Deforestation : Cutting down of trees leads to soil erosion as the roots of trees bind the soil firmly.
2. Ploughed farm land which has loose soil is also susceptible to erosion by air and water.
Question 6.
Give two steps that can be taken to prevent soil erosion.
Answer:
Following steps can be taken to conserve soil.
(i) Step farming : In hilly areas, steps are cut in slopes for farming This reduces the speed of flow of water and thus prevents soil erosion.
(ii) Afforestation : Soil can also be conserved by planting bare areas of land with trees.
Question 7.
What do you mean by crop rotation ? Explain with examples.
Answer:
Crop rotation : Fertility of soil is also maintained by crop rotation. It is the practice of growing different crops in a given area each season. For example, if a cereal crop is grown in one season, leguminous crops like peas, beans or grams are grown before the next crop of cereals. Leguminous plants have special bacteria in their root nodules which have the capacity to convert free nitrogen of the air to soluble nitrates which make the soil fertile.
Question 8.
What is rain water harvesting and how does it help in raising the level of groundwater ?
Answer:
For proper utilization of rainwater, rainwater harvesting should be done in residential areas and parks, Rainwater which falls on the roof of a building flows into a deep trench in the ground. It, thus, replenishes groundwater instead of just flowing into open drains. This method has helped to some extent in raising the level of groundwater in certain areas. It is being encouraged by the government.
Question 9.
Why is forest an important natural resource for mankind ?
Answer:
Forests are an important renewable resource. They provide habitat for many kinds of living organisms. They help in soil conservation as roots of trees hold the soil particles and prevent soil erosion by water and wind. They also help in causing more rainfall as they play an important role in the water cycle.
Forests are being constantly destroyed by human beings for their selfish needs. Due to increase in human population more land is required for cultivation, housing, construction of roads and mining. Trees are also being cut for obtaining raw materials to be used in paper, timber and rubber industries.
Question 10.
In India, what are the various steps taken to conserv e wildlife ?
Answer:
We can conserve wildlife by the following methods.
a. Stop deforestation.
b. Create wildlife sanctuaries, National parks and bird sanctuaries by setting aside permanent protected areas where animals can live and breed in their natural habitat. India has a wide network of 96 National parks and over 500 sanctuaries located in different parts of the country.
c. Do not use products such as coats, bags, belts, ivory and musk made out of skin, fur or other body parts of endangered animals. Unless the use of these products is discouraged, the killing of animals will continue.
d. Hunting of animals should be prohibited. Although there are laws and regulations related to hunting but it is important that these laws are implemented effectively. In India hunting of tigers is banned under ‘Project Tiger’ which was initiated when the population of tigers declined sharply.
e. Worldwide Fund for Nature (WWF) and International Union for Conservation of Nature and Natural Resources (IUCN) are two organizations that are working towards conservation of wildlife.
f There are many treaties or conventions made towards the protection of wildlife. Some of these are the Ramsar Conservation on wetlands and the Convention on International trade in Endangered species of wild fauna and flora.
Question 11.
What is pollution ? What are the cause of water pollution ?
Answer:
Pollution is the introduction of unwanted, usually harmful material into the environment. A pollutant is a material that contaminates and harms the environment. Unfortunately, almost all pollution of water, air and land has been caused by human activities.
Water pollution refers to the presence of harmful material into water. Pollution makes water unsafe for drinking, washing, cooking and many other activities. Sometimes it is so much”polluted that it is unfit even for irrigation. Causes of water pollution – Untreated Sewage, that is, wastewater from sink, shower and toilet causes water pollution. When it is released into rivers, it is broken down by aerobic bacteria. These bacteria use oxygen in this process. When large amounts of sewage are dumped, the oxygen in water decreases. As a result, fish and other living organisms in water may die from lack of oxygen.
Release of Industrial Waste (Effluents)
Release of industrial waste into rivers also causes water pollution. The waste released contains certain metals like lead, mercury and arsenic. Wastes also contain acids, plastics and other poisonous chemicals which are harmful for living organisms.
Excessive use of chemical fertilizers and pesticides – Excessive use of chemical fertilizers and pesticides also cause water pollution since they are carried to water sources with rainwater. Chemical fertilizers and pesticides being non-biodegradable do not decompose by natural methods. Therefore, they go on accumulating and increase the pollution level. They also seep into the ground and pollute groundwater.
High concentration of nitrates and phosphates in water makes the water poisonous and unfit for aquatic animals. Marine water contamination : The major source of marine pollution is the production and transportation of petroleum products. Coastal water also gets polluted by industrial waste which are directly released into the water. Oil spills from oil tankers create huge patches in the ocean and kill fish, molluscs, water birds and other marine animals. The life cycle of coral reefs are also affected by marine water contamination.
Hot water – Power plants use cold water from lakes or rivers to cool their heated machines. The discharge of hot water by these power plants into the lakes and rivers causes thermal pollution. Even small change in temperature of water can kill many organisms living there.
Oxygen-Demanding waste
Organic waste from food processing industries and farms are usually discharged into the water. Microorganisms such as bacteria are responsible for decomposition of these organic waste. During this process these bacteria consume available dissolved oxygen and deprive other organisms from it.
OTHER CAUSES
a. Throwing of dead animals and dumping of other solid wastes into water.
b. Excessive use of detergents.
c. Bathing and washing of clothes by human beings in ponds and rivers.
d. Human beings and animals defecating in or near water sources.
Question 12.
List various effect of water pollution.
Answer:
The waste generated by all above mentioned activities contain marly harmful microorganisms that pollute water and people drinking this water suffers from waterborne diseases.
(a) Polluted water caft cause serious waterborne diseases like cholera, jaundice and dysentery.
(b) It destroys aquatic plants and animals.
(c) It leads to abnormal growth of plants.
(d) Pesticides such as DDT can get into the bodies of fishes through the water. Animals and humans, receive poisonous substances if they eat these contaminated fishes.
Question 13.
Describe various cause of air pollution How can you control air pollution ?
Answer:
The presence of harmful gases and solid particles in air leads to air pollution. Air pollution is increasing at an alarming rate in big cities. It has an adverse effect not only on human beings but on other animals and plants too.
Cause of air pollution :
Burning of Fossil Fuels – Air pollution is mainly caused by burning of fossil fuels in power houses, industries and vehicles. This gives off gases, such as carbon monoxide (CO), sulphur dioxide (S02) and nitrogen dioxide (N02).
Acid Rain – Sulphur dioxide is formed when coal that contains sulphur is burned. This gas is also present in car exhaust. Oxides of sulphur and nitrogen when combines with oxygen and water in the air form sulphuric and nitric acids. The mixture of acid and rainwater that falls on the earth is called acid rain.
Greenhouse Effect – Excess of carbon dioxide, methane, water vapour and a few other gases in the atmosphere traps the heat of sun leading to rise in the temperature of the earth over a period of time. This is called greenhouse effect. This increase in temperature across the globe, can lead to melting of polar ice caps resulting in flood in coastal regions and forcing many plant and animal species towards extinction which cannot adapt the temperature change.
a. Carbon dioxide as a gas in the right percentage in the air is not harmful. But this gas is increasing in the air due to excessive burning of fuel as well as massive deforestation.
b. Biomass is total dry mass or weight of an organism. Biomass-based fuels such as wood, cow dung, crop residue also cause pollution by releasing gases such as carbon dioxide and methane.
c. Minute solid particles suspended in air are known as suspended particulate matter or SPM. Some examples of SPM are unbumt carbon particles during burning of fuel, exhaust of vehicles, and so on. They also cause air pollution.
Control of air pollution –
a. The Central Pollution Control Board has laid down some rules and regulations to control air pollution. According to that pollution check certificate should be obtained after every three months by the owners of cars, scooters and other vehicles.
b. Use of CNG (Compressed Natural Gas) as a fuel for buses instead of diesel in all the states.
c. Use of unleaded petrol.
d. Use of car pools of office goers and school children.
e. Use of bicycle for travelling short distance within the colony.
f. Shifting of industrial units from residential areas to industrial areas which are far away from the cities. Besides, the chimneys should be tall enough to dispose the emissions of harmful gases by wind.
g. Industries should treat the gases before released them from the chimney. The gases given off should be scrubbed down using scrubbers before being released. This removes the poisonous gases such as sulphur dioxide and nitrogen dioxide by dissolving them. Some industries make use of gravity setting chamber for removal of air (pollutants).
Question 14.
Why is acid rain harmful to mankind ?
Answer:
Oxides of sulphur and nitrogen when combines with oxygen and water in the air form sulphuric and nitric acids. The mixture of acid and rainwater that falls on the i earth is called acid rain. Acid rain is responsible for the destruction of textures of buildings. Acid rain corrodes metals and damages marble. Taj Mahal, a beautiful monument made up of marble has been affected by acid rain. Acid rain also affects fertility of soil by making soil. acidic. Plants do not survive in acidic soil. Acid rain also
causes death of many aquatic animals. It also causes skin diseases.
Question 15.
Explain the working of a solar water heater.
Answer:
A solar water heater is a device that uses solar energy to heat water. Sunlight is allowed to fall on copper pipes painted black. The pipes are fixed on a wooden box with a glass cover. Reflectors may also be used to increase the effective area over which sunlight is collected. Water flowing through the copper pipes gets heated up.
Solar water heaters are commonly seen on roofs of large buildings and hotels. They supply hot water for various purposes.
Question 16,.
List five steps in which we can contribute to protect our environment.
Answer:
Each one of us can contribute in our own way to protect our environment.
a. Plant a tree in your neighbourhood and look after it.
b. Avoid using plastic bags as they are non-biodegradable, instead cany a cloth bag for shopping.
c. Avoid wastage of clean water.
d. Do not let the water tap run while brushing or shaving.
e. Travel by public transport or use car pools.
f. Never uproot wild plants in forest area.
Living Science Biology Class 8 ICSE Solutions