BIOLOGY NCERT SOLUTION SOURCE OF ENERGY OUR ENVIRONMENT MANAGEMENT OF NATURAL RESOURCES

                          source of energy 

                               class x

Question 1:

What is a good source of energy?

Answer 1:

A good source of energy should have the following qualities:

Ø It should be easily available.

Ø It should do a large amount of work (or produce large amount of heat) per unit volume/mass.

Ø It should be easy to store and transport.

Ø It should be economical.

Ø It should cause less environmental pollution.

 Question 2:

What is a good fuel?

Answer 2:

A good fuel produces a large amount of heat on burning, does not produce a lot of smoke and is easily available.

 Question 3:

If you could use any source of energy for heating your food, which one would you use and why?

Answer 3:

We shall use LPG/CNG gas or electricity for heating our food because these are efficient ways of supplying energy. Thermal efficiency of the energy source is large, there is less pollution and the source can be used easily.

  

Question 1:

What are the disadvantages of fossil fuels?

Answer 1:

There are following disadvantages of fossil fuels like coal and petroleum:

Ø Burning of coal or petroleum causes air pollution.

Ø Acidic oxides like oxides of carbon, nitrogen and sulphur are released on burning fossil fuels. These oxides lead to acid rains, which affect our water and soil resources.

Ø Carbon dioxide gas also causes greenhouse effect in atmosphere.

Ø Fossil fuels are non-renewable sources of energy.

 Question 2:

Why are we looking at alternate sources of energy?

Answer 2:

Fossil fuels, which have been traditionally used by human beings as an energy sources, are non-renewable sources of energy. These sources of energy are limited and cannot replenish on their own. They are being consumed at a large rate. If this rate of consumption continues, then the fossil fuels would be exhausted from the Earth. Therefore, we should look for alternate sources of energy.

 Question 3:

How has the traditional use of wind and water energy been modified for our convenience?

Answer 3:

To use energy of flowing water large dams are built in hilly regions to store huge amount of water at a height. The stored water from high level in dam is carried through pipes to the turbine at the bottom of the dam and runs hydropower plant. Similarly, the wind energy is used to generate electricity. For the same purpose, the rotatory motion of windmill is used to tum the turbine of the electric generator.

Question 1:

What kind of mirror – concave, convex or plain – would be best suited for use in a solar cooker? Why?

Answer 1:

A solar cooker uses heat of the sunlight to cook the food. A concave mirror is used in order to reflect and focus sunlight at a particular area. The mirror focuses all the incident sunlight at a point. The temperature at that point increases, thereby cooking and heating the food placed at that particular area.

 Question 2:

What are the limitations of the energy that can be obtained from the oceans?

Answer 2:

Energy from the oceans can be obtained in the form of tidal energy, wave energy and ocean thermal energy. But these energy sources suffer from the following limitations:

Ø There are very few locations where dams to utilise tidal energy can be built.

Ø Cost of installation of power houses is extremely high and efficiency of plants is comparatively small.

Ø Power plants built in oceans or at sea-shores will need high continuous maintenance as chances of corrosion are extremely high.

 Question 3:

What is geothermal energy?

Answer 3:

Geothermal energy is the heat energy present inside earth in certain regions called hot spots. Due to geological changes, molten rocks formed in the deeper hot regions of earth’s crust are pushed upwards and are trapped in hot spots. When underground water comes in contact with the hot spot, steam is generated. This steam is routed through a pipe to a turbine and used to generate electricity.

Question 4:

What are the advantages of nuclear energy?

Answer 4:

The advantages of nuclear energy are as follows:

Ø Large amount of energy is produced per unit mass.

Ø It does not produce smoke. It is a clean energy.

Ø Fission of one atom of uranium produces 10 million times the energy released by burning of one atom of carbon.

Ø Fusion of four hydrogen atoms produces huge amount of energy.

Question 1:

Can any source of energy be pollution-free? Why or why not?

Answer 1:

No source of energy can be pollution-free. It is considered that solar cells are pollution-free. However, even their making causes environmental damage indirectly. Also, in the case of nuclear energy, there is no waste produced after the fusion reactions. However, it is not totally pollution-free. To start the fusion reactions, approximately 107 K temperature is required, which is provided by fission reactions. The wastes released from fission reactions are very hazardous. Hence, no source of energy is pollution-free.

 Question 2:

Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?

Answer 2:

Hydrogen can be considered a cleaner fuel because its burning produces water vapour which is non-polluting. However, due to explosive nature of hydrogen, its storage and transportation is difficult

 Question 1:

Name two energy sources that you would consider to be renewable. Give reasons for your choices.

Answer 1:

Solar energy, wind energy, ocean energy etc., are renewable sources of energy due to the following reasons:

Ø These forms of energy are available in plenty in our natural environment in the form of continuous currents of energy.

Ø These energy sources will not be depleted because their supply is large and extraction of usable energy from these sources is negligible.

 Question 2:

Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.

Answer 2:

Coal and petroleum are two exhaustible sources of energy. These fuels were formed over millions of years ago and there are only limited reserves. If we continue to use them as at present, these reserves will be exhausted very soon.

 Question 1:

What is a good source of energy?

Answer 1:

A good source of energy should have the following qualities:

Ø It should be easily available.

Ø It should do a large amount of work (or produce large amount of heat) per unit volume/mass.

Ø It should be easy to store and transport.

Ø It should be economical.

Ø It should cause less environmental pollution.

  Question 2:

What is a good fuel?

Answer 2:

A good fuel produces a large amount of heat on burning, does not produce a lot of smoke and is easily available.

  Question 3:

If you could use any source of energy for heating your food, which one would you use and why?

Answer 3:

We shall use LPG/CNG gas or electricity for heating our food because these are efficient ways of supplying energy. Thermal efficiency of the energy source is large, there is less pollution and the source can be used easily.

Question 1:

Why are some substances biodegradable and some non-biodegradable?

Answer 1:

Some substances which are degraded and broken down into simpler substances by the microorganisms, are called biodegradable substances.

For example: Cotton, wood, paper, wool, etc.

Substance (mainly man-made) that do not degraded or broken down into simpler substances by the action of enzymes secreted by microorganisms are called non- biodegradable substances.

For example: Plastic, polythene, DDT, etc.

Question 2:

Give  any  two  ways  in  which  biodegradable  substances  would  affect  the environment.

Answer 2:

Ø During decomposition process of biodegradable substances foul smell and some harmful gases are released which make problem for the nearby living person.

Ø During decomposition it provide a breeding ground for mosquitoes, insects and microbes responsible for diseases like cholera, diarrhoea, etc.

Question 3:

Give any two ways in which non-biodegradable substances would affect the environment.

Answer 3:

Ø Chemicals like BHC and DDT induce carcinoma (muscle cancer) and growth of tumours.

Ø Handling of waste materials may cause skin, respiratory and intestinal infections.

Ø Non-biodegradable substances do not decompose easily so it produces land and water pollution.

            

                     our environment 

 

Question 4:

What will happen if we kill all the organisms in one trophic level?

Answer 4:

If we kill all the organisms in one trophic level, the transfer of food energy to the next trophic level will stop. This will cause a break in the food chain resulting in ecosystem imbalance. As a result, the organisms of the higher trophic level will also die, while the individuals of the lower trophic level will exhibit enormous growth in their population. Both the conditions will result in ecological upset.

  

Question 5:

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 5:

Yes, the impact of removing all organisms in a trophic level will be different for different trophic levels. If all the producers are killed, it will cause death or migration of the primary consumers in the ecosystem. In the absence of producers, subsequent level of consumers will also be affected. But if primary consumers are removed, organisms of higher trophic level will die, while those of lower level (producers) show exponential growth much beyond the carrying capacity of the environment. Removal of the organisms in a trophic level will upset the whole ecosystem as all categories of organisms are linked through food chain. The survival of organisms of one trophic level depends on the existence of the members of other trophic level.

Question 6:

What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer 6:

Progressive increase in the concentration of non-biodegradable substances in a food chain is called biological magnification. The level of these harmful substances will go on increasing from one trophic level to the next. When certain harmful substances enter the food chain at the level of primary producers,-they get concentrated many times at each subsequent trophic level.

 Question 7:

What are the problems caused by the non-biodegradable wastes that we generate?

Answer 7:

Non-biodegradable wastes cannot be broken-down into simpler substances. Their volume keeps on increasing creating the problem of their safe disposal. Some of the non-biodegradable wastes like heavy metals and pesticides enter into the food chain and increases in the upper trophic levels. Non-biodegradable wastes reduce the soil fertility by changing the natural pH balance.

 Question 8:

If all the waste we generate is biodegradable, will this have no impact on the environment?

Answer 8:

Biodegradable wastes are decomposed by microorganisms into simpler substances themselves and provide raw materials for producers, but they also have adverse effects on the environment:

Ø Slow decomposition of biodegradable waste will result in the release of foul smell and harmful gases. When inhaled by human beings, they may cause irritation, nausea, giddiness, etc.

Ø Decomposing waste provides breeding ground for some harmful organisms. Abundance of harmful microorganisms may cause diseases in animals, plants and human beings.

Ø Increase in the number of microorganisms in aquatic medium will- cause oxygen deficiency in waterbodies.

Question 9:

Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Answer 9:

Ozone layer is a protective shield around the earth. It prevents harmful ultraviolet radiation of the sun from reaching the earth. Air pollutants, like chlorofluorocarbons (CFCs), are causing depletion of ozone layer. This is allowing greater amount of UV radiation to reach the earth. UV radiation

upset the ecosystem by affecting photosynthesis in plants, destroying planktons and decomposers. In human beings, UV radiation may cause skin cancer, cataract of eyes and damage to immune system. Several developed as well as developing nations of the world have agreed to sign and obey the directions of TINEP (United Nations Environment Programme) to freeze the production of CFCs or to 1imit their production to some extent.

Question 1:

What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

Answer 1:

The various steps in food chain at which transfer of food energy takes place are called trophic levels.

Example: Food chain operating in a grassland.

Grass → Insects → Frogs → Snakes

1.   Grass       → 1st trophic level

2.   Insects     → 2nd trophic level

3.   Frogs       → 3rd trophic level

4.   Birds       → 4th trophic level

Question 2:

What is the role of decomposers in the ecosystem?

Answer 2:

Decomposers are microorganisms that act on dead and decaying bodies of producers and consumers and break them into simple inorganic compounds. They absorb some of the substances and release the rest into the environment to be recycled and to be used in future by producers. Thus, decomposers have a key role in the cycling of material in the biosphere and provide the raw materials to the producers. So in this way they make the soil fertile.

Question 1:

What is ozone and how does it affect any ecosystem?

Answer 1:

Ozone (O3) is a molecule formed by three atoms of oxygen. Ozone, is a deadly poison. However, at the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun.

This radiation is highly damaging to organisms, for example, it is known to cause skin cancer, cataract and damage the immune system in human beings. It also destroys plants and reduces photosynthesis process.

Question 2:

How can you help in reducing the problem of waste disposal? Give any two methods.

Answer 2:

Ø By minimising the use of disposal items and promoting the use of recycled articles.

Ø Separating biodegradable and non-biodegradable waste before dumping them.

Ø Recycling the non-biodegradable waste material.

                       management of natural resources 

 Question 4:

How can you as an individual contribute or make a difference to the management of (a) forests and wildlife, (b) water resources and (c) coal and petroleum?

Answer 4:

(a)  Forests and Wildlife

Ø Take part in community activities with focus on conserving forests and wildlife.

Ø As a tourist follow all principles of conservation.

Ø Help organisations engaged in conservation of forests and wildlife

(b)  Water Resources

Ø Save water in domestic use.

Ø Install a system for rainwater harvesting.

(c)  Coal and Petroleum

Ø Save electricity whenever required.

Ø Install electric gadgets that use less power.

Ø Use public transport.

Question 5:

What can you as an individual do to reduce your consumption of the various natural resources?

Answer 5:

Ø Save electricity.

Ø Do not waste food.

Ø Save water.

Ø Use cooking gas instead of wood for cooking.

Ø Observe the principle of three R's (Reduce, Recycle and Reuse).

  Question 6:

List five things you have done over the last one week to –

(a)  conserve our natural resources.

(b)  increase the pressure on our natural resources.

Answer 6:

(a)  Five things done to conserve natural resources are:

Ø Used energy efficient electrical appliances.

Ø Used only as much of electricity as was required.

Ø Kept the water tap closed while brushing the teeth.

Ø Convinced mother to cook the food in a solar cooker.

Ø Used public transport for school instead of parent's car.

(b)  Five things done to increase the pressure on natural resources:

Ø Went to school on a bike instead of cycle.

Ø Forgot to switch off fan while going out

Ø Wasted food.

Ø Used more paper than required for printing on computer.

Ø Wastage of water resource.

 Question 7:

On the basis of the issues raised in this chapter, what changes would you incorporate in your life-style in a move towards a sustainable use of our resources?

Answer 7:

Three methods of producing magnetic field are as follows:

Ø Will move in public transport system to conserve petrol.

Ø Instead of coal or natural gas, will prefer to use solar energy for cooking.

Ø Wilt obey rationalised husbanding of all renewable resources.

Ø Take care not to pollute the environment with waste.

Ø Should realise that we are living in a community and are not alone.

Question 1:

What changes can you make in your habits  to become  more environment- friendly?

Answer 1:

Ø Stop wastage of water.

Ø Switching off unnecessary lights and fans.

Ø Don't waste food. Take as much as you require.

Ø Walking down or use cycle for going to nearby market instead of using vehicle.

Ø Separate wastes into recyclable and non-recyclable.

Ø Reuse carry bags, packing materials, plastic containers and other reusable material.

  Question 2:

What would be the advantages of exploiting resources with short-term aims?

Answer 2:

The  advantage  of  exploiting  resources  with  short  term  aim  is  to  meet  the immediate basic human needs.

 Question 3:

How would these advantages differ from the advantages of using a long-term perspective in managing our resources?

Answer 3:

Short term exploitation of natural resources fulfil the current demand. It is beneficial for the present generation only, whereas, management of resources with long term perspective is aimed to fulfil the needs of future generations. Long term use of resources can be achieved through its sustainable use.

Question 4:

Why do you think there should be equitable distribution of resources? What forces would be working against an equitable distribution of our resources?

Answer 4:

Equitable distribution of resources will ensure benefits to all the sections of the society rich as well as poor. This is necessary for the growth and development of a country. Money force is the main factor which is working against an equitable distribution of resources as rich people and rich nations try to encroach upon the share of the poor people or poor nations.

Question 1:

Why should we conserve forests and wildlife?

Answer 1:

Wildlife and forests should be conserved for the following reasons:

Ø To prevent loss of ecological stability

Ø To preserve biodiversity

Ø To obtain medicine, wood, fruits, etc., products in a sustainable manner

Ø To promote social and economic growth.

 Question 2:

Suggest some approaches towards the conservation of forests.

Answer 2:

Ø Forests can be conserved by:

Ø Preventing the process of deforestation

Ø Preventing cattle ranching in the forest

Ø Promoting afforestation

Ø Preventing the soil erosion

Ø Mobilising people's active cooperation

Question 1:

Find out about the traditional systems of water harvesting/management in your region.

Answer 1:

The traditional systems of water harvesting/management in different region are different. The system of water harvesting in our region are ponds, pits, lakes and other reservoirs where rainwater is stored.

  

 Question 2:

Compare the above system with the probable systems in hilly/mountainous areas or plains or plateau regions.

Answer 2:

In mountainous areas instead of traditional water harvesting system, check dams are built across the seasonally flooded gullies. In this system running water is stored and diverted to the required places such water does not remain stagnant for long, hence there is less chance of it becoming polluted like that of pond water.

 Question 3:

Find out the source of water in your region/locality. Is water from this source available to all people living in that area?

Answer 3:

In our locality water is available from the following sources:

Ø Through pipe line supply by municipal corporation department to the houses.

Ø People also obtain water from hand pumps installed nearby.