12th Class Biology Chapter 13 Man and His Environment Short Questions Answer

This may lead to rapid melting of ice caps and glaciers bringing floods and path of major air and ocean currents drastically affecting the global weather conditions.

The decline in thickness of the ozone layer is caused by increasing level of chlorofluorocarbon which contains chlorine fluorine and carbon.The chlorine released destroys the ozone molecule in ozone layer.

They are never depleted and are recycled in the nature Air, water ,food,land, forests and wild life are renewable recurses.

Some main types of pollution are: Air pollution or atmospheric pollution.

Trees are called environmental buffers as they intercept heavy rainfall and release the water steadily and slowly to soil beneath and to the streams and river that strats in or flows through them the tree roots hold the soil in place.

They are called fossil fuels because they are the remains of plants and animals of past which became buried due to environmental hazards and were fossilized in deeper layers of earth and sea.

The kinetic energy of falling water is harnessed to turn turbines fixed at the base of dams. The turning turbines will then drive generator to produce electricity which is known as then drive generator to produce electricity which is known as hydroelectric power or electricity.

Soil plays following vital roles: i) Supporting life on land plants depends directly on soil to be anchored firmly. A large number of organisms are living on land. ii) Soil provides water organic and inorganic nutrients to the plants. iii) Soil is used for cultivation house building industrialization and road making.

i) Untreated Sewag untreated sewage must not be emptied into rivers.Sewage tains harmful bacteria and poisonous chemicals.Certain bacteria cause diseases like typhoid adn cholera when they get into the human intestine.ii) Oil and detergent: Oil pollution of the sea has become a familiar event killing life in water and life  dependent on aquatic producers.

The steady internal state of homeostasis is known as normal health.Where as disease may refer to the departure from normal or steady internal state of homeostasis through structural or functional of the body.

The basic constituents of soil are soil particles soil water organic and inorganic matter and soil organisms.

Each nuclear power station only can last for about 30 years and trict safety measures have to be taken to avoid radiation pollution.

Ozone is a layer of atmosphere extending from 10- 50 kilometres above earth which filters most of UV radiation and protects us from these harmful rays of the sun.In pure form ozone is bluish explosive and highly poisonous gas.Ozone molecule is mage up of three oxygen atoms bounded together.

These resources are exhaustible and once consume3d cannot be replaced.They include various metals non-metallic minerals and fossil fuels.

Clearnace of vast areas of forest for lumber planting subsistence crops or grazing cattle is called as deforestation.While establisment of new forest where no forests existed previously is called a-forestation.

Biodiversity refers to the total number of different species within an ecosystem and resulting complexity of interactions among them.

Contamination of streams lakes underground water bays or oceans by substances harmful to living things is called water pollution.

The capacity of certain gases in the atmosphere to trap heat emitted from the Earth’s surface thereby indulating and warming the Earth is called greenhouse effect.

Acid Rain is a form of air pollution in which airborne acids produced by electric utility plants and other sources fall to Earth in distant regions.The corrosive nature of acid rain causes widespread damage to the environment.

Vast quantities of algae feed and reproduce on the nutrients causing the water to trun green.This is called algal bloom.

Enviroment is a treasure of all types of resources essential to maintain life on earth.Environment is a direct or indirect source for food shelter clothing fuel etc.For humans. Therefore it must be protected and conserved.

This is the natural process of excessive enrichment of water with nutrients such as nitrates and phosphates.

Wild life refers to all non-cultivated plants and non-domesticated animals.

In nature there is no such thing as waste dead materials decay and become food for other living things.This food is consumed or decays and become food again.This is the nutrient cycle.

The balance in the nutrient cycle can be upset when: i) Not enough food is produced. ii) Too much is consumed. iii) Decayed nutrients are not returned to the ground.

It is several kilometres thick blanket of atmosphere surrounding the earth.Air is very important natural resource.

It consists of nitrogen(79%) oxygen(20%) carbon dioxide (0.03%) and traces of inert gases called noble gases.

Green house effects and acid rains are global effects of the pollution.

Main uses of water are: i) Domestic/irrigation use 10% ii) Industrial utilization 90%.

Soil can be defined as the upper layer of earth’s crust.

Game animals and plants have been major source of food for humans.Wild life play very important role in food chain.Without these the food chain can be disturbed to such an extent that it will be very difficult to maintain the balance.

The resources which are vas and can not finished are called inexhaustible resources.These include solar energy falling water wind ocean thermal gradients waves tides currents geothermal and biomass.

The resources which are likely to be depleted are called exhaustible resources.These include fossil fuels like coal oil and natural gas.

Tides are mainly caused by the gravitational pull of the moon to a lesser extent and the gravitational pull of sun on the water in sea and oceans.

In nuclear power station large amount of heat is generated by nuclear fission which takes place in a nuclear reactor.The heat energy is then used to convert water into steam which drives steam turbines for generating electricity.

The natural heat energy trapped underground is called geothermal energy.

i) Sulphur emission. ii) Release of polluted water. iii) Disposal of organic sludge produced in bioconversion.

In oceans especially in tropical regions temperature of surface water is about 25ᵒC and that at the depth of few hundred meters only 5ᵒC.

Develop and use energy efficient machines engines and manufacturing processes.Switch off lights and electrical appliances when they are not in use.

Reforestation is the replacement of deforestation i.e.trees may be replanted.

Regions with high rain fall are suitable for trees growth.They are called Environmental buffers they intercept heavy rainfall and release the water steadily and slowly.

Any thing produced by humans which is or may be harmful to human life and other living organisms is called environmental pollution.

Harmful substance such as sulphur dioxide carbon monoxide and oxide of nitrogen lead compounds and chlorofluorocarbons are known as air pollutants.

If more ultrabiolet rays reach the earth’s surface they will effect all life on earth by increasing temperature increase in skin cancers and cataracts in human.It can also affect crops plants trees and even marine plankton and distort weather patterns.

Over urbanization deforestation industrialization are the causes of green house effect which is gradually increasing temperature on earth now being termed as global warming.

1) Acid rain damages life in lakes farms and forests. 2) Plants poisoned and deprived of nutrients become weak and vulnerable to infection and insect attack.

Human activity is the main cause to pollute canais streams lakes rivers and even seawater.

A pesticide is a chemical which destroys agricultural pests or competitors.The examples are insecticide fungicide and herbicide.

An insecticide is a chemical that kills the insects while fungicide kills the parasitic tungi and herbicide kills the weeds.

These are the chemical substances used to add additional nutrient in soil to increase the fertility.

Man adopted agriculture about 10,000 years ago.

The human beings depend on the environment directly as well as indirectly for food, shelter clothing, fuel and other necessities of life.

These are the air, water, food, land, forests, fish and wildlife.

These are various metals, non-metallic minerals and fossil fuels such as coal, oil and natural gas.

The air consists of about 79% nitrogen, 20% oxygen. 0.03% carbon dioxide, traces of inert (noble) gases and varying amount of water vapours.

These are carbon monoxide, hydrocarbons and oxides of nitrogen and sulphur.

These are greenhouse effect and acid rains.

The water comprises about 70% to 90% of the body weight of animals and plants.

The fossil fuels meet 95% of our daily energy needs.

The electric power (electricity) generated by the energy of falling water is known as hydroelectric power.

The tides are caused due to a lesser gravitational pull of the moon and higher of the sun on the water in the seas and oceans.

The power of rising and falling tides is called as the tidal power.

The air in motion is called wind.

The windmills (wind turbines) harness wind energy to drive generators, which produce electricity.

Nuclear (atomic) energy is obtained from nuclear fuel by the process of nuclear fission which takes place in a nuclear reactor.

It is about thirty years.

The natural heat energy trapped underground is called geothermal energy. It comes up to earth’s surface as heat in the form of hot water of steam.

The geothermal energy is frequently available in New Zealand and Ice Land.

The study of human populations and the factors that affect them is called demography.

It was 32.5 million people.

The ozone layer has developed a hole over the Antarctica.

These rays affect all life on earth by increasing temperature, causing increase in sin cancer and cataract cases in human beings. They also affect crops, plants, trees and even marine plankton.

The thick layer of carbon dioxide in the atmosphere, like the glass of a greenhouse, allows the sun energy to reach the earth and heat it but it prevents the re-radiation of this absorbed heat back into the space. This causes increased heating of the earth’s atmosphere, a phenomenon known as greenhouse effect.

It may be global warming.

Increased heating of earth due to greenhouse effect can cause rapid melting of ice caps and glaciers bringing more floods and affecting global weather conditions.

The sources of sulphur dioxide in the air are power stations and fossil fuels. Its harmful effects are acid rains, breathing disorders and lung cancer.

These are scurvy, beriberi, anaemia, goiter and Kwashiorkor.

These are osteoarthritis and arteriosclerosis.

Diphtheria, malaria, smallpox, tuberculosis, cholera, gonorrhea and AIDS are some parasitic diseases of man.

The names of these diseases are diabetes mellitus, cretinism and goiter.