Science Answer the questions.[Bio-3M]

Some methods to prevent soil erosion are:

• Stopping deforestation and planting more and more trees so that roots bind to the soil and hold the soil together, thus preventing it from being eroded away.
• Making windbreakers from trees on the land to prevent erosion of soil by wind blowing across it.

Nitrogen fixation is the process of fixing free nitrogen into compounds.

This takes place by the following means:

• Certain blue-green algae and bacteria can fix atmospheric nitrogen.
• Nitrogen fixing bacteria found in the nodules of roots of legumes such as gram, bean, pulses etc. fix atmospheric nitrogen into nitrogen containing compounds.
• Lightning also helps in the formation of nitrogen containing compounds.

Lead compounds are added to petrol so that petrol burns smoothly in vehicles. The harmful effect of these lead compounds in petrol is that toxic lead compounds are released through the silencer/ exhaust pipes of vehicles. Inhalation of these compounds causes diseases like brain damage, anaemia etc.

Air contains oxygen. The latter is needed by most organisms and plants for all respiration to go on. It is therefore rightly called the breath of life. Air is an inexhaustible natural resource. In a world without air, there would be no plant or animal life, no winds, clouds or rain, no fires and no protection against harmful solar radiations. This is because the atmosphere covers the Earth, like a blanket. Air is a bad conductor of heat. The atmosphere keeps the average temperature of the Earth fairly steady during the day and even during the course of whole year. The atmosphere prevents the sudden increase in temperature during the daylight hours. And at night, atmosphere slows down the escape of heat into outer space.

Unequal heating of landmasses causes the warm/ heated air to rise up. As the warm air rises up it expands and cools down. Warm air can hold water vapour well but cool air is incapable of holding water vapour. So the water vapour condenses on the dust particles already present in air and a tiny droplet is formed around the dust particles thus forming clouds. Clouds are formed in the earth’s Troposphere where weather phenomenon occurs.

In 1985, Farmen found that ozone layer had thinned out over Antarctica. It was called an ozone hole.

Effects of widening of ozone hole are:

• Skin cancer.
• Damage of eyes.
• Damage of immune system.
• Decreased crop yields.

The harmful effects of ozone depletion are:

• More skin cancer in humans due to ultraviolet radiations which will easily reach the skin cells through stratosphere if ozone layer depletes.
• UV radiations would also damage parts of eyes thus causing cataracts, blindness and other diseases.
• Immuno suppression. UV radiations could damage the immune system.

The process of evaporation of water and falling on the land as rain and later flowing back into the sea via rivers is known as the water-cycle. The other name for water cycle is Hydrological cycle.

The removal and transportation of the top layer of soil from its original position to another place, under the effect of strong winds and fast running rainwater is called soil erosion.

Soil erosion can be prevented by:

• Intensive cropping.
• Sowing grasses and planting xerophytes.
• Terrace farming.

Biological magnification is the phenomenon where certain pollutants get accumulated in tissues in increasing concentration along the food chain. It is a process where chemicals or pesticides enter the plants through soil and are passed on through the food chain. Highest amount of chemicals get accumulated in the organism at top of a food chain.

Ozone shield or ozone layer is a layer that protects earth from the harmful ultraviolet radiations coming from the sun thereby protecting us from serious ailments and thus acting as a shield. Ozone molecules form when a single O atm reacts with oxygen O₂ molecule.

Chlorine containing compounds are major reason for the corrosion of ozone layer. Chlorofluorocarbons and certain other ozone depleting substances that contain chlorine and/or bromine are responsible for depletion of ozone layer. CFCs are made of chlorine. One single atom of chlorine destroys 1000 molecules of ozone.

The conversion of atmospheric nitrogen into ammonia NH₃ is known as nitrogen fixation. Bacteria that perform nitrogen fixation are either free living or they may form symbiotic associations with other organisms. Eg- protozoans, termites.

Methane burp refers to release of methane in large quantities. Usually methane burp occurs in ruminants like Cows. Methane hydrates/ methane clatharate have large amount of methane trapped in them. When they melt, a large amount of methane is released known as methane burp.

Humus is the dark organic matter that forms in the soil when plant and animal matter decays. It contains many useful nutrients for healthy soil.

Functions of humus in soil are:

• Humus increases the fertility of soil.
• It also helps soil absorb and retain moisture.
• Humus also promotes the formation of good soil structure.
• It supports microbial activity in soil, through which roots absorb nutrients.

Global warming: An increase in the carbon dioxide content in the atmosphere leads to global warming. The global warming is quite dangerous as it tends to melt polar ice and glaciers existing on mountains, rise in the water level of the oceans and submerge several coastal areas and islands. This could further lead to floods.

Chemicals, pesticides and heavy metals move up the food chain, get into aquatic bodies and are eaten by organisms like fishes which are in turn eaten by hawks/ eagles. This process where the chemical enters the food chain and increase in concentration with increasing trophic level is known as biological magnification. Heavy metals that result in diseases when magnified are mercury, cadmium, copper, lead etc.

An increase in content of harmful substances like oxides of nitrogen and suphur from fossil fuels, hydrocarbons, etc in air is called air pollution. Basically, icrease of any unwanted substance in the air is air pollution.

Air pollution may be caused by burning of fossil fuels like coal and petroleum that release nitrogen and sulphur. These nitrogen and sulphur molecules form oxides of nitrogen and sulphur in air and later fall as acid rain too. Smog from combustion of fossil fuels also a cause of air pollution.

Effects of air pollution can be very lethal. When polluted air is breathed it results in allergies, cancer, bronchitis and other heart diseases.

1. Hygroscopic water is the film of water tightly held by the soil particles and it is not available to the plant.
2. Combined water is the amount of water that is present in the chemical compounds, which are present in the particles of soil. Combined water is also not available to the plant.

Biological weathering refers to weathering by living organisms. Disintegration of rocks by activities of living organisms like plants grow in the cracks of rocks, break the rocks and withers them.

• Lichens that grow on rock surface release chemical substances that cause rock to powder down and form thin layers of soil.
• Small plants like moss live on rock surface and cause the rock to break down.

The dangers of global warming are:

• It leads to the melting of polar ice caps and rise in sea level.
• Increase in the temperature of the earth due to green house effect will cause a change in weather and precipitation patterns on the earth.
• It leads to methane burp which is caused by the melting of methane hydrates in permafrost and on sea floor.

Natural resources refer to those resources that occur naturally without the interference of mankind. These are resources available in abudance for mankind. They may be renewable and non-renewable.

• Renewable resources are those that can be replenished. For eg- air, water, wind, sun energy.
• Non-renewable resources are those that cannot be replenished once exhausted. For eg- minerals, fossils and soil.

Natural resources are raw materials or substances that are found naturally in nature and have no interference of mankind. These resources are benefical to mankind.

They are of two types:

1. Renewable resources are those that can be regenerated, replaced, recovered and are constantly available. Eg: water, wind and sun are renewable resources.
2. Non-renewable resources are those that cannot be replenished once exhausted. Eg: minerals and fossil fuels are non-renewable resources.

1. Asbestosis occurs due to inhalation of asbestos dust that is used in making ceilings. Asbestos is also a cancer causing agent.
2. Silicosis occurs due to inhalation of free silica SiO₂ while working in ceramic industries.
3. Byssinosis caused by inhalation of cotton fibres, is a respiratory disease wherein pulmonary ways narrow resulting in bronchitis.

Capillary water is the water present in soil that can be absorbed by plants. This water is present in the soil after gravitational water has been removed. Capillary water forms a film around the soil grains and is pulled up by roots of plants and thus absorbed.

Fertilizers like phosphates, phosphorous and nitrogen result in algal growth in water bodies. Eutrophication is a phenomenon wherein excess of nutrients, chemicals in water body result in algal growth which stops the sunlight from reaching to the aquatic plants due to which plants do not produce oxygen and the aquatic animals die due to lack of it. Thus, eutrophication reduces the oxygen content (biological oxygen demand increases) due to which life forms are affected and they die. Water quality is drastically reduced as the toxicity is increased.

1. Bronchitis characterized by the inflammation and swelling of the air passages between nose to lungs and throat to lungs.
2. Immune system defects, it occurs due to constant breathing in polluted air.
3. Pneumonia an infection of lungs caused by breathing a flying bacteria.
4. Asthma attacks because of inhaling various poisonous gases and constant suffocation owing to polluted air.

1. Inexhaustible resource: These are resources that are available in abundance and cannot be exhausted ever. Eg- Air.

2. Renewable exhaustible resource: These are those resources that may get exhausted by excessive use but can be re-obtained in nature. Eg- Forests; they might disappear one day if deforestation continues but planting seeds can regenerate them.

3. Non-renewable exhaustible resource: These resources once exhausted cannot be replenished. Eg- Fossil fuels, minerals.

Three water pollutants are:

1. Waste from farms i.e. fertilizers and pesticides. The chemicals in them pollute the water.
2. Industries release their waste products directly into the rivers thus degrading water quality.
3. Disease causing agents like bacteria, viruses and protozoans enter the sewage system. This sewage is ultimately discharged into water bodies like sea.

1. Use of refrigerators by humans is one such activity. Refrigerators use chlorofluorocarbons (CFCs). These CFCs have chlorine molecule that have the capability to destroy ozone molecules.
2. Emission of halogen source gas like bromine from human activities cause depletion of ozone in stratosphere.
3. Air conditioners too use chlorofluorocarbons. CFCs are ozone depleting substances. When they are emitted from air conditioners they adeplete ozone layer.

1. Minamata disease is a disease that first occurred in people of Japan. The water bodies polluted with high levels of mercury were consumed by people which caused toxicity in their bodies and lead to this disease. The symptoms noticed were-ataxia, numbness in the hands and feet, muscular weakness, and damage to hearing and speech.
2. Itai-Itai is a disease that also occurred in people of Japan in 1912 by consuming water polluted with high levels of Cadmium. The disease is characterized by severe pain in joints.

Main sources of water pollution are:

• Waste from farms i.e. fertilizers and pesticides. The chemicals in them pollute the water.
• Industries release their waste products directly into the rivers thus degrading water quality. Industries also contribute to thermal pollution as the coolants discharged by them causes a change in the average temperature of water, thereby degrading the water quality.
• Disease causing agents like bacteria, viruses and protozoans enter the sewage system. This sewage is ultimately discharged into water bodies like sea.

Sulphur and nitric oxides present in acid rain corrode the marble, limestone, sandstone. When acid rain falls on them it breaks them down into fine powdery substances which is later washed away by rain. Taj mahal that is made of marble is being corroded by acid rain as the acid rects with the marbles.

When the water bodies get heated by solar radiations during the day, a large amount of water evaporates and goes in the air. The air carrying water vapours also gets heated. This hot air rises up carrying water vapours with it. As the air rises, it expands and cools. This cooling causes the water vapour in the air to condense as tiny droplets which slowly grow bigger by the condensation of more water droplets and forms clouds. When the droplets have grown big and heavy, they fall down in the form of rain.

Nitrogen exists as free nitrogen in the atmosphere. This free nitrogen is fixed into compounds of ammonia and nitrates. Most of the organisms cannot utilise nitrogen as molecular nitrogen. Plants take compounds containing nitrogen from the soil. From plants nitrogen passes into the food web. Decay of dead plants, animals and excreta causes return of nitrogen compounds to the soil. Denitrifying bacteria cause liberation of free nitrogen in the atmosphere.

Biological weathering: Is done by living organisms such as lichens and bryophytes. Lichens growing on rock surface extract minerals from the rocks. This creates small crevices at places where a thin layer of soil builds up. Mosses grow over these crevices causing deepening of crevices and results in the buildup of more soil inside them. The roots of short lived herbs also passes into them and the cracks gradually widen and cause slow fragmentation and eventually pulverisation of rocks.

The movement of air from one region to another creates winds. When the solar radiations fall on the earth, some are absorbed and majority of these are reflected back by the land and water bodies. These reflected solar radiations heat up the atmosphere from below. As a result convection currents are set up in the air but since land gets heated faster than the water, the air above the land gets heated faster than the air over water bodies. During the day the air above the land gets heated and starts rising, creating a region of low pressure below. As a result the air over the sea moves into this region of low pressure and forms the wind.

When the water bodies get heated by solar radiations during the day, a large amount of water evaporates and goes in the air. The air carrying water vapours also gets heated. This hot air rises up carrying water vapours with it. As the air rises it expands and cools. This cooling causes the water vapours in the air to condense as tiny droplets which slowly grow bigger by the condensation of more water droplets and forms clouds.

CFC's are chlorofluoro carbons which deplete the ozone layer. They are rich in chlorine, fluorine and carbon.

Effects of chlorofluoro carbons:

1. Skin cancer.
2. Damage of eyes.
3. Damage of immune system.
4. Decreased crop yields.

1. Soil is the major resource require for plant to grow and produce food.
2. Without soil no plants will exist and animals will die due to starvation.
3. Soil holds the plants and prevents them from being eroded by environmental calamities.
4. Soil is a habitat to many insects and microorganisms.

A-Food molecules: Photosynthesis produces food molecules i.e. glucose.

B¾ Photosynthesis: CO₂ is used in photosynthesis.

C¾ Respiration: Respiration releases CO₂ so C is respiration.

Water is one of the most important physical components which is essential for the survival of live on earth. Ocean is the biggest storehouse of water. Water on evaporation forms clouds and which after condensation falls down as rain. After rain, it passes through rivers and gets collected again in the ocean. The circulation of water in this manner is called water cycle. The cycle is also performed through living beings in the processes like absorption and transpiration of water by plants and drinking by animals. Animals lose water during respiration and evaporation, perspiration and excretion.

1. Acid rain: Burning of fossil fuels release oxides of Sulphur, and nitrogen into the air. Nitrogen gets oxidized and forms its oxides. These chemicals fall along with rainwater on earth thus causing acid rain.

2. Global Warming: Global warming refers to an increase in earth’s temperature due to effect of greenhouse gases like carbon dioxide and methane. These gases traps the infrared rays and doesn’t let them escape out from the earth’s surface which results in an increase in earth’s temperature as all the heat gets trapped in. This causes global warming.

1. Eutrophication is nutrient enrichment (i.e., addition of nitrates and phosphates) of water body that results in the growth of aquatic plants, especially algae causing colouration of water known as algal bloom. It leads to depletion of dissolved oxygen in water resulting in killing of aquatic organisms (e.g., fish).
2. The phenomenon of increase in the concentration of harmful non-biodegradable substances in the body of living organisms at each trophic level of the food chain is called biomagnification. Two heavy metals which are biomagnified are mercury and cadmium. Due to biomagnification fish-eating predatory birds such as kingfishers and loon become poisoned.

Air pollution is of two main types:

1. Natural: It is the pollution caused by nature. It includes forest fires, dust storms, pollen etc.

2. Human made: It is the pollution caused by human activities. It includes burning of fossil fuels in industries, vehicles and thermoelectric plants, gaseous emission from industries, mining, processing and stone crushing.

The factors that influence the movement of air are:

1. Uneven heating of land at different parts of the earth.
2. Differences in heating and cooling of land and water bodies.
3. Vapourisation and condensation of water vapours.
4. Rotation of earth.
5. Presence of high mountain ranges in the paths of wind.
6. Difference in topography over which the wind passes.
    

Water is replenished in the seas by the means of water or hydrological cycle. We know that the oceans or seas are the largest global reservoir of water. Water evaporates from these reservoirs in large quantities and helps in the formation of clouds. The winds blows the clouds over to the lands where after getting cooled enough, the water in clouds falls on the earth or directly over the seas as rain and hail. Some water from rain and melting snow soaks into the ground, but most of it flows in rivers and returns directly to the seas.

Humification: The process of formation of humus during decomposition of organic material in soils is known as humification.

Mineralization: The decomposition or oxidation of the chemical compounds in organic matter into forms that are accessible by plants is known as mineralization.

Carbon is an important constituent of organic compounds found in all living beings in the form of carbohydrates, fats, proteins and nucleic acids. Carbon is trapped in the surrounding air and water in the form of carbon dioxide. The consumers devour the organic carbon compounds that producers manufacture. Through respiration, both consumers and producers return carbon to the non-living environment in the form of carbon dioxide. Some carbon accumulates in wood for many years and is eventually returned to the atmosphere by fires or through consumption and respiration by fungi, bacteria and other detrivores. Volcanic eruption also releases carbon dioxide to the atmosphere.