Science Answer the questions.[Bio-2M]

When fossil fuels such as coal and petroleum products are burnt, they produce oxides of nitrogen and sulphur. On dissolving in rain these oxides form nitric acid and sulphuric acid respectively. This causes acid rain. These acids wash down into the soil and make it highly acidic, thus, affecting the growth of plants and ultimately the forest growth. It also affects the surface of buildings by eroding the stone and brick works.

Life is not possible on Mars and Venus because these planets have 95-97% of carbon dioxide and no oxygen to sustain life.

Lead compound is added to petrol to ensure smooth burning of petrol in the vehicles. Lead compounds in petrol are harmful because the exhaust pipes of the vehicles release these toxic lead compounds whose inhalation leads to diseases like anemia, brain damage, and may even cause death.

2.5-2.75% of water on earth is fresh water. The major part of this fresh water is present in glaciers, ice and snow (1.75-2%), 0.5-0.75% as fresh groundwater and about 0.01% as surface water in lakes and rivers.

Non-biodegradable substances are those that cannot be broken down or decayed by microorganisms into its base compounds or compounds that are safe for the environment. Plastic and metal products are non biodegradable substances.

Topsoil is the uppermost layer of soil, having the maximum concentration of organic matter and microorganisms & supporting the earth’s diversity.

Thermal pollution is defined as change in average temperature of water that results in degradation of water quality. Industries use water as coolants in power plants thus causing thermal pollution.

The major reasons for increase in concentration of carbon dioxide in the atmosphere are burning of fossil fuels and cutting down of trees. Fossil fuels like coal and petroleum when burned, they release carbon dioxide. Use of carbon dioxide present in the atmosphere also decreases when trees don’t are cut down thereby constantly helping in increasing the carbon dioxide content in the atmosphere.

Terracing refers to cutting plane piece of land into several coninous platforms to perform effective farming. Terracing slows down water flow and thus prevents soil erosion.

Soil pollution is defined as contamination of soil with toxic chemicals, pollutants, fertilizers and pesticides that make the soil unfit for plant growth and degrade its quality.

Paedogenesis is reproduction by young or larval animals which retain its larval features, on rocks. It is the process of formation of soil from rocky crust of earth’s surface.

Ozone layer or ozone umbrella is a region in the earth, stratosphere that absorbs Ultraviolet radiations coming from the sun and stops them from reaching living organisms on earth, thus preventing living organisms from a large number of diseases.

Ozone hole is a part of ozone layer that has been depleted by ozone depleting substances in the atmosphere. It is found over Antarctica during winters. Ozone hole results in passage of UV radiations into earth’s surface thus causing diseases in people on earth.

Ozone depleting substances are those substances that contain chlorine and/ or bromine. These substances destroy the ozone layer. One single atom of chlorine destroys 1000 molecules of ozone.

Process of formation of humus during decomposition of organic material in soils is known as humification.

A greenhouse is a glass house where plants, flowers and vegetables are grown. These greenhouses warm up during daytime due to solar radiations thereby heating plants and soil. This heat escapes throughout the night.

Greenhouse effect is a phenomenon that heats the earth’s surface. The greenhouse gases prevent infrared dilations from escaping the earth which results in heating of the earth’s surface.

A windbreak is a shelterbelt made of rows of trees planted in a manner to provide shelter from wind and protect soil from erosion.

The loss or removal of nitrogen usually bu escape into the air from soil is known as denitrification.

Climate is the average weather of an area. It represents the general pattern of atmospheric or weather conditions, seasonal variations and weather extremes, in a region over an extended period, say 50 years or 100 years. For example, desert areas have a hot climate whereas snowbound mountains have a cold climate.

The atmosphere is a division of 3 spheres of earth, Lithosphere, hydrosphere and atmosphere. Atmosphere surrounds the earth and provides conditions that allow life to sustain on earth. There are 4 major divisions of atmosphere- Stratosphere, Troposphere, Mesosphere and Thermosphere.

When increased organic waste enters the water bodies it serves as a food to microorganisms, thereby increasing the number of these microorganisms in the water bodies which need more and more dissolved oxygen to utilize for their metabolism. This results in an increase in the biological oxygen demand in water body.

Unequal heating of landmass and water bodies by sun’s heat generate air movement and as a result wind blows. When the air around landmass gets heated, it becomes lighter and rises up creating a region of low pressure. Air from high pressure region escapes to the low pressure region thus generating wind currents.

Effects of air pollution on human beings:

1. Suspended particulate matter causes asthma, bronchitis and allergic cold.
2. Pollutant gases cause irritation in eyes, throat and lungs. Heart related diseases tend to increase.
3. Hydrocarbon vapours not only damage the internal organs but also cause cancer.

Greenhouse gases are gases that trap infrared radiations and prevent them from escaping the earth’s surface. This trapping of infrared rays thus results in an increase in temperature of earth known as global warming.

A biogeochemical cycle is a pathway by which essential chemical substances move through the biotic and abiotic components of Earth. Nitrogen, oxygen, phosphorous, Sulphur, water cycles are some important biogeochemical cycles.

Two measures to prevent soil erosion are:

1. 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.
2. Making windbreakers from trees on the land to prevent erosion of soil by wind blowing across it.

Carbon dioxide and methane are two greenhouse gases which contribute maxium toward global warming by trapping the infrared rays and not letting them escape the earth’s atmosphere thereby increasing the earth’s temperature.

Pathogens like bacteria, viruses, protozoan worms and protozoa usually from sewage waste, cause water pollution. Eg-Coliform bacteria cause water pollution.

Sulphuric acid (H₂OS₄) and Nitirc acid (HNO₃) are present in acid rain. Sulphur oxides and oxides of nitrogen combine with water and oxygen in air and fall on earth as acid rain in the form of Sulphur and nitric oxides.

Physical agents that cause weathering of rocks are:

1. Thermal stress i.e. Contraction and expansion of rocks by changes in temperature.
2. Wind is another strong physical agent that brings about weathering of rocks.
3. Heavy rainfall.

Weathering occurs by three processes:

1. Physical/ Mechanical: Breakdown of rocks into smaller pieces. Eg- frost shattering.

2. Biological: Disintegration of rocks by activities of living organisms.

3. Chemical: it occurs when rocks are worn away by chemical changes.

There are two types of bacteria involved in nitrification-nitrite and nitrate.

1. Nitrite bacteria like Nitrosomonas oxidize ammonium to nitrite.
2. Nitrate bacteria like Nitrobacter oxidize nitrite to nitrate.

Two processes that contribute to soil formation are:

1. Weathering of rocks by mechanical, biological and chemical processes.
2. Decomposition of organic matter in the crust adds to humus content and thus healthens soil growth.

Two important biological processes in which air is essential is:

1. Respiration i.e. breathing in of oxygen from the atmosphere for sustaining life.
2. Photosynthesis- uptake of carbon dioxide from the air to produce food and release oxygen.

Sulphuric and nitric acids are the two acids present in acid rain. Oxides of nitrogen and Sulphur dioxide in the atmosphere react with water, oxygen and other chemicals and fall on earth as Sulphur and nitric oxides in the form of acid rain.

Troposphere/ lower atmosphere is the region of atmosphere where most of the atmospheric gases are present. It is this region where most of the weather phenomenons take place.

Formation of carbonate and limestone rocks causes a long term withdrawl of carbon from the carbon cycle as they take a large amount of carbon and once formed they take years to degrade.

Biosphere has three divisions:

1. Lithosphere (land).
2. Hydrosphere (water).
3. Atmosphere (air).

Disease caused by mercury pollution in water is known as Minamata disease. It was first observed in the people of Japan. Methylmercury poisoning occurred in several places of japan because industries discharged mercury into rivers.

Dust particles act as nucleus for water droplets to form around in the atmosphere. Water condenses around the dust particles to form clouds high in the atmosphere. When the clouds can no longer hold more water vapour, i.e. when they reach saturation, the water falls down on earth as rainfall.

The types of bacteria that are involved in nitrogen cycle are Nitrosomonas, Nitrobacter, Rhizobium, Azotobacter, Species of Clostridium and Pseudomonas.

Nitrification is the conversion of ammonia into nitrate. It is carried out by bacteria like Nitrobacter, amd Nitrocystis.

Pseudomonas is a denitrifying bacteria that converts nitrates in soil to free atmospheric nitrogen.

Azobacter, Cyanobacteria, Anabaena and Clostridium are some bacterias that play a role in biological nitrogen fixation i.e. they convert nitrogen in earth’s atmosphere to ammonia NH₃.

Oxygen is replenished or released in nature by photosynthesis. Green plants take up carbon dioxide to prepare food. The results of the process is food (glucose) and oxygen molecules.

The atmosphere keeps the average temperature of the earth fairly steady during the day as the atmosphere prevents the sudden increase in temperature during the daylight hours and at night atmosphere slows down the escape of heat into the outer space.

Marine organisms receive continuous supply of nutrients from the rivers that come down from high altitudes. These rivers bring down silt that has nutrients, obtained by flowing over rocks at high altitudes.

Oxygen is required by all living beings for respiration and for burning materials. This is balanced by green plants. Green plants take in carbon dioxide and release oxygen during the process of photosynthesis.

Carbon dioxide is fixed by the following proceses:

1. a-Plants fix carbon dioxide by using it in photosynthesis and relasing oxygen.
2. b-Aquatic animals use dissolved carbon dioxide to make carbonate shells.