Science Que-Ans (Each of 2 Mark )

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.

1. Thermal pollution.
2. Addition of poisonous (mercury) compounds in water.
3. Due to blockage of gills of fishes with any water pollutant.

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.

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.

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.

The main sources of carbon are:

1. Burning of fossil fuels like coal, petroleum.
2. Decomposition of organic material by decomposers results in release of carbon dioxide in the atmosphere.

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

Contamination of water bodies with undesirable substances like fertilizers, pesticides or poisonous substances, thus degrading the water quality and making it unfit for drinking and other purposes is defined as water pollution.

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

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.

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.

When the solar radiations fall on the earth, some are absorbed and majority of these are reflected back or re-radiated by the land and water bodies. These reflected or re-radiated solar radiations heat the atmosphere from below. As a result convection currents are set up in the air.

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.

The short term changes in the properties of the troposphere forms the weather. The weather changes take place everyday. It tells us about the temperature, rain, cloud and sunshine of an area.

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

In coastal areas, during daytime, there is a regular flow of cool air from the sea towards the land. At night, there is a reverse flow of air from land to sea. This happens because during the daytime, land gets heated faster than water.

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.

It is done through denitrification in this process d bacteria converts nitrates n nitrites into atmospheric nitrogen again.

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.

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.

Two effects of soil erosion are:

1. Reduction in growth of new plants as the topsoil erodes away and the remaining soil is not that fertile to support growth.
2. Soil erosion leads to contamination of water sources and pollutes the public areas.

Rainwater harvesting is a technique used to capture and store rain water by making special water harvesting structures so that there is an increase in the recharge of underground water resources.

Smog is a photochemical haze caused by the action of solar ultra violet radiation on atmosphere polluted with primary pollutants such as hydrocarbons and oxides of nitrogen from automobile exhaust. It reduces visibility and is highly suffocating and toxic to humans, animals and plants.

Due to the flow of high pressure air present over the lake blows towards the low pressure air present over land, we feel relief from heat. The air present over lake is comparatively cooler as compared to the air present over the land.

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.

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.

Renewable exhaustible resources 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.

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

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.

Carbon monoxide is a colourless, odourles gas produced by burning of wood, fuels etc. The replacement of oxygen with carbon monoxide in red blood cells in our body leads to carbon monoxide poisoning. Carbon monoxide poisoning causes tissue damage and may even lead to death.

The major components of air pollution are soot, fly ash, dust particles, smoke and some gases like sulphur dioxide, carbon monoxide, nitrogen oxide, ammonia etc.

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.

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

Marine water is not useful for human and plant life directly. Uneven distribution of limited fresh water resources need conservation to cater to the demands.

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.

Fertile soil has lots of humus because it contains microorganisms that decompose dead organic matter present in soil and help in the formation of humus. Flumus is a sources of mineral, absorbs water and makes the soil porous for easy passage of plant roots.

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.

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

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.