NATURAL RESOURCES

IMPORTANT TERMS

Biosphere:           It is a life-supporting zone of the earth where the atmosphere, hydrosphere and lithosphere interact and make life possible.

 Air pollution:                 An undesirable change in the physical, chemical or biological characteristics of the air making it harmful for the living organisms is termed as air pollution.

Water pollution:             An undesirable change in the physical, biological or chemical qualities of water (due to addition for foreign organic, inorganic, biological or radioactive substances) that adversely affects the aquatic life, and makes water less fit or unfit for use, is called water pollution.

Soil pollution:                 Removal of useful components from the soil or addition of other substances, which adversely affect the fertility of the soil and kill the diversity of organisms that live in it, is called soil pollution.

Soil erosion:                  Soil erosion is defined as the wearing-away of topsoil. Topsoil is the top most layer of soil and is the most fertile because it contains the organic, nutrient-rich materials. 

Water cycle:                  The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the earth.

Nitrogen Cycle:              It is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen-containing compounds in nature.

Carbon cycle:                It is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.

Oxygen cycle              : It is the biogeochemical cycle that describes the movement of oxygen within and between its three main reservoirs: the atmosphere (air), the biosphere (living things), and the lithosphere (earth’s crust).

Ozone Layer:                The ozone layer is mainly located in the lower portion of the stratosphere which contains relatively high concentrations of ozone. This layer absorbs 93-99% of the sun’s high frequency ultraviolet light, which is potentially damaging to life on earth.

Global warming:             Global warming is the increase of earth's average surface temperature due to the effect of greenhouse gases. Global warming has emerged has one of the biggest environmental issue in last two decades.

 

Biosphere

Biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere, and atmosphere.

• Living things constitute the biotic component of the biosphere.
• The air, the water and the soil form the non-living or abiotic component of the biosphere.
• The air that covers the whole of the earth like a blanket is called the atmosphere.
• The water bodies are called hydrosphere
• The surface layers are collectively called lithosphere.

Air

• Air is a mixture of many gases like nitrogen (78%), oxygen (21%), argon (0.93%), carbon dioxide (0.04%), and small amounts of other gases and water vapour.
• Oxygen is required to break down glucose molecules by all living beings to get energy for their activities. This results in the production of carbon dioxide.
• In the process of combustion, oxygen is consumed and there is resultant production of carbon dioxide. Human activities, which burn fuels to get energy and forest fires, are examples of combustions.
• Carbon dioxide constitutes up to 95-97% of the atmosphere on Venus and Mars.

 

Carbon dioxide fixation

There are two ways to fix carbon dioxide:

·     Green plants convert carbon dioxide into glucose in the presence of Sunlight.

·       Many marine animals use carbonates dissolved in sea-water to make their shells.

 

The role of the atmosphere in climate control

•  Atmosphere helps earth by restricting the increase in temperature in daytime while in night it also protects Earth by slowing down the escape of heat to the outer space. Therefore, it plays an important role in maintaining the temperature of the earth fairly steady.
• The moon is almost at the same distance from Sun, as the Earth is from the Sun but the temperature on moon ranges from -190º C to 110º C. Because it has no atmosphere.
• Thus atmosphere acts like a blanket for the Earth.

                                                                                      

Winds

• Movement of air is called wind. Wind is the result of changes that take place in our atmosphere due to the heating of air and the formation of water vapour.
• Water vapour is formed due to the heating of water bodies and the activities of living organisms.
• The rise in temperature creates a low pressure zone which attracts cool air from high pressure zone and pushes up the hot air. Air movement occurs from high pressure region to low pressure region. Thus the atmosphere can be heated from the radiation that is reflected back or re-radiated by the land or water bodies. On being heated, convection currents are set up in the air.  

Rain

• A large amount of water evaporates when water bodies gets heated during the day and goes up into the air. Some amount of water vapour also gets into the atmosphere because of various biological activities. Heated air rises up carrying the water vapour with it.
• As the air rises, it expands and cools. This cooling causes the water vapour in the air to condense in the form of tiny droplets.
• This condensation of water is facilitated if dust and other suspended particles in the air could act as the ‘nucleus’ for these drops to form around. Once the water droplets are formed, they grow bigger by the ‘condensation’ of these water droplets. When the drops have grown big and heavy, they fall down in the form of rain.
• Prevailing wind patterns decide patterns of rainfall. In large parts of India, rains are mostly brought by the southwest or north-east monsoons.

Air Pollution

• An undesirable change in the physical, chemical or biological characteristics of the air making it harmful for the living organisms is known as air pollution.
• The substances which cause air pollution are known as air pollutants. Pollutants can be in the form of solid particles, liquid droplets, or gases. Pollutants can be classified as either primary or secondary.
• Usually, primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulphur dioxide released from factories.
• Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground-level ozone that make up photochemical smog.
• Air pollution can be a result of human activities as well as natural processes.
• Man-made activities that results in air pollution are: transportation, industries, construction, mining etc.
• Natural processes like volcanic eruptions and wildfires also pollute the air. Global warming and degradation of ozone layer are the major causes of air pollution.
• Formation of smog (a mixture of fog and smoke) is a visible indication of air pollution.

Water

• Water covers about 75% of the Earth’s surface, 97% of which forms ocean and only 3% forms fresh water.
• Water is also present in a form of water vapour in atmosphere. It is also present in solid state (in form of snow, glaciers, ice packs and icebergs) and gaseous state (in a form of steam and water vapour, dew and humidity).

Importance of Water

• All cellular processes take place in an aqueous medium. All the reactions that take place within a living organism and within the cells occur between substances that are dissolved in water. Substances are also transported from one part of the body to the other in a dissolved form.
• Terrestrial life-forms require fresh water for their cellular activities because their bodies cannot tolerate the high amounts of dissolved salts in saline water. Thus, water sources should be easily accessible for animals and plants to survive on land.
• An adequate level of water should be maintained in our body for regulating our body temperature and other body functions and to stay healthy and alive.
• Our economy also depends on water as agriculture, fishing and other industries relies on water. Water is a source of various sports like swimming, boating, fishing etc.

Water Pollution

• Addition of harmful substances and chemicals to water bodies by human activities that adversely affects the aquatic life, and makes water less fit or unfit for use is called water pollution.
• Agents or substances that pollute the water are called water pollutants.

 

 The term water-pollution is used to cover the following effects:

• The addition of undesirable substances to water-bodies: The fertilizers and pesticides used in farming or any poisonous substances, like mercury salts which are used by paper-industries are water pollutants. These could also be disease-causing organisms, like the bacteria which cause cholera.

• The removal of desirable substances from water-bodies: Live animals and plants present in water uses dissolved oxygen. Any change that reduces the amount of dissolved oxygen would adversely affect these aquatic organisms. Other nutrients could also deplete from the water bodies.

• A change in temperature: The eggs and larvae of various aquatic animals are susceptible to temperature changes. The aquatic organisms are used to a certain range of temperature in the water bodies where they live, and a sudden marked change in this temperature would be dangerous for them or affect their breeding.

 Soil

• Soil is considered as an important resource as it determines the diversity of life in an area. The outermost layer of planet Earth is called Crust and the minerals found in this layer supply a variety of nutrients to life-forms.
• The factors that make soil are:

• Sun: It helps rocks in expanding, by heating it up in daytime. At night, these rocks cool down and contract. Since the rate of contraction and expansion of all parts of the rock are not same, the formation of cracks takes place and ultimately the rock breaks up into smaller pieces.
• Water: Water gets into the cracks of the rocks formed by continuous heating and contraction during daytime and night respectively, which then freezes inside these cracks and widens the cracks. Thereafter, flowing water carries small particles from rocks which further results in formation of soil after abrasion of rocks in smaller particles.
• Wind: It helps in formation of soil by disintegration of rocks in smaller pieces and then carrying away sand particles from one place to another.

• Quality of soil: It is determined by the content of humus and microscopic organisms found in it. Humus is a major factor in deciding the soil structure since it causes the soil to become more porous and allows water and air to penetrate deep underground.
• The nutrient content of a soil, the amount of humus present in it and the depth of the soil are some of the factors that determines which plants will thrive on that soil.
• The topmost layer of the soil that contains humus and living organisms in addition to the soil particles is called the topsoil.
• The removal and transportation of top layer of soil from its original position to another place with the help of certain agents such as strong winds and fast running rain water, is called soil erosion. Roots of plants prevent soil erosion by firmly holding the soil particles.
• Removal of useful components from the soil and addition of other substances, which adversely affect the fertility of the soil and kill the diversity of organisms that live in it, is called soil pollution.

 

Bio-geochemical Cycles

A biogeochemical cycle is the flow of matter from non-living environment to the living organisms and its return back to the non-living environment.

 

THE WATER CYCLE

Water is naturally recycled through the water cycle.

• The water cycle is the continuous process by which water moves through the living and nonliving parts of the environment.
• The sun is the source of energy that drives the water cycle.
• The water cycle is crucial to the existence of life on the planet Earth.
• During part of the water cycle, the sun heats up liquid water and changes it to a gas by the process of evaporation. Water that evaporates from Earth’s oceans, lakes, rivers, and moist soil rises up into the atmosphere.
• The process of evaporation from plants is called transpiration. 
• As water (in the form of gas) rises higher in the atmosphere, it starts to cool and become a liquid again. This process is called condensation. When a large amount of water vapor condenses, it results in the formation of clouds.
• As the water in the clouds gets too heavy, the water falls back to the earth.  This is called precipitation.
• When rain falls on the land, some of the water is absorbed into the ground forming pockets of water called groundwater.  Most groundwater eventually returns to the ocean.  Other precipitation runs directly into streams or rivers.  Water that collects in rivers, streams, and oceans is called runoff.

THE NITROGEN CYCLE

Nitrogen is essential for the synthesis of proteins in plants and animals. Atmospheric air contains about 78 percent nitrogen, but it is not of much use for plants and animals. Animals need nitrogen in the form of amino acids to form proteins, and plants need nitrogen in the form of soluble salts, nitrates for the synthesis of amino acids and proteins.

It is also a part of many molecules essential to life like proteins, nucleic acids (DNA and RNA), alkaloids and urea. Nitrogen is thus an essential nutrient for all life-forms. The nitrogen cycle produces the fixed form of nitrogen these organisms need. Following are the steps of nitrogen cycle:

• Nitrogen Fixation:

• By lightning: During lightning flashes, extremely high temperatures is generated, which results in nitrogen combining with oxygen to form nitrous and nitric oxide gases. These gases dissolve in rainwater and form nitrous and nitric acid. These acids soak up into the soil where they react with other chemicals to form nitrates. These are then utilised by various life forms.
• By bacteria: Molecular nitrogen is converted into nitrates and nitrites by free living bacteria like Rhizobium present in the root nodules of legumes. There are some special bacteria that convert the nitrogen gas to ammonia that plants can use.

• Nitrification:

It is the process which converts ammonia or ammonium to nitrite and then nitrite to nitrate that the plants can take in as nutrients. The bacteria Nitrosomonas and Nitrococcus convert the ammonia into nitrite and then Nitrobacter converts nitrite to nitrate by the process of oxidation. The nitrates and nitrites are used by plants to make amino acids which are then used to make plant proteins. The plant may be eaten by animals and their biomasses are used to produce animal protein

• Ammonification:

When an animal or plant dies they release wastes from their bodies, nitrogen is released in the organic form. This organic nitrogen is converted into ammonium by fungi and bacteria through the process ammonification.

• Denitrification:

It is the final step in which the simple nitrogen compound are converted back into nitrogen gas, which is then released back into the atmosphere to begin the cycle again. When the ammonia is converted back into inert nitrogen, the process is called denitrification. Anaerobic bacteria Pseudomonas and Clostridium are responsible for the process of denitrification.

 

THE OXYGEN CYCLE

The oxygen cycle elaborates how oxygen circulates in various forms through nature. Oxygen occurs freely in the air, trapped in the earth crust as chemical compounds, or dissolved in water. Oxygen in the atmosphere is about 21%, and it is the second most abundant gas after nitrogen. It is mostly utilized by living organisms, especially man and animals in respiration. Oxygen is also the most common element of human body.

• Processes that use oxygen:

• Respiration: Animals combine glucose and oxygen and release carbon dioxide, water and energy.
• Combustion: Oxygen, fuel and heat is required to burn a substance.
• Decomposition: Decomposition occurs when plants and animals die. When this happens, they decompose and such process uses oxygen and releases carbon dioxide.
• Rusting: When things rust, they use oxygen. This is also called as oxidation.

• Processes that produce oxygen:

• Photosynthesis: Plants produce oxygen during the process of photosynthesis by using carbon dioxide, sunlight, and water to create energy. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for Earth's atmosphere and life.

THE CARBON CYCLE

Most of the chemicals that make up living tissue contain carbon. When organisms die the carbon is recycled so that it can be used by future generations.

• Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
• Carbon dioxide is absorbed by producers to make carbohydrates during photosynthesis.
• Animals feed on the plant and pass the carbon compounds along the food chain. Most of the carbon they consume is exhaled as carbon dioxide during respiration. The animals and plants eventually die.
• The dead organisms are eaten by decomposers and the carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.
• In the sea, marine animals may convert some of the carbon in their diet to calcium carbonate which is used to make their shells. Over time the shells of dead organisms collect on the seabed and form limestone. Due to Earth movements this limestone may eventually become exposed to the air where it is weathered and the carbon is released back into the atmosphere as carbon dioxide. Volcanic action may also release carbon dioxide.

The Greenhouse Effect

• The greenhouse effect refers to the change in the steady-state temperature of a planet or moon by the presence of an atmosphere containing gas that absorbs and emits infrared radiation.
• Greenhouse gases, which include water vapour, carbon dioxide and methane, warm the atmosphere by efficiently absorbing thermal infrared radiation emitted by the earth’s surface, by the atmosphere itself, and by clouds.
• As a result of its warmth, the atmosphere also radiates thermal infrared in all directions, including downward to the earth’s surface.
• Thus, greenhouse gases trap heat within the surface-troposphere system. The greenhouse effect is one of the several factors that affect the temperature of the earth.

Ozone Layer

• The ozone layer or ozone shield is a region of earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation.
• It contains high concentrations of ozone (O3) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere.
• Various man-made compounds like CFC persist in the atmosphere and once they reach the ozone layer, they react with the ozone molecules and result in a reduction of the ozone layer.
• One such hole is discovered in the ozone layer above the Antarctica.

Interesting Facts

• Pollution is one of the biggest global killers, affecting over 100 million people. That’s comparable to global diseases like malaria and HIV.
• The rays from the sun contain Ultra Violet Rays (UV Rays). UV rays are not all bad, because it helps human with Vitamin D. But too much of it is very dangerous.
• Stratospheric ozone is called good ozone while tropospheric ozone is called bad ozone. 
• Global warming can lead to massive food and water shortages and has a life threatening impact on the wildlife.
• Greenhouse gases are naturally produced; however humans produce additional amounts of certain greenhouse gases.
• Without some greenhouse gases and the Greenhouse Effect, Earth’s temperature would be close to -18°C.
• All living things, including us, require nitrogen to build proteins. Humans cannot obtain nitrogen directly from the air because of the chemical nature of nitrogen gas.