English: This figure shows the variations in concentration of carbon dioxide (CO2) in the atmosphere during the last 300 thousand years. (Photo credit: Wikipedia)
English: Carbon dioxide (Photo credit: Wikipedia)
Česky: Pitná voda – kohoutek Español: Agua potable (Photo credit: Wikipedia)
NATURAL RESOURCES
Resources on the Earth
Biosphere
The whole combination of animals, plants and non-living beings which by their
interaction make the planet earth a live and vibrant place is called biosphere.
Biotic Components: Living things constitute the biotic component of the biosphere.
Abiotic Components: The air, the water and the soil form the non-living or a biotic
component of the biosphere. The air is called the hygrosphere, the water is
hydrosphere and the soil is called lithosphere.
The Earth seen from Apollo 17. (Photo credit: Wikipedia)
Air
Air is a mixture of many gases like nitrogen, oxygen, carbon dioxide and water vapour.
All living beings need oxygen to break down glucose molecules and get energy for their
activities. This results in the production of carbon dioxide. Another process which
results in the consumption of oxygen and the concomitant production of carbon dioxide
is combustion. This includes not just human activities, which burn fuels to get energy,
but also forest fires. Despite this, the percentage of carbon dioxide in our atmosphere
is a mere fraction of a percent because of carbon dioxide fixation.
Carbon Dioxide Fixation
(i) Green plants convert carbon dioxide into glucose in the presence of Sunlight
and
(ii) Many marine animals use carbonates dissolved in sea-water to make their
shells.
THE ROLE OF THE ATMOSPHERE IN CLIMATE CONTROL
Atmosphere covers the Earth, like a blanket. We know that 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 the whole year. The atmosphere prevents the
sudden increase in temperature during the daylight hours. And during the night, it
slows down the escape of heat into outer space. The moon, which is about the same
distance from the Sun that the Earth is, with no atmosphere, the temperature ranges
from –190º C to 110º C.
THE MOVEMENT OF AIR: WINDS
These phenomena are 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. Thus the atmosphere can be heated from below by 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.
AIR POLLUTION
An air pollutant is known as a substance in the air that can cause harm to humans and
the environment. Pollutants can be in the form of solid particles, liquid droplets, or
gases. In addition, they may be natural or man-made.
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 sulfur 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 – one of the many secondary pollutants that make up photochemical smog.
RAIN
When water bodies are heated during the day, a large amount of water evaporates and
goes into the air. Some amount of water vapour also gets into the atmosphere because
of various biological activities. This air also gets heated. The hot air rises up carrying
AIRS maps the distribution of carbon dioxide in the atmosphere. (Photo credit: Wikipedia)
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 some particles 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.
Rainfall patterns are decided by the prevailing wind patterns. In large parts of India,
rains are mostly brought by the southwest or north-east monsoons.
Water: A Wonder Liquid
Water occupies a very large area of the Earth’s surface and is also found underground.
Some amount of water exists in the form of water vapour in the atmosphere. Most of
the water on Earth’s surface is found in seas and ocean sand is saline. Fresh water is
found frozen in the ice-caps at the two poles and on snow covered mountains. The
underground water and the water in rivers, lakes and ponds is also fresh. However, the
availability of fresh water varies from place to place. Practically every summer, most
places have to face a shortage of water. And in rural areas, where water supply systems
have not been installed, people are forced to spend considerable amounts of time in
fetching water from faraway sources.
Importance of Water
All cellular processes take place in a water medium. All the reactions that take place
within our body 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. Hence, organisms need to maintain the level of water within their
bodies in order to stay alive. Terrestrial life-forms require fresh water for this because
their bodies cannot tolerate or get rid of the high amounts of dissolved salts in saline
water. Thus, water sources need to be easily accessible for animals and plants to
survive on land.
WATER POLLUTION
Water pollution is the contamination of water bodies such as lakes, rivers, ocean and
gropundwater caused by human activities, which can be harmful to organisms and
plants that live in these water bodies.
We use the term water-pollution to cover the following effects:
1. The addition of undesirable substances to water-bodies. These substances could
be the fertilizers and pesticides used in farming or they could be poisonous substances,
like mercury salts which are used by paper-industries. These could also be diseasecausing organisms, like the bacteria which cause cholera.
2. The removal of desirable substances from water-bodies. Dissolved oxygen is
used by the animals and plants that live in water. Any change that reduces the amount
of this dissolved oxygen would adversely affect these aquatic organisms. other
nutrients could also be depleted from the water bodies.
3. A change in temperature. Aquatic organisms are used to a certain range of
temperature in the water-body where they live, and a sudden marked change in this
temperature would be dangerous for them or affect their breeding. The eggs and larvae
of various animals are particularly susceptible to temperature changes.
Soil
Soil is an important resource that decides the diversity of life in an area. The outermost
layer of our Earth is called the crust and the minerals found in this layer supply a variety
of nutrients to life-forms.
The factors or processes that make soil:
• The Sun: The Sun heats up rocks during the day so that they expand. At night,
these rocks cool down and contract. Since all parts of the rock do not expand and
contract at the same rate, this results in the formation of cracks and ultimately the
huge rocks break up into smaller pieces.
• Water: Water helps in the formation of soil in two ways. One, water could get
into the cracks in the rocks formed due to uneven heating by the Sun. If this water
later freezes, it would cause the cracks to widen. Two, flowing water wears away even
hard rock over long periods of time. Fast flowing water often carries big and small
particles of rock downstream. These rocks rub against other rocks and the resultant
abrasion causes the rocks to wear down into smaller and smaller particles. The water
then takes these particles along with it and deposits it further down its path. Soil is
thus found in places far away from its parent rock.
• Wind: In a process similar to the way in which water rubs against rocks and
wears them down, strong winds also erode rocks down. The wind also carries sand
from one place to the other like water does.
• Living organisms also influence the formation of soil. The lichen also grows on
the surface of rocks. While growing, they release certain substances that cause the
rock surface to powder down and form a thin layer of soil. Other small plants like moss
are able to grow on this surface now and they cause the rock to break up further. The
roots of big trees sometimes go into cracks in the rocks and as the roots grow bigger,
the crack is forced bigger.
Biogeochemical Cycles
A constant interaction between the biotic and abiotic components of the biosphere
makes it a dynamic, but stable system. These interactions consist of a transfer of
matter and energy between the different components of the biosphere.
THE 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. Since the water
cycle is truly a “cycle,” there is no beginning or end. Water can change states among
liquid, vapour and ice at various places in th e water cycle. Although the balance of
water on Earth remains fairly constant over time, individual water molecules can come
and go.
The sun, which drives the water cycle, heats water in the oceans. Water evaporates as
vapor into the air. Ice and snow can sublimate directly into water vapor. Rising air
currents take the vapor up into the atmosphere where cooler temperatures cause it to
condense into clouds. Air currents move clouds around the globe, cloud particles
collide, grow, and fall out of the sky as precipitation. Some precipitation falls as snow
and can accumulate as ice caps and glaciers, which can store frozen water for
thousands of years. Snow packs can thaw and melt, and the melted water flows
overland as snowmelt. Most precipitation falls back into the oceans or onto land, where
the precipitation flows over the ground as surface runoff. A portion of runoff enters
rivers in valleys in the landscape, with stream flow moving water towards the oceans.
Runoff and groundwater, are stored as freshwater in lakes. Not all runoff flows into
rivers. Much of it soaks into the ground as infiltration. Some water infiltrates deep into
the ground and replenishes aquifers, which store huge amounts of freshwater for long
periods of time. Some infiltration stays close to the land surface and can seep back
into surface-water bodies (and the ocean) as groundwater discharge. Some
groundwater finds openings in the land surface and emerges as freshwater springs.
Over time, the water reenters the ocean, where our water cycle started.
Water Cycle
THE NITROGEN-CYCLE
The nitrogen cycle is the biogeochemical cycle that describes the transformations of
nitrogen and nitrogen-containing compounds in nature. It is a cycle which includes
gaseous components.
Earth’s atmosphere is about 78% nitrogen, making it the largest pool of nitrogen.
Nitrogen is essential for many biological processes; it is crucial for any life here on
Earth. It is in all amino acids, is incorporated into proteins, and is present in the bases
that make up nucleic acids, such as DNA and RNA. In plants, much of the nitrogen is
used in chlorophyll molecules which are essential for photosynthesis and further
growth.
Processing, or fixation, is necessary to convert gaseous nitrogen into forms usable by
living organisms. Some fixation occurs in lightning strikes, but most fixation is done
by free-living or symbiotic bacteria. These bacteria have the nitrogenase enzyme that
combines gaseous nitrogen with hydrogen to produce ammonia, which is then further
converted by the bacteria to make its own organic compounds. Some nitrogen fixing
bacteria, such as Rhizobium, live in the root nodules of legumes (such as peas or
beans). Here they form a mutualistic relationship with the plant, producing ammonia
in exchange for carbohydrates. Nutrient-poor soils can be planted with legumes to
enrich them with nitrogen. A few other plants can form such symbioses. Nowadays, a
very considerable portion of nitrogen is fixated in ammonia chemical plants.
THE CARBON-CYCLE
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among
the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.
The cycle is usually thought of as four major reservoirs of carbon interconnected by
pathways of exchange. These reservoirs are:
(II)The atmosphere.
(III) The terrestrial biosphere, which is usually defined to include fresh water
systems and non-living organic material, such as soil carbon.
(IV) The oceans, including dissolved inorganic carbon and living and
nonliving marine biota,
(V)The sediments including fossil fuels.
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 vapor, 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 surfacetroposphere system. The greenhouse effect is one of several factors that affect the
temperature of the Earth.
THE OXYGEN-CYCLE
The oxygen cycle 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). The m ain driving factor of the
oxygen cycle is photosynthesis, which is responsible for the modern Earth’s
atmosphere and life.
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