Life on earth depends on many factors. Life forms need an ambient
temperature, water and food to survive. The resources available on earth
and the energy from the sun are necessary to meet the basic requirement of
all life forms on the earth. The resources on earth are the land, water and
air. Water covers about 75% of earth surface it is also found underground
and it comprises the hydrosphere. The outer crust of the earth is called
the lithosphere. The hydrosphere and the lithosphere interact and make life
possible and is also known as the biosphere.
The breath of life: air
Air is a mixture of many gases like nitrogen, oxygen, carbon dioxide and
water vapour. The unique composition of air supports life on earth. Other
planets like Venus and Mars have no life most of the atmosphere found their
contains carbon dioxide.
The percentage of carbon dioxide in our atmosphere is a near fraction of a
percentage because carbon dioxide is fixed in two ways:
Green plants absorb and convert carbon dioxide into glucose in the presence
of sunlight.
Many marine animals use carbonate dissolved in water to make their shells.
Role of atmosphere in climate control
The atmosphere covers the earth like a blanket. Air is a bad conductor of
heat and therefore the average temperature of earth is really study during
the day continues for the whole year which helps in supporting life.
Atmosphere prevent the sudden increase in temperature during the day hours
and during night it slows down the escape of heat into the outer space.
Movement of air: winds
We feel relaxed due to the cool evening breeze after a hot day and sometime
lucky enough to get rains after some days of really hot weather. This
happens due to the movement of air i.e. the winds. This phenomenon of
movement results due to the changes takes place in our atmosphere due to
the heating of air and the formation of water vapour. The water vapour is
formed due to the heating of water bodies during the day time and other
activities of living organism. When the air gets heated, convection
currents are setup in the air due to the radiations that is reflected back
or radiated by the land or water bodies.
In coastal region during day the air above the land gets heated faster and
starts rising. As the air rises a region of low pressure is created and air
over the sea moves into the area of low pressure. This movement of air from
one region to another creates wind. During the day the direction of wind is
from the sea to the land. At night both land and sea start to cool, since
water cool down slower than the land so the air above the sea remains warm
and moves up and the cool air from the land comes towards the sea, this
also cause wind. So, all movement of air are results of diverse atmospheric
phenomena that are caused by uneven heating of the atmosphere in different
region of the earth.
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 get into
the atmosphere because of various biological activities. This air also gets
heated and rises up carrying water vapour with it. As the air rises it
expands and cools. Cooling causes water vapour in the air to condense in
the form of tiny droplet.
Condensation of water is facilitated if some particle act as the nucleus of
these drops to form around. Numerous dust and suspended particles in the
air perform this function.
Once the water droplet is formed, they grow bigger and bigger by the
condensation of droplets and becomes heavy. This result the water to fall
down in the form of rain.
Air pollution
Increasing levels of oxides of nitrogen and Sulphur in air reduces the
quality of air and this affect us and other life forms around us.
Fossil fuels like coal and petroleum contain small amount of nitrogen and
Sulphur which when burnt releases the oxides of these nitrogen and Sulphur.
Inhaling this gas is dangerous for health and they also dissolve in rain to
give rise to acid rain.
Combustion of fossil fuel also increases the amount of suspended particle
in air which can be unburnt carbon particles or substance called
hydrocarbon. Presence of high level of this pollutant cause low visibility
especially in cloudy weather. This is known as smog and is
visible indication of air pollution.
An increase in the content of the above harmful substances in air is called
air pollution.
Water: a wonderful liquid
Water occupies a very large area of the earth surface and is also found
underground. Freshwater is found in frozen ice cap of the two poles and on
snow covered mountains. Underground water and the water in river, lake and
pond are also fresh.
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. Hence, organism need to maintain the level of
water to stay alive. Terrestrial life form requires fresh water because
their bodies cannot tolerate high amount of dissolved salts in saline
water.
Water pollution
Water dissolve the fertilizers and pesticides; some percentage of these
substance are washed into the water bodies. Sewage from our towns and
cities and waste from factories are also dumped into rivers and lakes. Few
industries also use water for cooling operation and later return the hot
water in water bodies. All this affects the lifeform found in water bodies
in various ways and this phenomenon is called water pollution.
Water pollution covers the following effects:
Addition of undesirable substance to water bodies, these substances could
be fertilizer, pesticides, mercury salts and other disease-causing
organisms.
Removal of desirable substance from water bodies that is dissolved oxygen
and other nutrients used by animals and plants lives in water.
Change in temperature also cause water pollution as aquatic organisms are
used to certain range of temperature in the water body. The eggs and larva
of various animals susceptible to a particular temperature are damaged and
reduces their breeding.
Mineral riches in the soil
The outermost layer of earth is called the crust and the minerals found in
this layer supply a variety of nutrients to life forms. These minerals will
not be available to the organisms if the minerals are bounded up in huge
rocks.
Rock present in the earth's surface are broken down into small particles
and forms soil by various physical, chemical and some biological processes.
Factors or processes that make soil:
The sun
: repeated heating and cooling down of rocks during day and night, expands
and contracts the rock at different rate in different positions helps in
formation of crack and ultimately huge rock break into smaller pieces.
Water:
Water helps in formation of soil in two ways:
When water get into the crack of rocks formed due to uneven heating by the
sun due to cooling down of water it freezes and expands, that exerts
pressure on the rock which helps facilitate the rock to break down into
small particles.
Fast flowing water in a river carries big and small particles of rock
downstream. These rocks rub against each other and the resultant abrasion
causes the rock to wear down into smaller and smaller particles.
Wind:
a process like that of water, wind also help rocks rub against each other
and are then break down. Strong winds erode the rock down into small
particles.
Living organism
: organism like lichen grows on the surface of rock and releases certain
substance, that causes the rock surface to powder down and form into thin
layers of soil. Other small plant like mosses also grow on the surface and
breaks down the rocks. The roots of big tree sometimes go into cracks of
the rock and break it down.
Topsoil
The topmost layer of the soil contains humus and living organism in
addition to the soil particles is called the top soil. The quality of
topsoil is an important factor that decides biodiversity in a particular
area.
Soil erosion
Soil of any particular place is created over a very long period of time.
Fine particles of the soil may be carried away by flowing water or by the
wind as the top layer of the soil is loosely packed so to prevent the soil
to erode away measures have to be taken. So, the roots of plants have a
very important role in preventing the soil erosion. Large scale
deforestation happening in an area destroy the biodiversity and leads to
soil erosion. If the soil gets washed away and the rock underneath are
exposed then we lose a valuable resource because very little plants will
grow on the rocky surface.
Biochemical cycle
A constant interaction between the biotic and abiotic components of the
biosphere makes it a dynamic but stable system. This interaction consists
of a transfer of matter and energy between the different components of the
biosphere.
The water cycle
Water evaporates from water body subsequently condenses and comes down as
rain. The process by which water evaporates and falls on the land as rain
and later flow back into the sea via river is known as water cycle. All the
water that falls on the land does not immediately flow back into the sea it
is also absorbed by the soil and becomes underground freshwater; this water
may come out from underground in the form of springs.
Nitrogen cycle
Nitrogen gas makes up 78% of the atmosphere. Nitrogen cycle contains five
stages:
Nitrogen fixation:
in this atmospheric nitrogen occurs primary in an inert form which few
organisms can use. Therefore, it must be converted to an organic or fixed
form in a process called nitrogen fixation. This is done by certain
microorganisms like bacteria living in symbiotic relationship with certain
plants, free anaerobic bacteria and algae.
Nitrification:
While ammonia can be used by some plants most of the nitrogen taken up by
plant is converted by bacteria from ammonia which is highly toxic to many
organisms this process is called nitrification and these bacteria are known
as nitrifying bacteria.
Assimilation:
compound of nitrogen in various forms such as nitrate, nitrite taken up
from soil by plants and are used in formation of plant and animal proteins.
Ammonification:
When plants and animals die or when animal emits waste the nitrogen in the
organic matter re-enters the soil which are broken down by other
microorganisms, known as decomposers.
Denitrification:
Nitrogen makes its way back into the atmosphere through a process called
denitrification in which nitrate is converted back to gaseous nitrogen.
Organisms known as denitrifying bacteria will process nitrate to gain
oxygen leaving free nitrogen gas as a byproduct.
The carbon cycle
In the atmosphere carbon is attached to some oxygen in a gas called carbon
dioxide. All living things are made of carbo. Carbon is also a part of the
ocean and even rocks. Plant use carbon dioxide and sunlight to make their
own food. Carbon becomes a part of the plant and when the plant dies and
are buried it turns into fossil fuel made of carbon like coal and oil over
millions of years. When human burns this fossil fuel most of the carbon
quickly enters the atmosphere as carbon dioxide. Carbon dioxide is a
greenhouse gas and traps heat in the atmosphere. Without it and other
greenhouse gases earth would be a frozen world.
Greenhouse effect
As we know that carbon dioxide is a greenhouse gas and helps in trapping
the heat energy inside the earth atmosphere. An increase in the percentage
of such gases in the atmosphere would cause the average temperature to
increase worldwide and this is called the greenhouse effect. An increase in
the carbon dioxide content in the atmosphere would cause more heat to be
retained by atmosphere and lead to global warming.
Oxygen cycle
Oxygen is very abundant element on our earth. Oxygen cycle is the process
that maintains the level of oxygen in the atmosphere. Oxygen from the
atmosphere is used up in three process namely combustion and respiration
and in the formation of oxides of nitrogen. Oxygen is returned to the
atmosphere in only one major process that is photosynthesis.
Ozone layer
Elemental oxygen is normally found in the form of diatomic molecules. The
upper layers of the atmosphere we found a single molecule of oxygen
contains three atoms of oxygen. And this is called the ozone. Ozone is
poisonous and are unstable near the earth's surface. It performs an
essential function of preventing the harmful radiations of the Sun reaching
the surface of the earth that may damage many forms of life but recently it
is seen that the Ozone layers is getting depleted due to man-made compounds
like CFCs. Once it reaches the ozone layer, they react with the ozone
molecules and results in the reduction of ozone layer which as an outcome
made a hole in the ozone layer above Antarctica.