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BASIC BIOLOGICALCONCEPTS AND PRINCIPLES
A Written Report Submitted
in Partial Fulfillment
of the subject Ecology (NASC 1093)
Prepared by:
Lasco, Mark Alvin T.
Nofuente, Dhona Mae L.
Robedillo, Daneli Caesa P.
Saamong, Dawnnel G.
Velitario, Ma. Beneliza B.Vitan, Cheyenne Faith L.
July 7, 2011
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I.Planet Earth
Earth (or the Earth) is the third planet from the Sun, and the densest and
fifth-largest of the eight planets in the Solar System. It is also the largest of the
Solar System's four terrestrial planets. It is sometimes referred to as the World, the
Blue Planet, or by its Latin name, Terra .
Home to millions of species, including humans, Earth is currently the only
astronomical body where life is known to exist. The planet formed 4.54 billion
years ago, and life appeared on its surface within one billion years. Earth's
biosphere has significantly altered the atmosphere and other abiotic conditions
on the planet, enabling the proliferation of aerobic organisms as well as the
formation of the ozone layer which, together with Earth's magnetic field, blocks
harmful solar radiation, permitting life on land. The physical properties of the
Earth, as well as its geological history and orbit, have allowed life to persist
during this period. The planet is expected to continue supporting life for at least
another 500 million years.
Earth's outer surface is divided into several rigid segments, or tectonicplates, that migrate across the surface over periods of many millions of years.
About 71% of the surface is covered by salt water oceans, with the remainder
consisting of continents and islands which together have many lakes and other
sources of water that contribute to the hydrosphere. Liquid water, necessary for
all known life, is not known to exist in equilibrium on any other planet's surface. [
Earth's poles are mostly covered with solid ice (Antarctic ice sheet) or sea ice
(Arctic ice cap). The planet's interior remains active, with a thick layer ofrelatively solid mantle, a liquid outer core that generates a magnetic field, and
a solid iron inner core.
Earth interacts with other objects in space, especially the Sun and the
Moon. At present, Earth orbits the Sun once every 366.26 times it rotates about its
own axis, which is equal to 365.26 solar days, or one sidereal year. The Earth's axis
of rotation is tilted 23.4 away from the perpendicular of its orbital plane,
producing seasonal variations on the planet's surface with a period of one
tropical year (365.24 solar days). Earth's only known natural satellite, the Moon,
which began orbiting it about 4.53 billion years ago, provides ocean tides,
stabilizes the axial tilt, and gradually slows the planet's rotation. Between
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approximately 3.8 billion and 4.1 billion years ago, numerous asteroid impacts
during the Late Heavy Bombardment caused significant changes to the greater
surface environment.
Both the mineral resources of the planet, as well as the products of the
biosphere, contribute resources that are used to support a global human
population. These inhabitants are grouped into about 200 independent
sovereign states, which interact through diplomacy, travel, trade, and military
action. Human cultures have developed many views of the planet, including
personification as a deity, a belief in a flat Earth or in the Earth as the center of
the universe, and a modern perspective of the world as an integrated
environment that requires stewardship.
Evolution of life
At present, Earth provides the only example of an environment that has
given rise to the evolution of life. Highly energetic chemistry is believed to have
produced a self-replicating molecule around 4 billion years ago and half a
billion years later the last common ancestor of all life existed. The development
of photosynthesis allowed the Sun's energy to be harvested directly by life forms;
the resultant oxygen accumulated in the atmosphere and formed a layer of
ozone (a form of molecular oxygen [O 3]) in the upper atmosphere. The
incorporation of smaller cells within larger ones resulted in the development of
complex cells called eukaryotes. True multicellular organisms formed as cells
within colonies became increasingly specialized. Aided by the absorption of
harmful ultraviolet radiation by the ozone layer, life colonized the surface of
Earth.
Since the 1960s, it has been hypothesized that severe glacial action
between 750 and 580 Ma, during the Neoproterozoic, covered much of the
planet in a sheet of ice. This hypothesis has been termed "Snowball Earth", and is
of particular interest because it preceded the Cambrian explosion, whenmulticellular life forms began to proliferate.
Following the Cambrian explosion, about 535 Ma, there have been five
major mass extinctions. The most recent such event was 65 Ma, when an
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asteroid impact triggered the extinction of the (non-avian) dinosaurs and other
large reptiles, but spared some small animals such as mammals, which then
resembled shrews. Over the past 65 million years, mammalian life has diversified,
and several million years ago an African ape-like animal such as O rrorin
tugenensis gained the ability to stand upright. This enabled tool use and
encouraged communication that provided the nutrition and stimulation
needed for a larger brain, which allowed the evolution of the human race. The
development of agriculture, and then civilization, allowed humans to influence
the Earth in a short time span as no other life form had, affecting both the nature
and quantity of other life forms.
The present pattern of ice ages began about 40 Ma and then intensified
during the Pleistocene about 3 Ma. High-latitude regions have since undergone
repeated cycles of glaciation and thaw, repeating every 40100,000 years. The
last continental glaciation ended 10,000 years ago.
Composition and structureMain article: Earth science
Further information: Earth physical characteristics tables
Earth is a terrestrial planet, meaning that it is a rocky body, rather than a gas
giant like Jupiter. It is the largest of the four solar terrestrial planets in size and
mass. Of these four planets, Earth also has the highest density, the highest
surface gravity, the strongest magnetic field, and fastest rotation. [60] It also is theonly terrestrial planet with active plate tectonics. [61]
Shape
Size comparison of inner planets (left to right): Mercury, Venus, Earth and Mars
The shape of the Earth is very close to that of an oblate spheroid, a sphere
flattened along the axis from pole to pole such that there is a bulge around the
equator. This bulge results from the rotation of the Earth, and causes the
diameter at the equator to be 43 km larger than the pole to pole diameter. The
average diameter of the reference spheroid is about 12,742 km, which is
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approximately 40,000 km/ , as the meter was originally defined as 1/10,000,000
of the distance from the equator to the North Pole through Paris, France. [64]
Local topography deviates from this idealized spheroid, though on a
global scale, these deviations are very small: Earth has a tolerance of about one
part in about 584, or 0.17%, from the reference spheroid, which is less than the
0.22% tolerance allowed in billiard balls. The largest local deviations in the rocky
surface of the Earth are Mount Everest (8848 m above local sea level) and the
Mariana Trench (10,911 m below local sea level). Because of the equatorial
bulge, the surface locations farthest from the center of the Earth are the summits
of Mount Chimborazo in Ecuador and Huascarn in Peru.
Chemical composition
The mass of the Earth is approximately 5.9810 24 kg. It is composed mostly
of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%),
nickel (1.8%), calcium (1.5%), and aluminium (1.4%); with the remaining 1.2%
consisting of trace amounts of other elements. Due to mass segregation, thecore region is believed to be primarily composed of iron (88.8%), with smaller
amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements.
The geochemist F. W. Clarke calculated that a little more than 47% of the
Earth's crust consists of oxygen. The more common rock constituents of the
Earth's crust are nearly all oxides; chlorine, sulfur and fluorine are the only
important exceptions to this and their total amount in any rock is usually much
less than 1%. The principal oxides are silica, alumina, iron oxides, lime, magnesia,
potash and soda. The silica functions principally as an acid, forming silicates,
and all the commonest minerals of igneous rocks are of this nature. From a
computation based on 1,672 analyses of all kinds of rocks, Clarke deduced that
99.22% were composed of 11 oxides (see the table at right). All the other
constituents occur only in very small quantities.
Internal structure
The interior of the Earth, like that of the other terrestrial planets, is divided into
layers by their chemical or physical (rheological) properties, but unlike the other
terrestrial planets, it has a distinct outer and inner core. The outer layer of the
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Earth is a chemically distinct silicate solid crust, which is underlain by a highly
viscous solid mantle. The crust is separated from the mantle by the Mohorovi i
discontinuity, and the thickness of the crust varies: averaging 6 km under the
oceans and 3050 km on the continents. The crust and the cold, rigid, top of the
upper mantle are collectively known as the lithosphere, and it is of the
lithosphere that the tectonic plates are comprised. Beneath the lithosphere is
the asthenosphere, a relatively low-viscosity layer on which the lithosphere rides.
Important changes in crystal structure within the mantle occur at 410 and
660 kilometers below the surface, spanning a transition zone that separates the
upper and lower mantle. Beneath the mantle, an extremely low viscosity liquid
outer core lies above a solid inner core. The inner core may rotate at a slightly
higher angular velocity than the remainder of the planet, advancing by 0.10.5
per year.
Surface
The Earth's terrain varies greatly from place to place. About 70.8% of the
surface is covered by water, with much of the continental shelf below sea level.
The submerged surface has mountainous features, including a globe-spanning
mid-ocean ridge system, as well as undersea volcanoes, oceanic trenches,
submarine canyons, oceanic plateaus and abyssal plains. The remaining 29.2%
not covered by water consists of mountains, deserts, plains, plateaus, and other
geomorphologies.
The planetary surface undergoes reshaping over geological time periods
because of tectonics and erosion. The surface features built up or deformed
through plate tectonics are subject to steady weathering from precipitation,
thermal cycles, and chemical effects. Glaciation, coastal erosion, the build-up
of coral reefs, and large meteorite impacts also act to reshape the landscape.
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The continental crust consists of lower density material such as the igneous
rocks granite and andesite. Less common is basalt, a denser volcanic rock that
is the primary constituent of the ocean floors. Sedimentary rock is formed fromthe accumulation of sediment that becomes compacted together. Nearly 75%
of the continental surfaces are covered by sedimentary rocks, although they
form only about 5% of the crust. The third form of rock material found on Earth is
metamorphic rock, which is created from the transformation of pre-existing rock
types through high pressures, high temperatures, or both. The most abundant
silicate minerals on the Earth's surface include quartz, the feldspars, amphibole,
mica, pyroxene and olivine. Common carbonate minerals include calcite(found in limestone) and dolomite.
The pedosphere is the outermost layer of the Earth that is composed of soil
and subject to soil formation processes. It exists at the interface of the
lithosphere, atmosphere, hydrosphere and biosphere. Currently the total arable
land is 13.31% of the land surface, with only 4.71% supporting permanent crops
Close to 40% of the Earth's land surface is presently used for cropland and
pasture, or an estimated 1.310 7 km 2 of cropland and 3.410 7 km 2 of
pastureland.
The elevation of the land surface of the Earth varies from the low point of
418 m at the Dead Sea, to a 2005-estimated maximum altitude of 8,848 m at
the top of Mount Everest. The mean height of land above sea level is 840 m.
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Orbit and rotation
Rotation
Earth's axial tilt (or obliquity) and its relation to the rotation axis and plane of orbit
Earth's rotation period relative to the Sunits mean solar dayis
86,400 seconds of mean solar time (86,400.0025 SI seconds). As the Earth's solar
day is now slightly longer than it was during the 19th century because of tidal
acceleration, each day varies between 0 and 2 SI ms longer.
Earth's rotation period relative to the fixed stars, called its stellar day by the
International Earth Rotation and Reference Systems Service (IERS), is
86164.098903691 seconds of mean solar time (UT1), or 23 h 56 m 4.098903691 s.
Earth's rotation period relative to the precessing or moving mean vernal
equinox, misnamed its sidereal day , is 86164.09053083288 seconds of mean solar
time (UT1) (23 h 56 m 4.09053083288 s). Thus the sidereal day is shorter than the
stellar day by about 8.4 ms. The length of the mean solar day in SI seconds is
available from the IERS for the periods 16232005 and 19622005.
Apart from meteors within the atmosphere and low-orbiting satellites, the
main apparent motion of celestial bodies in the Earth's sky is to the west at a
rate of 15/h = 15'/min. For bodies near the celestial equator, this is equivalent to
an apparent diameter of the Sun or Moon every two minutes; from the planet's
surface, the apparent sizes of the Sun and the Moon are approximately thesame.
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Earth, along with the Solar System, is situated in the Milky Way galaxy,
orbiting about 28,000 light years from the center of the galaxy. It is currently
about 20 light years above the galaxy's equatorial plane in the Orion spiral
arm. [136]
Axial tilt and seasons
Because of the axial tilt of the Earth, the amount of sunlight reaching any given
point on the surface varies over the course of the year. This results in seasonal
change in climate, with summer in the northern hemisphere occurring when the
North Pole is pointing toward the Sun, and winter taking place when the pole is
pointed away. During the summer, the day lasts longer and the Sun climbs
higher in the sky. In winter, the climate becomes generally cooler and the days
shorter. Above the Arctic Circle, an extreme case is reached where there is no
daylight at all for part of the yeara polar night. In the southern hemisphere the
situation is exactly reversed, with the South Pole oriented opposite the direction
of the North Pole.
By astronomical convention, the four seasons are determined by the
solsticesthe point in the orbit of maximum axial tilt toward or away from the
Sunand the equinoxes, when the direction of the tilt and the direction to the
Sun are perpendicular. In the northern hemisphere, Winter Solstice occurs on
about December 21, Summer Solstice is near June 21, Spring Equinox is around
March 20 and Autumnal Equinox is about September 23. In the Southern
hemisphere, the situation is reversed, with the Summer and Winter Solstices
exchanged and the Spring and Autumnal Equinox dates switched.
The angle of the Earth's tilt is relatively stable over long periods of time.
However, the tilt does undergo nutation; a slight, irregular motion with a main
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period of 18.6 years. The orientation (rather than the angle) of the Earth's axis
also changes over time, precessing around in a complete circle over each
25,800 year cycle; this precession is the reason for the difference between a
sidereal year and a tropical year. Both of these motions are caused by the
varying attraction of the Sun and Moon on the Earth's equatorial bulge. From
the perspective of the Earth, the poles also migrate a few meters across the
surface. This polar motion has multiple, cyclical components, which collectively
are termed quasiperiodic motion. In addition to an annual component to this
motion, there is a 14-month cycle called the Chandler wobble. The rotational
velocity of the Earth also varies in a phenomenon known as length of day
variation.
In modern times, Earth's perihelion occurs around January 3, and the
aphelion around July 4. However, these dates change over time due to
precession and other orbital factors, which follow cyclical patterns known as
Milankovitch cycles. The changing Earth-Sun distance results in an increase of
about 6.9%in solar energy reaching the Earth at perihelion relative to aphelion.
Since the southern hemisphere is tilted toward the Sun at about the same time
that the Earth reaches the closest approach to the Sun, the southern
hemisphere receives slightly more energy from the Sun than does the northern
over the course of a year. However, this effect is much less significant than the
total energy change due to the axial tilt, and most of the excess energy is
absorbed by the higher proportion of water in the southern hemisphere.
Moon
Characteristics
Diameter 3,474.8 km
Mass 7.34910 22 kg
Semi-major axis 384,400 km
Orbital period 27 d 7 h 43.7 m
The Moon is a relatively large, terrestrial, planet-like satellite, with a
diameter about one-quarter of the Earth's. It is the largest moon in the Solar
System relative to the size of its planet, although Charon is larger relative to the
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dwarf planet Pluto. The natural satellites orbiting other planets are called
"moons" after Earth's Moon.
The gravitational attraction between the Earth and Moon causes tides on
Earth. The same effect on the Moon has led to its tidal locking: its rotation period
is the same as the time it takes to orbit the Earth. As a result, it always presents
the same face to the planet. As the Moon orbits Earth, different parts of its face
are illuminated by the Sun, leading to the lunar phases; the dark part of the face
is separated from the light part by the solar terminator.
Because of their tidal interaction, the Moon recedes from Earth at the rate
of approximately 38 mm a year. Over millions of years, these tiny modifications and the lengthening of Earth's day by about 23 s a yearadd up to significant
changes. During the Devonian period, for example, (approximately 410 million
years ago) there were 400 days in a year, with each day lasting 21.8 hours.
The Moon may have dramatically affected the development of life by
moderating the planet's climate. Paleontological evidence and computer
simulations show that Earth's axial tilt is stabilized by tidal interactions with theMoon. Some theorists believe that without this stabilization against the torques
applied by the Sun and planets to the Earth's equatorial bulge, the rotational
axis might be chaotically unstable, exhibiting chaotic changes over millions of
years, as appears to be the case for Mars.
Viewed from Earth, the Moon is just far enough away to have very nearly
the same apparent-sized disk as the Sun. The angular size (or solid angle) ofthese two bodies match because, although the Sun's diameter is about 400
times as large as the Moon's, it is also 400 times more distant. This allows total and
annular solar eclipses to occur on Earth.
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The most widely accepted theory of the Moon's origin, the giant impact
theory, states that it formed from the collision of a Mars-size protoplanet called
Theia with the early Earth. This hypothesis explains (among other things) the
Moon's relative lack of iron and volatile elements, and the fact that its
composition is nearly identical to that of the Earth's crust.
Earth has at least five co-orbital asteroids, including 3753 Cruithne and
2002 AA 29 . As of 2011, there are 931 operational, man-made satellites orbiting
the Earth.
II.BIOSPHERE
The biosphere is the biological component of earth systems, which also
include the lithosphere, hydrosphere, atmosphere and other "spheres" (e.g.
cryosphere, anthrosphere, etc.). The biosphere includes all living organisms on
earth, together with the dead organic matter produced by them.
The "spheres" of earth systems. (Source: Institute for Computational Earth
System Science)
The biosphere concept is common to many scientific disciplines including
astronomy, geophysics, geology, hydrology, biogeography and evolution, and
is a core concept in ecology, earth science and physical geography. A keycomponent of earth systems, the biosphere interacts with and exchanges
matter and energy with the other spheres, helping to drive the global
biogeochemical cycling of carbon, nitrogen, phosphorus, sulfur and other
elements. From an ecological point of view, the biosphere is the "global
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ecosystem", comprising the totality of biodiversity on earth and performing all
manner of biological functions, including photosynthesis, respiration,
decomposition, nitrogen fixation and denitrification.
The biosphere is dynamic, undergoing strong seasonal cycles in primary
productivity and the many biological processes driven by the energy captured
by photosynthesis. Seasonal cycles in solar irradiation of the hemispheres is the
main driver of this dynamic, especially by its strong effect on terrestrial primary
productivity in the temperate and boreal biomes, which essentially cease
productivity in the winter time.
The biosphere has evolved since the first single-celled organismsoriginated 3.5 billion years ago under atmospheric conditions resembling those
of our neighboring planets Mars and Venus, which have atmospheres
composed primarily of carbon dioxide. Billions of years of primary production by
plants released oxygen from this carbon dioxide and deposited the carbon in
sediments, eventually producing the oxygen-rich atmosphere we know today.
Free oxygen, both for breathing (O 2, respiration) and in the stratospheric ozone
(O 3) that protects us from harmful UV radiation, has made possible life as we
know it while transforming the chemistry of earth systems forever.
As a result of long-term interactions between the biosphere and the other
earth systems, there is almost no part of the earth's surface that has not been
profoundly altered by living organisms. The earth is a living planet, even in terms
of its physics and chemistry. A concept related to, but different from, that of the
biosphere, is the Gaia hypotheses, which posits that living organisms have andcontinue to transform earth systems for their own benefit.
History of the Biosphere Concept
The term "biosphere" originated with the geologist Eduard Suess in 1875,
who defined it as "the place on earth's surface where life dwells". Vladimir I.
Vernadsky first defined the biosphere in a form resembling its current ecological
usage in his long-overlooked book of the same title, originally published in 1926.
It is Vernadsky's work that redefined ecology as the science of the biosphere
and placed the biosphere concept in its current central position in earth systems
science.
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The Biosphere in Education
Levels of organization of Ecology, highlighting the Biosphere. (Credit: Erle Ellis)
The biosphere is a core concept within Biology and Ecology, where it
serves as the highest level of biological organization, which begins with parts of
cells and proceed to populations, species, ecoregions, biomes and finally, thebiosphere. Global patterns of biodiversity within the biosphere are described
using biomes.
In earth science, the biosphere represents the role of living organisms and
their remains in controlling and interacting with the other spheres in the global
biogeochemical cycles and energy budgets. The biosphere plays a central role
in the biogeochemical processing of carbon, nitrogen, phosphorus, sulfur and
other elements. As a result, biogeochemical processes such as photosynthesis
and nitrogen fixation are critical to understanding the chemistry and physics of
earth systems as a whole. The physical properties of the biosphere in terms of its
surface reflectance (albedo) and exchange of heat and moisture with the
atmosphere are also critical for understanding global circulation of heat and
moisture and therefore climate. Alterations in both the physics (albedo, heat
exchange) and chemistry (carbon dioxide, methane, etc.) of earth systems by
the biosphere are fundamental in understanding anthropogenic global
warming.
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III. COMPONENTS OF AN ECOSYSTEM
A. ABIOTIC COMPONENTS
The way in which plants and animals grow and carry out their differentactivities is a result of several abiotic factors. These factors are light,
temperature, water, atmospheric gases, wind as well as soil (edaphic) and
physiographic (nature of land surface) factors.
The abiotic components of a grassland ecosystem are the non-living
features of the ecosystem that the living organisms depend on. Each abiotic
component influences the number and variety of plants that grow in an
ecosystem, which in turn has an influence on the variety of animals that live
there. The four major abiotic components are: climate, parent material and
soil, topography, and natural disturbances.
The sun, which drives the water cycle, heats water in oceans and seas.
Water evaporates as water vapor into the air. Ice
and snow cansublimate directly into water vapor. Evapotranspiration is
water transpired from plants and evaporated from the soil. Rising air currentstake the vapor up into the atmosphere where cooler temperatures cause it to
condense into clouds. Air currents move water vapor around the globe, cloud
particles collide, grow, and fall out of the sky as precipitation. Some
precipitation falls as snow or hail, and can accumulate as ice caps and glaciers,
which can store frozen water for thousands of years. Snowpacks can thaw and
melt, and the melted water flows over land as snowmelt. Most water falls back
into the oceans or onto land as rain, where the water flows over the groundas surface runoff. A portion of runoff enters rivers in valleys in the landscape, with
streamflow 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 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 comes out as freshwater springs. Over time,
the water returns to the ocean, where our water cycle started.
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i.ORGANIC COMPOUNDS
Organic Compounds are synthesize products utilized by producers that
will be source of nutrients of consumers and decomposers. ( Carbohydrates,
protein, lipids and humic substances). Humus is a brown or black organic
substances consisting of decayed vegetable and animal matter that provide
nutrients for plants and increase the ability of soil to retain water.
An ecosystem is a community of organisms that interact with each other
and with the abiotic and biotic factors in their environment. Abiotic factors are
chemical and physical factors such as temperature, soil composition, and
climate, along with the amount of sunlight, salinity, and pH. Biotic means living,and biotic factors are the other, living parts of the ecosystem with which an
organism must interact. The biotic factors with which an organism interacts
depend on whether it is a producer, a consumer, or a decomposer.
Producers are also known as autotrophs, or self-feeders. Producers
manufacture the organic compounds that they use as sources of energy and
nutrients. Most producers are green plants or algae that make organic
compounds through photosynthesis. This process begins when sunlight is
absorbed by chlorophyll and other pigments in the plant. The plants use energy
from sunlight to combine carbon dioxide from the atmosphere with water from
the soil to make carbohydrates, starches, and cellulose. This process converts
the energy of sunlight into energy stored in chemical bonds with oxygen as a
by-product. This stored energy is the direct or indirect source of energy for all
organisms in the ecosystem.
A few producers, including specialized bacteria, can extract inorganic
compounds from the environment and convert them to organic nutrients in the
absence of sunlight. This process is called chemosynthesis. In some places on the
floor of the deep ocean where sunlight can never reach, hydrothermal vents
pour out boiling hot water suffused with hydrogen sulfide gas. Specialized
bacteria use the heat to convert this mixture into the nutrients they need.
Only producers can make their own food. They also provide food for the
consumers and decomposers. The producers are the source of the energy that
drives the entire ecosystem. Organisms that get their energy by feeding on other
organisms are called heterotrophs, or other-feeders.
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Some consumers feed on living plants and animals. Others, called
detrivores, get their energy from dead plant and animal matter, called detritus.
The detrivores are further divided into detritus feeders and decomposers. The
detritus feeders consume dead organisms and organic wastes directly.
Decomposers break the complex organic compounds into simpler molecules,
harvesting the energy in the process.
The survival of any individual organism in an ecosystem depends on how
matter and energy flow through the system and through the body of the
organism. Organisms survive through a combination of matter recycling and the
one-way flow of energy through the system.
The biotic factors in an ecosystem are the other organisms that exist in
that ecosystem. How they affect an individual organism depends on what type
of organism it is. The other organisms (biotic factors) can include predators,
parasites, prey, symbionts, or competitors.
A predator regards the organism as a source of energy and matter to be
recycled. A parasite is a type of consumer organism. As a consumer, it does not
make its own food. It gets its food (energy and matter to be recycled) from its
host. The organism's prey is a source of energy and matter. A symbiont is a
factor that does not provide energy to the organism, but somehow aids the
organism in obtaining energy or matter from the ecosystem. Finally, a
competitor reduces the organism's ability to harvest energy or matter to be
recycled. The distribution and abundance of an organism will be affected by its
interrelationships with the biotic environment.
Humans are one of the few organisms that can control how the other
biotic factors affect them. Humans are omnivores, consuming both producers
and other consumers. Humans can also adjust the length of the food chain as
needed. For example, humans who must deal with shortages of food resources
usually alter their eating habits to be closer to the energy source. This is
sometimes called eating lower on the food chain. Since approximately 90
percent of the energy available at each level of the food chain is lost to thenext higher level, shortening the food chain saves energy and uses food more
efficiently.
Humans are also biotic factors in ecosystems. Other organisms are
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affected by human actions, often in adverse ways. We compete with some
organisms for resources, prey on other organisms, and alter the environment of
still others.
Organic compounds are the complex compounds of carbon. Because
carbon atoms bond to one another easily, the basis of most organic
compounds is comprised of carbon chains that vary in length and shape.
Hydrogen, nitrogen, and oxygen atoms are the most common atoms that are
generally attached to the carbon atoms. Each carbon atom has 4 as its
valence number which increases the complexity of the compounds that are
formed. Since carbon atoms are able to create double and triple bonds with
other atoms, it further also raises the likelihood for variation in the molecular
make-up of organic compounds.
All living things are composed of intricate systems of inorganic and
organic compounds. For example, there are many kinds of organic compounds
that are found in nature, such as hydrocarbons. Hydrocarbons are the
molecules that are formed when carbon and hydrogen combine. They are not
soluble in water and easily distribute. There are also aldehydes the molecular
association of a double-bonded oxygen molecule and a carbon atom.
There are many classes of organic compounds. Originally, they were
believed to come from living organisms only. However, in the mid-1800s, it
became clear that they could also be created from simple inorganic proteins.
Yet, many of the organic compounds are associated with basic processes oflife, such as carbohydrates, proteins, nucleic acids, and lipids.
Carbohydrates are hydrates of carbon and include sugars. They are quite
numerous and fill a number of roles for living organisms. For example,
carbohydrates are responsible for storing and transporting energy, maintaining
the structure of plants and animals, and in helping the functioning of the
immune system, blood clotting, and fertilization to name just a few.
Proteins are a class of organic compounds that are comprised of carbon,
hydrogen, nitrogen, and oxygen. Proteins are soluble in water. The protein itself is
composed of subunits called amino acids. There are 20 different amino acids
found in nature organisms can convert them from one to another for all but
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eight of the amino acids.
Lipids comprise a class of organic compounds that are insoluble in water
or other polar solvents; however, they are soluble in organic solvents. Lipids are
made of carbon, hydrogen, oxygen, and a variable of other elements. Lipids
store energy, protect internal organs, provide insulation in frigid temperatures,
among other features. Lipids can be broken down into several groups ranging
from triglycerides, steroids, waxes, and phospholipids.
Nucleic acids are another group of organic compounds. They are
universal in all living organisms. In fact, they are found in cells and viruses. Some
people may not consider a virus to be a living thing. Friedrich Miescher
discovered nucleic acids in 1871.
Organic compounds may be classified in a variety of ways. One major
distinction is between natural and synthetic compounds. Organic compounds
can also be classified or subdivided by the presence of heteroatoms, e.g.
organometallic compounds which feature bonds between carbon and a metal,
and organophosphorus compounds which feature bonds between carbon and
a phosphorus.
Another distinction, based upon the size of organic compounds,
distinguishes between small molecules and polymers.
> Natural compounds - refer to those that are produced by plants or animals.
Many of these are still extracted from natural sources because they would be
far too expensive to be produced artificially. Examples include most sugars,
some alkaloids and terpenoids, certain nutrients such as vitamin B12, and in
general, those natural products with large or stereoisometrically complicated
molecules present in reasonable concentrations in living organisms.
> Synthetic compounds - Compounds that are prepared by reaction of other
compounds are referred to as "synthetic". They may be either compounds that
already are found in plants or animals (semi-synthetic compounds), or those that
do not occur naturally.
Most polymers (a category which includes all plastics and rubbers), are organic
synthetic or semi-synthetic compound.
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Ii.Inorganic Substances
*Chemical compounds that do not contain carbon as the principalelement (excepting carbonates, cyanides, and cyanates), that is, matter other
than plant or animal.
Traditionally, inorganic compounds are considered to be of a mineral, not
biological origin. Complementarily, most organic compounds are traditionally
viewed as being of biological origin. Over the past century, the precise
classification of inorganic vs organic compounds has become less important to
scientists, primarily because the majority of known compounds are synthetic and
not of natural origin. Furthermore, most compounds considered the purview of
modern inorganic chemistry contain organic ligands. The fields
of organometallic chemistry andbioinorganic chemistry explicitly focus on the
areas between the fields of organic, biological, and inorganic chemistry.
Inorganic compounds can be formally defined with reference to what
they are notorganic compounds. Organic compounds contain carbon bonds
in which at least one carbon atom is covalently linked to an atom of another
type (commonly hydrogen, oxygen or nitrogen). Some carbon-containing
compounds are traditionally considered inorganic. When considering inorganic
chemistry and life, it is useful to recall that many species in nature are not
compounds per se, but are ions. Sodium, chloride, and phosphate ions are
essential for life, as are some inorganic molecules such as carbonic
acid, nitrogen, carbon dioxide, water and oxygen. Aside from these simple ionsand molecules, virtually all compounds covered by bioinorganic chemistry
contain carbon and can be considered organic or organometallic.
Furthermore it is any substance in which two or more chemical elements
other than carbon are combined, nearly always in definite proportions
( see bonding), as well as some compounds containing carbon but lacking
carbon-carbon bonds (e.g.,carbonates, cyanides). Inorganic compounds may
be classified by the elements or groups they contain (e.g., oxides, sulfates). Themajor classes of inorganic polymers are silicones, silanes, silicates, and borates.
Coordination compounds (or complexes), an important subclass of inorganic
compounds, consist of molecules with a central metal atom (usually a transition
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element) bonded to one or more nonmetallic ligands (inorganic, organic, or
both) and are often intensely coloured
Inorganic Carbon Compounds
Many compounds that contain carbon are considered inorganic; for
example, carbon
monoxide, carbondioxide, carbonates, cyanides,cyanates, carbides,
and thyocyanates. In general, however, the workers in these areas are not
concerned about strict definitions.
iii.BIOGEOCHEMICAL CYCLES
In ecology , a biogeochemical cycle is a circuit or pathway by which achemical element or molecule moves through both biotic ("bio-") and abiotic("geo-") compartments of an ecosystem . In effect, the element is recycled,although in some such cycles there may be places (called "sinks") where theelement is accumulates for a long period of time.
All chemical elements occurring in organisms are part of biogeochemicalcycles. In addition to being a part of living organisms, these chemical elementsalso cycle through abiotic factors of ecosystems, such as water (hydrosphere),land (lithosphere), and air (atmosphere); the living factors of the planet can bereferred to collectively as the biosphere. The biogeochemical cycles provide aclear demonstration of one of the fundamental principles of biological systems:The harmonious interactions between organisms and their environment, bothbiotically and abiotically.
All the chemicals, nutrients, or elements used in ecosystems by living organisms such as carbon , nitrogen , oxygen , and phosphorusoperate on a closedsystem, which means that these chemicals are recycled, instead of lost, as theywould be in an open system. The energy of an ecosystem occurs in an open
system; the sun constantly gives the planet energy in the form of light , which iseventually used and lost in the form of heat, throughout the trophic levels ofa food web .
Although components of the biogeochemical cycle are not completely lost,they can be held for long periods of time in one place. This place is called
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a reservoir, which, for example, includes such things as coal deposits that arestoring carbon for a long period of time. When chemicals are held for only shortperiods of time, they are being held in exchange pools. Generally, reservoirs areabiotic factors while exchange pools are biotic factors. Examples of exchange
pools include plants and animals , which temporarily use carbon in their systemsand release it back into a particular reservoir. Carbon is held for a relatively shorttime in plants and animals when compared to coal deposits. The amount oftime that a chemical is held in one place is called its residence time.
The most well-known and important biogeochemical cycles include the carboncycle , the nitrogen cycle , the oxygen cycle, the phosphorus cycle , andthe water cycle .
Biogeochemical cycles always involve equilibrium states: A balance in thecycling of the element between compartments. However, overall balance mayinvolve compartments distributed on a global scale.
a.Nitrogen Cycles
Schematic representation of the flow of nitrogen through the
environment. The importance of bacteria in the cycle is immediately recognized
as being a key element in the cycle, providing different forms of nitrogen
compounds assimilable by higher organisms.
The nitrogen cycle is the process by which nitrogen is converted between
its various chemical forms. This transformation can be carried out via both
biological and non-biological processes. Important processes in the nitrogen
cycle include fixation, mineralization, nitrification, and denitrification. The
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majority of Earth's atmosphere (approximately 78%) is nitrogen, making it the
largest pool of nitrogen. However, atmospheric nitrogen has limited availability
for biological use, leading to a scarcity of usable nitrogen in many types of
ecosystems. The nitrogen cycle is of particular interest to ecologists because
nitrogen availability can affect the rate of key ecosystem processes, including
primary production and decomposition. Human activities such as fossil fuel
combustion, use of artificial nitrogen fertilizers, and release of nitrogen in
wastewater have dramatically altered the global nitrogen cycle.
Ecological function
Nitrogen is essential for many processes; it is crucial for any life on Earth. It
is a component 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. Although Earths atmosphere is an abundant
source of nitrogen, most is relatively unusable by plants. Chemical processing, or natural fixation (through processes such as bacterial conversionsee rhizobium),
are necessary to convert gaseous nitrogen into forms usable by living organisms,
which makes nitrogen a crucial component of food production. The
abundance or scarcity of this "fixed" form of nitrogen, (also known as reactive
nitrogen), dictates how much food can be grown on a piece of land.
The processes of the nitrogen cycle
Nitrogen is present in the environment in a wide variety of chemical forms
including organic nitrogen, ammonium (NH 4+), nitrite (NO 2-), nitrate (NO 3-), and
nitrogen gas (N 2). The organic nitrogen may be in the form of any living
organism, or humus, and in the intermediate products of organic matter
decomposition or humus built up. The processes of the nitrogen cycle transformnitrogen from one chemical form to another. Many of the processes are carried
out by microbes either to produce energy or to accumulate nitrogen in the form
needed for growth. The diagram above shows how these processes fit together
to form the nitrogen cycle.
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Nitrogen fixation
Atmospheric nitrogen must be processed, or "fixed" (see page on nitrogen
fixation), to be used by plants. 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 their own
organic compounds. Most biological nitrogen fixation occurs by the activity of
Mo-nitrogenase, found in a wide variety of bacteria and some Archaea. Mo-
nitrogenase is a complex two component enzyme that contains multiple metal-
containing prosthetic groups. 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. Today, about 30% of
the total fixed nitrogen is
Conversion of N 2
The conversion of nitrogen (N 2) from the atmosphere into a form readily
available to plants and hence to animals and humans is an important step in
the nitrogen cycle, which distributes the supply of this essential nutrient. There
are four ways to convert N 2 (atmospheric nitrogen gas) into more chemically
reactive forms [
1. Biological fixation: some symbiotic bacteria (most often associated with
leguminous plants) and some free-living bacteria are able to fix nitrogen
as organic nitrogen. An example of mutualistic nitrogen fixing bacteria
are the Rhizobium bacteria, which live in legume root nodules. These
species are diazotrophs. An example of the free-living bacteria is
Azotobacter .
2. Industrial N-fixation: Under great pressure, at a temperature of 600 C, and
with the use of an iron catalyst, atmospheric nitrogen and hydrogen
(usually derived from natural gas or petroleum) can be combined to form
ammonia (NH 3). In the Haber-Bosch process, N 2 is converted together with
hydrogen gas (H 2) into ammonia (NH 3), which is used to make fertilizer
and explosives.
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3. Combustion of fossil fuels: automobile engines and thermal power plants,
which release various nitrogen oxides (NO x).
4. Other processes: In addition, the formation of NO from N 2 and O 2 due to
photons and especially lightning, can fix nitrogen.
Assimilation
Plants get nitrogen from the soil, by absorption of their roots in the form of
either nitrate ions or ammonium ions. All nitrogen obtained by animals can be
traced back to the eating of plants at some stage of the food chain.
Plants can absorb nitrate or ammonium ions from the soil via their root hairs. If
nitrate is absorbed, it is first reduced to nitrite ions and then ammonium ions for
incorporation into amino acids, nucleic acids, and chlorophyll. In plants that
have a mutualistic relationship with rhizobia, some nitrogen is assimilated in the
form of ammonium ions directly from the nodules. Animals, fungi, and other
heterotrophic organisms obtain nitrogen as amino acids, nucleotides and other
small organic molecules.
Ammonification
When a plant or animal dies, or an animal expels waste, the initial form of
nitrogen is organic. Bacteria, or fungi in some cases, convert the organic
nitrogen within the remains back into ammonium (NH 4+), a process called
ammonification or mineralization. Enzymes Involved:
y GS: Gln Synthetase (Cytosolic & PLastid)
y GOGAT: Glu 2-oxoglutarate aminotransferase (Ferredoxin & NADH
dependent)
y GDH: Glu Dehydrogenase:
o Minor Role in ammonium assimilation.
o Important in amino acid catabolism.
Nitrification
The conversion of ammonium to nitrate is performed primarily by soil-living
bacteria and other nitrifying bacteria. The primary stage of nitrification, the
oxidation of ammonium (NH 4+) is performed by bacteria such as the
N itrosomonas species, which converts ammonia to nitrites (NO 2-). Other
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bacterial species, such as the N itrobacter , are responsible for the oxidation of
the nitrites into nitrates (NO 3-). It is important for the nitrites to be converted to
nitrates because accumulated nitrites are toxic to plant life.
Due to their very high solubility, nitrates can enter groundwater. Elevated
nitrate in groundwater is a concern for drinking water use because nitrate can
interfere with blood-oxygen levels in infants and cause methemoglobinemia or
blue-baby syndrome. [6] Where groundwater recharges stream flow, nitrate-
enriched groundwater can contribute to eutrophication, a process leading to
high algal, especially blue-green algal populations and the death of aquatic life
due to excessive demand for oxygen. While not directly toxic to fish life like
ammonia, nitrate can have indirect effects on fish if it contributes to this
eutrophication. Nitrogen has contributed to severe eutrophication problems in
some water bodies. As of 2006, the application of nitrogen fertilizer is being
increasingly controlled in Britain and the United States. This is occurring along the
same lines as control of phosphorus fertilizer, restriction of which is normally
considered essential to the recovery of eutrophied waterbodies.
Denitrification
Denitrification is the reduction of nitrates back into the largely inert
nitrogen gas (N 2), completing the nitrogen cycle. This process is performed by
bacterial species such as P seudomonas and Clostridium in anaerobic
conditions [ They use the nitrate as an electron acceptor in the place of oxygen
during respiration. These facultatively anaerobic bacteria can also live in
aerobic conditions.
Anaerobic ammonium oxidation
In this biological process, nitrite and ammonium are converted directly
into elemental nitrogen (N 2) gas. This process makes up a major proportion of
elemental nitrogen conversion in the oceans.
Human influences on the nitrogen cycle
Main article: H uman impacts on the nitrogen cycle
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As a result of extensive cultivation of legumes (particularly soy, alfalfa, and
clover), growing use of the Haber-Bosch process in the creation of chemical
fertilizers, and pollution emitted by vehicles and industrial plants, human beings
have more than doubled the annual transfer of nitrogen into biologically-
available forms. In addition, humans have significantly contributed to the
transfer of nitrogen trace gases from Earth to the atmosphere, and from the land
to aquatic systems. Human alterations to the global nitrogen cycle are most
intense in developed countries and in Asia, where vehicle emissions and
industrial agriculture are highest.
N2O (nitrous oxide) has risen in the atmosphere as a result of agricultural
fertilization, biomass burning, cattle and feedlots, and other industrial sources.
N2O has deleterious effects in the stratosphere, where it breaks down and acts
as a catalyst in the destruction of atmospheric ozone.
N2O in the atmosphere is a greenhouse gas, currently the third largest
contributor to global warming, after carbon dioxide and methane. While not as
abundant in the atmosphere as carbon dioxide, for an equivalent mass, nitrous
oxide is nearly 300 times more potent in its ability to warm the planet.
NH3 (ammonia) in the atmosphere has tripled as the result of human
activities. It is a reactant in the atmosphere, where it acts as an aerosol,
decreasing air quality and clinging on to water droplets, eventually resulting in
nitric acid (HNO 3) acid rain. Atmospheric NH 3 and HNO 3 damage respiratory
systems.
All forms of high-temperature combustion have contributed to a 6 or 7
fold increase in NO x flux to the atmosphere. It is a function of combustion
temperature - the higher the temperature, the more NO x is produced. Fossil fuel
combustion is a primary contributor, but so are biofuels and even burning
hydrogen. The higher combustion temperature of hydrogen produces more NO x
than natural gas combustion. The very-high temperature of lightning produces
small amounts of NO x, NH3, and HNO 3.
NH3 and NO x actively alter atmospheric chemistry. They are precursors of
tropospheric (lower atmosphere) ozone production, which contributes to smog,
acid rain, damages plants and increases nitrogen inputs to ecosystems. [2]
Ecosystem processes can increase with nitrogen fertilization, but anthropogenic
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input can also result in nitrogen saturation, which weakens productivity and can
damage the health of plants, animals, fish, and humans.
Decreases in biodiversity can also result if higher nitrogen availability
increases nitrogen-demanding grasses, causing a degradation of nitrogen-poor,
species diverse heathlands.
Wastewater treatment
Onsite sewage facilities such as septic tanks and holding tanks release
large amounts of nitrogen into the environment by discharging through a
drainfield into the ground. Microbial activity consumes the nitrogen and other
contaminants in the wastewater.
However, in certain areas, the soil is unsuitable to handle some or all of the
wastewater, and, as a result, the wastewater with the contaminants enters the
aquifers. These contaminants accumulate and eventually end up in drinking
water. One of the contaminants concerned about the most is nitrogen in the
form of nitrates. A nitrate concentration of 10 ppm (parts per million) or 10
milligrams per liter is the current EPA limit for drinking water and typical
household wastewater can produce a range of 2085 ppm.
The health risk associated with drinking water (with >10 ppm nitrate) is the
development of methemoglobinemia and has been found to cause blue baby
syndrome. Several American states have now started programs to introduce
advanced wastewater treatment systems to the typical onsite sewage facilities.
The result of these systems is an overall reduction of nitrogen, as well as other
contaminants in the wastewater.
Environmental impacts
Additional risks posed by increased availability of inorganic nitrogen in
aquatic ecosystems include water acidification; eutrophication of fresh and
saltwater systems; and toxicity issues for animals, including humans.
Eutrophication often leads to lower dissolved oxygen levels in the water column,
including hypoxic and anoxic conditions, which can cause cause death of
aquatic fauna. Relatively sessile benthos, or bottom-dwelling creatures, are
particularly vulnerable because of their lack of mobility, though large fish kills are
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not uncommon. Oceanic dead zones near the mouth of the Mississippi in the
Gulf of Mexico are a well-known examples of algal bloom-induced hypoxia.
The New York Adirondack Lakes, Catskills, Hudson Highlands, Rensselaer
Plateau and parts of Long Island are examples of the impact of nitric acid raid
deposition, killing fish and many other aquatic species.
Ammonia (NH 3) is highly toxic to fish and the water discharge level of
ammonia from wastewater treatment facilities must often be closely monitored.
To prevent fish deaths, nitrification prior to discharge is often desirable. Land
application can be an attractive alternative to the mechanical aeration
needed for nitrification.
b.Water Cycles
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The water cycle, also known as the hydrologic cycle or H 2O cycle,
describes the continuous movement of water on, above and below the surface
of the Earth. Water can change states among liquid, vapor, and ice at various
places in the water cycle. Although the balance of water on Earth remains fairly
constant over time, individual water molecules can come and go, in and out of
the atmosphere. The water moves from one reservoir to another, such as from
river to ocean, or from the ocean to the atmosphere, by the physical processes
of evaporation, condensation, precipitation, infiltration, runoff, and subsurface
flow. In so doing, the water goes through different phases: liquid, solid, and gas.
The hydrologic cycle involves the exchange of heat energy, which leads
to temperature changes. For instance, in the process of evaporation, water takes up energy from the surroundings and cools the environment. Conversely,
in the process of condensation, water releases energy to its surroundings,
warming the environment.
The water cycle figures significantly in the maintenance of life and
ecosystems on Earth. Even as water in each reservoir plays an important role,
the water cycle brings added significance to the presence of water on our
planet. By transferring water from one reservoir to another, the water cycle
purifies water, replenishes the land with freshwater, and transports minerals to
different parts of the globe. It is also involved in reshaping the geological
features of the Earth, through such processes as erosion and sedimentation. In
addition, as the water cycle also involves heat exchange, it exerts an influence
on climate as well.
The sun, which drives the water cycle, heats water in oceans and seas.Water evaporates as water vapor into the air. Ice
and snow cansublimate directly into water vapor. Evapotranspiration is
water transpired from plants and evaporated from the soil. Rising air currents
take the vapor up into the atmosphere where cooler temperatures cause it to
condense into clouds. Air currents move water vapor around the globe, cloud
particles collide, grow, and fall out of the sky as precipitation. Some
precipitation falls as snow or hail, and can accumulate as ice caps and glaciers,which can store frozen water for thousands of years. Snowpacks can thaw and
melt, and the melted water flows over land as snowmelt. Most water falls back
into the oceans or onto land as rain, where the water flows over the ground
as surface runoff. A portion of runoff enters rivers in valleys in the landscape, with
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streamflow 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 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 comes out as freshwater springs. Over time,
the water returns to the ocean, where our water cycle started.
c. Phosphorus cycle
Part III of "Matter cycles": The phosphorus cycle
Phosphorus is an essential nutrient for plants and animals in the form of
ions PO 43- and HPO 42-. It is a part of DNA-molecules, of molecules that store
energy (ATP and ADP) and of fats of cell membranes. Phosphorus is also a
building block of certain parts of the human and animal body, such as the
bones and teeth.
Phosphorus can be found on earth in water, soil and sediments. Unlike the
compounds of other matter cycles phosphorus cannot be found in air in the
gaseous state. This is because phosphorus is usually liquid at normal
temperatures and pressures. It is mainly cycling through water, soil and
sediments. In the atmosphere phosphorus can mainly be found as very small
dust particles.
Phosphorus moves slowly from deposits on land and in sediments, to living
organisms, and than much more slowly back into the soil and water sediment.
The phosphorus cycle is the slowest one of the matter cycles that are described
here.
Phosphorus is most commonly found in rock formations and ocean
sediments as phosphate salts. Phosphate salts that are released from rocksthrough weathering usually dissolve in soil water and will be absorbed by plants.
Because the quantities of phosphorus in soil are generally small, it is often the
limiting factor for plant growth. That is why humans often apply phosphate
fertilizers on farmland. Phosphates are also limiting factors for plant-growth in
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marine ecosystems, because they are not very water-soluble. Animals absorb
phosphates by eating plants or plant-eating animals.
Phosphorus cycles through plants and animals much faster than it does through
rocks and sediments. When animals and plants die, phosphates will return to the
soils or oceans again during decay. After that, phosphorus will end up in
sediments or rock formations again, remaining there for millions of years.
Eventually, phosphorus is released again through weathering and the cycle
starts over.
Phosphorus Cycle.
Biological importance: Phosphorus is a component of nucleic acids,
phospholipids, as well as bones and teeth.
Forms available to life: Inorganic phosphate (PO 43-) is absorbed by plants.
Reservoirs: The largest reservoirs are in sedimentary rocks .
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Key processes: Weathering of rocks adds phosphorus to soil; some leaches into
groundwater and soil and find its way to sea.
Phosphate taken up by producers cycle through the food web via consumers .
d.The oxygen cycle
The oxygen cycle is the biogeochemical cycle that describes the movementof oxygen within and between its three main reservoirs: The atmosphere , thebiosphere, and the lithosphere (the crust and the uppermost layer of themantle). The main driving factor of the oxygen cycle is photosynthesis , which is
responsible for the modern Earth's atmosphere and life as it is today. If allphotosynthesis were to cease, the Earth's atmosphere would be devoid of allbut trace amounts of oxygen within 5000 years. The oxygen cycle would nolonger exist.
Reservoirs and fluxes
The vast amount of molecular oxygen is contained in rocks and minerals withinthe Earth (99.5 percent). Only a small fraction has been released as free oxygento the biosphere (0.01 percent) and atmosphere (0.49 percent). The main
source of oxygen within the biosphere and atmosphere is photosynthesis, whichbreaks down carbon dioxide and water to create sugars and oxygen:
CO 2 + H2O + energy CH 2O + O 2. An additional source of atmospheric oxygencomes from photolysis, whereby high energy ultraviolet radiation breaks downatmospheric water and nitrite into component molecules. The free H and
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N atoms escape into space leaving O 2 in the atmosphere: 2H 2O + energy 4H+ O 2.
The main way oxygen is lost from the atmosphere is via respiration and decaymechanisms in which animal life consumes oxygen and releases carbon dioxide.Because lithospheric minerals are reduced in oxygen, surface weathering ofexposed rocks also consumes oxygen. An example of surface weatheringchemistry is formation of iron-oxides (rust), such as those found in the red sandsof Australia:
4FeO + 3O 2 2Fe 2O 3. Oxygen is also cycled between the biosphere andlithosphere. Marine organisms in the biosphere create carbonate shell material(CaCO 3) that is rich in molecular oxygen. When the organism dies, its shell isdeposited on the shallow sea floor and buried over time tocreate limestone rock. Weathering processes initiated by organisms can alsofree oxygen from the land mass. Plants and animals extract nutrient mineralsfrom rocks and release oxygen in the process.
e. Carbon Cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchangedbetween the biosphere, lithosphere, hydrosphere, and atmosphere of the Earth .(Other bodies may have carbon cycles, but little is known about them.)
All of these components are reservoirs of carbon. The cycle is usually discussedas four main reservoirs of carbon interconnected by pathways of exchange. Thereservoirs are the atmosphere, terrestrial biosphere (usually includes freshwater systems), oceans, and sediments (includes fossil fuels). The annual movements ofcarbon, the carbon exchanges between reservoirs, occur because of variouschemical, physical, geological, and biological processes. The ocean containsthe largest pool of carbon near the surface of the Earth, but most of that pool isnot involved with rapid exchange with the atmosphere . Major molecules ofcarbon are carbon dioxide (CO 2), carbon monoxide (CO), methane (CH 4),calcium carbonate (CaCO 3), and glucose (in plant organic matter,C 6H12O 6),and many others, as well as many ions containing carbon.
The global carbon budget is the balance of the exchanges (incomes and losses)of carbon between the carbon reservoirs or between one specific loop (e.g.,atmosphere-biosphere) of the carbon cycle. An examination of the carbonbudget of a pool or reservoir can provide information about whether the pool or reservoir is functioning as a source or sink for carbon dioxide.
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f.Sulfur Cycle
Sulfur is mainly found on Earth as sulfates in rocks or as free sulfur. The
largest deposits of sulfur in the United States are in Louisiana and Texas. Sulfur
also occurs in combination with several metals such as lead and mercury, as
PbS and HgS. Sulfur appears as the yellow aspects of soil in many regions.
Sulfur was mined early in the form of the yellow element and used for
gunpowder and fireworks. While bacteria digest plant matter, they emit H 2S,hydrogen sulfide, a gas that has the "rotten egg" smell characteristic of swamps
and sewage. Sulfur is an essential element of biological molecules in small
quantities. (Source: UniBremen)
Sulfur and its compounds are important elements of industrial processes.
Sulfur dioxide (SO 2) is a bleaching agent and is used to bleach wood pulp for
paper and fiber for various textiles such as wool, silk, or linen. SO 2 is a colorless
gas that creates a choking sensation when breathed. It kills molds and bacteria.
It is also used to preserve dry fruits, like apples, apricots, and figs, and to clean
out vats used for preparing fermented foods such as cheese and wine.
Sulfuric acid, H 2SO 4, is a very widely used chemical. Over 30 million tonnes
of sulfuric acid are produced every year in the U.S. alone. The acid has a very
strong affinity for water. It absorbs water and is used in various industrial
processes as a dehydrating agent. The acid in the automobile battery is H 2SO 4. It
is used for "pickling" steel, that is, to remove the oxide coating from the steel
surface before it is coated with tin or electroplated with zinc.
Sulfur is also a biologically important atom. Although only small amounts of
sulfur are necessary for biological systems, disulfide bridges form a critical
function in giving biological important molecules specific shapes and properties.
Sulfur is released into the atmosphere through the burning of fossil fuels --
especially high sulfur coal--and is a primary constituent of acid rain. Sulfuric acid
(H2SO 4) is the primary constituent of acid rain in about all regions other than
California. Sulfur dioxide and carbonyl sulfide (COS) occur in small quantities in
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the atmosphere; but due to its high reactivity, sulfur is quickly deposited as
compound (sulfates) on land and other surfaces.
Figure S1: The Sulfur Cycle.
Figure S1 shows the biogeochemical cycle of sulfur. As in the case of nitrogen,
the figure shows the large quantities. Local activities such as coal burning can
release large amounts in a small area. Sulfur compounds can also be
transported from the higher altitudes from tall "smoke stacks" and contribute to
acid rain far from the sources.
g.Mercury Cycle
The essence of the Mercury Cycle is the evaporation of inorganic Mercury
from both natural and man-made sources into the atmosphere where it is then
oxidized in the upper atmosphere and returned back to earth, most commonly
in precipitation, in its inorganic mercury form. It is dispersed evenly throughout
the environment and the inorganic mercury is biomethylized by bacteria into
the more toxic formation, methyl mercury. Once converted, the methyl mercury
then enters the food chain and biomagnifies up the food chain (Clarkson, 2002).
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There are 6 universally recognized steps to the Mercury Cycle (UWEC and
Purdue):
1. Degassing of Mercury from rock, soils, and surface waters, or emissions from
volcanoes and from human activities.
2. Movement in gaseous form through the atmosphere.
3. Deposition of Mercury on land and surface waters.
4. Conversion of the element into insoluble Mercury sulfide.
5. Precipitation or bioconversion into more volatile or soluble forms such as
methyl mercury.
6. Reentry into the atmosphere or biomagnified up the food chain.
Mercury cycles in the environment as a result of natural (ex: geothermal
activity) and anthropogenic (human) activities. The primary anthropogenic
sources are: fossil fuel combustion and smelting activities. Both these natural andhuman activities release elemental mercury vapor (Hg0) into the atmosphere.
Once in the atmosphere, the mercury vapor can circulate for up to a year, and
hence become widely dispersed. The elemental mercury vapor can then
undergo a photochemical oxidation to become inorganic mercury that can
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combine with water vapors and travel back to the Earths surface as rain. This
mercury-water is deposited in soils and bodies of water. Once in soil, the
mercury accumulates until a physical event causes it to be released again. (See
forest fire research below) In water, inorganic mercury can be converted into
insoluble mercury sulfide which settles out of the water and into the sediment, or
it can be converted by bacteria that process sulfate into methylmercury. The
conversion of inorganic mercury to methylmercury is important for two reasons:
y Methylmercury is much more toxic than inorganic mercury.
y Organisms require a long time to eliminate methylmercury, which leads to
bioaccumulation.
Now the methylmercury-processing bacteria may be consumed by the next
higher organism up the food chain, or the bacteria may release the
methylmercury into the water where it can adsorb (stick) to plankton, which can
also be consumed by the next higher organism up the food chain. This pattern
continues as small fish/organisms get eaten by progressively bigger and bigger
fish until the fish are finally eaten by humans or other animals. Alternatively, both
elemental mercury and organic (methyl) mercury can vaporize and re-enter the
atmosphere and cycle through the environment.
Sources of Mercury
Though many sources of Mercury are naturally existing, the current levels
of mercury level is estimated to be 2 to 5 times greater than its preindustrial level
due to high levels of mining and coal combustion (Princeton, 2004). Sources
include:
y Burning of Fossil Fuels, especially [coal]
o [Coal] fired power plants are the largest source of inorganic
Mercury release in the US and account for 33% of all man-made
inorganic mercury released into the environment worldwide
(Princeton, 2004).
y Liquid mercury used in mining
o Large quantities of liquid Mercury are used to extract gold after the
Mercury is heated and evaporates (Clarkson, 2002).
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o Release also occurs when virgin Mercury is also mined from Mercury
ore (EPA, 2006).
y Industrial Uses
o Fluorescent lamps, dental fillings, thermometers, manometers,
electrical and electronic switches
y Waste Disposals
o Combustion of waste and medical waste products release both
inorganic and organic Mercury into the atmosphere. Mercury also
leeches into the soil and groundwater surrounding landfills
(Princeton, 2004).
y Natural Sources including Volcanic Activity, Forest Fires
iv.CLIMATE REGIME
Climate is the characteristic condition of the atmosphere near the earth's
surface at a certain place on earth. It is the long-term weather of that area (at
least 30 years). This includes the region's general pattern of weather conditions,seasons and weather extremes like hurricanes, droughts, or rainy periods. Two of
the most important factors determining an area's climate are air temperature
and precipitation.
Some facts about climate
The sun's rays hit the equator at a direct angle between 23 N and 23 S
latitude. Radiation that reaches the atmosphere here is at its most intense.
In all other cases, the rays arrive at an angle to the surface and are less
intense. The closer a place is to the poles, the smaller the angle and therefore
the less intense the radiation.
Our climate system is based on the location of these hot and cold air-
mass regions and the atmospheric circulation created by trade winds and
westerlies.
Trade winds north of the equator blow from the northeast. South of the
equator, they blow from the southeast. The trade winds of the two hemispheres
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meet near the equator, causing the air to rise. As the rising air cools, clouds and
rain develop. The resulting bands of cloudy and rainy weather near the equator
create tropical conditions.
Westerlies blow from the southwest on the Northern Hemisphere and from
the northwest in the Southern Hemisphere. Westerlies steer storms from west to
east across middle latitudes.
Both westerlies and trade winds blow away from the 30 latitude belt.
Over large areas centered at 30 latitude, surface winds are light. Air slowly
descends to replace the air that blows away. Any moisture the air contains
evaporates in the intense heat. The tropical deserts, such as the Sahara of Africaand the Sonoran of Mexico, exist under these regions.
Seasons
The Earth rotates about its axis, which is tilted at 23.5 degrees. This tilt and
the sun's radiation result in the Earth's seasons. The sun emits rays that hit the
earth's surface at different angles. These rays transmit the highest level of energy
when they strike the earth at a right angle (90 ). Temperatures in these areas
tend to be the hottest places on earth. Other locations, where the sun's rays hit
at lesser angles, tend to be cooler.
As the Earth rotates on it's tilted axis around the sun, different parts of the
Earth receive higher and lower levels of radiant energy. This creates the seasons.
Kppen Climate Classification System
The Kppen Climate Classification System is the most widely used for classifying
the world's climates. Most classification systems used today are based on the
one introduced in 1900 by the Russian-German climatologist Wladimir Kppen.
Kppen divided the Earth's surface into climatic regions that generally
coincided with world patterns of vegetation and soils.
The Kppen system recognizes five major climate types based on the annualand monthly averages of temperature and precipitation. Each type is
designated by a capital letter.
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A - Moist Tropical Climates are known for their high temperatures year round
and for their large amount of year round rain.
B - Dry Climates are characterized by little rain and a huge daily temperature
range. Two subgroups, S - semiarid or steppe, and W - arid or desert, are used
with the Bclimates.
C - In Humid Middle Latitude Climates land/water differences play a large part.
These climates have warm,dry summers and cool, wet winters.
D - Continental Climates can be found in the interior regions of large land
masses. Total precipitation is not very high and seasonal temperatures vary
widely.
E - Cold Climates describe this climate type perfectly. These climates are part of
areas where permanent ice and tundra are always present. Only about four
months of the year have above freezing temperatures.
Further subgroups are designated by a second, lower case letter which
distinguish specific seasonal characteristics of temperature and precipitation.
f - Moist with adequate precipitation in all months and no dry season. This letter
usually accompanies the A, C , and D climates.
m - Rainforest climate in spite of short, dry season in monsoon type cycle. This
letter only applies to A climates.
s - There is a dry season in the summer of the respective hemisphere (high-sunseason).
w - There is a dry season in the winter of the respective hemisphere (low-sun
season).
To further denote variations in climate, a third letter was added to the code.
a - Hot summers where the warmest month is over 22C (72F). These can befound in C and D climates.
b - Warm summer with the warmest month below 22C (72F). These can also be
found in C and D climates.
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c - Cool, short summers with less than four months over 10C (50F) in
the C and Dclimates.
d - Very cold winters with the coldest month below -38C (-36F) in the D climate
only.
h - Dry-hot with a mean annual temperature over 18C (64F) in B climates only.
k - Dry-cold with a mean annual temperature under 18C (64F) in B climates
only.
Three basic climate groups
Three major climate groups show the dominance of special combinations of air-
mass source regions.
Group I
Low-latitude Climates: These climates are controlled by equatorial a tropical air
masses.
Tropical Moist Climates (Af) rainforest
Rainfall is heavy in all months. The total annual rainfall is often more than 250 cm.
(100 in.). There are seasonal differences in monthly rainfall but temperatures of
27C (80F) mostly stay the same. Humidity is between 77 and 88%.
High surface heat and humidity cause cumulus clouds to form early in the
afternoons almost every day.
The climate on eastern sides of continents are influenced by maritime tropical
air masses. These air masses flow out from the moist western sides of oceanic
high-pressure cells, and bring lots of summer rainfall. The summers are warm and
very humid. It also rains a lot in the winter
y Average temperature: 18 C (F)
y Annual Precipitation: 262 cm. (103 in.)
y Latitude Range: 10 S to 25 N
y Global Position: Amazon Basin; Congo Basin of equatorial Africa; East
Indies, from Sumatra to New Guinea.
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Wet-Dry Tropical Climates (Aw) savanna
A seasonal change occurs between wet tropical air masses and dry tropical air
masses. As a result, there is a very wet season and a very dry season. Trade
winds dominate during the dry season. It gets a little cooler during this dry
season but will become very hot just before the wet season.
y Temperature Range: 16 C
y Annual Precipitation: 0.25 cm. (0.1 in.). All months less than 0.25 cm. (0.1
in.)
y Latitude Range: 15 to 25 N and S
y Global Range: India, Indochina, West Africa, southern Africa, SouthAmerica and the north coast of Australia
y Dry Tropical Climate (BW) desert biome
These desert climates are found in low-latitude deserts
approximately between 18 to 28 in both hemispheres. these
latitude belts are centered on the tropics of Cancer and
Capricorn, which lie just north and south of the equator. They
coincide with the edge of the equatorial subtropical high pressure
belt and trade winds. Winds are light, which allows for the
evaporation of moisture in the intense heat. They generally flow
downward so the area is seldom penetrated by air masses that
produce rain. This makes for a very dry heat. The dry arid desert is
a true desert climate, and covers 12 % of the Earth's land surface.
o Temperature Range: 16 C
o Annual Precipitation: 0.25 cm (0.1 in). All months less than
0.25 cm (0.1 in).
o Latitude Range: 15 - 25 N and S.
o Global Range: southwestern United States and northern
Mexico; Argentina; north Africa; south Africa; central part of
Australia.
Group II
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o L Mid-latitude Climates: Climates in this zone are affected by two
different air-masses. The tropical air-masses are moving towards the
poles and the polar air-masses are moving towards the equator.
These two air masses are in constant conflict. Either air mass may
dominate the area, but neither has exclusive control.
o Dry Midlatitude Climates (BS) steppe
Global Range: southwestern United States and northern Mexico; Argentina;
north Africa; south Africa; central part of Australia.
Characterized by grasslands, this is a semiarid climate. It can be found between
the desert climate (BW) and more humid climates of the A, C, and D groups. If itreceived less rain, the steppe would be classified as an arid desert. With more
rain, it would be classified as a tallgrass prairie.
This dry climate exists in the interior regions of the North American and Eurasian
continents. Moist ocean air masses are blocked by mountain ranges to the west
and south. These mountain ranges also trap polar air in winter, making winters
very cold. Summers are warm to hot.
y Temperature Range: 24 C (43 F).
y Annual Precipitation: less than 10 cm (4 in) in the driest regions to 50 cm
(20 in) in the moister steppes.
y Latitude Range: 35 - 55 N.
y Global Range: Western North America (Great Basin, Columbia Plateau,
Great Plains); Eurasian interior, from steppes of eastern Europe to the Gobi
Desert and North China.
Mediterranean Climate (Cs) chaparral biome
This is a wet-winter, dry-summer climate. Extremely dry summers are
caused by the sinking air of the subtropical highs and may last for up to five
months.
Plants have adapted to the extreme difference in rainfall and
temperature between winter and summer seasons. Sclerophyll plants range in
formations from forests, to woodland, and scrub. Eucalyptus forests cover most
of the chaparral biome in Australia.
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Fires occur frequently in Mediterranean climate zones.
y Temperature Range: 7 C (12 F)
y Annual Precipitation: 42 cm (17 in).
y Latitude Range: 30 - 50 N and S
y Global Position: central and southern California; coastal zones bordering
the Mediter