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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

ecology edited!!

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