Biology Presentation

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BIOLOGY

BY: BY: -NUR HAFIQAH -NUR HAFIQAH -AIMI ZAFIRAH -AIMI ZAFIRAH -NURSHAFIQAH -NURSHAFIQAH -NUR

-NUR FFAATINITINI

-NUR AMIRA HUSNA -NUR AMIRA HUSNA -KHAIRUN NIDA -KHAIRUN NIDA -NUR NABILAH -NUR NABILAH

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INTRODUCTION INTRODUCTION

The ozone layer acts like a giant sunshade, protecting plants and The ozone layer acts like a giant sunshade, protecting plants and animals from much of the sun's harmful ultraviolet radiation.

animals from much of the sun's harmful ultraviolet radiation.

Ozone (O3) forms a layer in the stratosphere, 15-40 km above earth Ozone (O3) forms a layer in the stratosphere, 15-40 km above earth surface. If the ozone in the atmosphere from ground level to

surface. If the ozone in the atmosphere from ground level to a heighta height of 60 km could be assembled at the earth's surface, it would comprise of 60 km could be assembled at the earth's surface, it would comprise a layer of gas only about 3 mm thick.

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LAYER OF EARTH’S ATMOSPERE

1.THE TROPOSPERE 1.THE TROPOSPERE

•

• TheThe tropospheretroposphere is the lowest is the lowest layerlayer of Earth's of Earth's atmosphereatmosphere.. •

•The troposphere starts at Earth's surface and goes up The troposphere starts at Earth's surface and goes up to a heightto a height of 7 to 20 km (4 to 12

of 7 to 20 km (4 to 12 miles, or 23,000 to 65,000 miles, or 23,000 to 65,000 feet) above seafeet) above sea

level.

•

•Most of the mass (about 75-80%) of the atmosphere is in theMost of the mass (about 75-80%) of the atmosphere is in the troposphere.

troposphere.

•

•Almost allAlmost all weatherweather occurs within this layer. Air is occurs within this layer. Air is warmest at thewarmest at the bottom of the troposphere near ground level. Higher up it

bottom of the troposphere near ground level. Higher up it getsgets

colder

colder..

•

•Air pressureAir pressure and the density of the air are also less at high and the density of the air are also less at high altitudes.

altitudes.

•

•Nearly all of the water vapor and Nearly all of the water vapor and dust particles in thedust particles in the atmosphere are in the

atmosphere are in the troposphere.troposphere.

•

•The bottom of the troposphere, right next to the surface of EThe bottom of the troposphere, right next to the surface of Earth,arth, is called the "boundary layer". In

is called the "boundary layer". In places where Earth's surface isplaces where Earth's surface is

"bumpy" (mountains, forests) winds in the boundary layer are all

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2.THE STRATOSPEHERE 2.THE STRATOSPEHERE

•

•The stratosphere is the second layer, as The stratosphere is the second layer, as one moves upward from Earth'sone moves upward from Earth's

surface, of the

surface, of the atmosphereatmosphere..

•

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THE MESOSPHERE THE MESOSPHERE

•

•The mesosphere is above the stratosphere layeThe mesosphere is above the stratosphere layer.r. •

•The layer above the mesosphere is called the thermosphere.The layer above the mesosphere is called the thermosphere. •

•The mesosphere starts at 50 km (31 The mesosphere starts at 50 km (31 miles) above Earth's surface andmiles) above Earth's surface and

goes up to 85 km (53 miles) high. goes up to 85 km (53 miles) high.

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THE THERMOSPHERE THE THERMOSPHERE

•

•The thermosphere is directly above theThe thermosphere is directly above themesospheremesosphere and below the and below the

exosphere

exosphere..

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•It extends from about 90 km (56 miles) to between 500 and 1,000 km (311 toIt extends from about 90 km (56 miles) to between 500 and 1,000 km (311 to

621 miles) above our planet. 621 miles) above our planet.

•

•Below the thermosphere,Below the thermosphere, gasesgases made of different types of made of different types of atomsatoms and and

molecules

molecules are thoroughly mixed together by are thoroughly mixed together byturbulenceturbulence in the atmosphere. in the atmosphere.

•

•Air in the lower atmosphere is mainly composed of the familiar blend of aboutAir in the lower atmosphere is mainly composed of the familiar blend of about

80% nitrogen molecules (N

80% nitrogen molecules (N₂₂) and about 20% oxygen molecules (O) and about 20% oxygen molecules (O₂₂).).

•

•In the thermosphere and above, gas particles collide so infrequently that theIn the thermosphere and above, gas particles collide so infrequently that the

gases become somewhat separated

gases become somewhat separated based on the types of based on the types of chemicalchemical

elements

elements they contain. they contain.

•

•EnergeticEnergetic ultravioletultraviolet and and X-rayX-ray photonsphotons from the Sun also from the Sun also break apartbreak apart

molecules

molecules in the thermosphere. in the thermosphere.

•

•In the upper thermosphere,In the upper thermosphere, atomic oxygenatomic oxygen (O), (O), atomic nitrogenatomic nitrogen (N), and (N), and

helium (He) are the main components of air. helium (He) are the main components of air.

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THINNING OF OZONE LAYER

THINNING OF OZONE LAYER 

The thinning of the ozone layer is mainly due to chlorofluorocarbonsThe thinning of the ozone layer is mainly due to chlorofluorocarbons (CFC).

(CFC).



Once in the stratosphere, CFC are broken down by ultraviolet raysOnce in the stratosphere, CFC are broken down by ultraviolet rays



As a result, the highly reactive chlorine radicals (Cl) are releaseAs a result, the highly reactive chlorine radicals (Cl) are release



These chlorine radicals break down ozone molecules, O3 in a chainThese chlorine radicals break down ozone molecules, O3 in a chain reaction

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CAUSES OF THINNING OF OZONE LAYER CAUSES OF THINNING OF OZONE LAYER

CFCs and related halocarbon gases are the main

CFCs and related halocarbon gases are the main cause ofcause of

ozone depletion all over the world.

CFCs released from Western countries take several

CFCs released from Western countries take several years toyears to

reach the stratosphere where the ozone layer is. During that

time winds spread them all over the world.

In the presence of ultraviolet light these gases release chlorine

and bromine atoms which destroy some of the ozone in the

ozone layer. This is called ozone depletion. The ozone hole is a

related but different phenomenon.

Reaction that take place in

Reaction that take place in polar stratospheric clouds speedpolar stratospheric clouds speed

up the depletion of Antartica (where such clouds are

common)were much faster than elsewhere.

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THE EFFECTS OF THINNING OF OZONE LAYER

Earth's surface receives more UltraViolet-B, as ozone is the

Earth's surface receives more UltraViolet-B, as ozone is the onlyonly

gas currently in our atmosphere that absorbs UltraViolet-B.

UltraViolet-B is also absorbed by soil, meters depth of water,

and directly by the DNA of all surface life.

DNA absorbing UltraViolet-B ends up increasing rates of

cancer, mutation, and decreases crop yields.

UltraViolet-B also causes cataracts to form in

UltraViolet-B also causes cataracts to form in eye structures ineye structures in

animals (including Man).

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Effects on the environment

Increases the temperature of the environment (which causes

the greenhouse effect).

Changes in the climate and weather patterns.

Changes in wind direction.

Effects on plants

The rate of

The rate of photosynthesis decreases due to the destruction ofphotosynthesis decreases due to the destruction of

the stomata and chlorophyll in the leaves.

Disturbs the ecological balance by destroying aquatic

organisms such as planktons.

A number of

A number of economically importeconomically important species of plants, ant species of plants, suchsuch

as

as ricerice, depend on cyanobacteria residing on their roots for the, depend on cyanobacteria residing on their roots for the

retention of

retention of nitrogennitrogen. Cyanobacteria are sensitive to UV light. Cyanobacteria are sensitive to UV light

and would be affected by its increase.

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Effects on human health

Causes skin cancer (melanoma).

Damages eyesight and causes

Damages eyesight and causes cataract.cataract.

Weakens the human immune system.

Skin cancer (melanoma)

The chemical shorthand for these r

The chemical shorthand for these reactions are:eactions are:

Cl + O3 → Cl + O3 → _{ClO + O2}_{ClO + O2} ClO ClO + O → Cl + O2+ O → Cl + O2 In sum In sum O3 + O → O2 + O2O3 + O → O2 + O2

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WAYS OF REDUCE OF OZONE DEPLETION WAYS OF REDUCE OF OZONE DEPLETION

Reduce or stop the use of CFC.

Reduce or stop the use of CFC. For example, reduce the use ofFor example, reduce the use of

air conditioner.

Replace CFC with

Replace CFC with hydrochlorofluorocarbhydrochlorofluorocarbon(HCFC) andon(HCFC) and

hydrofluorocarbon (HF)C. Unlike CFC, these gases break down

in the atmosphere and return to earth in

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SPECIAL:

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The ozone layer is a thin layer of ozone in the atmosphere, 10 - 50 The ozone layer is a thin layer of ozone in the atmosphere, 10 - 50 kilometres above the earth.

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The ozone layer absorbs most of the harmful ultraviolet-B (UV-B) The ozone layer absorbs most of the harmful ultraviolet-B (UV-B) radiation from the sun.

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Wonder gas CFCs were invented in 1928 for commercial applications. Wonder gas CFCs were invented in 1928 for commercial applications.

Use of CFCs increases rapidly.

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Scientists discover a link between CFC Scientists discover a link between CFCss

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If the ozone layer depletes, more harmful UV-B radiation will reach the If the ozone layer depletes, more harmful UV-B radiation will reach the earth through the damaged ozone layer.

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More UV-B radiation means more skin cancers. More UV-B radiation means more skin cancers.

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In 1977, the United Nations Environment Programme (UNEP) sets up a

coordinating committee to study the ozone layer coordinating committee to study the ozone layer..

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Governments agree to study, exchange information and pro

Governments agree to study, exchange information and protect thetect the ozone layer - through the Vienna

ozone layer - through the Vienna Convention for the Protection of theConvention for the Protection of the Ozone Layer .

Ozone Layer .

Scientists continue to find proof of that. Scientists continue to find proof of that.

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The British Antarctic Team discovers severe thinning in the ozone layer The British Antarctic Team discovers severe thinning in the ozone layer over Antarctica - the ozone hole.

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In year 87, 46 governments agree to a fifty per cent cut in the production In year 87, 46 governments agree to a fifty per cent cut in the production and consumption of CFCs by the year took.

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UNEP Assessment Panels recommend that more substances (HCFCs, UNEP Assessment Panels recommend that more substances (HCFCs, methyl bromide) are controlled and that the phase out of CFCs is methyl bromide) are controlled and that the phase out of CFCs is advanced

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Parties agree to completely phase out CFCs by the year 2000, and to Parties agree to completely phase out CFCs by the year 2000, and to

establish a Multilateral Fund to assist developing countries. US$ 240 million establish a Multilateral Fund to assist developing countries. US$ 240 million was allocated for 1991 - 1993

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And people starts to realize the importance of reducing ozone depletion. And people starts to realize the importance of reducing ozone depletion.

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