Biology Presentation

BIOLOGY

BY: -NUR HAFIQAH -AIMI ZAFIRAH -NURSHAFIQAH -NUR FATINI -NUR AMIRA HUSNA -KHAIRUN NIDA -NUR NABILAH

INTRODUCTION The ozone layer acts like a giant sunshade, protecting plants and animals from much of the sun's harmful ultraviolet radiation. Ozone (O3) forms a layer in the stratosphere, 15-40 km above earth surface. If the ozone in the atmosphere from ground level to a height of 60 km could be assembled at the earth's surface, it would comprise a layer of gas only about 3 mm thick.

LAYER OF EARTH’S ATMOSPERE

1.THE TROPOSPERE

The troposphere troposphere is  is the lowest layer layer of  of Earth's atmosphere atmosphere.. The troposphere starts at Earth's surface and goes up to a height of 7 to 20 km (4 to 12 miles, or 23,000 to 65,000 feet) above sea level. Most of the mass (about 75-80%) of the atmosphere is in the troposphere. Almost all weather weather occurs  occurs within this layer. Air is warmest at the bottom of the troposphere near ground level. Higher up it gets colder.. colder Air pressure and pressure and the density of the air are also less at high altitudes. Nearly all of the water vapor and dust particles in the atmosphere are in the troposphere. The bottom of the troposphere, right next to the surface of Earth, E arth, is called the "boundary layer". In places where Earth's surface is "bumpy" (mountains, forests) winds in the boundary layer are all •

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2.THE STRATOSPEHERE The stratosphere is the second layer, as one moves upward from Earth's surface, of the atmosphere atmosphere.. The stratosphere is above the troposphere troposphere and  and below the mesosphere mesosphere.. •

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THE MESOSPHERE The mesosphere is above the stratosphere layer. laye r. The layer above the mesosphere is called the thermosphere. The mesosphere starts at 50 km (31 miles) above Earth's surface and goes up to 85 km (53 miles) high. •

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THE THERMOSPHERE The thermosphere is directly above the mesosphere mesosphere and  and below the exosphere.. exosphere It extends from about 90 km (56 miles) to between 500 and 1,000 km (311 to 621 miles) above our planet. Below the thermosphere, gases gases made  made of different types of atoms atoms and  and molecules are molecules  are thoroughly mixed together by turbulence turbulence in  in the atmosphere. Air in the lower atmosphere is mainly composed of the familiar blend of about 80% nitrogen molecules (N2) and about 20% oxygen molecules (O2). In the thermosphere and above, gas particles collide so infrequently that the gases become somewhat separated based separated based on the types of chemical elements they elements  they contain. Energetic ultraviolet ultraviolet and  and X-ray photons photons from  from the Sun also break apart molecules in molecules  in the thermosphere. In the upper thermosphere, atomic oxygen (O), oxygen (O), atomic nitrogen (N), nitrogen (N), and helium (He) are the main components of air. •

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THINNING OF OZONE LAYER The

thinning of the ozone layer is mainly due to chlorofluorocarbons (CFC). Once in the stratosphere, CFC are broken down by ultraviolet rays As a result, the highly reactive chlorine radicals (Cl) are release These chlorine radicals break down ozone molecules, O3 in a chain reaction

CAUSES OF THINNING OF OZONE LAYER CFCs and related halocarbon gases are the main cause of ozone depletion all over the world. CFCs released from Western countries take several years 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 polar stratospheric clouds speed up the depletion of Antartica (where such clouds are common)were much faster than elsewhere.

THE EFFECTS OF THINNING OF OZONE LAYER

Earth's surface receives more UltraViolet-B, as ozone is the only 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 eye structures in animals (including Man).

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 photosynthesis 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 economically important important species of plants, such as rice rice,, depend on cyanobacteria residing on their roots for the retention of nitrogen nitrogen.. Cyanobacteria are sensitive to UV light and would be affected by its increase.

Effects on human health Causes skin cancer (melanoma). Damages eyesight and causes cataract. Weakens the human immune system. Skin cancer (melanoma)

The chemical shorthand for these reactions r eactions are: Cl + O3 →

ClO + O2

ClO + O → Cl + O2 In sum O3 + O → O2 + O2

WAYS OF REDUCE OF OZONE DEPLETION

Reduce or stop the use of CFC. For example, reduce the use of air conditioner. Replace CFC with hydrochlorofluorocarb hydrochlorofluorocarbon(HCFC) on(HCFC) and hydrofluorocarbon (HF)C. Unlike CFC, these gases break down in the atmosphere and return to earth in the form of rainwater.

SPECIAL:

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

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

Wonder gas CFCs were invented in 1928 for commercial applications.

Use of CFCs increases rapidly.

Scientists discover a link between CFC s

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

More UV-B radiation means more skin cancers.

In 1977, the United Nations Environment Programme (UNEP) sets up a coordinating committee to study the ozone layer.

Governments agree to study, exchange information and protect pro tect the ozone layer - through the Vienna Convention for the Protection of the Ozone Layer . Scientists continue to find proof of that.

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

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

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

Parties agree to completely phase out CFCs by the year 2000, and to establish a Multilateral Fund to assist developing countries. US$ 240 million was allocated for 1991 - 1993

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