Unit 4 ecology and ecosystem lecture 1

| Jul 2012| © 2012 UPES

ECOLOGY &ECOSYSTEM

Arti JainAssistant ProfessorHSE

Structure of the Earth

What does it consist of?

Structure of the Earth

What does it consist of?

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ATMOSPHERE

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Our earth is surrounded by an envelop of gases.

This blanket of gases hanging over our earth is called ATMOSPHERE.

It is integral part of our earth like lithosphere and hydrosphere.

Pure air is colourless, odourless, tasteless and not to be felt unless it is in motion.

It is mobile compressible and expansible and has weight.

About half the mass of atmosphere lies below the height of 5500 meters and about 99 percent lies below 40 kms.

Life is impossible without atmosphere. There will not no weather and climate without it.

It protects us from the full range of solar effects.

INTRODUCTION

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COMPONENTS OF ATMOSPHERE

Air or atmosphere is a mixture of some gases.

Only 4 gases namely nitrogen (78.084%), oxygen (20.947%), argon (0.934%) and carbon dioxide (0.031%) account for 99% of dry air.

Oxygen

No life is possible without it

Necessary for combustion

Necessary for animal metabolism

Constitutes one fifth of the dry air

It is replenished by photosynthesis in plants

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Nitrogen

Important constituent for many organic compounds

Most important function is to dilute oxygen and regulate combustion and oxidation

Carbon dioxide

Green plants extract carbon dioxide from atmosphere for photosynthesis

Has great climatic significance

Efficient absorber of heat and emits half of the heat absorbed to earth.

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Ozone

It absorbs ultraviolet radiation and protects us from full range of solar effects.

Water vapor

The atmospheric moisture causes precipitation, in different forms like rain, hail, fog, mist, snow etc.

It causes rainbow

It causes halo around sun and moon

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Some important characteristics of atmosphere

Denser gases predominate the lower layers. This is due to gravitational pull exercised by earth.

Carbon dioxide disappears at the height of 20km, oxygen at 110 km and nitrogen at 130 km . Beyond the height of 80 km atmosphere mainly consists of hydrogen.

There is horizontal variation in atmosphere also. Heavier gases are least over equator and predominate polar areas.

The composition of atmosphere is fairly uniform upto the height of 6 km

The contents of water vapor vary with temperature. The % decreases from equator towards pole

The composition changes during daytime. At noon, light gases predominate..

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STRUCTURE OF ATMOSPHERE

Generally four different layers of atmosphere are recognized:

Troposphere

Stratosphere

Mesosphere

Thermosphere

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TROPOSPHERE Derived from greek word tropos meaning mixing

Height places from place to place and season to season. Generally its height is 17 kms over equator and 8 km over poles.

Average altitude is 11 kms

Clouds, storms, cyclones, dust particles and water vapours are confined to this layer.

The temperature decreases with height at the rate of 6.5 degree celsius for every 1000 meters. This is called lapse rate.

The temperature in this layer ranges upto -56 degree celsius

This layer contains nitrogen, oxygen, carbon dioxide and water vapour.

75% of the mass of atmosphere lies in this layer.

A shallow layer called ‘ tropopause’ ( = where mixing stops) marks its upper limit

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STRATOSPHERE

The layer above tropopause is called stratosphere

The temperature in the lower layers is constant and the lower layer is called ‘isothermal layer’.

Beyond that the temperature increases due to absorption of ultraviolet rays by ozone.

The temperature comes upto – 2 degree celsius

There are no clouds, no dust particles, no water vapour, no cylcones, no storms and no convection currents in stratosphere.

The layer goes upto the height of 50 km

Ozone dominates this layer

A shallow layer of stratopause marks its upper layer.

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Ozone Layer

There is maximum concentration of ozone from 30-60 km above the surface of earth.

It is a warm layer as ozone absorbs extremely hot ultra violet rays.

This absorption protects the man from sun burn and many other diseases and health problems which can happen due to ultra violet rays.

Its formation starts at an altitute of 16 km from the surface of earth.

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MESOSPHERE

The layer at an altitude of 50-80 km is called mesosphere.

The temperature decreases with height and reaches -92ºC at the height of 80 km. Beyond this height the temperature increases rapidly.

THERMOSPHERE Thermosphere also known as ionosphere is the highest

layer.

It extends from 80 to 500 kms in height

It is of greatest interest as it reflects radio waves.

The temperature in this layer reaches upto 1200ºC

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THERMOSPHERE/IONOSPHERE cont…

Ionosphere has been divided into ionised layers:

• D-Layer: it reflects low frequency radio waves. It disappears with sunset . It extends from 60-99 km

• E-Layer: It is also called kenelly heaviside layer. It reflects medium and high frequency radio waves. It disappears in night and extends from 90 -130 km.

• Other layers are sporadic E-layer, E2, F1, F2 and L1 layers.

Study of troposphere and stratosphere is a subject of Meteorology

Study of mesophere and thermosphere is called Aerology

Some meteorologists call the outer layer, 500-100 km, as Exosphere. Hydrogen and helium predominate this layer.

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The liquid layer of the Earth is called the hydrosphere.

It represents the entire conglomeration of water bodies enveloping the earth's surface. The hydrosphere consists of the rivers, streams, lakes and oceans, while its sub-category, the cryosphere, is made up of the temporarily frozen, solid water bodies such as ice, snow and glaciers.

Hydrosphere which extends over 70% of the earth’s surface, is the major source of water.

The water reaches the land through a process called water cycle. ( discussed in previous lectures.)

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The Sun's heat evaporates the water of the hydrosphere.

The newly-created water vapor rises into the atmosphere, cools, condenses, and becomes precipitation, falling back onto the land and into the oceans, lakes, and rivers.

The hydrologic cycle describes the movement of water in its three states: solid, liquid and gas. The evaporation and precipitation of the water, the hydrosphere of planet Earth, recycles and rejuvenates the Earth and its water supply each and every day.

Evaporation and precipitation across the Earth is in total balance, though evaporation is greater than precipitation over the oceans and the reverse is true over the land.

Water vapor usually averages twelve days in the atmosphere before coming back down to Earth again as rain or snow. This difference is corrected by the flow of rivers into the oceans and balance is maintained.

Hydrological cycle

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Major sources of water:

Rain water Surface water in the form of gullies streams, rivers, ponds, lakes Ground water is the water that remains under the earth’s crust in the

form of ground water storage.

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Major uses of water are

Municipal use/ domestic usedrinking water purposes, washing flushing toilets, garden irrigation, air coolers etc.

Water for Industry:There are many industries which use huge quantities of water e.g. iron and steel, jute, paper, fertilizer etc.

Water in Agriculture:Water is used for irrigating the agricultural areas.

Water for generating Powerto generate hydroelectric power

Other uses:navigation, fisheries, swimming, boating, water skiing etc.

Use of Water

Unit 4 ecology and ecosystem lecture 1

Technology

Transcript of Unit 4 ecology and ecosystem lecture 1