Maharashtra Board Class 11 Environmental Science Chapter 1 Environment and Sustainable Development PDF Download

1. Environment And Sustainable Development

Environment provides us with a basic life support system through air, water and food. We can not continue to survive without protecting the earth's environmental resources.

Basic Terms Related To The Environment

1. Environment: It includes all aspects of the world around us in which humans, animals and plants live.

2. Ecology: The science that studies the relationships between living and non-living things. It studies the structure and function of nature.

3. Environmental Science: It is the systematic and scientific study of our environment. It integrates knowledge from the pure sciences, ecology, engineering, management, social sciences and other aspects.

4. Environment Education: A subject concerned with learning on all environmental issues. It has a wider coverage than environmental science or ecology. It also includes the social aspects of the environment.

5. Environmental Degradation: It is the damage caused to the environment due to various human activities which harm our surrounding. For example: Deforestation, pollution of water, air, soil etc.

6. Environmental Conservation: It includes ways in which to protect nature and control the damage caused to our natural environment. For example when we prevent the killing of wildlife, or we turn a barren land into a forest, we are conserving the environment.

The environment consist of four segments. These are 1. Atmosphere 2. Hydrosphere 3. Lithosphere 4. Biosphere

1.1 Interdisciplinary Nature Of Environment

"Environmental studies deal with every issue that affects living organisms. It is essentially a multidisciplinary approach that brings about an appreciation of our natural world and human impact on its integrity."

The word environment is derived from the French word "Environ" meaning "Surroundings" i.e. everything around us is environment.

World Environment Day is celebrated on 5th June every year.

The Stockholm Conference

United Nations International Conference on Human Environment, was held at Stockholm, Sweden, from 5th June to 14th June 1972. It was attended by representatives of 114 nations. For the first time respective governments at the highest level came together to take note of how mankind had misused our environment of which we are an integral part. 150 Action plans and 20 principles were approved to protect the delicate balance of ecosystems and to preserve them for the coming generation. The conference adopted the motto "Only one earth" for the entire humanity. The conference declared 5th June as World Environment Day.

Teacher's Note

The environment gives us everything we need to live. Just like a farmer's field gives rice and vegetables, our environment gives us air, water and food every day. We must protect it.

Exam Trick

Remember: World Environment Day = 5th June. Think of it like your birthday but for our Earth. Mark it on your calendar and never forget it for exams.

Points to Remember

Environment = everything around us like air, water, plants and animals.
Ecology = science that studies how living things and nature work together.
Environmental Degradation = damage caused by humans like cutting trees and pollution.
Environmental Conservation = protecting nature and saving forests and wildlife.
Atmosphere, Hydrosphere, Lithosphere and Biosphere = four parts of our environment.

1. Atmosphere

About 99% of the total earths atmospheric mass is concentrated in the first 30 km above Earth's surface. Based on characteristics such as temperature and composition, the earth's atmosphere can be divisible into following layers – Troposphere, Stratosphere, Ionosphere, Exosphere.

Layers Of Atmosphere

1) Troposphere: Troposphere is at about 12 km from Earth's surface. The lowest layer from the surface of the earth is known as "Troposphere". The temperature decreases according to the height at this level. The drop of temperature rate at every 160 m height is about 10°C. The temperature differs at different heights and at different layers. Although this layer is smaller than the other layers, it is important as regards the weight of the air and it covers 80% of the atmospheric air. Other elements of the air are vapour, water molecules, dust and microscopic organisms are found in this layer. This layer is very important and useful for the life of living beings. in which rain, wind, storm, hail, snow, clouds etc. exist.

Tropopause the layer that separates troposphere and stratosphere layers is called as tropopause which is at 2 to 3 km above the troposphere. It is umbrella like coat of air which has stable air. Rain, wind, lightning, clouds, storm, etc., do not exist in this layer. The tropopause has a width of 1.5 km, and temperature of this layer is about -53° C. It also contains high amount dry ozone.

2) Stratosphere: Stratosphere is a layer between tropopause and stratopause. The height of this layer keeps changing according to seasons. Temperatures remain constant for certain height of the layer. But beyond 32 Km of height, the temperature increases. This layer is called 'Isothermal Zone'. The heat from the sun is absorbed in this layer hence temperature is retained. The extension of this layer is much higher in the summer than in the winter. The air in this part of the atmosphere is sparse. Humidity, dust, clouds, etc. are not exactly the same.

Ozonosphere is a layer of Ozone which cover at a height of about 20 to 35 km from the surface of the earth. When the ultraviolet radiation from sunlight come in contact with oxygen, they are processed and ozone (O₃) gas is produced. Ozone layer absorbs the harmful ultraviolet rays radiated from Sun, hence the temperature of Ozone layer increases. This layer protects life on Earth. Hence ozone layer is called "Protective umbrella of earth". Today, due to increasing pollution, the layer of ozone is becoming weak, that results in increase in global temperature, (Global Warming). This has become a serious matter in terms of survival of living organisms.

3) Ionosphere: Ionosphere is a layer found beyond the stratosphere, around 360 to 400 km from the surface of the earth, which is until the end of atmosphere. It extends from 104 to 112 km from the surface of the earth. The radio waves travel from this layer to the Earth, because of which we can listen to the radio. Only 1% of the air is present in this layer of the total atmospheric air.

The mesosphere extends upto 85 km from stratosphere. The top of the mesosphere, called mesopause, is the coldest part of Earth's atmosphere with temperatures avaranging about -130° F (-90°C). Jets and ballons don't go high enough in this layer.

4) Exosphere: Exosphere extends from 500 to 750 km from the surface of the earth. At a height of about 490 km radio waves of a temperature of 1700° C has been detected through rocket and radio waves. This layer predominantly contains neutral atoms of Oxygen, Helium and Hydrogen. At a height of about 2000 km, the Neutral atoms have an effect called a magnetic circle.

Role Of Atmosphere In Climate

Earth is able to support a wide variety of living beings because of its diverse regional climate, that ranges from extreme cold at the poles to tropical heat at the Equator. A region's climate is often described, for example, as sunny, windy, dry or humid, but while the weather can change in just a few hours, climate changes over a longer span of time.

Earth's global climate is an average of regional climates. Today, we are experiencing unusually rapid warming. The scientific consensus is that, the greenhouse gases are increasing because of human activities and trapped heat in the atmosphere.

Teacher's Note

The atmosphere is like a blanket around Earth that keeps us warm and safe. Without it, we would not be able to live. It gives us air to breathe and protects us from the sun's harmful rays.

Exam Trick

Remember: Troposphere = where we live and where weather happens. Stratosphere = where the ozone layer protects us. Just remember Troposphere is the lowest and closest to us.

Points to Remember

Troposphere = the lowest layer where we live and where rain and clouds form.
Stratosphere = the layer above troposphere that contains the ozone layer.
Ozone layer = protects us from harmful sun rays and is called Earth's protective umbrella.
Ionosphere = the layer where radio waves travel so we can listen to radio.
The atmosphere = has 99% of air in the first 30 km above Earth.

2. Hydrosphere

Hydrosphere covers more than 71% of the earth's surface either as oceans (salt water) or as fresh water. Hydrosphere includes (both surface and underground water) sea, rivers, oceans, lakes, ponds, streams and wetlands.

3. Lithosphere

It includes the Earth's crust and upper mantle. It contains the fossil fuels and minerals and the soil chemicals (nutrients) needed to support plant life.

4. Biosphere

The portion of earth where living (biotic) organisms are found and interact with one another and with their non-living (abiotic) environment. This zone of life includes, plants, animals, and their habitat.

Figure 1.1: Our Life Support System: The General Structure Of The Earth

Atmosphere, Biosphere, Hydrosphere, Lithosphere, Upper Mantle, Crust, Mantle, Core, Rock, Soil, Vegetation and animals

Teacher's Note

The Earth has four main parts - air, water, land and all living things. All four parts work together to help us live. If one part gets damaged, all others suffer too.

Exam Trick

Remember: AHBH - Atmosphere, Hydrosphere, Biosphere, Hydrosphere. Wait, I mean: Atmosphere = air, Hydrosphere = water, Lithosphere = land, Biosphere = life.

Points to Remember

Hydrosphere = covers 71% of Earth and includes all water - oceans, rivers, lakes and ponds.
Lithosphere = the hard rock and soil of Earth that contains fossils and minerals.
Biosphere = where all living things like plants, animals and insects live and work together.
All four parts = Atmosphere, Hydrosphere, Lithosphere and Biosphere work as a team for life.

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