- Environment is derived from the French word Environner, which means to encircle or surround. All the biological and non-biological entities surrounding us are included in environment.
- The flora, fauna and micro-organisms as well as the man- made structures in our surroundings have a bi-directional interaction with us directly or indirectly. The totality of all these components and their interactions constitute the environment.
TYPES OF ENVIRONMENT
- It is not just consists of the natural surroundings, but also those components of surrounding, which are man-made as well as the social and cultural aspects of the surroundings
- Three types of environment- Natural, Man-made, and Social.
- Natural Environment consists of two types of components abiotic and biotic.
- Abiotic components are those, which are non-living things, while the biotic components are living things in the natural environment.
- Man-made environment consists of those places, which are artificially made by man by planned manipulation which includes crops fields, cities, industrial space, airports, space station etc.
- Social Environment includes cultural norms and values. Political, economical and religious institutions constitute an important part of the social milieu and often decide how the environmental resources will be utilised by people and for whose benefit these will be utilised.
STRUCTURE OF ENVIRONMENT
- Earth’s environment can be further divided into the following four segment- Lithosphere, Hydrosphere, Atmosphere, and Biosphere.
- The Earth’s crust consists of the soil and rocks are lithosphere. The soil is made up of inorganic and organic matter and water.
- The earth’s crust is made up of various types of rocks that can be of different colour, size and texture.
- There are three major types of rocks: igneous rocks, sedimentary rocks and metamorphic rocks.
- They are formed, when the molten magma cools and becomes solid.
- There are two types of igneous rocks: intrusive rocks and extrusive rocks.
- An extrusive igneous rock is formed from molten magma coming from the interior of the earth on its surface, rapidly cools down and becomes solid. Example- Basalt
- An intrusive igneous rock is formed when the molten magma cools down deep inside the earth’s crust. Example- Granite
- It is formed by transported and deposited small fragmented rocks by wind, water etc and these loose sediments are compressed and hardened to form layers of rocks.
- These rocks contain fossils of dead plants, animals and other microorganisms.
- For example, sandstone is made from grains of sand.
These rocks are formed due to great heat and pressure over igneous and sedimentary rocks.
For example, clay changes into slate and limestone into marble.
WEATHERING OF ROCKS
- Chemical weathering- This is a relatively slow and simple process. The major agents responsible for chemical weathering are water, air, oxygen, carbon dioxide, and other material.
- Physical weathering- This is brought about by a mechanical process due to changes in temperature water and wind.
- Biological weathering- This is caused by a number of organisms, which aid in the disintegration of rocks. A root of plants growing in cracks and fissure creates considerable pressure and causes the rocks to disintegration.
- This comprises all water resources both surface and ground water. The world’s water is found in ocean and seas, lakes, reservoirs, rivers and streams, glaciers and snow caps in the Polar Regions in addition to ground water below the land areas.
- Water is very important for life .It continuously changes its form through water cycle.
- The process by which water continually changes its form and circulates between oceans, atmosphere and land is known as the water cycle.
- The major sources of fresh water are the rivers, ponds, springs and glaciers. The ocean bodies and the seas contain salty water.
- The water of the oceans is salty or saline as it contains large amount of dissolved salts. Most of the salt is sodium chloride or the common table salt that we eat.
- The earth is covered by three-fourth of water. 97.3% water is saline or salty in ocean and seas, 3% is fresh water that consisting ice-cape, ground water, fresh water lakes, inland and salt lakes.
Atmosphere is consists of mainly nitrogen (78%), oxygen (21%), argon (0.93%), carbon dioxide (0.03%) and other gases like helium, ozone, argon and hydrogen (0.04%).
Nitrogen is very important for plant’s survival. They cannot take nitrogen directly from the air. Bacteria that live in the soil and roots of some plants take nitrogen from the air and change its form so that plants can use it.
Oxygen is the second most plentiful gas in the air. Humans and animals take oxygen from the air. Green plants produce oxygen during photosynthesis.
Carbon dioxide is another important gas. Green plants use carbon dioxide to make their food and release oxygen. Humans or animals release carbon dioxide. The amount of carbon dioxide released by humans or animals seems to be equal to the amount used by the plants which make a perfect balance.
STRUCTURE OF THE ATMOSPHERE
- The atmosphere is divided into five layers starting from the earth’s surface. These are Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
- Troposphere: This layer is the most important layer of the atmosphere. Its average height is 13 km. The air we breathe exists here. Almost all the weather phenomena like rainfall, fog and hailstorm occur in this layer.
- Stratosphere: It lies above the troposphere which extends up to a height of 50 km. This layer is almost free from clouds and associated weather phenomenon, making conditions most ideal for flying aeroplanes. One important feature of stratosphere is that it contains a layer of ozone gas.
- Mesosphere: This is the third layer of the atmosphere. It lies above the stratosphere. It extends up to the height of 80 km. Meteorites burn up in this layer on entering from the space.
- Thermosphere: In thermosphere temperature rises very rapidly with increasing height. Ionosphere is a part of this layer. It extends between 80-400 km. This layer helps in radio transmission. In fact, radio waves transmitted from the earth are reflected back to the earth by this layer.
- Exosphere: The upper most layer of the atmosphere is known as exosphere. This layer has very thin air. Light gases like helium and hydrogen float into the space from here.