Notes on Hydrosphere

Water constitutes two-thirds of the Earth. Oceans, seas, rivers, etc., constitute the hydrosphere. Oceans are the largest storehouses of water. Life would not possible without water. Water is essential for life. It helps in carrying out many life processes in the living things. It is very good solvent. It dissolves many minerals. The roots of the plants absorb these minerals. Plants make their food with the help of these minerals. They will die if they do not get water.

Types of microbial habitat: 1. Hydrosphere 2. Lithosphere ...

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Oxygen dissolved in water is used by animals in living in water.


Water is also helps to control the Earth’s climate. Water heats up or cools slowly as compared to other solids or liquids. The sea breezes are caused by slow heating and cooling of water. At the coastal areas, by noon the land becomes hotter than the water in the sea. This causes wind to bow from sea to land (sea breeze). At night, the land becomes cooler than water. Therefore, the wind blows from the land towards the sea (land breeze). That’s why the climate in the coastal areas is moderate.

Oceans are important for the existence of life on the Earth. Water from oceans evaporates and falls as rain. Oceans absorb heat that reaches the Earth’s surface along with the sun’s rays.

Importance of Oceans/Seas:

  1. They regulate the temperature of the Earth.
  2. They are a medium for cheap transport.
  3. They are a reservoir of fossil fuels, minerals and salts. Most important minerals found in oceans are iodine and common salt.
  4. They support marine life.

Water Cycle:

Water never disappears from the Earth. Nature recycles or reuses every drop of water over and over again through a process called water cycle. Due to the heat of the sun, the water in oceans, lakes and rivers evaporates. Water from moist soil, trees and from living things is constantly evaporating. The heat of the sun warms up the air near the ground surface. This warm air containing the water vapor is lighter and hence rises up. And as the temperature of the atmosphere decreases with altitude, the warm air cools (condenses) at higher altitudes. On condensation, water vapor turns into water droplets which from clouds. These droplets come closer and combine to form drops of water, which fall as rain. The rainwater finally goes back to sea again. This is how the water cycle is completed. The source of energy for water cycle is the sun.

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