Maharashtra Board Class 6 Geography Chapter 6 Importance of Oceans PDF Download

Importance of Oceans

In the previous standard, we have studied the lithosphere and hydrosphere of the earth, the proportion of land and water on earth, and also the major oceans. Note the area of each ocean given in the following table.

The hydrosphere includes all the water bodies that exist on the earth. This covers all the oceans, seas, rivers and their tributaries, lakes, reservoirs and also groundwater. Of the total global waters, 97.7 % is contained in oceans.

We always see the living world around us. There is considerable diversity in the living world on land. The living world in the hydrosphere is many times greater than the living world on land. And it has a much greater diversity.

Teacher's Note

Our oceans are very big and have many living things in them. In India, we have the Arabian Sea and the Bay of Bengal which are very important for our fish and food.

Exam Trick

Remember: 97.7% water in oceans means almost all earth water is salty. Only 2.3% is fresh water. Think - if you drink ocean water, it tastes salty and your tongue burns.

Points to Remember

The Pacific Ocean is the biggest ocean in the world.
The hydrosphere has all water - oceans, seas, rivers, lakes, and underground water.
Most water on earth (97.7%) is salty ocean water.
Living things in oceans are much more different than on land.

Take some water in a steel dish. It is better if the water is from a borewell. Keep the water in direct sunlight. Do not remove the dish until all the water gets evaporated. Observe the dish after the water has evaporated completely. What do you see? Taste the substance in the dish.

You must have noticed that after the water evaporated completely, a whitish layer is left in the dish. If you taste it, you will find that it is salty. You will realize that these are the salts in the water. In drinking water, the proportion of salts is quite low. Water from oceans and seas has a greater amount of salt. Hence it tastes salty.

Teacher's Note

When water dries up, salt is left behind. This is how salt pans work in coastal India like Gujarat and Goa where salt is made by letting ocean water dry in the sun.

Exam Trick

Remember: Evaporation = water goes away, salt stays. Just like when your mother makes salt from seawater, the water disappears but the white salt remains.

Points to Remember

Ocean water has salt dissolved in it.
When water evaporates, salt is left behind as a white powder.
Drinking water has very little salt in it.
Ocean water tastes salty because of dissolved salts.

Use the following ingredients: One bowl of rice flakes (pohe). One teaspoon oil. One tomato and a small onion: diced. Chilli powder to taste. Mix all the ingredients well. Give the mixture to all your friends and ask them to taste it. Now add some salt to the mixture and taste it again.

What difference do you notice in the dish you tasted earlier and later?

What do you think made the dish really tasty?

For what other purposes do you use the last ingredient at home?

Discuss the source of this ingredient.

Where does the water flowing through the rivers go in the end?

Are there volcanic eruptions in the seas?

Teacher's Note

Salt makes our food tasty and is very important. In India, we eat salt with every meal and it comes from our oceans and seas.

Exam Trick

Remember: Salt makes food tasty - this is how you can remember that ocean water has salt. The more salt, the more "tasty" or salty the water becomes.

Points to Remember

Salt is very important for our food and health.
Ocean water has much more salt than river water.
Salt can be obtained from seawater by letting it evaporate.
We can taste salt - it makes things tasty and salty.

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