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THE EARTH-OURLIVING PLANET-8th Standard Social Science Notes

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THE EARTH-OURLIVING PLANET

l. Fill in the blanks with suitable answer:

1.The total geographical area of the Earth is______Sq. Kms

2.The shape of the Earth is ______

3.The equatorial and polar diameter of the Earth is _______ and _________ Kms.

4.The 23½° North latitude is called as ____________

5.The Indian Standard Time is based on _________ longitude.

Ans: (1) 510 million (2) Geoid (3) 12756, 12714

(4) Tropic of Cancer (5) 82½° East

II. Answer the following questions briefly:

1. Why is the Earth called 'Living Planet'?

Ans: The Earth is the home for all forms of life like plants, animals and human beings because of its suitable distance from the Sun, range of temperature, life supporting gases, atmosphere, water cycle, etc. It is the only planet that supports life that is why it is called 'Living Planet'.

2.Why are the Northern and Southern hemispheres called Land and Water Hemispheres?

Ans: The Northern Hemisphere has 60% of land and 40% of water. Therefore it is called the 'Land Hemisphere. The Southern Hemisphere has 81% of water and 19% of land in the Southern Hemisphere. So it is called the 'Water Hemisphere'.

3.What are latitudes and longitudes?

Ans: Latitude- is a horizontal imaginary line which joins all the places which have the same angular distance north or south of the equator. It is measured in degrees.

Longitude- The imaginary vertical lines that intersect equator at right angle joining the north and south are called longitudes.

4.Mention the difference between local time and standard time.

Ans: Local Time: The time according to the longitude of a place or according to the position of the Sun at the place is known as the Local time. This is based on the local meridian passing over that place. When the Sun is shining vertically over the longitude it is 12 noon at that place. All places situated on the same meridian have the same local time. Every longitude has its own local time.

Standard Time: To avoid much confusion that arises from following the local time which differs from place to place, many countries follow uniform time throughout the country. Such uniform time is based on the central meridian of the country or the meridian on which the most important city is located. This uniform time which is followed throughout a country is called Standard Time of that country.

5. What is the International Date Line?

Ans: The circum navigation of the world brought a new problem in keeping the correct date and day in the week for the travellers. Therefore a line passing through 180 degree meridian diametrically opposite to the GMT(Greenwich Meridian Time) was adopted as the point where circumnavigation should make adjustments. This line is supposed to pass Pacific Ocean along the 1800 meridian but makes short detours in order to avoid land masses. This is known as the International Date Line because the date and day is changed whenever people cross this line by ships or airplanes.

III. Define the following:

1.Unique planet: The Earth is called a Unique Planet because of its features. It is the only planet that supports life. The Earth is the home for all forms of life like plants, animals and human beings because of its suitable distance from the Sun, range of temperature, life supporting gases, atmosphere, water cycle, etc.

2.Size of the Earth planet: The Earth is the fifth largest planet in the Sun's family. The diameter of the earth is approximately four times greater than the Moon and it is around 107 times less than that of the Sun. The total geographical area is 510 million sq. kms.

3.Geoid: The shape of the earth is often described as Geoid, which literally means 'Earth shaped', or 'Oblate spheroid'. The earth is flattened at the poles and bulges at the equator. The equatorial diameter of the Earth is 12756 kms and the Polar diameter is 12714 kms, Equatorial circumference 40,008 kms. The difference of 42 kms in diameter is the proof for regarding the Geoid shape of the Earth.

4.Continents: The land bodies of the Earth are known as
Continents. There are seven continents, namely Asia, Africa, North America, and South America. Antarctica, Europe and Australia. The continents are land masses of large size. Asia is the largest continent and Australia is the smallest continent in the world.

5.Prime Meridian: Lines of longitude are called Meridians
(‘meri'-mid and 'dian'-day) because all places along the same meridian of longitude experience noon or mid-day at the same time. The meridian passing through Greenwich (England) has been chosen as Prime Meridian. It is marked as 00 longitude.

6.Indian Standard Time: In India, 82½° East longitude is
considered as the Standard Meridian of the country. It passes through Allahabad of Uttar Pradesh. The time based on this Meridian is called the Indian Standard Time (IST). It is five hours and 30 minutes ahead of GMT.

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