The Earth:Our Living Planet
I. Fill in the blanks.
1. The total geographical area of the earth is 510 billion sq Kms.
2. The shape of the earth is geoid.
3. The equatorial and polar diameters of the earth is 12756 and 12714 Kms.
4. The 23 1/2° North latitude is called as Tropic of cancer
5. The Indian standard time is based on 82½0 longitude.
II. Answer The Following Questions
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 both on land & water bodies. Also it is situated in a suitable distance from Sun, range of temperature, life-supporting gasses, atmosphere, water cycle etc.
2. Why are the Northern and Southern hemispheres called Land and Water Hemispheres?
Ans: The land and water bodies are unevenly distributed between the Northern and the Southern hemispheres. The Northern Hemisphere has 60% of land & 40% of water. So it is called the ‘Land Hemisphere’. On the other hand, there is 81% of water and 19% of land in the Southern Hemisphere and so it is called as the ‘Water Hemisphere’.
3. What are latitudes and longitudes?
Ans: Latitudes are an imaginary line which joins all the places which have the same angular distance north or south of the equator. Longitudes are the imaginary lines which intersect the equator at a right angle joining the north and south.
4. Mention the difference between local time and standard time.
Local time: The time according to the longitudes of a place or according to the position of Sun at that particular place is known as the local time. This is based on the local meridian passing over that place. Standard time:- The longitude which passes in the center of a particular nation is known as standard Meridian. The time of standard Meridian is taken as Standard time. Ex. Indian Standard Time is based on 82½ East longitude.
5. What is the International Date Line?
Ans: A line passing through 180° meridian diametrically opposite to the G.M.T. was appointed as the point where circumnavigators should make adjustments. This line supposed to pass the Pacific ocean along the 180° Meridian but make short detours in order to avoid landmasses.
This is known as the International Dateline because the date and day are changed whenever people cross this line by ships or airplanes. Any ship crossing this line from west to east gains a day, while the ship crossing this line from east to west loses a day.
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, that is why it is called “Living Planet”. The Earth is the home of 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:
The Earth is the fifth largest planet in the Sun’s family. The diameter of the Earth is approximately 4 times greater than the Moon and it is around 107 times less than that of the Sun. The total geographical area of the Earth is 51 Million sq.kms.
3. Geoid:
The Earth’s shape 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 is 40,076 kms and Polar circumference is 40,008 kms. The difference of 42 kms in diameter is proof 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, South America, Antarctica, Europe and Australia. The continents are landmasses of large size. Asia is the largest continent in the world while Australia is the smallest continent in the world.
5. Prime Meridian:
Line of longitudes are called Meridians (meri-mid and dian -day) because of 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 0° 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 5 hours and 30 Minutes ahead of G.M.T (+5.30).
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