Earth: A Unique Planet – Introduction, Life on it

The Earth is a Unique Planet as it is the only planet that supports life in the solar system. Earth is also called a blue planet or water planet. It is the third planet from the Sun and the fifth largest planet in the solar system. Earth’s spherical shape is best represented using the globe. Man has constantly explored the four realms of the Earth- lithosphere, hydrosphere, atmosphere, and Biosphere.

The land on Earth is occupied by several towns, villages, cities, countries, agricultural lands, etc. The apparent movement of the Sun, moon, stars and other celestial bodies gives an impression that all these bodies are moving while stationary. We little realize that the Earth is constantly on the move.

What is a Planet?

A planet is a celestial body that revolves around a particular star in orbit and gets all its light from that star. There are eight planets in our solar system that revolve around the Sun. In order of their distance from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Planets move in their fixed paths around the Sun, which are known as orbits.

Earth Definition

Earth is the third planet in the solar system. Earth consists of air, water, land, and life. The land contains valleys, mountains, and flat areas. The air is made up of different gases, mainly oxygen and nitrogen. The water includes lakes, rivers, oceans, streams, rain, ice, and snow.

Fig: Earth

The Earth’s circumference is about 40,000 km, and its diameter is 12,756 km across the equator. The surface of the Earth consists of different realms.

(a). Lithosphere: The lithosphere contains the entire top crust of the Earth, including the land surface and ocean floor.

(b). Hydrosphere: The hydrosphere is the water surface, including the oceans, lakes, and rivers.

(c). Atmosphere: The atmosphere is the blanket of air that surrounds the Earth. The five layers of the atmosphere are the troposphere, followed by the stratosphere, the mesosphere, the thermosphere, and the exosphere. 

(d) Biosphere: The Biosphere is also known as the ecosphere. The Biosphere includes parts of the atmosphere, hydrosphere, and the topmost part of the lithosphere where life exists.

Fig: The Realms of the Earth

Structure of the Earth

On the basis of the study of a physical property of the Earth’s surface, behaviour pattern of seismic waves of earthquakes and the lava erupted from volcanoes, it is believed that the Earth is composed of three parts and they are: crust, Mantle, and core.

(a) Crust (Lithosphere): The word lithosphere has been taken from the Greek word ‘Lithos’ meaning ‘rock’. The outer layers of the Earth’s structure are about 6 to 48 km thick and consist of two layers – sial and sima

(b) Mantle: Earth’s second layer is a mantle. It is the layer between the crust and the core. The depth of Mantle varies between 35 to 2900 km.

(c) Core: It consists of two layers: outer core and inner core. The central part of the Earth is known as the core. It probably consists of a dense nickel-iron alloy with a temperature estimated to be about 2700°C.

Fig: Structure of Earth

Atmosphere

Earth’s atmosphere consists of 78% nitrogen, 21% oxygen with traces of argon, carbon dioxide, and water.

1. The presence of oxygen is a remarkable feature of our planet.
2. Oxygen in the Earth’s atmosphere is produced and maintained by biological processes. Without oxygen, there would be no life.
3. The tiny amount of carbon dioxide present in the atmosphere is extremely important to maintain the Earth’s surface temperatures. Plants also take in carbon dioxide and give out oxygen. 
4. The greenhouse effect is the process by which radiation from a planet’s atmosphere warms the planet’s surface to a temperature above what it would be without this atmosphere. The Greenhouse effect raises the average surface temperature, and without it, the oceans wouldze, and life would be impossible.
5. The Earth is the only planet in the solar system where conditions are exactly favourable for the existence of life.

Distribution of Land and Water

The blue planet justifies the name given to the Earth as this is the only planet where there is more than twice as much water 71% as land 29%. Thus, the distribution of land and water is uneven, and in the Northern Hemisphere, the areas of land and water are nearly equal, whereas, in the Southern Hemisphere, there is nearly fifteen times as much water as land.

A careful study of the globe would reveal a number of outstanding points concerning the distribution of land and water, such as:

1. There is an antipodal arrangement of land and water on the directly opposite sides of the Earth. If there is land in one part of the globe, then there is water opposite to it on the other side of the Earth. Even the North polar ocean is opposite to the Antarctic landmass.
2. The greatest landmasses form an almost complete girdle in the Northern Hemisphere.
3. The landmasses are the narrowest in the Southern Hemisphere.
4. The Antarctic landmass has three protruding areas. One is extending towards South America, a second towards South Africa and a third towards Australia.

Earth – The Only Planet with Life on it

1. The Biosphere is the sphere of life that spreads over all the other three spheres. The term Biosphere was first used a century ago by the Austrian geologist Edward Suess as a sphere of living organisms or biological processes lying at the interfaces between the atmosphere, lithosphere and hydrosphere.
2. Air, water, man, animals, plants, plantations, soil and bacteria are all invisibly interlinked in a life-sustaining system called the environment. All living organisms – microbes, plants, animals and man have survived by adjusting themselves to the environment.
3. It is, therefore, absolutely necessary that a balance is maintained among the different cycles like energy cycle, heat cycle, carbon and nitrogen cycle, oxygen cycle and water cycle on which our environment depends.
4. The Biosphere supplies the essential requisites of life for all the species living on Earth, viz. light, heat, water, food and living space or habitats.
5. The Biosphere, or the ecosystem as it is called, is an evolutionary system. It represents a stable equilibrium of various physical and biological factors which have been operating in the past.

Unique Features of Earth

1. Earth is the third planet in the distance from the Sun and the fifth largest in the solar system. Our planet Earth is about 4.6, million years old. 
2. Earth’s orbit lies between mars and venus. Its average distance from the Sun is 149.6 (150) million km. It takes 23 hr, 56 min and 4 sec sec to complete one rotation, which accounts for one day. 
3. Earth completes its one revolution on its orbit around the Sun in 365 days (365 days 5 hrs 48 min and 45.51 sec to be precise). This revolution accounts for one year.
4. 71% of the Earth’s surface is covered with water. It is the only planet on which water exists in liquid form.
5. The water cycle is another special feature of the Earth.

Suitable Conditions for Life on Earth

Conditions favourable for life on Earth are the most remarkable feature of Earth is that life exists only on this planet because

1. Our Earth is the third planet with respect to its distance from the Sun. It is neither too close like Mercury and Venus nor too far like Uranus and Neptune. Hence, it receives just the right amount of heat necessary for life.
2. Earth’s atmosphere, extending up to 1600, km around, contains an adequate amount of oxygen 21% nitrogen 78% along with a small number of other gases like hydrogen, helium and ozone.
3. The ozone layer acts as a blanket preventing us from the harmful ultraviolet rays of the Sun and retains the heat radiated from the Earth’s surface.
4. Besides its favourable atmosphere, the Earth’s water cycle is its most unique feature. Life cannot exist without water.
5. To sum up, the Earth’s location in the solar system, its atmosphere containing oxygen and its water cycle have made life possible to exist on Earth.

Earth A Unique Planet: Summary

Earth is the only planet where life exists. There are eight planets in the solar system which are: Mercury, Venus, Earth, Mars, Jupiter, Uranus, and Neptune. All planets revolve around the Sun in their own paths called an orbit. Earth is also called the blue planet because three-fourths of the Earth’s surface is covered by water. Earth contains different realms such as the lithosphere, hydrosphere, atmosphere, and Biosphere. The Biosphere is the layer where life exists. Earth’s atmosphere contains a mixture of gases, but oxygen is a dominant gas which is the reason all living organisms can survive on Earth. The ozone layer acts as a blanket that protects the Earth from ultraviolet rays which come from the Sun. To sum up, it can be said that Earth has got some unique features and unique phenomena which have made it a unique planet that can support life.

FAQs

Q.1. Why is Earth called a unique planet?
Ans: Earth is called a unique planet because it is the only planet that supports life. Earth has oxygen to breathe, moderate temperatures to sustain life, water to drink, etc.

Q.2. Who is the closest celestial body to our Earth?
Ans: Moon is the closest celestial body to our Earth.

Q.3. What makes the Earth possible for life?
Ans: Earth is present at the right distance from the Sun. It is protected from harmful solar radiation by the ozone layer, and it is kept warm by an insulating atmosphere. It also has the right chemical ingredients for life, including water and carbon.

Q.4. Does Mars have oxygen?
Ans: Mars has only 0.13% of oxygen. It is dominated by a maximum amount of carbon dioxide.

Q.5. What was the first life on Earth?
Ans: The microbes are the first life on the Earth.

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