Which realm of the earth is the most important for human life and why?
Answers
Four Realms of the Earth:
The realm of land is called lithosphere, the realm of water is called hydrosphere and the realm of air is called atmosphere. The narrow zone where land, water and air meet is called biosphere. It is the fourth realm of the earth and it supports life. One of the reasons for supporting life is that the earth has plenty of water on its surface. The first life on the earth is originated in water. The outer solid layer of the earth is called crust or lithosphere. The word lithosphere comes from a Greek word Lithos which means rock. So, the crust or lithosphere is made up of rocks. About one-third of the earth’s surface is occupied by land and the rest is covered with water . Vast land masses rising above the sea level are called continents. There are seven continents in the world. They are Asia, Europe, Africa, North America, South America, Australia and Antarctica. The continents are separated from one another by huge bodies of water called oceans. The level of the oceans is all the same and this level of water is called the sea level. About 250 million years ago, all the continents were joined to form one huge landmass called Pangea. There are three Major Landforms of the earth. Highland region having pointed peaks are called mountains. Highland regions having flat summits are known as plateaus. Lowland regions of flat and level surface are called plains. Mountains rise several thousand meters above the sea level. When such highlands form a long chain, they are known as mountain range. At some places, they may occur in a series of parallel ranges. The Himalayas in the north of India have three parallel ranges. The highest point on the earth’s surface is Mount Everest (8,848 m) in the Himalayas (Asia). Silt deposits made by rivers are known as alluvium. Alluvial deposits form the most fertile lands. Thus, plains are suitable for agricultural activities. And plains are thickly populated.
The island of Mauna Kea in Hawaii is a submarine mountain. It is 10,203 m high if it is measured from the ocean bed – higher than Mt. Everest.
The Indian Ocean does not open out to the north because it is bounded by the continent Asia. Therefore, it is called half an ocean.
The Arctic Ocean is located around the North Pole. Being situated in North Frigid Zone, it remains frozen for most of the part of the year. This ocean is not important for trade and navigation.
The atmosphere is made up of gases like nitrogen, oxygen, carbon-dioxide, argon, etc.
Nitrogen is the most dominant gas. It constitutes about 78 % of the atmosphere. It helps the living organisms to grow.
Oxygen, the life of human beings, constitutes about 21 %.
The remaining 1 % is made up of other gases like argon, carbon-dioxide, hydrogen, etc.
The air is very dense near the surface of the earth. It becomes thinner and less dense when we go high up in the sky. The atmosphere keeps us warm and protects us from the harmful effects of the rays of the sun.
Plants need carbon-dioxide for their survival. The air we exhale is carbon-dioxide which plants take in. the plants, on the other hand, release oxygen which we inhale. So, there is a cycle in the atmosphere which helps in maintaining the natural balance on the earth.
Biosphere extends a few kilometers above and below the sea level. Human beings, plants, animals, birds, fishes and other microbes are found in this realm. Human beings are called Man because they can make decisions based on reason. Thus, we often say Man is a rational animal. All the realms of the earth are inter-related. When something happens to one realm that will affect other realms too. Therefore, we must try not to disturb the realms of the earth as much as we can.
Biosphere is one of the most important for human life as it provides the life for all . it is dynamic realm.