NIOS Class 12 Environmental Science Chapter 1 Origin of Earth and Evolution of The Environment

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NIOS Class 12 Environmental Science Chapter 1 Origin of Earth and Evolution of The Environment

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Origin of Earth and Evolution of The Environment

Chapter: 1

Module 1: Environment Through Ages

Textual Question Answer

INTEX QUESTIONS 1.1

1. Approximately how old is the earth?

Ans: 4.5 billion years.

2. Name the star around which the earth revolves along with other planets of the solar system.

Ans: The Sun.

3. What do you mean by “solar system”? 

Ans: Planets orbiting central star.

4. Why does the day and night cycle consist of only 24 hours? 

Ans: Because earth completes one full rotation on its axis in 24 hours.

5. If you were to view Earth from space, which colour would earth reflect? 

Ans: Blue.

INTEX QUESTIONS 1.2

1. List the conditions that make earth a unique planet. 

Ans: (i) Presence of water. 

(ii) Presence of Air.

(iii) Comfortable range of temperature.

(iv) Buffering capacity.

2. From where earth gets energy? 

Ans: Sun.

3. Why oxygen is essential for life? 

Ans: Oxygen is used in respiration to oxidize food for liberating energy.

INTEXT QUESTIONS 1.3

1. Name the gases that were found in the primitive atmosphere.

Ans: Methane, ammonia, carbon dioxide and hydrogen.

2. Which were the earliest organisms that evolved on earth? 

Ans: Bacteria.

3. How did oxygen come into atmosphere? 

Ans: Because of photosynthesis.

4. Name the five kingdoms of life.

Ans: Monera, Protista, Fungi, Plantae and Animalia.

INTEXT QUESTIONS 1.4

1. Define environment.

Ans: Surroundings or condition in which an organism lives and operates.

2. Name its biotic components.

Ans: Biotic – living organism of all kinds including microbes.

3. List its abiotic components.

Ans: Abiotic – light, humidity temperature, atmosphere and substratum.

4. In a sentence, mention why environmental degradation should be prevented. 

Ans: Because it threatens the survival of living organisms including humans.

TERMINAL EXERCISE

1. Trace the origin of the earth.

Ans: The earth was formed 4.5 billion years ago. It was a burning hot chunk of the white mass of gas and dust. Over a long period, dust and gas slowly condensed to form solid rock. Such condensation and shrinking made the earth heat up so much that the rock melted into a gluey liquid. The condensed gases formed the earth’s primitive atmosphere. After millions of years, the exterior surface of the earth or the earth’s crust cooled and formed hard rock again. The interior of the earth is still very hot.

2. Describe briefly the solar system to which the earth belongs.

Ans: Our Solar System has one star, the Sun, around which eight planets revolve in fixed orbits. The Sun is a huge ball of extremely hot, glowing gases and holds the planets in their orbits by its strong gravitational force. The planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. In addition to these, the Solar System also contains dwarf planets, dozens of moons, and millions of comets, asteroids, and meteoroids.

3. State the big bang theory of origin of universe.

Ans: According to the big bang theory, the universe started with a huge explosion, and matter (dust and gases) filled the entire space. At this time all matter was compacted into a small ball with infinite heat and infinite density called the singularity. It is proposed that the big bang happened about 15 to 20 billion years ago. The huge assemblage of dust and gases then started to spin. As it spun faster and faster, the centre became gradually very hot. It eventually became the Sun. From this, big blobs of dust broke off and formed our eight planets. This established our solar system. This theory was based on the observation that other galaxies are constantly moving away from their own at great speed in all directions.

4. Why is earth able to sustain life while no other planet is known to have life?

Ans: Earth is the only planet that can maintain life in the Solar system due to its unique features. 

The following conditions make Earth hospitable for life:

(i) Presence of water: During the evolution of the earth, water vapour in the primitive atmosphere condensed into liquid water. Three-fourth of the earth’s surface is covered with water. Water is a universal solvent and life originated in water.

(ii) Atmosphere: The earth is surrounded by a gaseous atmosphere that sustains life. The earth’s atmosphere comprises nitrogen (78%) and oxygen (21%), small amounts of carbon dioxide, water vapour, ozone, and rare gases like argon, and neon.

(iii) Temperature: The average temperature of the earth is 16°C. This is a suitable temperature for the living organisms to survive.

(iv) Buffering Capacity: It is one of the unique features of the earth. Due to which a neutral pH (pH7) is sustained in the soil and water bodies. The neutral pH is crucial for the survival and sustenance of living organisms.

5. Name the five kingdoms of living organisms.

Ans: The 5 kingdoms of life are: Monera, Protista, Fungi, Plantae, and Animalia.

6. Define environment. List the various components of the environment.

Ans: The environment is defined as the surroundings or conditions in which an organism lives or operates. There are 2 major components of the environment; biotic and abiotic factors. The Biotic factors are the living components of the environment, They can be broadly clubbed into; green plants and animals. The abiotic components are non-living components of the environment. They include the chemical and physical factors such as temperature, rainfall, substrate, light and atmosphere.