Question 1

Question 1Assertion (A): Earth's atmosphere is acting like a blanket.Reason (R): Earth's atmosphere contains different gases.Both A and R are true and R is the correct explanation of A.Both A and R are true and R is not the correct explanation of A.A is true but R is false.A is false but R is true.

Accepted Answer

Both A and R are true and R is not the correct explanation of A.Explanation — The assertion is true because Earth's atmosphere acts like a blanket by trapping heat and maintaining the planet’s temperature, making it suitable for life. The reason is also true, as the atmosphere is made up of different gases. However, the presence of gases alone does not explain how the atmosphere acts like a blanket—it is the greenhouse effect caused by certain gases like carbon dioxide and water vapour that provides this warming effect. So, while both statements are correct, the reason does not directly explain the assertion.

Question 2

Question 8Give two proofs about the shape of the earth.

Accepted Answer

Two proofs about the shape of the earth are:All celestial bodies are spherical — Spheres are the only geometrical shapes that are circular in outline. Sun, Moon amd all other celestial bodies appear to have circular outline. Since Earth too belongs to the same system, there is no reason why Earth should be an exception.Circumnavigation of the earth — Time and again people travelling round the world in different directions came back to the starting point.

Question 3

Question 10List the conditions favourable to life on earth.

Accepted Answer

The conditions favourable to life on earth are:The position of earth in solar system is such that it is neither too far nor too near to the sun. Hence, it receives just the right amount of heat necessary for life.The atmosphere of other planets is either too thin or too dense, full of poisonous gases, making it impossible for life to exist. On the other hand, earth's atmosphere extends up to 1600 km and contains adequate amount of nitrogen (78%), oxygen (21%) and other gases like helium, carbon dioxide and water vapour.It acts as a blanket, protecting us from harmful ultraviolet rays of the sun, and retains the heat radiated from the earth's surface.Earth's water cycle is the most unique feature. Water is essential for the existence of life.

Question 4

Question 13Name the gas that absorbs the harmful ultraviolet rays of the sun.OzoneOxygenCarbon dioxideNitrogen

Accepted Answer

Ozone

Question 5

Question 14Assertion (A): The earth is the only planet known to support life.Reason (R): The earth is a terrestrial planet like Mercury and Venus.Both A and R are true and R is the correct explanation of A.Both A and R are true but R does not explain A.A is true but R is false.A is false but R is true.

Accepted Answer

Both A and R are true but R does not explain A.Explanation — Earth supports life mainly because of its liquid water, protective atmosphere, and moderate temperature range. Merely being a terrestrial (rocky) planet, like Mercury and Venus, is not enough, those planets lack the life-supporting conditions that Earth has.

Question 6

Question 15Assertion (A): Earth is a watery planet that supports life.Reason (R): Distribution of water is responsible for moderating the surface condition of the earth.Both A and R are true and R is the correct explanation of A.Both A and R are true but R does not explain A.A is true but R is false.A is false but R is true.

Accepted Answer

Both A and R are true and R is the correct explanation of A.Explanation — Earth is a watery planet with 70 per cent of the earth's surface being covered by water. Distribution of water moderates the climate and surface condition of the earth, creating ideal conditions for Earth to support life.

Question 7

Question 16Earth has a very hospitable temperature and mix of chemicals that have made life abundant here. Most notably, earth is unique in that most of our planet is covered in liquid water, since the temperature allows liquid water to exist for extended periods of time. Besides liquid water and temperature identify the other features of our planet that make it great for sustaining life?Presence of an atmosphereSolid crustDistance from the sunAll of the above.

Accepted Answer

All of the above.

Question 8

Question 17What is the thickness of the Biosphere?20 km19 km15 km25 km

Accepted Answer

15 km

Question 9

Question 18What term refers to a self-regulating and self-sustaining unit of the biosphere?EcosystemFood cycleBiomeEcology

Accepted Answer

Ecosystem

Question 10

Question 19Name the cycle through which solar energy moves from non-living to living organisms and back.Carbon cycleNitrogen cycleNutrition cycleEnergy cycle

Accepted Answer

Nutrition cycle

Question 11

Question 20Name the basic raw material for life.NitrogenCarbonOxygensolar energy

Accepted Answer

Carbon

Question 12

Question 21Name the genius Indian mathematician astronomer from the ancient world who was the first proponent of the round shape of the earth.PythagorasAryabhattaBrahmaguptaBhaskara

Accepted Answer

Aryabhatta

Question 13

Question 22You are standing at a beach looking towards the horizon. You hear the horn of a ship. Which part of the ship will you see first?HullDeckMastAll of them.

Accepted Answer

Mast

Question 14

Question 23Where was the Bedford Level Experiment carried out?EnglandFranceIndiaCanada

Accepted Answer

England

Question 15

Question 9Trace the cyclical movement of carbon in the three realms of the earth.

Accepted Answer

Cyclical Movement of Carbon in the three realms of the EarthCarbon is present in the atmosphere as carbon dioxide (CO₂).Plants absorb CO₂ from the atmosphere during photosynthesis, and convert it into organic matter.When animals eat plants, carbon enters their bodies.Both plants and animals release CO₂ back into the atmosphere during respiration.When plants and animals die and decay, some of the carbon gets stored in the lithosphere as fossil fuels (like coal and petroleum).When these fossil fuels are burnt, CO₂ is released back into the atmosphere.Oceans in the hydrosphere absorb CO₂ from the air. Some marine organisms also use it to form shells.When these organisms die, carbon settles to the ocean floor and becomes part of the marine sediments (lithosphere).

Question 16

Question 1(c)Give a geographical reason for each of the following:(i) The sunrise and sunset occur at different times at different places.(ii) The earth is not a perfect sphere.(iii) Venus is hotter than Mercury.

Accepted Answer

(i) The sunrise and sunset occur at different times at different places because the earth rotates from west to east and therefore, people in the east can see the sun earlier than those in the west.(ii) The earth is not a perfect sphere because the diameter of the earth varies at the equator and at the poles. This difference is due to the centrifugal force of the earth's rotation at a great speed which forms a bulge at the equator and a compression at the poles.(iii) Venus is hotter than Mercury because Venus is mainly composed of carbon dioxide which produces Greenhouse effect on the surface of Venus. Thus, the temperature on its surface remains very high.

Question 17

Question 1(d)Draw a well labelled diagram to show that the horizon of the earth is circular in shape.

Accepted Answer

Please refer to the full solution above.

Question 18

Question 2(a)Describe the role of atmosphere in making earth a habitable planet.

Accepted Answer

The atmosphere of the earth is composed of gases like nitrogen (78%), oxygen (21%), carbon dioxide, helium and argon (less than 1%). Atmosphere plays a major role in making earth a habitable planet as-The atmosphere receives heat from the sun by solar radiation and loses heat by earth's radiation. In this way, a balance is maintained.The earth's atmos[here is made up of life-supporting gases like nitrogen, oxygen and carbon dioxide.Ozone present in the earth's atmosphere absorbs harmful ultraviolet rays of the sun.The atmosphere also prevents loss of heat from the earth's surface and helps to keep earth warm.

Question 19

Question 2(b)Describe the role of water in making earth a habitable planet.

Accepted Answer

Earth is a watery planet with 70% of the earth's surface being covered by water. Water plays a major role in making earth a habitable planet as-Distribution of water is responsible for moderating the climate and surface condition of the earth.Water bodies like lakes, ponds, rivers etc. are important parts of the ecosystems and biosphere.Water moves in a continuous hydrological cycle. There is a proper balance between evaporation, condensation and precipitation without which life would not be possible.Water bodies help to maintain the temperature of the earth's surface. They rapidly absorb enormous amount of heat during the day, and keep the earth fairly cool. At night, they release the heat absorbed during the day, which along with other atmospheric effects, keep most of the surface from freezing at night.

Question 20

Question 2(c)Describe the role of temperature in making earth a habitable planet.

Accepted Answer

Temperature plays a major role in making earth a habitable planet as the earth is the third planet from the sun. It has an average temperature of 17 degrees Celsius which is suitable for life to exist. Other planets of the solar system are either too hot or too cold to support life.

Earth as a Planet

Analytical Questions

Answer The Following Questions

Choose The Correct Option

Short Answer Questions

Structured Questions

Thinking Skills