Test: Natural Resources- 1 - Class 9 MCQ

Major component of the atmosphere on Mars and Venus:

• Carbon dioxide: The major component of the atmosphere on both Mars and Venus is carbon dioxide.


• Mars: The atmosphere on Mars is composed mainly of carbon dioxide (95.32%), with traces of nitrogen (2.7%) and argon (1.6%).


• Venus: The atmosphere on Venus is predominantly made up of carbon dioxide (96.5%), with small amounts of nitrogen (3.5%) and traces of other gases such as sulfur dioxide and water vapor.

Explanation:
- Mars and Venus are both terrestrial planets in our solar system, but their atmospheres differ significantly from Earth's.
- The high concentration of carbon dioxide in the atmospheres of Mars and Venus is due to various factors, including volcanic activity and the absence of processes that remove carbon dioxide from the atmosphere.
- The lack of liquid water on Mars and the extreme temperatures on Venus prevent the formation of water vapor as a major component of their atmospheres.
- Oxygen, which is the major component of Earth's atmosphere, is not present in significant amounts on Mars or Venus.
- Nitrogen, another major component of Earth's atmosphere, is present in small amounts on Mars and Venus but is not the dominant component.
- Overall, carbon dioxide dominates the atmospheres of both Mars and Venus, making it the major component in their atmospheric compositions.

Rainfall patterns depend on:
1. The underground water table:
- The underground water table plays a significant role in determining rainfall patterns.
- It affects the availability of water for evaporation, which is essential for the formation of clouds and subsequent rainfall.
- Areas with a high water table are more likely to have higher rainfall, as there is an abundant source of moisture for evaporation.
2. The number of water bodies in an area:
- Water bodies such as lakes, rivers, and oceans contribute to the moisture content in the atmosphere.
- Evaporation from these water bodies increases the amount of water vapor in the air, leading to the formation of clouds and precipitation.
- Areas with a higher number of water bodies tend to have more rainfall compared to areas with fewer water bodies.
3. The density pattern of human population in an area:
- The density of human population in an area can indirectly influence rainfall patterns.
- Urban areas with high population densities often have more impervious surfaces like concrete and asphalt, which reduce infiltration and increase surface runoff.
- This can lead to localized increases in rainfall intensity and a disruption of natural rainfall patterns.
4. The prevailing season in an area:
- The prevailing season is an important factor in determining rainfall patterns.
- Different seasons, such as the monsoon season or the dry season, have distinct rainfall characteristics.
- The change in solar radiation, wind patterns, and temperature during different seasons affects the formation and movement of weather systems, ultimately influencing rainfall patterns.
In conclusion, rainfall patterns depend on various factors, including the underground water table, the number of water bodies in an area, the density pattern of human population, and the prevailing season. These factors interact and contribute to the complex nature of rainfall distribution across different regions.

Explanation:
The life supporting gases such as O₂, CO₂, and N₂ are chiefly concentrated in the troposphere. Here's a detailed explanation of why the troposphere is the correct answer:
Troposphere:
- The troposphere is the lowest layer of the Earth's atmosphere, extending from the Earth's surface up to an altitude of approximately 12 kilometers (7.5 miles).
- It is the layer where weather occurs and where most of the Earth's air mass is located.
- The troposphere contains about 99% of the atmosphere's total mass.
- It is where the majority of the life-supporting gases, such as oxygen (O₂), carbon dioxide (CO₂), and nitrogen (N₂), are concentrated.
Stratosphere:
- The stratosphere is the layer above the troposphere, extending from approximately 12 to 50 kilometers (7.5 to 31 miles) above the Earth's surface.
- It contains the ozone layer, which plays a crucial role in protecting life on Earth by absorbing the majority of the Sun's harmful ultraviolet (UV) radiation.
- The stratosphere is not primarily responsible for the concentration of life-supporting gases.
Exosphere:
- The exosphere is the outermost layer of the Earth's atmosphere, extending from approximately 500 kilometers (310 miles) above the Earth's surface and merging with interplanetary space.
- It is composed mainly of very low densities of hydrogen (H) and helium (He) atoms, with trace amounts of other gases.
- The exosphere is not where the majority of the life-supporting gases are concentrated.
Ionosphere:
- The ionosphere is a region of the Earth's upper atmosphere, extending from approximately 60 kilometers (37 miles) to 1,000 kilometers (620 miles) above the Earth's surface.
- It is ionized by solar radiation, and it plays a crucial role in the propagation of radio waves.
- The ionosphere is not primarily responsible for the concentration of life-supporting gases.
Therefore, the correct answer is A: troposphere.

Explanation of the answer:
The correct answer is B: thinning of the ozone layer. Here's a detailed explanation:
Ozone layer:
- The ozone layer is a region in the Earth's stratosphere that contains a high concentration of ozone molecules.
- It plays a crucial role in protecting life on Earth by absorbing most of the sun's ultraviolet (UV) radiation.
Ozone depletion:
- Ozone depletion refers to the destruction of the ozone layer, primarily caused by human-made chemicals called ozone-depleting substances (ODS).
- ODS include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and halons, which were commonly used in aerosol propellants, refrigerants, and fire extinguishers.
Ozone hole:
- The term "ozone hole" refers to a specific phenomenon where there is a significant depletion or thinning of the ozone layer over certain regions, particularly over Antarctica.
- It is called a "hole" because the depletion is so severe that it creates an area with extremely low ozone concentrations.
Causes and effects:
- The ozone hole is primarily caused by the release of ODS into the atmosphere.
- These chemicals break down ozone molecules, leading to a reduction in ozone concentration.
- The thinning of the ozone layer allows more UV radiation to reach the Earth's surface, which can have harmful effects on humans, animals, and the environment.
- Increased UV radiation can cause skin cancer, cataracts, reduced crop yields, and disruptions in marine ecosystems.
Monitoring and international agreements:
- The discovery of the ozone hole led to global concern and prompted international action to address ozone depletion.
- The Montreal Protocol, signed in 1987, is an international agreement aimed at phasing out the production and use of ODS.
- Over time, the implementation of the Montreal Protocol has resulted in a gradual recovery of the ozone layer, although complete restoration may take several decades.
In conclusion, the term "ozone hole" refers to the thinning or depletion of the ozone layer, particularly over Antarctica. This phenomenon is primarily caused by human-made chemicals called ozone-depleting substances, and it has significant environmental and health impacts.

Explanation:
The maximum percentage of gases in air is as follows:
Nitrogen:
- Nitrogen makes up approximately 78% of the Earth's atmosphere.
- It is the most abundant gas in the air.
- Nitrogen is a non-reactive gas and is essential for various biological processes.
Oxygen:
- Oxygen makes up about 21% of the Earth's atmosphere.
- It is the second most abundant gas in the air.
- Oxygen is vital for the survival of most living organisms, as it is used in the process of respiration.
Hydrogen:
- Hydrogen is present in the air but in a very small amount.
- It constitutes only about 0.00005% of the Earth's atmosphere.
- Hydrogen is a highly flammable gas and is mainly found in compounds such as water.
Carbon dioxide:
- Carbon dioxide is present in the air in trace amounts.
- It constitutes only about 0.04% of the Earth's atmosphere.
- Carbon dioxide is a greenhouse gas and plays a role in climate change.
Therefore, the gas with the maximum percentage in air is Nitrogen.

Fate of Nitrogen in Inhaled Air:
The fate of nitrogen inhaled along with oxygen can be explained as follows:
1. Absorption in the bloodstream:
- When we breathe in air, oxygen and nitrogen enter our respiratory system.
- The oxygen is primarily absorbed by the alveoli in the lungs and then transported to the bloodstream.
- However, nitrogen is relatively inert and does not participate in the respiratory process.
- It remains in the alveoli and does not get absorbed into the bloodstream.
2. Exhalation:
- Nitrogen, being non-reactive, is exhaled back into the atmosphere along with carbon dioxide during the process of exhalation.
- The concentration of nitrogen in the exhaled air is relatively unchanged from the inhaled air.
3. Nitrogen in the environment:
- Nitrogen is the most abundant gas in our atmosphere, accounting for about 78% of its composition.
- The nitrogen we inhale and exhale is a part of this atmospheric nitrogen cycle.
- It plays a crucial role in various ecological processes, such as nitrogen fixation by certain bacteria, which convert atmospheric nitrogen into forms that can be utilized by plants.
Therefore, the nitrogen inhaled during respiration does not actively participate in the respiratory process or get absorbed into the cells. It is simply exhaled back into the environment along with carbon dioxide.

Given:

The average amount of N₂ in the atmosphere is to be determined.

To solve this problem, we need to know the composition of the Earth's atmosphere:

• Nitrogen (N₂): 78%


• Oxygen (O₂): 21%


• Argon (Ar): 0.9%


• Carbon dioxide (CO₂): 0.04%


• Other trace gases: 0.06%

Now we can calculate the average amount of N₂ in the atmosphere:

• Nitrogen (N₂) constitutes about 78% of the Earth's atmosphere.


• Therefore, the average amount of N₂ in the atmosphere is 78%.

Therefore, the correct answer is option D: 78%.

Explanation:
The correct answer is C: photosynthesis. Here is a detailed explanation:
Photosynthesis:
- Photosynthesis is the process by which plants and some other organisms convert sunlight, carbon dioxide, and water into glucose and oxygen.
- During photosynthesis, plants use sunlight energy to convert carbon dioxide and water into glucose, a type of sugar, and oxygen is released as a byproduct.
- The oxygen produced during photosynthesis is released into the atmosphere, contributing to the oxygen levels in the air.
Burning of fossil fuels:
- Burning of fossil fuels, such as coal, oil, and natural gas, releases carbon dioxide into the atmosphere.
- While the burning of fossil fuels does release oxygen, it is not the primary source of oxygen in the atmosphere. The carbon dioxide released during combustion contributes to the greenhouse effect and climate change.
Respiration:
- Respiration is the process by which living organisms, including humans and animals, take in oxygen and release carbon dioxide.
- While respiration does release some carbon dioxide, it is not the primary source of oxygen in the atmosphere. It is a process that helps maintain the balance of oxygen and carbon dioxide in living organisms.
Fungi:
- Fungi are organisms that obtain nutrients by decomposing organic matter.
- While fungi play a role in the carbon cycle and decomposition, they do not directly release oxygen into the atmosphere.
In summary, the main source of oxygen in the atmosphere is photosynthesis, where plants convert carbon dioxide and water into glucose and release oxygen as a byproduct. The burning of fossil fuels, respiration, and fungi do not play the same significant role in returning oxygen to the atmosphere.

When water mixes with carbon dioxide in the air, it forms carbonic acid.
Explanation:
- When carbon dioxide (CO2) dissolves in water (H2O), it reacts chemically to form carbonic acid (H2CO3). This reaction occurs naturally in the atmosphere and in bodies of water.
- Carbonic acid is a weak acid that is formed when carbon dioxide dissolves in water. It is a common component in carbonated beverages.
- The reaction between carbon dioxide and water can be represented by the equation: CO2 + H2O → H2CO3
- Carbonic acid is responsible for the acidification of rainwater, which leads to the phenomenon known as acid rain.
- Acid rain can have harmful effects on the environment, including damage to plants, buildings, and aquatic ecosystems.
- The formation of carbonic acid is an important process in the carbon cycle, as it helps regulate the pH of the Earth's oceans.
- Carbonic acid can also dissociate into bicarbonate ions (HCO3-) and hydrogen ions (H+), which play a role in buffering the pH of aqueous solutions.
In summary, when water mixes with carbon dioxide in the air, it forms carbonic acid. This reaction is important in various natural processes and has implications for environmental chemistry.

Preventing soil erosion is crucial for maintaining the health and productivity of land. Here are several effective methods to prevent soil erosion:
Raising forests:
- Planting and maintaining forests can significantly reduce soil erosion.
- Tree roots hold the soil in place, preventing it from being washed away by rain or wind.
- Forest canopies also intercept rainfall, reducing the impact of raindrops on the soil surface.
Avoiding deforestation:
- Deforestation, which involves clearing large areas of trees, increases soil erosion.
- Removing trees exposes the soil to the erosive forces of wind and water, leading to the loss of fertile topsoil.
- Protecting existing forests and implementing sustainable logging practices can help prevent soil erosion.
Managing fertilizers:
- Excessive use of fertilizers can contribute to soil erosion.
- When fertilizers are applied in excessive amounts or during heavy rainfall, they can be washed away into water bodies, causing water pollution and reducing soil fertility.
- Properly managing and applying fertilizers according to soil test results can help minimize soil erosion.
Implementing rotational grazing:
- Overgrazing by animals can lead to soil compaction and erosion.
- Implementing rotational grazing systems, where animals are moved between different pastures, allows vegetation to recover and minimizes soil erosion.
- This practice also promotes the growth of deep-rooted grasses, which help stabilize the soil.
In conclusion, preventing soil erosion requires a combination of measures such as raising forests, avoiding deforestation, managing fertilizers, and implementing rotational grazing. Implementing these practices can help maintain the integrity of the soil, protect its fertility, and ensure sustainable land use.