Olympiad Test: Natural Resources And Their Conservation -1 - Class 7 Science

The solid part of the earth is called the lithosphere.
Explanation:
The lithosphere is the outermost layer of the Earth, comprising the solid part of the planet. It is composed of the crust and the uppermost part of the mantle. Here is a detailed explanation of each option:
A: Hydrosphere:
- The hydrosphere refers to all the water on Earth's surface, including oceans, lakes, rivers, and groundwater. It does not include the solid part of the Earth.
B: Lithosphere:
- The lithosphere is the solid part of the Earth, which includes the crust and the uppermost part of the mantle. It is divided into several tectonic plates.
C: Atmosphere:
- The atmosphere is the layer of gases surrounding the Earth. It consists of different gases, such as nitrogen, oxygen, carbon dioxide, and others. It does not include the solid part of the Earth.
D: All of these:
- The correct answer is not "all of these" as the hydrosphere and the atmosphere do not represent the solid part of the Earth. Therefore, option B (lithosphere) is the correct answer.
To summarize, the solid part of the Earth is called the lithosphere, which includes the crust and the uppermost part of the mantle.

The correct answer is B: Groundwater.
Explanation:
Groundwater is the most commonly used source of drinking water by humans. Here is a detailed explanation:
1. Groundwater: Groundwater refers to the water that is stored beneath the Earth's surface in porous rocks and soil. It accumulates in underground aquifers and can be accessed through wells or springs. Groundwater is considered a reliable and sustainable source of drinking water.
2. Advantages of Groundwater: There are several reasons why groundwater is preferred as a drinking water source:
- Purity: Groundwater is often naturally filtered as it seeps through layers of soil and rock, making it relatively free from pollutants and contaminants.
- Availability: Groundwater is abundant in most regions, providing a consistent supply of water throughout the year.
- Reliability: Unlike surface water sources like rivers and lakes, groundwater is less susceptible to variations in weather conditions or seasonal changes.
- Protection: Groundwater is less vulnerable to contamination from external sources, such as industrial pollution or surface runoff, as it is stored underground and protected by layers of soil and rock.
3. Other Options: While there are alternative sources of drinking water, they are not as commonly used as groundwater:
- Sea water: Sea water is abundant but requires extensive desalination processes to remove the high salt content, making it expensive and less accessible for drinking purposes.
- Glaciers: Glaciers are a significant source of freshwater, but they are typically found in remote and inaccessible locations, limiting their use as a drinking water source for most populations.
In conclusion, groundwater is the most widely used source of drinking water due to its purity, availability, reliability, and protection from contamination.

Answer:

Introduction:

Freshwater is a precious resource that is essential for human survival and various activities. However, it is important to understand the availability of freshwater on Earth to manage and conserve this resource effectively.

Percentage of Freshwater for Human Use:

The correct answer is C: 0.03%. Only a small fraction of the total water on Earth is freshwater that is accessible for human use. Below are the details explaining why option C is the correct answer:

1. Total Water on Earth:

- The Earth's surface is covered by approximately 71% water.
- However, most of this water is in the form of saltwater in oceans and seas, making it unsuitable for human use.

2. Freshwater Availability:

- Out of the total water on Earth, only about 2.5% is freshwater.
- The majority of freshwater is locked in ice caps, glaciers, and underground aquifers, making it inaccessible for immediate human use.

3. Usable Freshwater:

- The usable freshwater available on Earth is approximately 0.5% of the total freshwater.
- This usable freshwater includes surface water in lakes, rivers, and swamps, as well as groundwater in aquifers.

4. Freshwater for Human Use:

- The freshwater that is directly available for human use is a fraction of the usable freshwater.
- This accessible freshwater is estimated to be only about 0.03% of the total water on Earth.
- It is important to note that this small percentage needs to be shared among the growing global population, agriculture, industry, and other activities.

Conclusion:

Freshwater for human use on Earth is a scarce resource, with only about 0.03% of the total water available. This highlights the importance of sustainable water management, conservation efforts, and responsible water usage to ensure its availability for future generations.

The percentage of water in the human body is 70%. Here is a detailed explanation:
Water in the Human Body:
- Water is an essential component of the human body and plays a vital role in various physiological processes.
- It is present in every cell, tissue, and organ of the body.
- Water helps regulate body temperature, transports nutrients and oxygen, aids in digestion, lubricates joints, and removes waste products.
- The human body constantly loses water through sweating, breathing, and urine, so it is important to replenish it by drinking fluids and consuming water-rich foods.
Percentage of Water in the Human Body:
- The exact percentage of water in the human body can vary depending on factors such as age, gender, and body composition.
- On average, adult males have a slightly higher percentage of water in their bodies compared to adult females.
- The percentage of water in the human body is generally higher in infants and decreases with age.
- The estimated percentage of water in the human body is approximately 60-70%.
- However, the commonly accepted average percentage is around 60% for adult males and 55% for adult females.
- This means that approximately 70% of the human body consists of water.
Conclusion:
In conclusion, the correct answer is B: 70%. The human body is composed of approximately 70% water, which is vital for maintaining overall health and functioning properly.

Answer:
The correct answer is A: decomposers. Decomposers play a crucial role in breaking down dead plants and animals into humus, which is a dark organic material rich in nutrients. Here is a detailed explanation of why decomposers are responsible for this process:
Decomposers:
- Decomposers are organisms such as fungi, bacteria, and certain insects that feed on dead organic matter.
- They break down the complex organic compounds present in dead plants and animals into simpler forms.
- These simpler forms are then converted into humus, which enriches the soil and provides nutrients for new plant growth.
- Decomposers accelerate the decomposition process by secreting enzymes that break down the organic matter.
- They also help in recycling nutrients back into the ecosystem, making them available for other organisms.
Other options:
- Consumers: Consumers are organisms that obtain energy by consuming other organisms. While they may contribute to the breakdown of organic matter through digestion, they do not convert it into humus like decomposers.
- Chemicals: While chemicals can have an impact on decomposition processes, they do not directly convert dead plants and animals into humus.
- Scavengers: Scavengers, such as vultures or some insects, feed on dead animals. However, they primarily consume the flesh and do not play a significant role in the conversion of dead plants and animals into humus.
In summary, decomposers are the organisms responsible for converting dead plants and animals into humus through the process of decomposition.

Plants and animals help in maintaining the balance of:
1. Oxygen and carbon dioxide:
- Plants perform photosynthesis, a process that converts carbon dioxide into oxygen, helping to maintain the balance of these gases in the atmosphere.
- Animals, including humans, breathe in oxygen and release carbon dioxide through respiration, which is then used by plants for photosynthesis.
2. Ecosystems:
- Plants and animals play crucial roles in maintaining the balance within ecosystems.
- Plants provide food and shelter for animals, while animals help in pollination and seed dispersal.
- The presence of different species in an ecosystem helps maintain biodiversity, which is important for the overall health and stability of the ecosystem.
3. Nutrient cycling:
- Plants and animals contribute to the cycling of nutrients in ecosystems.
- Animals eat plants, obtaining nutrients from them, and then release the nutrients back into the environment through their waste.
- Decomposers, such as bacteria and fungi, break down dead plants and animals, releasing nutrients that can be taken up by plants again.
4. Food chains and food webs:
- Plants are primary producers that convert sunlight into energy through photosynthesis.
- Herbivores eat plants, carnivores eat herbivores, and so on, forming a complex network of interactions in food chains and food webs.
- This balance in predator-prey relationships helps control population sizes and maintains the overall health and stability of ecosystems.
5. Air and water quality:
- Plants help improve air quality by absorbing pollutants and releasing oxygen.
- Trees, especially, play a significant role in reducing air pollution and providing shade.
- Animals, such as aquatic organisms, help maintain water quality by filtering and consuming organic matter, preventing the accumulation of pollutants.
In conclusion, plants and animals are integral to maintaining the balance of oxygen and carbon dioxide, ecosystems, nutrient cycling, food chains and webs, as well as air and water quality. Their interactions and interdependence contribute to the overall health and stability of our planet's natural systems.

Answer:
Quinine is obtained from the bark of the cinchona tree. Here is a detailed explanation of why quinine is obtained from the bark of the cinchona tree:
1. Cinchona Tree:
- The cinchona tree, also known as the quinine tree, is a tropical evergreen tree native to South America.
- It belongs to the Rubiaceae family and is primarily found in countries like Peru, Ecuador, Colombia, and Bolivia.
2. Bark Extraction:
- Quinine is extracted from the bark of the cinchona tree.
- The bark is harvested from mature trees, typically around 8-10 years old, as they contain higher levels of quinine.
3. Quinine Content:
- The bark of the cinchona tree contains varying levels of quinine alkaloids.
- Quinine is the primary alkaloid of interest, known for its antimalarial properties.
4. Quinine Extraction Process:
- The extraction process involves grinding and powdering the bark of the cinchona tree.
- The powdered bark is then mixed with a solvent like alcohol or water to extract the quinine alkaloids.
- The extracted solution undergoes further purification and concentration to obtain pure quinine.
5. Uses of Quinine:
- Quinine has been widely used as an antimalarial drug for centuries.
- It is known to treat and prevent malaria by killing the Plasmodium parasites in the bloodstream.
- Quinine also possesses antipyretic (fever-reducing) and analgesic (pain-relieving) properties.
6. Other Sources:
- While quinine is primarily obtained from the cinchona tree, it can also be synthetically produced in laboratories.
- However, natural extraction from the cinchona bark remains the primary and most common method.
In conclusion, quinine is obtained from the bark of the cinchona tree due to its high concentration of quinine alkaloids, which possess antimalarial properties. The bark is harvested, extracted, and processed to obtain pure quinine, which is then used for various medicinal purposes.

Explanation:
Key Points:
- Natural vegetation refers to the plant life that grows in a specific region without any human intervention or interference.
- It includes all types of plants, such as trees, shrubs, grasses, and other vegetation that grow naturally in a particular area.
- Natural vegetation plays a crucial role in maintaining the ecological balance and providing habitat and food for various organisms.
Answer:
The correct answer is B: Interference of human.
Reasoning:
- Natural vegetation grows without the interference of human activities, meaning it develops and thrives on its own without any human intervention.
- Human interference can include activities such as deforestation, urbanization, agriculture, and the introduction of invasive species, which can disrupt or destroy natural vegetation.
- Natural vegetation is influenced by various factors such as climate, topography, soil conditions, and natural disturbances like fire and floods.
- It is adapted to the specific environmental conditions of a region and can vary in different areas based on these factors.
Conclusion:
Natural vegetation grows without the interference of human activities and is influenced by various environmental factors. It plays a vital role in maintaining the balance of ecosystems and providing habitat and resources for various organisms.

The answer is A: soil.
Explanation:
Here is the detailed explanation for why soil is not considered a forest product:
1. Forest Products:
- Forest products are materials derived from forests that have economic or commercial value.
- These products are obtained from various parts of trees, such as wood, bark, leaves, fruits, roots, etc.
- Forest products are used for various purposes, including construction, furniture making, paper production, energy generation, and more.
2. Lac:
- Lac is a resinous substance secreted by insects and is commonly found on the branches of certain trees.
- It is used in the production of lacquer, which is applied as a protective coating or varnish.
- Lac is considered a forest product because it is obtained from trees.
3. Fodder:
- Fodder refers to food that is given to livestock, such as cattle, horses, and goats.
- Fodder is often derived from crops that are grown in agricultural fields, not from forests.
- While forests may provide natural grazing areas for some animals, fodder production is primarily associated with agriculture.
4. Timber:
- Timber is wood that is specifically harvested and processed for construction, furniture, and other purposes.
- It is one of the most well-known forest products and is obtained from trees through logging and milling.
5. Soil:
- Soil is a natural resource that consists of minerals, organic matter, water, and air.
- While forests play a crucial role in maintaining soil health and preventing erosion, soil itself is not considered a forest product.
- Soil is essential for the growth of trees and other vegetation, but it is not directly derived from forests.
In conclusion, soil is not considered a forest product because it is not obtained from trees and does not have direct economic or commercial value like other forest products such as lac, fodder, and timber.

The water table of a place
The water table is the level at which the ground is saturated with water. It plays a crucial role in determining the availability of groundwater in a particular area. Here are some key points to consider:
1. Changes from place to place:
- The water table is not uniform and varies from one location to another.
- Factors such as geology, climate, vegetation, and human activities influence the water table's depth and availability in different regions.
2. Changes from time to time:
- The water table is not static but fluctuates over time.
- It can rise or fall depending on factors such as rainfall, evaporation, groundwater extraction, and recharge rates.
3. Goes down when rains are less:
- When there is less rainfall, the recharge of groundwater is reduced, leading to a decline in the water table.
- Prolonged droughts or periods of low precipitation can significantly impact the water table, causing it to drop.
4. All of these:
- The correct answer to the given question is option D, which states that all of the above factors affect the water table.
- The water table is influenced by both spatial and temporal variations, as well as changes in precipitation patterns.
In conclusion, the water table is not fixed and is subject to change based on various factors. It varies from place to place, changes over time, and decreases when there is a decrease in rainfall. Understanding these dynamics is essential for managing and utilizing groundwater resources effectively.

Factors in balancing the amount of fresh water on earth:
1. Water Cycle:
- The water cycle is a continuous process that involves the evaporation of water from the earth's surface, condensation in the atmosphere, and precipitation back to the surface.
- It helps in the redistribution of water from oceans, lakes, and rivers to the land, ensuring a constant supply of fresh water.
2. Transpiration:
- Transpiration is the process by which water is released into the atmosphere through the leaves of plants.
- It contributes to the water cycle by adding moisture to the air, which later condenses and falls as precipitation.
- Transpiration also helps in cooling the environment and maintaining the balance of moisture in the ecosystem.
3. WWTP (Wastewater Treatment Plants):
- While WWTPs play a crucial role in treating and purifying wastewater before it is released back into the environment, they do not directly balance the amount of fresh water on earth.
- WWTPs primarily focus on removing pollutants and contaminants from wastewater to minimize the impact on ecosystems and human health.
4. Greenhouse Effect:
- The greenhouse effect is the process by which certain gases in the atmosphere trap heat, leading to an increase in global temperature.
- While the greenhouse effect affects the overall climate and weather patterns, it does not directly impact the amount of fresh water on earth.
Conclusion:
- Among the options provided, the most important factor in balancing the amount of fresh water on earth is the water cycle.
- The water cycle ensures the continuous movement and redistribution of water, maintaining a constant supply of fresh water for various ecological and human needs.

Separating Large Solids in a Sewage Treatment Plant
Introduction:
In a sewage treatment plant, the separation of large solids is an essential step in the overall treatment process. This helps to prevent clogging and damage to the equipment further down the line. There are various mechanisms in place to achieve this separation, and one of the options is the use of strainers.
Explanation:
The correct answer to the question is option B: strainers. Here is a detailed explanation of why strainers are used to separate large solids in a sewage treatment plant:
1. Function of strainers: Strainers are designed to remove large solids from wastewater by trapping them in a mesh or screen. They act as a physical barrier and allow only liquid and smaller particles to pass through.
2. Types of strainers: There are different types of strainers used in sewage treatment plants, including bar screens and fine screens. Bar screens consist of vertical or inclined bars spaced apart to trap large debris, such as leaves, rags, plastic, and other solid materials. Fine screens have smaller openings and are used to capture smaller particles.
3. Location in the treatment process: Strainers are typically placed at the beginning of the treatment process, known as the preliminary treatment stage. This ensures that large solids are removed early on, preventing damage to downstream equipment and facilitating the effective treatment of wastewater.
4. Benefits of using strainers: The use of strainers offers several advantages in sewage treatment plants, including:
- Preventing blockages and damage to pumps and other equipment.
- Reducing the risk of clogging in pipes and channels.
- Protecting biological treatment processes by removing large solids that can interfere with microbial activity.
5. Other separation mechanisms: While strainers are effective in separating large solids, it's important to note that other mechanisms are also used in sewage treatment plants. These include sedimentation tanks and aeration tanks, which serve different purposes in the treatment process.
In conclusion, strainers are an integral part of the sewage treatment process as they effectively separate large solids such as leaves, rags, and plastic from wastewater. This helps to prevent clogging, protect equipment, and ensure the smooth operation of the treatment plant.

The correct answer is A: aeration tank.
The aeration tank is where aerobic bacteria breaks down organic waste present in sewage. Here is a detailed explanation:
Definition:
- An aeration tank is a component of a sewage treatment plant where the process of biological oxidation of organic matter takes place.
- It is also known as an activated sludge tank.
Function:
- The aeration tank provides an environment that promotes the growth of aerobic bacteria.
- These bacteria utilize oxygen to break down the organic waste present in sewage through the process of aerobic digestion.
Process:
- Sewage is initially collected in the primary settling tanks, where solid particles settle to the bottom and form sludge.
- The liquid portion, known as sewage effluent, is then transferred to the aeration tank.
- In the aeration tank, air or oxygen is continuously supplied to create a favorable environment for aerobic bacteria.
- The aerobic bacteria digest the organic waste, including organic compounds and nutrients, present in the sewage effluent.
- This digestion process results in the conversion of organic matter into carbon dioxide, water, and bacterial biomass.
- The bacterial biomass formed is known as activated sludge.
Advantages of Aeration Tank:
- The aeration tank facilitates the removal of organic matter, nutrients, and pathogens from sewage, leading to improved water quality.
- It helps in reducing the biochemical oxygen demand (BOD) and chemical oxygen demand (COD) of the sewage effluent.
- The process of aerobic digestion in the aeration tank is efficient in breaking down complex organic compounds.
- It provides a controlled environment for the growth of beneficial bacteria, preventing the release of harmful substances into the environment.
In conclusion, the aeration tank is where aerobic bacteria breaks down organic waste present in sewage.