All questions of Natural Resources & Their Conservation for Class 7 Exam

Option a is answer..^_^

Aeration Tank
Aeration tank is the correct option where aerobic bacteria breaks down organic waste present in sewage.
- Function:
In the aeration tank, sewage is mixed with oxygen to create an aerobic environment. This environment is conducive to the growth of aerobic bacteria, which break down organic waste through the process of oxidation.
- Process:
The aerobic bacteria in the aeration tank utilize the organic matter in the sewage as a food source. As they break down the organic waste, they also reproduce, increasing their population and further accelerating the breakdown process.
- Importance:
This aerobic breakdown of organic waste is crucial in sewage treatment as it helps to reduce the level of pollutants in the sewage, making it safer to discharge into the environment.
- Result:
By the time the sewage leaves the aeration tank, a significant portion of the organic waste would have been broken down by the aerobic bacteria, resulting in a cleaner effluent that can move on to further treatment processes.
In conclusion, the aeration tank plays a vital role in sewage treatment by providing the ideal conditions for aerobic bacteria to break down organic waste present in the sewage.

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.

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Understanding Decomposers
Decomposers play a crucial role in the ecosystem by breaking down dead plants and animals. Here’s how they convert organic matter into humus:
What are Decomposers?
- Decomposers are organisms such as bacteria, fungi, and certain insects that feed on dead organic material.
- They break down complex organic substances into simpler ones, facilitating nutrient recycling in the ecosystem.
Process of Decomposition
- When plants and animals die, their bodies begin to decompose.
- Decomposers secrete enzymes that help break down the dead material at a molecular level.
- This process transforms the organic matter into simpler compounds.
Formation of Humus
- As decomposition progresses, the breakdown products accumulate and eventually form humus, a dark, organic component of soil.
- Humus improves soil structure, fertility, and moisture retention, providing essential nutrients for plants.
Importance of Decomposers
- They play a vital role in nutrient cycling, ensuring that essential elements like nitrogen, phosphorus, and potassium are returned to the soil.
- Without decomposers, ecosystems would become overwhelmed with dead matter, and nutrient availability would diminish.
Conclusion
In summary, decomposers are essential to converting dead plants and animals into humus, thus supporting soil health and the overall ecosystem. Their role is fundamental in maintaining the balance of nature by recycling nutrients back into the environment.

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.

Freshwater for human use on earth

The amount of freshwater available for human use on earth is a significant concern as it is essential for human survival and economic development. The answer to the question is option 'C,' which is 0.03%.

Reasoning

- The earth is covered with 71% of water, but only 2.5% of it is freshwater.
- Out of this 2.5%, 68.7% is frozen in glaciers and ice caps, while 30.1% is stored underground.
- Only 0.3% of freshwater is easily accessible for human use from rivers, lakes, and the atmosphere.
- But, this freshwater is not evenly distributed globally, and some regions face water scarcity due to less rainfall and high population density.
- Hence, the amount of freshwater available for human use on earth is only 0.03%.

Conclusion

The availability of freshwater is crucial for human survival, and the limited amount of freshwater available for human use on earth is a significant concern. The increasing population and climate change are also contributing to the depletion of freshwater resources. Therefore, it is essential to conserve and manage freshwater resources effectively for sustainable development.

Because urine,animal dung and vegetable wastes are the wastes from animals, kitchen and toilets.These wastes are ORGANIC so option c is right.

Bathing under a shower

Understanding Waste Water from Kitchens
The waste water coming from kitchens is primarily considered municipal waste water. Let's break down why this is the correct answer.
Definition of Waste Water
- Waste water refers to any water that has been used and contaminated by human activities.
- It includes water from various sources such as households, industries, and stormwater.
Types of Waste Water
- Municipal Waste Water:
- This is the waste water generated from residential areas, including kitchens, bathrooms, and laundry facilities.
- It typically contains organic matter, food particles, oils, and cleaning agents.
- Industrial Waste Water:
- This type of waste water is produced by manufacturing processes and industries.
- It may contain harmful chemicals, heavy metals, and other pollutants that are not usually found in municipal waste water.
Why Option B is Correct
- Kitchen waste water falls under the category of municipal waste water because:
- It originates from domestic activities.
- It is treated by municipal sewage systems designed to handle household waste.
- The inclusion of industrial waste water (option c) is incorrect in this context, as kitchen waste does not stem from industrial processes.
Conclusion
In conclusion, the waste water from kitchens is classified as municipal waste water, making option 'B' the correct choice. Understanding the distinctions between different types of waste water is essential for effective waste management and environmental protection.

Explanation:

Nutrients present in sewage:

• Phosphorus: Sewage contains phosphorus, which is a vital nutrient for plants and organisms. Phosphorus is present in detergents, cleaning products, human waste, and food scraps that end up in sewage.


• Nitrogen: Nitrogen is another essential nutrient found in sewage. It is present in human waste, urine, and organic matter. Nitrogen is a key component of proteins and is necessary for plant growth.

Other substances in sewage:

• Chlorine: While chlorine may be present in sewage due to its use in disinfection processes, it is not considered a nutrient.

Therefore, the correct answer is (D) both (a) and (c) - phosphorus and nitrogen are present in sewage.

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.

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.

Statement 1: An underground pipe which carries away dirty drainage water is called a sewer.
Statement 2: The wastewater treatment plant is also called a sewage treatment plant.
Let's analyze each statement separately:
Statement 1: An underground pipe which carries away dirty drainage water is called a sewer.
This statement is correct. A sewer is a system of underground pipes that carries wastewater, including dirty drainage water, away from homes, buildings, and other structures to a treatment plant or a disposal point.
Statement 2: The wastewater treatment plant is also called a sewage treatment plant.
This statement is also correct. The terms "wastewater treatment plant" and "sewage treatment plant" are often used interchangeably to refer to a facility that processes and treats wastewater to remove contaminants before it is discharged back into the environment or reused for various purposes.
Therefore, both statements are correct, and the correct answer is option C: Both statements are correct.

Answer:
Introduction:
Waste water can contain various types of microbes, including bacteria, viruses, and parasites. These microbes can cause a range of diseases when they contaminate water sources and are ingested by humans.
Diseases caused by microbes in waste water:
The following diseases can be caused by microbes present in waste water:
1. Cholera:
- Cholera is an infectious disease caused by the bacterium Vibrio cholerae, which can be present in contaminated water sources.
- The bacterium is typically transmitted through the consumption of water or food that has been contaminated by fecal matter containing the bacteria.
- Cholera can cause severe diarrhea and dehydration, and if left untreated, it can be fatal.
2. Typhoid:
- Typhoid fever is caused by the bacterium Salmonella typhi, which can also be present in contaminated water sources.
- The bacterium is usually transmitted through the consumption of water or food that has been contaminated by fecal matter containing the bacteria.
- Typhoid fever can cause high fever, abdominal pain, and gastrointestinal symptoms, and it can be life-threatening if not treated properly.
3. Dysentery:
- Dysentery is a gastrointestinal infection caused by various types of bacteria, including Shigella and Campylobacter.
- These bacteria can be present in contaminated water sources and can be transmitted through the consumption of contaminated water or food.
- Dysentery can cause severe diarrhea, abdominal pain, and fever.
Conclusion:
All of the mentioned diseases, including cholera, typhoid, and dysentery, can be caused by microbes present in waste water. It is crucial to ensure proper sanitation and water treatment to prevent the spread of these diseases.

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.

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 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.

The correct statement is B: Forests do not influence the climate and water cycle. This statement is not correct because forests play a crucial role in influencing the climate and water cycle.
Here is a detailed explanation:
A: Plants and animals in a forest are dependent on one another.
- Forests are complex ecosystems where various plants and animals interact and depend on each other for survival.
- Plants provide food and shelter for animals, while animals help in pollination and seed dispersal for plants.
C: Forests protect the soil from erosion.
- Forests act as a natural barrier against wind and water erosion.
- The roots of trees help bind the soil together, preventing soil erosion and the loss of valuable topsoil.
D: Soil helps the forests to grow and regenerate.
- Soil provides essential nutrients and minerals to support the growth of trees and other vegetation in forests.
- It acts as a medium for roots to anchor and absorb water and nutrients necessary for plant growth.
B: Forests do not influence the climate and water cycle.
- This statement is incorrect.
- Forests play a vital role in regulating climate by absorbing carbon dioxide (a greenhouse gas) through photosynthesis and releasing oxygen.
- They also help in maintaining the water cycle by reducing evaporation and transpiration, increasing humidity, and promoting rainfall.
In conclusion, all the statements except B are correct. Forests are not only important for the interdependence of plants and animals, but they also protect the soil from erosion and have a significant influence on climate and the water cycle.

The major source of water in the northernmost region of the world is rainfall.
- The northernmost region of the world refers to areas near the North Pole, such as the Arctic.
- Glaciers: While glaciers do exist in this region, they are not the major source of water.
- Rivers: Rivers are not the primary source of water in this region, as they are typically frozen for a significant portion of the year.
- Rainfall: Rainfall is the major source of water in the northernmost region. The Arctic experiences precipitation in the form of rain, snow, and sleet.
- Sea: The sea is not considered the major source of water in this context, as it is a body of saltwater.
In summary, the northernmost region of the world relies on rainfall as its major source of water.

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.