All questions of Our Environment for Class 10 Exam

UV Rays as the name suggests Ultra Violent rays causes a lot of harm to our body and to our environment like :-

The producers convert inorganic compounds into organic compounds by converting light energy given by the sun into chemical energy.

Crop fields are man made and some biotic and abiotic components are manipulated by humans. Artificial ecosystems are those ecosystems which are modified and managed by human beings.

Tropical rain forests have disappeared mainly due to man’s activities. Due to overpopulation in countries like India, rain forests are cut to make space available for man to live and build houses. To build buildings and factories man has incessantly cut down trees. This has caused the depletion of rainforests.

Understanding the Assertion and Reason
The Assertion (A) states that biodegradable substances have a positive impact on the environment. The Reason (R) explains that these substances break down naturally into harmless compounds.
Analysis of Assertion (A)
- Biodegradable substances, such as food waste and paper, undergo natural decomposition.
- This process reduces pollution and minimizes landfill waste, contributing positively to environmental health.
Analysis of Reason (R)
- The breakdown of biodegradable materials into harmless compounds is a fundamental characteristic.
- This natural decomposition process prevents the accumulation of harmful substances in the environment, thus supporting sustainability.
Connection Between Assertion and Reason
- The reason provided (R) directly supports the assertion (A).
- If biodegradable substances break down into harmless compounds, they indeed have a positive impact on the environment by reducing waste and pollution.
Conclusion
- Since both the Assertion and Reason are true, and the Reason effectively explains why the Assertion is true, the correct answer is option 'A'.
- This relationship highlights the significance of choosing biodegradable materials in fostering a healthier ecosystem.
In summary, biodegradable substances play a crucial role in environmental preservation by breaking down naturally and minimizing harmful waste.

Herbivores obtain their food from plants. Hence, they are known as first order carnivores. The carnivores like tigers cannot be preyed upon further, lie at the top of the food chain and hence termed as top carnivores.

In the food web different food chains are interconnected. Each chain consists of different trophic levels i.e., producers, consumers and detritivores. So, kite can also be a part of food web

Explanation:

Assertion and reason both statements are true and the reason is the correct explanation of the assertion. Let's break down the explanation:

- First Trophic Level in a Food Chain:
- The first trophic level in a food chain always consists of green plants. These plants are known as producers because they are capable of producing their own food through photosynthesis.

- Green Plants as Producers:
- Green plants are called producers because they can convert sunlight into energy through the process of photosynthesis. They are able to synthesize their own food using water, carbon dioxide, and sunlight.

- Explanation of Assertion:
- The reason why the first trophic level in a food chain is always a green plant is that green plants are the primary producers in the ecosystem. They form the base of the food chain by converting energy from the sun into a form that can be consumed by other organisms.

Therefore, in this case, both the assertion and reason are true, and the reason provides a correct explanation for why the first trophic level in a food chain is always a green plant.

The flow of energy through different steps in the food chain is unidirectional. This means that energy captured by autotrophs does not revert back to the solar input and it passes to the herbivores.

Assertion and Reason Overview
The assertion (A) claims that all organisms, including plants, animals, microorganisms, and humans, interact with each other and maintain a balance in nature. The reason (R) explains that an ecosystem consists of biotic components (living organisms) and abiotic components (physical factors like temperature, rainfall, etc.).

Analysis of Assertion (A)
- The assertion is true.
- Organisms interact in various ways, such as through food webs, nutrient cycling, and competition.
- These interactions contribute to the ecological balance, ensuring that populations of different species remain stable.

Analysis of Reason (R)
- The reason is also true.
- An ecosystem is indeed composed of both biotic and abiotic factors, which together create the environment in which organisms live and interact.
- Abiotic factors influence the types of organisms that can thrive in an ecosystem and their interactions.

Connection Between Assertion and Reason
- While both statements are true, the reason does not directly explain the assertion.
- The assertion focuses on the interactions and balance among organisms, while the reason provides a broader context about what constitutes an ecosystem.
- The dynamics of interaction among organisms involve more complex relationships than just the presence of abiotic factors.

Conclusion
- Therefore, the correct option is (b): both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
- This distinction highlights that while the structure of ecosystems is essential, the interactions among organisms are crucial for maintaining ecological balance.

Understanding the Assertion and Reason
In this question, we are presented with two statements: an assertion (A) and a reason (R) related to trophic levels and food chains.
Assertion (A): Trophic levels are formed by only plants.
- This statement is false.
- Trophic levels include not only plants (producers) but also herbivores (primary consumers), carnivores (secondary and tertiary consumers), and decomposers. Thus, plants are just one part of the trophic level hierarchy.
Reason (R): Food chains and webs are formed due to linked organisms on the basis of their nutrition.
- This statement is true.
- Food chains and webs illustrate the flow of energy and nutrients through various organisms, linking them based on their roles in an ecosystem (producers, consumers, and decomposers).
Correct Answer Explanation
Given the evaluation of both statements:
- Assertion (A) is false as it incorrectly suggests that trophic levels are exclusive to plants.
- Reason (R) is true as it accurately describes how organisms are interconnected in food chains and webs.
Since the assertion is false and the reason is true, the correct choice is:
Option D: Assertion (A) is false but reason (R) is true.
This distinction clarifies that while the reason correctly explains the ecology of food chains, the assertion misrepresents the concept of trophic levels.

The energy transfer in this scenario would be from a primary consumer (grasshopper) to a secondary consumer (frog). The grasshopper is considered a primary consumer because it eats plants, which are producers. When the frog eats the grasshopper, it is consuming the energy that was obtained by the grasshopper from the plants it ate. Therefore, the energy transfer is from a primary consumer to a secondary consumer.

The Concept of Trophic Levels
In an ecosystem, energy flows through various trophic levels, which are hierarchical stages represented by producers, consumers, and decomposers. Each level plays a crucial role in the energy transfer process.
Energy Loss at Each Trophic Level
Energy diminishes significantly at each trophic level due to several factors:
- Energy Conversion Efficiency: Only about 10% of the energy from one trophic level is passed on to the next. The rest is lost primarily as heat through metabolic processes.
- Metabolic Processes: Organisms at each level use energy for growth, reproduction, and maintenance, resulting in energy loss during cellular respiration and other metabolic activities.
- Incomplete Consumption: Not all biomass of one trophic level is consumed by the next. For instance, a herbivore may not eat all parts of a plant, leading to further energy loss.
Hierarchy of Trophic Levels
In a typical food chain:
- Producers: These are autotrophs (like plants) that convert solar energy into chemical energy through photosynthesis. They form the base of the food chain.
- Primary Consumers: Herbivores that feed on producers, obtaining energy but losing a significant portion in the process.
- Secondary and Tertiary Consumers: Carnivores that consume herbivores and other carnivores. With each step up the chain, energy diminishes further.
Conclusion
The correct answer is option 'C' because the energy available at each trophic level diminishes progressively due to losses incurred at each trophic level. Understanding this concept is vital for ecological studies and conservation efforts.

Understanding Trophic Levels
In an ecosystem, organisms are categorized into different trophic levels based on their role in the food chain. This classification helps in understanding the flow of energy and nutrients within an ecosystem.
What Are Autotrophs?
- Autotrophs, also known as producers, are organisms that can produce their own food through photosynthesis or chemosynthesis.
- Examples include plants, algae, and certain bacteria.
Position of Autotrophs in the Trophic Levels
- Autotrophs occupy the first trophic level in a food chain.
- This is because they are the primary source of energy for all other organisms.
Why are They Called Primary Producers?
- The term "primary producer" signifies their role in converting inorganic substances (like sunlight, water, and carbon dioxide) into organic matter (food).
- They form the base of the food chain and support all other trophic levels.
Flow of Energy in Ecosystems
- Energy flows from autotrophs to herbivores (primary consumers) and then to carnivores (secondary and tertiary consumers).
- Each subsequent trophic level relies on the energy produced by the level below it.
Conclusion
- Therefore, the correct answer to the question is option 'A': Autotrophs or producers are at the primary trophic level in a food chain.
- Understanding this fundamental concept is crucial for studying ecology and environmental science.

Understanding the Assertion and Reason
The assertion states that "CFCs deplete the ozone layer." This is indeed true. Chlorofluorocarbons (CFCs) are chemicals that have been widely used in various applications, particularly as refrigerants in air conditioning systems and in fire extinguishers. When released into the atmosphere, CFCs rise up and eventually reach the stratosphere, where they break down ozone molecules, leading to the depletion of the ozone layer.
Role of CFCs in Ozone Layer Depletion
- CFCs release chlorine atoms when they are exposed to ultraviolet (UV) radiation in the stratosphere.
- These chlorine atoms react with ozone (O3) molecules, resulting in the breakdown of ozone into oxygen (O2).
- The depletion of the ozone layer increases UV radiation reaching the Earth's surface, leading to harmful effects like skin cancer and cataracts.
Connection Between Assertion and Reason
The reason provided states that "CFCs are used as refrigerants and in fire extinguishers." This statement is also true as CFCs have historically been used in these applications. However, while the reason accurately describes the use of CFCs, it does not explain why they deplete the ozone layer. Therefore, while both statements are true, the reason does not provide a valid explanation for the assertion.
Conclusion
Given that both the assertion and the reason are true, but the reason does not correctly explain the assertion, the correct choice is:
- Option (b): Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).

All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem. Thus, an ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals.

Harmful chemicals accumulate progressively at each trophic level. Since man is at the apex of all the food chains, the concentration of harmful chemicals may be higher in human beings. The phenomenon involved is known as biomagnification.

The assertion is correct because plants can synthesize food due to the presence of abiotic components like carbon dioxide and sunlight, due to which energy is produced. This energy is transferred at each trophic level.

90% of naturally occurring atmospheric ozone occurs in the stratosphere. Stratospheric ozone is very important, it removes almost all incoming UVA, and 70% of the incoming UVB at equator, 90% at poles. All aircraft produce water, CO₂, CO etc. in exhaust gases. Most commercial flights are confined to the troposphere, but high-level supersonic aircraft inject pollutants into the stratosphere, which leads to the thinning of the ozone layer. Of these nitrogen oxides are especially harmful.

Man is an example of an omnivorous animal because Omni means all and vore means eater. An organism which can feed on the plant, as well as the meat of the animal, are called omnivorous.

Assertion : Polythene bags and plastic containers are non-biodegradable substances.

Reason: They can be broken down by microorganisms into natural simple harmless substances.

The correct answer is option 'C', i.e., Assertion (A) is true but reason (R) is false.

Explanation:

Polythene bags and plastic containers are indeed non-biodegradable substances. Biodegradable substances are those that can be broken down by microorganisms into natural simple harmless substances. However, the reason given here is incorrect because polythene bags and plastic containers cannot be broken down by microorganisms into natural harmless substances.

Here is a detailed explanation of why Assertion (A) is true but reason (R) is false:

Polythene bags and plastic containers are non-biodegradable substances:
- Polythene bags and plastic containers are made from synthetic polymers, primarily polyethylene and polypropylene.
- These synthetic polymers are derived from petroleum or natural gas, which are non-renewable fossil fuels.
- These polymers are composed of long chains of carbon and hydrogen atoms, which make them highly resistant to degradation by natural processes.
- Due to their chemical structure, polythene bags and plastic containers cannot be broken down by microorganisms like bacteria and fungi.
- As a result, they persist in the environment for hundreds of years, causing pollution and harm to ecosystems.

Reason: They can be broken down by microorganisms into natural simple harmless substances:
- This reason is incorrect because polythene bags and plastic containers cannot be broken down by microorganisms.
- Microorganisms, such as bacteria and fungi, require specific conditions and enzymes to degrade organic matter.
- While some types of plastics, such as biodegradable plastics, can be broken down by certain microorganisms under specific conditions, polythene bags and plastic containers are not biodegradable.
- These plastics do not provide the necessary nutrients or structure for microorganisms to break them down.
- As a result, they persist in the environment, causing pollution and posing a threat to wildlife.

In conclusion, while the assertion that polythene bags and plastic containers are non-biodegradable substances is true, the reason provided, stating that they can be broken down by microorganisms into natural harmless substances, is false.

Crown files are most destructive. These destroy the canopies of trees and entire vegetational cover of that particular area. Due to this fire, the temperature rises upto 700°C and may adversely affect the vegetation.

Ozone is damaging as it is a deadly poison. It is beneficial as it shields the surface of the earth from UV radiations of the Sun. We should stop the release of Chlorofluorocarbons (CFCs) to protect the ozone.

Assertion: Biotic components of the ecosystem continuously require energy to carry on life processes.
Reason: Abiotic components are the nonliving factors of the ecosystem.

The correct answer is option B.

Explanation:
Biotic Components Require Energy:
- The biotic components of an ecosystem include all living organisms such as plants, animals, and microorganisms.
- These organisms require energy to carry out various life processes such as growth, reproduction, movement, and metabolism.
- Energy is obtained through various sources such as sunlight, organic matter, or other organisms.
- Green plants, for example, use sunlight to carry out photosynthesis and convert it into chemical energy in the form of glucose.
- Animals, on the other hand, obtain energy by consuming plants or other animals.

Abiotic Components of Ecosystem:
- Abiotic components are the nonliving factors of an ecosystem.
- They include physical and chemical factors such as sunlight, temperature, water, air, soil, and minerals.
- These factors provide the necessary conditions for the survival and functioning of the biotic components.
- While abiotic components do not require energy for their own life processes, they play a crucial role in determining the availability of resources and environmental conditions for the biotic components.

Relationship between Assertion and Reason:
- The assertion states that biotic components of the ecosystem continuously require energy to carry on life processes, which is true.
- The reason states that abiotic components are the nonliving factors of the ecosystem, which is also true.
- However, the reason does not provide a direct explanation for why biotic components require energy.
- The reason simply provides additional information about the nature of abiotic components and their role in the ecosystem.
- The requirement of energy by biotic components is primarily due to their physiological processes and the need to maintain their biological functions.

Therefore, both the assertion and reason are true, but the reason is not the correct explanation of the assertion. Hence, option B is the correct answer.

Autotrophs means organisms who prepare their own food and heterotrophs are organisms who depend on autotrophs directly or indirectly and as you may be knowing that tree or plants prepare their own food by the process of photosynthesis , so c is the correct answer

Green plants (grasses) are autotrophic. They perform photosynthesis by using solar energy to synthesize their own food. Hence they are the producers in an ecosystem.

Understanding the Assertion and Reason
The assertion states that the praying mantis is green in color, which helps it blend in with plant foliage. This is a well-known fact about the praying mantis, which utilizes camouflage as a survival strategy.
Assertion (A) Analysis
- The color of the praying mantis is indeed predominantly green.
- This coloration allows it to merge with the green leaves and branches of plants, making it less visible to predators and prey.
Reason (R) Analysis
- The reason provided states that animals adopt different strategies to survive in a hostile environment.
- This statement is true, as many animals have evolved various adaptations, including camouflage, to enhance their chances of survival.
Connection Between Assertion and Reason
- The reason (R) explains a broader concept of survival strategies among animals.
- In the case of the praying mantis, its green color is a specific adaptation that aligns with this broader strategy.
Conclusion
- Both assertion (A) and reason (R) are true.
- The reason (R) directly supports the assertion (A) by explaining that the green coloration is a strategy for survival through camouflage.
Therefore, the correct answer is option 'A': Both assertion (A) and reason (R) are true, and reason (R) is the correct explanation of assertion (A).

Organisms which break down the complex organic compounds present in dead and decaying matter are called decomposers, e.g., certain bacteria and fungi. Decomposers act as cleaning agents of the environment by decomposing the dead bodies of plants and animals. They also help in recycling of materials, replenishment of soil's nutrients etc. The consequence of their absence in an ecosystem can be disastrous as discussed below

Explanation:

Assertion (A) and Reason (R) Analysis:
- Assertion (A): Decomposers keep the environment clean.
- Reason (R): They recycle matter by breaking down the organic remains and waste products of plants and animals.

Explanation of Correct Answer:
- Both the assertion and reason are true.
- Decomposers play a vital role in maintaining a clean environment by breaking down dead organisms and waste materials.
- They recycle nutrients back into the ecosystem, allowing for the growth of new plants and organisms.
- This process helps in maintaining the balance of nutrients in the environment and prevents the accumulation of waste.
- Therefore, the reason provided correctly explains why decomposers are essential for keeping the environment clean.
- Hence, option 'A' is the correct choice where both assertion and reason are true, and the reason correctly explains the assertion.

Aquatic food chain is the food chain present in water bodies, e.g. phytoplankton → zooplankton → fish → shark

Assertion (A): Green plants of the ecosystem are the transducers.
Reason (R): Producers trap the radiant energy of the sun and change it into chemical energy.

Explanation:

Transducers are devices or organisms that convert one form of energy into another. In the case of green plants, they are able to convert radiant energy from the sun into chemical energy through the process of photosynthesis. Let's analyze the given assertion and reason in more detail:

Assertion (A): Green plants of the ecosystem are the transducers.
- This statement is true. Green plants are considered transducers because they have the ability to convert radiant energy from the sun into chemical energy. They do this through the process of photosynthesis, where they use sunlight, carbon dioxide, and water to produce glucose (a form of chemical energy) and release oxygen as a byproduct.

Reason (R): Producers trap the radiant energy of the sun and change it into chemical energy.
- This statement is also true. Producers, which include green plants, algae, and some bacteria, are able to trap the radiant energy of the sun through pigments like chlorophyll. These pigments absorb sunlight and convert it into chemical energy in the form of glucose. This process is called photosynthesis.

Explanation of the Correct Choice:
The correct choice is option 'A' - Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

Both the assertion and reason are true. Green plants are transducers because they can convert radiant energy into chemical energy. The reason provided explains how producers, including green plants, are able to trap the radiant energy of the sun and convert it into chemical energy through photosynthesis. Therefore, the reason is the correct explanation for the assertion.