All questions of Environment for Class 10 Exam

The energy transfer will be from c) primary consumer to secondary consumer.

Explanation: In a food chain, energy is transferred from one trophic level to another as organisms consume other organisms. A grasshopper, being an herbivore, feeds on plants (producers) making it a primary consumer. A frog, on the other hand, is a carnivore that feeds on other animals, such as grasshoppers, making it a secondary consumer. When a frog eats a grasshopper, the energy stored in the grasshopper's body is transferred to the frog, thus the transfer is from primary consumer (grasshopper) to the secondary consumer (frog).

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

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.

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.

Decomposers keep the environment clean by decomposing or consuming the dead remains of other organisms.

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

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.

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

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.

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.

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.

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.

Assertion: A network of food chains existing together in an ecosystem is known as the food web.
Reason: An animal like a kite cannot be a part of a food web.

The correct answer for this question is option 'C'.

Explanation:
To understand why option 'C' is the correct answer, let's break down the assertion and reason given in the question.

Assertion: A network of food chains existing together in an ecosystem is known as the food web.
- This statement is true. A food web is a complex network of interconnected food chains that shows the flow of energy and nutrients in an ecosystem. It represents the feeding relationships between different organisms in the ecosystem.

Reason: An animal like a kite cannot be a part of a food web.
- This statement is false. An animal like a kite can indeed be a part of a food web. In a food web, organisms are interconnected through feeding relationships. Each organism occupies a specific trophic level and interacts with multiple other organisms as both predator and prey. A kite, for example, can be a predator that feeds on smaller animals like rodents or insects and can also be preyed upon by larger predators like eagles or owls. Thus, it is an integral part of the food web.

Therefore, while the assertion is true, the reason provided is false. This is why option 'C' is the correct answer.

Understanding the 10% Rule
The 10% Rule is a fundamental concept in ecology that describes the efficiency of energy transfer in an ecosystem.
Energy Transfer Between Trophic Levels
- In a typical food chain, energy is transferred from one trophic level to the next.
- Only about 10% of the energy from one level is passed on to the next level.
- This phenomenon occurs due to energy losses through metabolic processes such as respiration, movement, and heat.
Importance of the 10% Rule
- The 10% Rule highlights the inefficiency of energy transfer in ecosystems, emphasizing that only a fraction of energy is available to higher trophic levels.
- For example, if a plant (producer) captures 1000 calories of energy from the sun, only about 100 calories will be available to the herbivore (primary consumer) that eats it, and merely 10 calories will be available to the carnivore (secondary consumer) that eats the herbivore.
Implications on Ecosystem Structure
- The limitation imposed by the 10% Rule affects the number of trophic levels in an ecosystem.
- It explains why food chains are typically short, as significant energy loss restricts the number of levels that can be sustained.
Conclusion
The correct answer is option 'A' because it accurately reflects the principle of energy transfer in ecological systems, emphasizing that only about 10% of energy is passed to the next trophic level. Understanding this rule is crucial for studying energy dynamics and the structure of ecosystems.

Substances like polythene bags and plastics are non- biodegradable because they cannot be broken down by micro-organisms into simpler harmless substances in nature. Substances that can be broken down by microorganisms in natural simple harmless substances are biodegradable substances.

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.

Green plants are producers. The first trophic level in a food chain is a producer i.e. those organisms which produce food by photosynthesis.

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 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).

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.

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.

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.

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

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.

A trophic level is the position of an organism in a food chain. A food chain starts with producers which are green plants and occupy the lowest trophic level. The highest trophic level is occupied by carnivores which feed on lower trophic levels for energy. A simple food chain is represented as