13. Our Environment

CBSE Class 10 Science Chapter 13. Our Environment

Chapter 13. Our Environment

Class 10 Science Chapter 13. Our Environment CBSE Previous Years Questions and Answers:

Question : How is the increasing demand for energy adversely affecting our environment ? [2010 1Mark]

Answer : The increasing demand for energy leads to higher emissions of greenhouse gases, air and water pollution, habitat destruction, and resource depletion, exacerbating climate change and environmental degradation.

Question : Select two non-biodegrable substances from the following waste general in a kitchen : Spoilt food , paper bags , milk bags , vegetable peels , tin cans , used tea leaves solution . [2012 1 Mark]

Answer : Two non-biodegradable substances from the waste generated in a kitchen are tin cans and Milk bags .

Question : Mention one negative effect of our affluent life style on the environment . [2013 , 2014 1M]

Answer : One negative effect of our affluent lifestyle on the environment is increased consumption and waste generation, leading to resource depletion and environmental degradation.

Question : Why should biodegradable and non- biodegradable wastes be discarded in two separate dust bins ? [2013 1M]

Answer : Biodegradable wastes decompose naturally, while non-biodegradable wastes do not. Separating them prevents contamination, allows for proper recycling or disposal methods, and reduces environmental pollution and landfill pressure.

Question : In a food chain , grass , insect and snake , assign trophic level to frog . [2016]

Answer : Grass - Trophic Level 1 (Producer)

Insect - Trophic Level 2 (Primary Consumer)

Snake - Trophic Level 3 (Secondary Consumer)

Frogs typically occupy a trophic level similar to that of insects, so the frog would also be classified as a Trophic Level 2 organism (Primary Consumer).

Question : In the following food chain, 20,000 J of energy was available to the plants . How much energy would be available to man in this chain ?

[2017 2Marks ]

Answer : In general, each trophic level in a food chain only transfers about 10% of the energy from one level to the next. This phenomenon is known as the 10% rule.

Since, 20,000 J of energy is available to the plants, then each trophic level transfers only 10% of the energy, the energy available to man

Thus, 200 Joules of energy would be available to man in this food chain.

Question : Answer question numbers 6(a) to 6(d) on the basic of your understanding of the following paragraphs and the related studied concepts .

Human body is made up of live important components , of which water is the main component .Food as well as portable water are essential for every human being . The food is obtained from plants through agriculture. Pesticides are being used extensively for a high yield in the fields . There pesticides are absorbed by the plants from to soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants . As these chemicals are not biodegradable , they get accumulated progressively at each trophic level .The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body .

(a) Why is the maximum concentration of pesticides found in human beings ? [2020]

(b) Give one method which could be applied to reduce our intake of pesticides through food to some extent .

(i) Food web (ii) Trophic level (iii) Ecosystem (iv) Biomagnification

(d) With regard to various food chain operating in an ecosystem, man is a :

(i) Consumer (ii) Producer (c) Producer and consumer (d) Producer and decomposer

Answer : (a) The maximum concentration of pesticides is found in human beings because these chemicals, being non-biodegradable, accumulate progressively at each trophic level, reaching higher concentrations in top consumers.

(b) One method to reduce pesticide intake is by choosing organic foods, as they are produced without synthetic pesticides.

(d) With regard to various food chains operating in an ecosystem, man is a: (i) Consumer

Question : In an ecosystem , 10% of energy available for transfer from one trophic level to the next is in the form of : [2020]

(a) heat energy (b) chemical energy (c) mechanical energy (d) light energy

Answer : In an ecosystem, 10% of the energy available for transfer from one trophic level to the next is typically in the form of : (a) heat energy

Question : Soil fertility is determined be its ability to : [2020]

(a) Decay organic matter (b) Hold organic matter (c) Hold water (d) Support life

Answer : (b) Hold organic matter .

Question : ‘‘Burning fossil fuels is a cause of global warming ’’ . Justify this statement . [2012 2M]

Answer : Burning fossil fuels releases carbon dioxide and other greenhouse gases into the atmosphere. These gases trap heat, leading to the greenhouse effect and global warming. The increased temperature disrupts climate patterns, melts polar ice caps, and threatens ecosystems and human livelihoods.

Question : We often observe domestic waste decomposing in the by lanes of residential colonies . Suggest ways to make people realize that the improper disposal of waste is harmful to the environment . [2013 2M]

Answer : Implementing educational programs, community workshops, and awareness campaigns can help people understand the environmental impact of improper waste disposal. Engaging in waste segregation initiatives, promoting recycling, and establishing stricter regulations for waste management can encourage responsible disposal practices and foster a cleaner environment.

Question : State with reason any two possible consequences of elimination of decomposers from the earth . [2014 2M]

Answer : Elimination of decomposers from the earth could lead to :

(i) Accumulation of organic matter: Decomposers play a vital role in breaking down organic matter, and without them, organic waste would accumulate, leading to pollution and habitat degradation.

(ii) Nutrient imbalance: Decomposers recycle nutrients back into the soil, and their absence could disrupt nutrient cycles, affecting plant growth and ecosystem health.

Question : You being an environmentalist are interested in contributing towards the conservation of nature resources . List four activities that you can do on your own . [2017 2M]

Answer : The four activities are :

Reduce Energy Consumption: Implement energy-saving practices at home, such as using energy-efficient appliances, turning off lights when not needed, and using renewable energy sources.

Water Conservation: Practice water conservation by fixing leaks, using water-efficient appliances, and minimizing water wastage in daily activities.

Waste Reduction: Adopt a zero-waste lifestyle by practicing reduce, reuse, and recycle principles. Minimize single-use plastics, compost organic waste, and properly dispose of hazardous materials.

Green Transportation: Choose sustainable transportation options, like biking, walking, or using public transport. If feasible, consider using electric or hybrid vehicles to reduce carbon emissions.

Question : In the following food chain , only 2J of energy was available to the peacocks . How much energy would have been present in grass ? Justify your answer .

Grass → Grass hopper → frog snake → peacock [2022 2 Marks]

Answer : In a typical food chain, energy decreases as it moves from one trophic level to the next, following the 10% rule. Only 10% of the energy is transferred from one trophic level to the next.

Given that only 2J of energy was available to the peacocks, we can trace back the energy flow:

Peacocks (Trophic level 4) received 2J of energy.

Since only 10% of the energy is transferred from one trophic level to the next, the energy available to the peacocks originated from the snake (Trophic level 3).

Therefore, the snake received 10% of the energy available to the frogs (Trophic level 2), which is 20J.

Likewise, the frogs received 10% of the energy available to the grasshoppers (Trophic level 1), which is 200J.

Finally, the grasshoppers received 10% of the energy available to the grass (Trophic level 1), which is 2000J.

So, 2000J of energy would have been present in the grass.

Question : (a) What is meant by garbage ? List two classes into which garbage is classified .

(b) What do we actually mean when we say that the “ enzymes are specific in their action” ? [2022 2 Marks]

Answer : Garbage refers to waste material that is no longer useful and needs to be disposed of properly. It includes various types of waste generated by human activities, such as household waste, industrial waste, and commercial waste. Improper disposal of garbage can lead to environmental pollution and health hazards.

Two classes into which garbage is commonly classified are:

Biodegradable Waste: Biodegradable Waste can be broken down by natural processes into simpler, environmentally friendly substances. Examples include kitchen waste, food scraps, and organic materials.

Non-Biodegradable Waste :

Non-Biodegradable waste does not easily decompose or break down in the environment. Examples include plastics, metals, glass, and certain chemicals. Non-biodegradable waste poses a significant challenge for waste management and environmental conservation.

(b) When we say that enzymes are specific in their action, it means that specific enzymes are required to break down particular substances. For instance, humans cannot derive energy from eating coal because the necessary enzymes to break down coal are not present in our bodies. Similarly, many human-made materials like plastics resist breakdown by biological processes, persisting in the environment due to their non-biodegradable nature.

Question : How is ozone formed in the upper atmosphere ? Why is damage to ozone layer a cause of concern to us ? What causes this damage ? [2008 3 Marks]

Answer : Ozone in the upper atmosphere is formed through a process involving UV (ultraviolet) radiation acting on oxygen ( ) molecules. The higher energy UV radiation, particularly in the stratosphere, causes the splitting of molecular oxygen () into free oxygen (O) atoms. These oxygen atoms can then react with other oxygen molecules () to form ozone ():

Damage to the ozone layer is concerning because ozone shields the Earth's surface from harmful ultraviolet (UV) radiation from the Sun, which can cause health issues like skin cancer. The decline in ozone levels, observed since the 1980s, is linked to synthetic chemicals like chlorofluorocarbons (CFCs) used in refrigerants and fire extinguishers. International agreements like the Montreal Protocol aim to mitigate this damage by phasing out CFC production.

Question : (a) what is an ecosystem ? List its two main components .

(b) We do not clean ponds or lakes ,but an aquarium needs to be cleaned regularly .Explain [2009 , 2013 3 Marks ]

Answer : (a) An ecosystem is a biological community of interacting organisms (biotic components) and their physical environment (abiotic components), where they collectively contribute to a balanced and dynamic system.

Two main components of an ecosystem are:

Biotic Components: Biotic components include all living organisms within the ecosystem. This encompasses plants, animals, microorganisms, and humans. Interactions among these organisms, such as predation, competition, and symbiosis, play crucial roles in shaping the dynamics of the ecosystem.

Abiotic Components: Abiotic components comprise the non-living factors or physical surroundings of the ecosystem. These factors include temperature, rainfall, wind, soil, minerals, sunlight, and other physical elements of the environment. Abiotic components influence the distribution, abundance, and behavior of organisms within the ecosystem.

(b) Ponds and lakes typically maintain a self-regulating balance due to the presence of natural processes and organisms. In contrast, an aquarium requires regular cleaning because it's a confined, artificial environment. Without cleaning, dead organisms and waste accumulate, leading to increased levels of toxins and pollutants. In an uncleaned aquarium, the absence of natural processes necessitates human intervention to maintain water quality and the health of aquatic life.

Question : Explain the phenomenon of “ biological magnification ”. How does it affect organisms belonging to different trophic levels particularly the tertiary consumers. [2010 3 Marks]

Answer : Biological magnification is a phenomenon where certain harmful chemicals, such as pesticides and pollutants, become increasingly concentrated in organisms at higher trophic levels within a food chain or web.

Initially, these chemicals enter the environment through various means, such as agricultural runoff or industrial discharge, and are absorbed by plants or directly ingested by animals. At each trophic level, the organisms accumulate these chemicals in their tissues, as they are unable to metabolize or eliminate them effectively.

Tertiary consumers, which occupy the highest trophic level in a food chain, are particularly affected by biological magnification. As they feed on organisms from lower trophic levels, they ingest not only the chemicals accumulated in those organisms but also the additional concentrations of chemicals that have been magnified through the food chain.

Because of this magnification effect, the concentration of harmful chemicals can be significantly higher in tertiary consumers compared to organisms at lower trophic levels. Consequently, tertiary consumers are at greater risk of adverse health effects due to the bioaccumulation of these chemicals in their bodies.

Overall, biological magnification highlights the interconnectedness of organisms within ecosystems and underscores the importance of understanding the implications of human activities on environmental and public health.

Question : “ Energy flow in a food chain is unidirectional ” . Justify this statement . Explain how the pesticides enter a food chain and subsequently get into our body . [2014 3 Marks]

Answer : The statement "Energy flow in a food chain is unidirectional" is justified by two main factors. First, the flow of energy through a food chain is indeed unidirectional because the energy captured by autotrophs (producers) from sunlight is not reverting back to the solar input. Likewise, the energy passed to herbivores (primary consumers) doesn't return to autotrophs. As energy moves through various trophic levels, it becomes unavailable to the previous level, creating a unidirectional flow of energy.

Secondly, the energy available at each trophic level diminishes progressively due to the loss of energy at each level. This loss occurs primarily through metabolic processes, heat production, and other forms of energy expenditure, resulting in a reduced amount of energy available to the subsequent trophic level.

As for the entry of pesticides into the food chain and subsequently into our bodies, pesticides and other chemicals used to protect crops from diseases and pests are washed down into the soil or water bodies. Plants absorb these chemicals along with water and minerals from the soil, and aquatic plants and animals take them up from water bodies. As these chemicals are not degradable, they accumulate progressively at each trophic level. As humans occupy the top level in any food chain, the maximum concentration of these chemicals accumulates in our bodies, a phenomenon known as biological magnification. This is why various food items such as grains, vegetables, fruits, and meat may contain varying amounts of pesticide residues, which cannot always be removed by washing or other means.

Question : Differentiate between biodegradable and non-biodegradable substance with the help of one example must adopt to dispose non-biodegradable waste , for saving the environment . [2015 3 Marks]

Answer : Biodegradable substances are those that can be broken down by natural processes into simpler, environmentally friendly substances. These substances include organic materials like food scraps, paper, and plant matter. Examples of biodegradable waste include fruit peels, vegetable scraps, and paper products. Biodegradable waste can be decomposed by bacteria, fungi, and other microorganisms present in the environment, returning nutrients to the soil and completing the natural nutrient cycle.

Non-biodegradable substances, on the other hand, are materials that do not easily decompose or break down in the environment. These substances include plastics, metals, glass, and certain chemicals. Examples of non-biodegradable waste include plastic bags, aluminum cans, and Styrofoam containers. Non-biodegradable waste poses a significant challenge for waste management and environmental conservation because it can persist in the environment for long periods, causing pollution and harming ecosystems.

One example of adopting a method to dispose of non-biodegradable waste for saving the environment is recycling. Recycling involves collecting used materials like plastics, glass, and metals, processing them, and reusing them to manufacture new products. Recycling reduces the amount of waste sent to landfills and incinerators, conserves natural resources, and minimizes pollution and greenhouse gas emissions associated with the production of new materials. By recycling non-biodegradable waste, we can contribute to sustainable resource management and protect the environment for future generations.

Question : The activities of man had adverse effects on all forms of living organisms in the biosphere . Unlimited exploration of nature by man disturbed the delicate ecological balance between the living and non living components of the biosphere . The unfavorable conditions created by man himself but also of the entire living organisms on the mother earth . One of your classmates is an active member of ‘Eco club ’ of your school which is creating environmental awareness amongst the school students , spreading the same in the society and also working hard of preventing environmental degradation of the surroundings.

(a) Why is it necessary to conserve our environment ?

(b) State the important of green and blue dustbins in the safe disposal of the household waste .

Answer : (a) It is necessary to conserve our environment because it sustains all forms of life on Earth. The environment provides essential resources like clean air, water, food, and shelter for humans and other organisms. Conservation helps maintain biodiversity, preserves natural habitats, and ensures the ecological balance necessary for the survival of ecosystems and the well-being of future generations.

(b) (b) The green and blue dustbins play crucial roles in the safe disposal of household waste. The green dustbin is typically used for disposing of biodegradable waste such as food scraps, paper, and plant matter, which can be composted or recycled. The blue dustbin is designated for non-biodegradable waste like plastics, metals, and glass, which can be recycled or properly disposed of to prevent environmental pollution and degradation.

Environmental Responsibility: By actively participating in the Eco-club and engaging in activities aimed at creating environmental awareness and preventing environmental degradation, your classmate demonstrates a sense of responsibility towards the environment and a commitment to protecting and preserving natural resources for future generations.

Community Service: By spreading environmental awareness among school students and the wider society and actively working to prevent environmental degradation in the surroundings, your classmate exhibits a spirit of community service and a dedication to making a positive impact on the local community and the environment.

Question: Students in a school listened to the news read in the morning assembly that the mountain of garbage in Delhi suddenly explore and various vehicles got buries under it . Several people were also injured and there was traffic jam all ground . In the brain storming session the teacher the teacher also discussed this issue and asked the students to find out a solution to the problem of garbage . Finally they arrived at two main points – one is self management of the garbage we produce and the second is to generate least garbage at individual level .

(a) Suggest two measures to manage the garbage we produce .

(b) As an individual , what can we do to generate the least garbage ? Give two points .

Answer : (a) Two measures to manage the garbage we produce are :

(i) Encouraging households and institutions to segregate waste into biodegradable and non-biodegradable categories facilitates more efficient recycling and disposal processes.

(ii) Encouraging composting of organic waste at individual and community levels reduces the amount of biodegradable waste sent to landfills and contributes to soil enrichment.

(b) To generate the least garbage as individuals, we can:

Reduce the use of single-use plastics and disposable items by opting for reusable alternatives.

Practice mindful consumption and avoid unnecessary packaging by purchasing products with minimal packaging or in bulk.

(i) The teacher instilled awareness about the consequences of unmanaged garbage and the importance of individual actions in waste management.

(ii) By encouraging students to brainstorm solutions to the garbage problem, the teacher fostered a sense of responsibility and problem-solving skills among the students.

Question : How can we help in reducing the problem of waste disposal ? Suggest any three methods . [2017 , 2019 3 Marks]

Answer : We can help in reducing the problem of waste disposal through various methods are :

Reduce, Reuse, Recycle (3Rs):

Reduce: Minimize waste generation by being mindful of consumption habits. Avoid unnecessary packaging and single-use items.

Reuse: Opt for reusable products and containers whenever possible. Donate or repurpose items instead of discarding them.

Recycle: Sort and recycle materials such as paper, plastics, glass, and metals according to local recycling guidelines. Support recycling programs and initiatives in the community.

Composting :

Composting organic waste, such as food scraps, yard trimmings, and other biodegradable materials, reduces the amount of waste sent to landfills.

Home composting bins or community composting programs can turn organic waste into nutrient-rich compost, which can be used to enrich soil in gardens and landscaping.

Source Separation and Segregation:

Implement source separation and segregation of waste at the household and community levels. Separate waste into categories such as biodegradable, non-biodegradable, recyclable, and hazardous.

Properly segregated waste facilitates more efficient recycling, composting, and disposal processes, reducing the burden on landfills and minimizing environmental pollution.

By adopting these methods, individuals can contribute to reducing the problem of waste disposal, conserving natural resources, and promoting environmental sustainability

Question: Define an ecosystem . Draw a block diagram to show the flow of energy in an ecosystem . [2017 , 2019 3 Marks]

Answer : An ecosystem is a biological community of interacting organisms (biotic components) and their physical environment (abiotic components), where they collectively contribute to a balanced and dynamic system. In an ecosystem, living organisms interact with each other and with their non-living surroundings, such as soil, water, air, and sunlight, forming complex networks of energy flow and nutrient cycling.

Diagram showing flow of energy in an ecosystem

Question: (a) We do not clear ponds or lake, but an aquarium needs to be cleared regularly . Why ?

(b) Why is ozone layer getting depleted at the higher levels of the atmosphere ? Mention one harmful effect caused by its depletion . [2022 3 Marks ]

Answer : (a) The need for regular cleaning in an aquarium arises because the enclosed environment lacks the natural processes that occur in ponds or lakes. In natural water bodies like ponds or lakes, a dynamic ecosystem with various organisms, including decomposers like bacteria and fungi, helps break down organic waste. In contrast, an aquarium is a closed system with limited natural processes. Without regular cleaning, dead fish, leftover food, and other organic waste can accumulate, leading to poor water quality, harmful bacterial growth, and potential health issues for the aquarium's inhabitants. Cleaning involves removing debris, changing a portion of the water, and maintaining a suitable environment for the aquatic organisms.

(b) The ozone layer is depleted at higher levels of the atmosphere due to the presence of synthetic chemicals like chlorofluorocarbons (CFCs). These chemicals are released into the atmosphere from various human activities such as refrigeration and the use of aerosol propellants. One harmful effect caused by the depletion of the ozone layer is the increase in the amount of ultraviolet (UV) radiation reaching the Earth's surface. This UV radiation can lead to various health issues in organisms, including an elevated risk of skin cancer in human beings.