Ultimate NCERT Solutions for Chapter 13 Our Environment

Updated Solution 2024-2025                                              Updated Solution 2024-2025

NCERT Solutions for Chapter 13 Our Environment Class 10 Notes, Question/Answers, Activity, Experiment’s & Science Projects

Chapter 13 Our Environment Class 10 Notes & Activities From Ncert Book

Activity 13.1

• You might have seen an aquarium. Let us try to design one.
• What are the things that we need to keep in mind when we create an aquarium? The fish would need a free space for swimming (it could be a large jar), water, oxygen and food.
• We can provide oxygen through an oxygen pump (aerator) and fish food which is available in the market.
• If we add a few aquatic plants and animals, it can become a self-sustaining system. Can you think how this happens? An aquarium is an example of a human-made ecosystem.
• Can we leave the aquarium as such after we set it up? Why does it have to be cleaned once in a while? Do we have to clean ponds or lakes in the same manner? Why or why not?

Some questions and answers based on the aquarium activity:

Q 1: What are the things we need to create an aquarium?

Ans 1: To create an aquarium, we need a container (like a jar or tank), water, space for the fish to swim, oxygen, and food for the fish. Adding aquatic plants and animals can also make the system self-sustaining.

Q 2: How do we provide oxygen in an aquarium?

Ans 2: We can provide oxygen in an aquarium by using an oxygen pump (also called an aerator), which helps the water stay oxygenated for the fish.

Q 3: Can an aquarium be a self-sustaining system? How does that happen?

Ans 3: Yes, an aquarium can become a self-sustaining system if we add aquatic plants and animals. The plants produce oxygen and absorb carbon dioxide from the water, while the fish provide nutrients for the plants, creating a balanced ecosystem.

Q 4: Do we need to clean the aquarium? Why?

Ans 4: Yes, we need to clean the aquarium regularly. Over time, waste from the fish and leftover food can build up and pollute the water, making it harmful for the fish. Cleaning helps keep the water fresh and the fish healthy.

Q 5: Do we need to clean ponds or lakes in the same way as aquariums? Why or why not?

Ans 5: No, we don’t need to clean ponds or lakes the same way we clean aquariums. Ponds and lakes are natural ecosystems that have their own processes for cleaning and filtering the water. For example, plants and animals in the water help break down waste naturally. However, human-made systems like aquariums need regular cleaning to maintain balance.

Activity 13.2

• While creating an aquarium did you take care not to put an aquatic animal which would eat others? What would have happened otherwise?

Ans: Yes, when creating an aquarium, it’s important to avoid placing predatory fish with smaller or non-aggressive species. If a predatory fish is added, it may eat the smaller or weaker organisms, disrupting the balance of the aquarium ecosystem. This could lead to the loss of certain species and potentially an unstable environment, where the food chain or the balance of nutrients is disturbed, affecting all organisms in the aquarium.

• Make groups and discuss how each of the above groups of organisms are dependent on each other.

Ans:

• Producers (e.g., algae, aquatic plants): These organisms convert sunlight into energy through photosynthesis and are the foundation of the aquatic food chain. They provide oxygen and food for primary consumers.

• Primary Consumers (e.g., small fish, zooplankton): These organisms feed on producers (plants or algae) and, in turn, become food for secondary consumers.
• Secondary Consumers (e.g., larger fish, carnivorous invertebrates): These feed on primary consumers and help control their population. They also provide food for tertiary consumers.
• Tertiary Consumers (e.g., top predators like large fish, aquatic mammals): These predators feed on secondary consumers and help maintain the balance of the ecosystem by controlling the population of lower trophic levels.
• Decomposers (e.g., bacteria, fungi): These organisms break down dead plants and animals, recycling nutrients back into the ecosystem, which supports the producers.

Each group is connected through the food chain, where the energy from one level is transferred to the next, ensuring that all organisms play a role in sustaining the ecosystem.

• Write the aquatic organisms in order of who eats whom and form a chain of at least three

 steps. _______ →   __________→_________

Ans: Here is an example of a simple food chain:

• Algae (Producer) → Small Fish (Primary Consumer) → Larger Fish (Secondary Consumer).

In this chain:

• Algae are eaten by small fish.
• Small fish are eaten by larger fish.
• Larger fish can be consumed by top predators, if present.

Q. Would you consider any one group of organisms to be of primary importance? Why or why not?

Ans: Yes, producers (such as algae and aquatic plants) can be considered of primary importance because they form the base of the food chain. Without producers, there would be no energy source for primary consumers, and the entire aquatic ecosystem would collapse. They also produce oxygen, which is essential for the survival of most aquatic organisms. Therefore, their role in sustaining life in the aquarium is critical.

Activity 13.3

• Newspaper reports about pesticide levels in ready-made food items are often seen these days and some states have banned these products. Debate in groups the need for such bans.

Ans: The debate around banning ready-made food items due to pesticide levels hinges on public health concerns. Pesticides, when present in food, can accumulate in the human body, leading to various health issues like cancer, hormonal imbalances, and neurological problems. Banning these products ensures that consumers are not exposed to such risks, particularly vulnerable groups like children and pregnant women.

However, some might argue that banning ready-made food items can have negative economic implications, such as loss of jobs in the food industry, and make convenience foods less accessible to busy people. There are alternatives, like regulating pesticide levels through better testing and implementing safer farming practices, rather than imposing outright bans.

• What do you think would be the source of pesticides in these food items? Could pesticides get into our bodies from this source through other food products too?

Ans: The primary source of pesticides in ready-made food items is typically from agricultural practices. Farmers use pesticides to protect crops from pests, fungi, and weeds. These chemicals can remain on the crops even after harvesting and processing, ending up in the food products. Additionally, pesticides can also leach into the soil and water, further contaminating crops.

Yes, pesticides can also get into our bodies through other food products, such as fruits, vegetables, and grains, that are treated with pesticides during farming. Even after washing, some pesticide residues may still remain.

• Discuss what methods could be applied to reduce our intake of pesticides

Ans: Several methods can be employed to reduce our intake of pesticides:

• Washing and peeling: Thorough washing and peeling of fruits and vegetables can help reduce pesticide residues on the surface.
• Choosing organic products: Organic farming typically uses fewer or no synthetic pesticides, reducing the amount of pesticide residues in food.
• Buying locally and seasonally: Local and seasonal produce may have fewer pesticides due to shorter transport times and smaller-scale production.
• Growing your own food: By growing your own fruits and vegetables, you can control the use of pesticides or avoid them altogether.
• Regulations and testing: Governments can impose stricter regulations on pesticide use and test food products to ensure they are within safe limits for consumption.

Incorporating these methods can help reduce overall pesticide exposure, promoting better public health outcomes.

Questions

Q 1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

Ans 1: Trophic levels refer to the different levels in a food chain or food web, representing the flow of energy and nutrients through an ecosystem. Each trophic level consists of organisms that share the same role in the food chain, based on their feeding relationships.

Here are the main trophic levels:

1. Producers (Trophic Level 1): These are typically plants and algae that produce their own food through photosynthesis. They form the base of the food chain.
2. Primary Consumers (Trophic Level 2): These are herbivores that feed on producers.
3. Secondary Consumers (Trophic Level 3): These are carnivores that feed on primary consumers.
4. Tertiary Consumers (Trophic Level 4): These are apex predators that feed on secondary consumers.
5. Decomposers (Not always included in trophic levels): These organisms break down dead plants and animals, returning nutrients to the ecosystem.

Example of a Food Chain:

1. Grass (Producer) → 2. Grasshopper (Primary Consumer) → 3. Frog (Secondary Consumer) → 4. Snake (Tertiary Consumer)

Trophic Levels in the Food Chain:

• Trophic Level 1: Grass (Producer)
• Trophic Level 2: Grasshopper (Primary Consumer)
• Trophic Level 3: Frog (Secondary Consumer)
• Trophic Level 4: Snake (Tertiary Consumer)

Q 2. What is the role of decomposers in the ecosystem?

Ans 2: Decomposers play a crucial role in ecosystems by:

1. Breaking down dead organic matter: They decompose plant and animal remains into simpler substances.
2. Recycling nutrients: They release essential nutrients like nitrogen, phosphorus, and carbon back into the soil, supporting plant growth.
3. Maintaining soil health: By decomposing organic matter, they enrich the soil with organic material.
4. Energy flow: They help transfer energy in the food chain by consuming dead organisms and recycling their energy.
5. Supporting biodiversity: Decomposers contribute to the stability of ecosystems by maintaining nutrient cycles, which support a variety of organisms.

Activity 13.4

• Find out from the library, internet or newspaper reports, which chemicals are responsible for the depletion of the ozone layer.

Ans: Chemicals Responsible for the Depletion of the Ozone Layer:

The chemicals most responsible for the depletion of the ozone layer are primarily chlorofluorocarbons (CFCs), halons, carbon tetrachloride (CCl₄), and methyl chloroform (CH₃CCl₃). These substances are commonly used in refrigeration, air conditioning, foam production, and as solvents.

• CFCs: Chlorofluorocarbons are the most notorious ozone-depleting chemicals. They contain chlorine and fluorine atoms. When these chemicals are released into the atmosphere, they slowly rise and reach the stratosphere, where they break down due to ultraviolet (UV) radiation from the sun. This process releases chlorine atoms that destroy ozone molecules (O₃) by breaking them apart.
• Halons: These are similar to CFCs but contain bromine. Bromine is even more effective than chlorine at destroying ozone molecules.
• Carbon Tetrachloride and Methyl Chloroform: These chemicals also release chlorine when broken down in the stratosphere, contributing to ozone depletion.

Q. Find out if the regulations put in place to control the emission of these chemicals have succeeded in reducing the damage to the ozone layer. Has the size of the hole in the ozone layer changed in recent years?

Ans: Regulations and Their Success in Reducing Damage:

Yes, the regulations designed to control the emission of these ozone-depleting chemicals have had significant success. The Montreal Protocol, signed in 1987, was a landmark international treaty that aimed to phase out the production and use of ozone-depleting substances (including CFCs and halons). The protocol has been ratified by nearly every country in the world, making it one of the most successful environmental agreements in history.

Since the adoption of the Montreal Protocol:

• The production of CFCs and other ozone-depleting substances has decreased significantly.
• The use of substitutes, such as hydrofluorocarbons (HFCs), which do not deplete the ozone layer, has become widespread.
• The result has been a slowdown in the rate of ozone depletion and the beginning of ozone recovery.

Change in the Size of the Ozone Hole in Recent Years:

Yes, the size of the ozone hole has been decreasing in recent years. The hole over Antarctica, which reached alarming sizes in the 1980s and 1990s, has shown signs of recovery due to the reductions in ozone-depleting substances. Satellite observations and atmospheric data indicate that the ozone layer is gradually recovering, although the process is slow and may take several decades.

The 2023 report from the United Nations Environment Programme (UNEP) indicated that the ozone layer is on track to heal by the middle of this century, with predictions that the ozone hole over Antarctica will close completely around 2060-2070, depending on global efforts to minimize emissions of certain substances.

In summary:

1. The chemicals responsible for ozone depletion are primarily CFCs, halons, carbon tetrachloride, and methyl chloroform.
2. The Montreal Protocol and subsequent regulations have been highly successful in reducing the emission of these chemicals.
3. The size of the ozone hole has been decreasing, and the ozone layer is expected to recover over the next several decades.

Activity 13.5

• Collect waste material from your homes. This could include all the waste generated during a day, like kitchen waste (spoilt food, vegetable peels, used tea leaves, milk packets and empty cartons), waste paper, empty medicine bottles/strips/bubble packs, old and torn clothes and broken footwear.
• Bury this material in a pit in the school garden or if there is no space available, you can collect the material in an old bucket/flower pot and cover with at least 15 cm of soil.
• Keep this material moist and observe at 15-day intervals.
• What are the materials that remain unchanged over long periods of time?

Ans: Materials that typically remain unchanged over long periods of time include:

• Plastic items (such as plastic wrappers, bottles, and packaging).
• Glass (like medicine bottles and jars).
• Metal items (such as aluminum cans or metal bottle caps).
• Synthetic fabrics or materials like nylon, polyester, or other non-biodegradable clothing. These materials are resistant to natural decomposition processes and can take hundreds of years to break down.

• What are the materials which change their form and structure over time?

Ans: Materials that change their form and structure over time include:

• Organic waste such as food scraps, vegetable peels, and tea leaves, which decompose into simpler substances.
• Paper (such as waste paper), which breaks down through microbial activity.
• Natural fibers (like cotton, wool, and torn clothes made from natural materials) undergo decomposition and may turn into compost or break down into smaller fibers.

• Of these materials that are changed, which ones change the fastest?

Ans: The materials that change the fastest are:

• Organic waste (such as food scraps, vegetable peels, and used tea leaves) because they are rich in moisture and nutrients, which encourage microbial activity and rapid decomposition.
• Paper products (like paper towels or napkins) also decompose relatively quickly due to their organic composition and ability to absorb moisture.

Activity 13.6

• Use the library or internet to find out more about biodegradable and non-biodegradable substances.

Ans: biodegradable and non-biodegradable substances:

• Biodegradable substances are materials that can be broken down naturally by microorganisms (like bacteria, fungi, and other decomposers) over time. These substances decompose into simpler compounds, such as carbon dioxide, water, and biomass, without causing significant harm to the environment. Examples include food waste, paper, wood, and some natural fibers.
• Non-biodegradable substances are materials that cannot be broken down by microorganisms or take a very long time to decompose. These substances accumulate in the environment and can cause pollution. Examples include plastics, metals, glass, and synthetic chemicals.

• How long are various non-biodegradable substances expected to last in our environment?

Ans: The persistence of non-biodegradable substances in the environment can vary significantly, but here are some general estimates:

• Plastic bags: Approximately 10–1,000 years to break down.
• Plastic bottles: Around 450 years or more.
• Aluminum cans: 200–500 years.
• Glass bottles: Can take up to 1 million years to decompose.
• Styrofoam: Hundreds to thousands of years, as it is resistant to decomposition.
• Cigarette butts (filters): Can take up to 10 years to decompose.
• Fishing nets (ghost nets): Can persist for hundreds of years, harming marine life during that time.

These materials break down very slowly, leading to long-lasting environmental damage such as pollution in water, soil, and air.

• These days, new types of plastics which are said to be biodegradable are available. Find out more about such materials and whether they do or do not harm the environment.

Ans: Biodegradable plastics are designed to break down more quickly than traditional plastics, often by the action of microorganisms. These plastics are typically made from plant-based materials like cornstarch or sugarcane (polylactic acid, or PLA), or from petroleum-based products with additives that encourage degradation.

While biodegradable plastics do reduce the persistence of waste, there are concerns:

• Incomplete degradation: Some biodegradable plastics break down into microplastics instead of completely decomposing, still causing environmental harm, especially in oceans.
• Conditions for degradation: Biodegradable plastics need specific conditions (such as heat and moisture) to break down, which are not always present in landfills or the environment.
• Toxic byproducts: In some cases, the degradation of biodegradable plastics may release harmful substances like methane, a potent greenhouse gas, if they break down anaerobically (without oxygen) in landfills.

In conclusion, while biodegradable plastics may have a lower environmental impact than conventional plastics, they still pose challenges and do not entirely eliminate environmental harm. Proper disposal and recycling methods are still essential for reducing their overall impact.

Questions

Q 1. Why are some substances biodegradables and some non-biodegradable?

Ans 1: Substances are biodegradable if they can be broken down by natural processes, such as the action of bacteria, fungi, or other microorganisms. Biodegradable substances typically contain organic compounds, like plant or animal matter, that can be decomposed over time.

Non-biodegradable substances, on the other hand, are resistant to decomposition due to their synthetic or complex chemical structure. These materials, like plastics and metals, do not break down easily in nature and can persist in the environment for long periods, causing pollution.

Q 2. Give any two ways in which biodegradable substances would affect the environment.

Ans 2:

1. Soil Enrichment: Biodegradable substances, such as food scraps and plant materials, break down naturally and release nutrients back into the soil, enriching its fertility and promoting healthy plant growth.
2. Pollution Reduction: Unlike non-biodegradable substances, biodegradable materials decompose more quickly, reducing the accumulation of waste in landfills and minimizing long-term environmental pollution.

Q 3. Give any two ways in which non-biodegradable substances would affect the environment.

Ans 3:

1. Soil Contamination: Non-biodegradable substances, like plastics, can accumulate in the soil, blocking water flow and harming plant growth. These materials don’t break down, leading to long-term soil degradation and pollution.
2. Harm to Wildlife: Animals can ingest non-biodegradable waste, mistaking it for food. This can lead to injuries, malnutrition, or death. Additionally, these materials can disrupt ecosystems by contaminating water sources and harming aquatic life.

Activity 13.7

• Find out what happens to the waste generated at home. Is there a system in place to collect this waste?

Ans: In most urban and semi-urban areas, waste generated at home is collected by the local municipal corporation, waste management companies, or resident welfare associations (RWAs). They follow a door-to-door collection system. The waste is usually segregated into two categories: biodegradable (organic) waste, like food scraps and garden waste, and non-biodegradable waste, such as plastic, glass, and metal items. Sometimes there is a third category for hazardous waste like batteries or electronics. In many places, the waste is collected in separate bins or bags for easy sorting.

• Find out how the local body (panchayat, municipal corporation, resident welfare association) deals with the waste. Are there mechanisms in place to treat the biodegradable and nonbiodegradable wastes separately?

Ans: Local bodies such as the municipal corporation or panchayat often have waste management programs in place. They segregate waste into biodegradable (wet) and non-biodegradable (dry) categories.

• Biodegradable waste is typically sent for composting, biogas generation, or landfill disposal if no treatment facility is available.
• Non-biodegradable waste (like plastics, metals, etc.) is sent for recycling or disposed of in landfills. Some areas have adopted zero-waste policies, with mechanisms to recycle, compost, or repurpose almost all waste. Additionally, local bodies may promote awareness campaigns to encourage households to segregate waste at source.

• Calculate how much waste is generated at home in a day.

Ans: To calculate the amount of waste generated at home, you can conduct an observation over a set period. Collect the total weight of waste generated over a day by weighing the bags or containers where waste is accumulated. Divide the total weight by the number of days to get the average waste produced in a day. For example:

• If a household generates 5 kg of waste in 7 days, the average daily waste would be: 5kg/7day = 0.71kg/day. The waste generated will vary depending on the number of people in the household, their lifestyle, and waste habits.

• How much of this waste is biodegradable?

Ans: To determine how much of the waste is biodegradable, separate the waste into organic (biodegradable) and non-organic (non-biodegradable) categories. For example, if 0.71 kg of waste is generated daily and 60% of it is biodegradable (like food scraps), then: 0.71 kg/day × 60% = 0.426 kg/day So, in this example, approximately 0.426 kg of the waste generated is biodegradable.

• Calculate how much waste is generated in the classroom in a day.

Ans: To calculate waste generated in a classroom, observe the amount of waste generated throughout the day, typically during breaks and after school hours. This includes paper, food wrappers, plastic bottles, and other materials. Weigh the total waste produced or estimate it based on the number of students and their activities. For example:

• If there are 30 students, and each student generates approximately 50 grams of waste per day, the total waste generated would be: 30 students × 50 grams=1500 grams or 1.5 kg of waste.

• How much of this waste is biodegradable?

Ans: Separate the waste generated into biodegradable and non-biodegradable categories. In the classroom, biodegradable waste might include food scraps, paper, and biodegradable packaging materials. For example, if 70% of the waste is biodegradable, then: 1.5 kg × 70% =1.05 kg  So, approximately 1.05 kg of the waste generated in the classroom is biodegradable.

• Suggest ways of dealing with this waste

Ans:  For Home Waste:

• Segregation: Encourage segregation of waste into biodegradable and non-biodegradable categories to make recycling and composting easier.
• Composting: Set up a home composting system to handle kitchen scraps and garden waste, reducing the amount of organic waste sent to landfills.
• Recycling: Recycle paper, plastics, and metals. Encourage the use of recyclable materials in household items.
• Upcycling: Repurpose certain items, like old clothes, furniture, or packaging, to reduce waste.
• Awareness: Educate household members about the importance of waste reduction, such as reducing packaging waste.

For Classroom Waste:

• Waste Segregation: Set up separate bins for biodegradable and non-biodegradable waste in the classroom.
• Paper Reduction: Encourage digital work to reduce paper usage, or promote the use of recycled paper.
• Composting: If food scraps are common, create a small composting system in the school for organic waste.
• Recycling Stations: Establish dedicated recycling stations for bottles, cans, and paper, encouraging students to use them.
• Waste Awareness Campaign: Conduct workshops or awareness programs to teach students the importance of reducing, reusing, and recycling waste.

Chapter 13 – Our Environment Class 10 Notes, Question/Answer, Activity & Projects

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Activity 13.8

• Find out how the sewage in your locality is treated. Are there mechanisms in place to ensure that local water bodies are not polluted by untreated sewage.

Ans: Sewage treatment in most localities involves several stages, including primary, secondary, and sometimes tertiary treatment. During primary treatment, large solids are removed by screening and settling. In secondary treatment, biological processes, such as the use of bacteria, break down organic matter in the sewage. If there is tertiary treatment, it involves more advanced filtration, chemical treatment, or ultraviolet (UV) light to remove pathogens and additional contaminants.

To ensure local water bodies are not polluted by untreated sewage, many areas have sewage treatment plants (STPs) designed to treat the wastewater before it is released into rivers, lakes, or oceans. In some cases, sewage is treated and then used for irrigation, industrial use, or even potable water after advanced treatment processes. Regulatory bodies often set discharge standards for treated sewage to protect water quality. Monitoring systems are put in place to check the quality of effluent being discharged and ensure that it meets the required safety standards.

• Find out how the local industries in your locality treat their wastes. Are there mechanisms in place to ensure that the soil and water are not polluted by this waste?

Ans: Industries typically treat their waste through various methods depending on the type of waste they generate. This can include physical, chemical, or biological treatments. For instance, chemical industries may use neutralization or filtration systems to treat hazardous substances, while manufacturing industries may recycle or treat their water and solid waste before disposal. Many industries have effluent treatment plants (ETPs) that treat wastewater before it is released into water bodies or reused.

To prevent pollution of soil and water, environmental regulations and pollution control boards ensure that industries comply with waste disposal standards. These regulations often include restrictions on the types and quantities of waste that can be disposed of, and industries are required to have permits and regular inspections to confirm compliance. Some localities also have designated industrial zones with proper waste management infrastructure. Monitoring systems are in place to track the levels of pollutants in air, water, and soil near industrial areas. If any violations occur, industries may be penalized, or their operations may be halted until corrective actions are taken.

Activity 13.9

• Search the internet or library to find out what hazardous materials have to be dealt with while disposing of electronic items. How would these materials affect the environment?

Ans: When disposing of electronic items, various hazardous materials can be present that pose a significant risk to the environment and human health. Some of these materials include:

• Lead: Found in older televisions, computer monitors, and circuit boards. Lead can leach into soil and water, causing contamination and long-term health issues such as neurological damage, particularly in children.
• Mercury: Found in fluorescent light bulbs, older televisions, and some components of computers. Mercury is highly toxic, affecting the nervous system and causing pollution in aquatic environments when it enters waterways.
• Cadmium: Present in rechargeable batteries, some types of plastics, and semiconductors. Cadmium can accumulate in the environment, damaging soil and water quality and leading to kidney and lung diseases in humans.
• Brominated Flame Retardants (BFRs): These are used in plastics for electronics to reduce flammability. They are persistent in the environment, toxic to aquatic life, and can accumulate in humans, potentially leading to hormone disruption and neurological effects.
• Polychlorinated Biphenyls (PCBs): Although banned in many countries, older electronic equipment may still contain PCBs, which are carcinogenic and can pollute water bodies and affect wildlife and human health.

Environmental Impact: These materials, if not properly disposed of, can seep into soil and water, leading to long-term contamination and harming wildlife. They also pose risks to human health, especially in areas where electronic waste is improperly handled or burned.

• Find out how plastics are recycled. Does the recycling process have any impact on the environment?

Ans: Plastics are recycled through several processes, primarily focusing on reducing waste, reusing plastic materials, and conserving resources. Here’s an overview of the recycling process:

• Collection and Sorting: Plastic waste is collected from various sources and sorted into different types (e.g., PET, HDPE). Sorting can be done manually or through automated systems using advanced technology like infrared sensors.
• Cleaning: The plastics are cleaned to remove contaminants, such as food residues or labels, to prepare them for the next steps in the recycling process.
• Shredding: The cleaned plastics are shredded into smaller pieces or pellets to make them easier to handle during the melting process.
• Melting: The shredded plastic is heated to a specific temperature to melt it, making it easier to form new products. Some plastics may undergo extrusion to produce new items like bottles or containers.
• Reforming: The melted plastic is reformed into new products, which can be sold or used in manufacturing new items, like clothing, carpets, or new containers.

Environmental Impact of Recycling Plastics:

• Energy Use: The recycling process requires energy, although it typically uses less energy compared to producing new plastic from raw materials.
• Contamination Risk: If the recycling process is not well-managed, it can lead to the release of toxic chemicals, such as dioxins and furans, especially when plastics are improperly burned or mishandled.
• Microplastic Pollution: During the recycling process, especially if plastics are shredded or processed in ways that cause degradation, small microplastic particles may be released into the environment, contributing to pollution.

Despite these impacts, plastic recycling helps reduce the amount of plastic waste in landfills and oceans and conserves raw materials, making it a critical practice in addressing plastic pollution. However, the efficiency and sustainability of plastic recycling depend on the technologies used and the quality of sorting and processing involved.

Questions

Q 1. What is ozone and how does it affect any ecosystem?

Ans 1: Ozone and its Impact on Ecosystems:

• What is Ozone?

• Ozone (O₃) is a molecule composed of three oxygen atoms.
• It is primarily found in two layers of the Earth’s atmosphere: the stratosphere and the troposphere.

• Stratospheric Ozone (Good Ozone)

• Located in the ozone layer, it absorbs the majority of the sun’s harmful ultraviolet (UV) radiation.
• Protects living organisms from UV damage, which can cause skin cancer, cataracts, and weaken immune systems.

• Tropospheric Ozone (Bad Ozone)

• Found near the Earth’s surface, it’s a harmful air pollutant.
• Forms when pollutants from vehicles, industries, and other sources react with sunlight.
• It can cause respiratory problems in humans and animals and damage plant life.

• Effects on Ecosystems

• UV Protection: Stratospheric ozone protects ecosystems by preventing excessive UV radiation that can harm plant growth, aquatic life, and terrestrial animals.
• Plant Growth: Tropospheric ozone can stunt plant growth, reduce crop yields, and affect photosynthesis.
• Marine Life: Excessive UV radiation can damage plankton, which are at the base of aquatic food webs.
• Human and Animal Health: High ozone levels in the troposphere can cause respiratory diseases, affecting ecosystem dynamics.

In summary, ozone plays a dual role—protecting ecosystems from UV radiation in the stratosphere while contributing to pollution and health issues near the surface.

Q 2. How can you help in reducing the problem of waste disposal? Give any two methods.

Ans 2: Here are two methods to help reduce the problem of waste disposal:

1. Recycling and Reusing: Encourage the recycling of materials like paper, glass, and plastics, and promote reusing products to reduce waste sent to landfills.
2. Composting: Organic waste like food scraps and yard waste can be composted to create nutrient-rich soil, reducing landfill waste and supporting sustainable agriculture.

Exercise

Q 1. Which of the following groups contain only biodegradable items?

(a) Grass, flowers and leather

(b) Grass, wood and plastic

(c) Fruit-peels, cake and lime-juice

(d) Cake, wood and grass

Ans 1: (d) Cake, wood and grass.

Q 2. Which of the following constitute a food-chain?

(a) Grass, wheat and mango

(b) Grass, goat and human

(c) Goat, cow and elephant

(d) Grass, fish and goat

Ans 2: (b) Grass, goat, and human.

A food chain represents the flow of energy from one organism to another in an ecosystem. In this chain:

• Grass is consumed by the goat (primary consumer).
• The goat is consumed by humans (secondary consumer).

This forms a simple food chain. The other options do not represent a complete or typical food chain.

Q 3. Which of the following are environment-friendly practices?

(a) Carrying cloth-bags to put purchases in while shopping

(b) Switching off unnecessary lights and fans

(c) Walking to school instead of getting your mother to drop you on her scooter

(d) All of the above

Ans 3: (d) All of the above

Each of these practices helps reduce waste and energy consumption:

• Using cloth bags reduces plastic waste.
• Switching off lights and fans saves energy.
• Walking instead of using a scooter reduces carbon emissions.

Q 4. What will happen if we kill all the organisms in one trophic level?

Ans 4: If all organisms in one trophic level are removed, it will disrupt the food web and affect the entire ecosystem. The organisms that depend on this trophic level for food will suffer, leading to a decrease in their population. Additionally, the organisms in higher trophic levels may face food shortages, while those in lower levels (producers) could experience overgrowth if herbivores are removed. This imbalance can lead to a collapse in ecosystem stability and biodiversity.

Q 5. Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?

Ans 5: Yes, the impact of removing all organisms from a trophic level will differ depending on the trophic level removed.

• Primary producers (e.g., plants, algae): Removing them would collapse the entire food web, as they are the foundation of energy flow. Without them, consumers in higher trophic levels would have no food source, leading to the collapse of the ecosystem.
• Primary consumers (herbivores): Their removal may affect the abundance of primary producers, as herbivores often regulate their populations. However, the effects on higher trophic levels may be less immediate.
• Secondary and tertiary consumers (carnivores): Removing them might have less direct impact on primary producers but can cause an overabundance of prey species, disrupting the balance.

In most cases, removing organisms from any trophic level will cause damage to the ecosystem, as each level plays a critical role in maintaining ecological balance.

Q 6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Ans 6: Biological magnification (also known as biomagnification) refers to the process where the concentration of toxic substances, such as pesticides or heavy metals, increases as they move up the food chain. These substances accumulate in organisms at higher trophic levels because they are not easily broken down or excreted.

Yes, the levels of biological magnification are different at different levels of the ecosystem. The concentration of harmful substances becomes more concentrated in organisms at higher trophic levels (e.g., carnivores), as they consume multiple prey that have accumulated toxins.

Q 7. What are the problems caused by the non-biodegradable wastes that we generate?

Ans 7: non-biodegradable wastes, such as plastics and certain chemicals, pose several environmental problems:

1. Pollution: They accumulate in landfills, water bodies, and oceans, causing pollution that harms ecosystems and wildlife.
2. Long Decomposition Time: Non-biodegradable materials take hundreds or even thousands of years to break down, leading to long-term environmental impact.
3. Harm to Wildlife: Animals can ingest or become entangled in non-biodegradable wastes, which can lead to injury or death.
4. Soil Contamination: Chemicals from non-biodegradable waste can leach into the soil, affecting plant growth and soil health.
5. Resource Wastage: The production and disposal of non-biodegradable materials consume resources and energy, contributing to environmental strain.

The persistence of non-biodegradable wastes significantly disrupts ecosystems, requiring sustainable waste management solutions.

Q 8. If all the waste we generate is biodegradable, will this have no impact on the environment?

Ans 8: Even if all waste is biodegradable, it can still impact the environment. The decomposition process can release harmful gases, like methane, especially in landfills with low oxygen. Additionally, the rate of decomposition depends on conditions like temperature, moisture, and available microorganisms, which might not always be ideal. Some biodegradable materials can also deplete soil nutrients, leading to ecological imbalances. Therefore, while biodegradable waste is less harmful than non-biodegradable waste, it can still have environmental consequences if not managed properly.

Q 9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Ans 9: Damage to the ozone layer is a cause for concern because it plays a crucial role in protecting life on Earth from harmful ultraviolet (UV) radiation. Increased UV exposure can lead to health issues such as skin cancer, cataracts, and weakened immune systems. It can also harm ecosystems, including marine life and plants.

To limit this damage, global efforts like the Montreal Protocol have been implemented, aiming to phase out the use of ozone-depleting substances (such as chlorofluorocarbons or CFCs). Additionally, there are ongoing international agreements and regulations to monitor and reduce emissions of harmful chemicals, alongside promoting sustainable practices.

Chapter 13 – Our Environment Class 10 Notes, Question/Answer, Activity, Experiment’s & Science Projects

Updated Solution 2024-2025                                                            Updated Solution 2024-2025

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