NCERT Solutions for Class 10 Science Chapter 15 Our Environment

NCERT Solutions for Class 10 Science Chapter 15: Our Environment helps students clearly understand how natural systems function and how living organisms depend on one another. This chapter explains important topics such as ecosystems, food chains, food webs, and energy flow in a simple and structured way. It also highlights the role of producers, consumers, and decomposers in maintaining ecological balance.

The question-and-answer format makes learning easier by breaking complex ideas into clear, step-by-step explanations. Students also learn about biodegradable and non-biodegradable waste, biomagnification, and the harmful effects of human activities on the environment. These concepts help develop environmental awareness and responsible thinking.

NCERT Solutions are strictly based on the CBSE syllabus and follow the latest exam pattern, making them ideal for board exam preparation. Important definitions, short answers, and long-answer questions are explained in simple language to improve answer-writing skills. Regular practice with these solutions helps students score better marks, revise effectively, and build a strong conceptual foundation while understanding the importance of protecting our environment for future generations.

Read More; CBSE Class 10 Books

Class 10 Science Chapter 15 Our Environment Questions Answers

Page: 260

Q1. What are the trophic levels? Give an example of a food chain and state the different

trophic levels in it.

Solution: Trophic levels are the different stages in a food chain through which energy is transferred. Each

level represents a step in the flow of energy from producers to various consumers.

Example of a Food Chain:

Grass → Goat → Man

In this food chain:

● Grass represents the first trophic level (producers) as it produces energy through

photosynthesis.

● Goat represents the second trophic level (primary consumers) as it eats the grass to

obtain energy.

● Man represents the third trophic level (secondary consumers) as he consumes the

goat to gain energy.

Q2. What is the role of decomposers in the ecosystem?

Solution: Decomposers play a crucial role in the ecosystem by performing the following functions:

Environmental Cleansing: They break down dead plants and animals, which helps in cleaning

the environment and preventing the accumulation of organic waste.

Nutrient Recycling: By decomposing organic matter, decomposers release essential nutrients

back into the soil, which are then used by plants and other producers, facilitating nutrient

recycling.

Space Creation: Their activity helps in making space for new organisms in the ecosystem by

breaking down and recycling dead matter.

Element Replenishment: Decomposers return various elements like carbon, nitrogen, and

phosphorus to the soil, water, and air, ensuring that these elements are available for reuse by

producers such as crop plants.

Environment Page: 262

Q1. Why are some substances biodegradable and some non-biodegradable?

Solution: Substances are categorized as biodegradable or non-biodegradable based on their ability to be

broken down by natural processes:

Biodegradable Substances: These are materials that can be decomposed by microorganisms, such as bacteria and fungi. Natural products like paper, food scraps, and wood fall into this category. Microorganisms can break these substances down into simpler compounds, which are then recycled back into the environment.

Non-Biodegradable Substances: These are materials that cannot be easily broken down by natural processes. Human-made products like plastics, metals, and synthetic chemicals do not decompose easily because they lack the necessary chemical structures that microorganisms can break down. As a result, non-biodegradable substances persist in the environment for long periods, contributing to pollution and environmental harm.

Q2. Give any two ways in which biodegradable substances would affect the environment.

Solution: Biodegradable substances can affect the environment in the following ways:

Environmental Cleaning: Biodegradable substances decompose naturally and are broken down into simpler compounds by microorganisms. This process helps keep the environment clean by reducing the accumulation of waste. As these substances break down, they do not contribute to long-term pollution or littering.

Nutrient Recycling: The decomposition of biodegradable substances contributes to the nutrient cycle. Decomposers break down these materials into essential nutrients, which are then released back into the soil, water, and air. This process enriches the soil, promoting plant growth and maintaining ecological balance.

Q3. Give any two ways in which non-biodegradable substances would affect the environment.

Solution: Non-biodegradable substances can affect the environment in the following ways: Pollution: Non-biodegradable substances, such as plastics and chemicals, persist in the environment for long periods. They contribute to pollution in the air, soil, and water. These

materials can release harmful toxins and contaminants, negatively impacting ecosystems, wildlife, and human health.

Bio-magnification: Non-biodegradable substances can accumulate in the food chain through a process known as bio-magnification. As these substances move up the food chain, their concentration increases, potentially reaching toxic levels in top predators, including humans. This can lead to serious health issues and disrupt ecological balance.

Page: 264

Q1. What is ozone, and how does it affect the ecosystem?

Solution: Ozone is a molecule composed of three oxygen atoms (O₃) and plays a crucial role in the Earth's atmosphere. It is primarily found in the stratosphere, where it forms the ozone layer. The ozone layer acts as a protective shield by absorbing and filtering out the majority of the Sun's harmful ultraviolet (UV) radiation. This protection is essential for maintaining the health of ecosystems and living organisms.

Here's how ozone affects the ecosystem: Protection from UV Radiation: By absorbing UV rays, the ozone layer prevents excessive ultraviolet radiation from reaching the Earth's surface. This helps protect living organisms, including plants, animals, and humans, from the harmful effects of UV radiation, such as skin cancer, cataracts, and damage to DNA. Preservation of Ecosystems: UV radiation can adversely affect marine and terrestrial ecosystems. For instance, high levels of UV radiation can harm phytoplankton, which forms the basis of aquatic food chains. This can disrupt marine ecosystems and affect fish populations. On land, UV radiation can damage crops and forests, impacting food production and biodiversity.

Q2. How can you help in reducing the problem of waste disposal? Give any two methods.

Solution: To help reduce the problem of waste disposal, consider the following methods:

Adopting the 3 Rs (Reduce, Reuse, Recycle):

● Reduce: Minimize waste generation by opting for products with less packaging and

avoiding single-use items. For instance, use reusable shopping bags and containers

instead of disposable ones.

● Reuse: Repurpose items rather than discarding them. For example, glass jars can be

used for storage, and old clothes can be turned into cleaning rags or craft projects.

● Recycle: Properly separate recyclable materials such as paper, plastic, glass, and

metal. Ensure they are placed in designated recycling bins so they can be processed

and reused.

Composting Biodegradable Waste:

● Preparation of Compost: Convert biodegradable waste, like fruit and vegetable scraps,

coffee grounds, and garden waste, into compost. This can be done using a compost bin

or pile. Composting helps reduce the volume of waste sent to landfills and provides

nutrient-rich soil for gardening, thereby supporting a circular waste management system.

NCERT Solutions for Class 10 Science Chapter 15 Our

Environment Page: 264

Q1. 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

Solution:

c) Fruit peels, cake, and lime juice

These items are all biodegradable as they decompose naturally with the help of

microorganisms.

● Grass, flowers, and leather: While grass and flowers are biodegradable, leather is

generally not considered biodegradable due to the chemicals used in its processing.

● Grass, wood, and plastic: Grass and wood are biodegradable, but plastic is

non-biodegradable.

● Fruit peels, cake, and lime juice: All these items are biodegradable as they

decompose naturally.

● Cake, wood, and grass: Cake and grass are biodegradable, but wood's

biodegradability can vary depending on treatment and conditions.

Q2. Which of the following constitutes a food chain?

a. Grass, wheat and mango

b. Grass, goat and human

c. Goat, cow and elephant

d. Grass, fish and goat

Solution:

b. Grass, goat, and human

In this food chain:

● Grass represents the producer, which synthesizes its own food through photosynthesis.

● Goat is the primary consumer that feeds on the grass.

● Human is the secondary consumer that consumes the goat.

Q3. 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

Solution: d) All of the above

Q4. What will happen if we kill all the organisms at one trophic level?

Solution:

If all the organisms at one trophic level are removed, several consequences can occur:

Disruption of the Food Chain: The organisms in the trophic levels above will lose their primary

food source, leading to starvation and a decline in their population. This disruption can cause a

cascade effect, impacting the entire food chain.

Imbalance in Ecosystem: The absence of organisms at one trophic level can lead to

overpopulation of the organisms at the lower trophic level, as they have no natural predators.

This imbalance can cause excessive growth or depletion of certain species, further affecting

other organisms and resources in the ecosystem.

Ecosystem Instability: The loss of one trophic level can destabilize the ecosystem, leading to

changes in species composition, loss of biodiversity, and the potential collapse of the

ecosystem's structure and function.

Q5. Will the impact of removing all the organisms in the trophic level be different for

different trophic levels? Can the organisms of any trophic level be removed without

causing any damage to the ecosystem?

Solution:

Yes, the impact of removing all the organisms in a trophic level will indeed differ depending on

which level is removed:

Producers: Removing all producers (such as plants and algae) would have the most severe

impact, as they form the base of the food chain. Without producers, primary consumers

(herbivores) would have no food source, leading to their extinction. This, in turn, would affect

secondary and tertiary consumers, causing widespread disruption and potential collapse of the

ecosystem.

Primary Consumers: If all primary consumers (herbivores) are removed, the producers would

experience overgrowth due to the lack of grazing. Secondary consumers (carnivores) that rely

on primary consumers for food would face starvation, leading to their decline. This would disrupt

the food chain and affect the stability of the ecosystem.

Secondary Consumers: Removing all secondary consumers (carnivores) would lead to an

increase in the population of primary consumers, which can cause overgrazing and depletion of

producers. This imbalance would also affect tertiary consumers and other parts of the

ecosystem.

Tertiary Consumers: Removing tertiary consumers (top predators) might lead to an increase in

secondary consumers, which could result in a decline of primary consumers due to

overpredation. This imbalance can cause cascading effects throughout the ecosystem.

Q6. What is biological magnification? Will the levels of this magnification be different at

different levels of the ecosystem?

Solution:

Biological magnification (or biomagnification) refers to the process by which the concentration

of non-biodegradable substances, such as toxins or pollutants, increases as they move up the

food chain. These substances accumulate in the bodies of organisms and become more

concentrated at each successive trophic level.

Here’s how it works:

Primary Producers: Non-biodegradable substances enter the ecosystem through producers

(e.g., plants or algae) from the environment (soil, water). These substances are taken up by the

producers.

Primary Consumers: Herbivores consume the producers and ingest the toxins. Since the

herbivores consume a large quantity of producers, the concentration of toxins in their bodies

increases compared to the producers.

Secondary Consumers: Carnivores that eat the herbivores accumulate these toxins in even

higher concentrations because they consume many herbivores over their lifetime.

Tertiary Consumers: Top predators, which are at the top of the food chain, accumulate the

highest concentrations of toxins, as they are at the highest trophic level and consume many

organisms from the lower levels.

Levels of Magnification:

Different Levels: Yes, the levels of magnification will be different at various levels of the

ecosystem. Each trophic level shows a higher concentration of toxins compared to the level

below it. For instance, while primary producers might have a low concentration of toxins,

secondary and tertiary consumers will have progressively higher concentrations.

Effect on Ecosystems: The higher the trophic level, the greater the concentration of the toxins,

which can lead to harmful effects on top predators, including reproductive failures, health issues,

and even death. This magnification can cause significant ecological damage and impact the

health of the entire ecosystem.

Q7. What are the problems caused by the non-biodegradable wastes that we generate?

Solution:

Non-biodegradable wastes, which are substances that cannot be broken down by natural

processes or microorganisms, pose several significant problems:

Persistence in the Environment: Non-biodegradable substances, such as plastics, metals,

and synthetic chemicals, do not decompose naturally. This means they persist in the

environment for long periods, leading to accumulation and pollution.

Waste Management Challenges: The increasing volume of non-biodegradable waste strains

waste management systems. Dumping and disposal become challenging, as these materials

occupy landfill space and require special treatment to manage.

Food Chain Contamination: Non-biodegradable wastes, particularly heavy metals and toxic

chemicals, can enter the food chain. As these substances accumulate in organisms at various

trophic levels, they can lead to bio-magnification, impacting the health of animals and humans.

Soil and Water Pollution: Non-biodegradable wastes can leach into groundwater,

contaminating water sources. This can lead to soil infertility, alter soil pH, and affect plant

growth. Contaminated water sources can further impact human health and ecosystems.

Q8. If all the waste we generate is biodegradable, will this have no impact on the

environment?

Solution:

Even if all the waste generated is biodegradable, it can still have significant environmental

impacts:

Decomposition Odors: The decomposition of biodegradable wastes, while a natural process,

can be slow and produce unpleasant odors. These smells can be harmful if inhaled by humans,

potentially causing respiratory issues or other health problems.

Harmful Organisms: Dumping areas for biodegradable waste can become breeding grounds

for harmful microorganisms and pests. These organisms can pose health risks to humans,

plants, and animals, spreading diseases and disrupting ecosystems.

Oxygen Depletion: In aquatic environments, an excess of biodegradable waste can lead to

eutrophication. As these wastes decompose, they consume oxygen in the water, which can

reduce the oxygen available for aquatic life. This can lead to the death of fish and other aquatic

organisms, disrupting the balance of the ecosystem.

Q9. Why is damage to the ozone layer a cause for concern? What steps are being taken

to limit this damage?

Solution:

Damage to the ozone layer is a significant cause for concern due to the following reasons:

Increased UV Radiation: The ozone layer acts as Earth's shield against harmful ultraviolet

(UV) rays from the sun. When this layer is damaged, more UV rays reach the Earth's surface,

increasing the risk of skin cancer, eye cataracts, and other health problems in humans.

Harmful Effects on Ecosystems: Excessive UV radiation can disrupt ecosystems by affecting

plant growth and photosynthesis. It can also damage aquatic ecosystems by harming plankton

and other microorganisms that form the base of the food chain.

Disruption of Climate: Changes in UV radiation can impact weather patterns and climate

systems, potentially leading to broader environmental and climatic issues.

To address and limit ozone layer damage, several steps have been taken:

International Agreements: The most significant measure is the Montreal Protocol, an

international treaty signed in 1987 aimed at phasing out the production and use of

ozone-depleting substances like chlorofluorocarbons (CFCs). Many countries, both developed

and developing, have committed to reducing and eliminating these substances.

Regulation and Monitoring: Governments and international organizations monitor the

production, use, and emission of ozone-depleting chemicals. Regulations are in place to control

and phase out these substances.

Alternative Chemicals: The development and adoption of alternative chemicals and

technologies that do not harm the ozone layer are encouraged. For instance, substances that

do not contribute to ozone depletion are being used in place of CFCs.

Public Awareness and Education: Efforts are made to raise awareness about the importance

of protecting the ozone layer and the impact of individual actions, such as using products that are free of ozone-depleting chemicals.

Check Out: CBSE Class 10 Sample Papers

Understanding Our Environment Class 10 Questions and Answers

Let’s be honest: Science can sometimes feel like a list of definitions to memorize, but this chapter is different. When you look into our environment class 10 questions and answers, you're looking at the literal "how-to" guide for Earth’s survival. It’s about seeing the invisible threads that connect a blade of grass to a top predator and understanding how our daily habits—like using a plastic straw or a certain hairspray—can ripple through the atmosphere.

One of the most important takeaways from these solutions is the "waste journey." By learning about how different materials break down (or don't), we start to see why our current way of living is putting a strain on the planet. This isn't just exam prep; it's a crash course in being a responsible human.

 

Check Out: CBSE Class 10th Question Banks

Our Environment Class 10 NCERT Solutions

To make your study sessions a bit easier, here is a breakdown of the big ideas found in class 10 science chapter our environment question answer

1. The Ecosystem: Nature’s Neighborhood

Think of an ecosystem as a neighborhood where everyone has a job. It’s made up of biotic (living) and abiotic (non-living) parts. If the temperature changes or the rain stops (abiotic), it affects the plants and animals (biotic) living there.

• Producers: These are the superstars. Plants and algae take sunlight and turn it into food. Without them, nothing else survives.

• Consumers: These are the ones that eat. You’ve got herbivores (the plant-eaters), carnivores (the meat-eaters), and omnivores (who eat both).

• Decomposers: The cleanup crew. Bacteria and fungi break down dead stuff and turn it back into nutrients for the soil.

2. Food Chains and the Energy Web

A food chain is basically a map of "who eats whom." But in the real world, it's more like a web because most animals eat more than one thing.

• Trophic Levels: These are just the rungs on the ladder.

• Level 1: Producers (Autotrophs)

• Level 2: Herbivores (Primary Consumers)

• Level 3: Small Carnivores (Secondary Consumers)

• Level 4: Large Carnivores (Tertiary Consumers)

Biological Magnification: This is a scary but important concept. If a poison like a pesticide enters the water, the plants soak it up. A small fish eats many plants, a big fish eats many small fish, and eventually, a human eats the big fish. By the time it reaches us, that poison is way more concentrated.

3. The 10 Percent Rule: Why Energy Runs Out

Energy doesn't last forever. In fact, it's a bit like a leaky bucket. When a herbivore eats a plant, it only gets about 10% of that plant's energy. The rest is lost as heat or used up while the animal moves and grows. This is why you rarely see a food chain with five or six levels—by that point, there’s just no energy left to give. This massive depletion means top predators require vast hunting grounds to find enough fuel, as the available calories shrink significantly at every single step of the biological ladder.

4. Our Impact: Ozone and Trash

We've left a pretty big footprint on the planet, and the chapter focuses on two main problems:

• The Ozone Shield: There’s a layer of ozone high in the sky that acts like sunglasses for the Earth, blocking harmful UV rays. Chemicals called CFCs (found in old fridges) started punching holes in it. We’ve worked hard to ban them, but it’s a slow healing process.

• The Plastic Problem: This is all about what happens to our trash.

• Biodegradable: Things that rot naturally (like an apple core).

• Non-biodegradable: Things that stay forever (like a plastic bottle). These are the ones clogging our oceans and soil.

Benefits of PW Class 10 Study Material

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Check out: CBSE Class 10th Previous Year Papers

NCERT Solutions for Class 10 Science Chapter 15 FAQs

What’s the difference between a food chain and a food web?

A food chain is a single, straight line of who eats whom. A food web is a messy, realistic map showing that one animal can be part of many different food chains at once.

Why does energy only flow one way?

Once energy is used by an animal to stay alive or is lost as heat, it's gone. It can't go back to the plant or back to the sun. It’s a one-way street.

What is the "10 percent law" in simple terms?

It means that every time you move up a step in the food chain, 90% of the energy is wasted. Only 10% makes it to the next level.

How is ozone actually made?

Up in the atmosphere, UV light hits regular oxygen (O2) and splits it into single atoms. Those single atoms then find other O2 molecules and join up to form O3—which is ozone.

Why is biological magnification dangerous for humans?

Because we are usually at the top of the food chain! We end up eating all the accumulated chemicals from everything below us in the chain.