NCERT Class 10th Science Chapter 15 Our Environment Notes- Download PDF Notes

According to CBSE Syllabus 2025-26, this chapter is renumbered as Chapter 13.

The NCERT Notes Chapter 13 Our Environment focuses on the importance of understanding the natural world around us and the importance of maintaining it. This chapter introduces students to the environment, which consists of biotic (living) components, such as plants and animals, and abiotic (non-living) components, like air, water, and soil, including the key concepts such as the food chain and food web, which explains the flow of energy through different organisms in an ecosystem. All these topics are covered in NCERT Class 10 Science notes in a easy and effective manner along with all labelled diagrams provided by our subject experts.

This Story also Contains

1. Ecosystem
2. Ozone Layer and How it is Getting Depleted
3. Important Topics of Class 10 Biology Chapter 13: Our Environment
4. Most Important Questions of Class 10 Science Chapter 13
5. Approach to solve questions of Class 10 Science Chapter 13 Our Environment
6. Chapter-Wise NCERT Class 10 Notes Science

The chapter also introduces the ozone layer and its vital role in protecting life on Earth from ultraviolet radiation. However, human activities have led to the depletion of the ozone layer, resulting in serious environmental consequences. Class 10 Science chapter 13 notes also cover all the important concepts, like this which are useful in various competitive exams. Our environment NCERT Notes Class 10 Science helps you revise these major concepts given in the NCERT Book in no time during CBSE exam preparation. Questions from this chapter have been frequently asked in various exams.

Also Read:

• NCERT Solutions for Class 10 Physics Chapter 13 Our Environment
• NCERT Exemplar Class 10 Science Chapter 13 Solutions Our Environment

Our Environment Class 10 Notes Science Chapter 13

To help in your study, the notes given below outline the most important points, with clear explanations and examples to help you grasp the subject matter and concept more effectively.

Biodegradable and Non-biodegradable Substances

Provided below are some of the key points to know the differences between the two different type of substances and their impact on the environment.

Biodegradable substances

• The substances that can be broken down by natural processes, such as by the action of microorganisms, bacteria, and fungi.
• Food waste, paper products, wood, cotton fabric, and animal waste are some common examples of biodegradable substances.
• These materials are less harmful to the environment as they break down naturally.

Non-biodegradable Substances

• These substances are those that do not break down naturally or take an extremely long time to decompose.
• Plastics bags, bottles, metals, nylon, pesticides, and chemicals are some examples of non-biodegradable substances.
• These materials contribute to pollution and degradation of ecosystems. They also harm wildlife and pollute the land and water bodies.
• Enzymes used in the degradation of substances have a unique effect, and certain enzymes are required for the breakdown of a given substrate. Cyanobacteria can decompose all types of waste.
• Physical processes such as heat and pressure act on non-biodegradable material.
• This waste requires recycling or proper waste management systems to prevent environmental damage.

Ecosystem

• G. Tansley coined the term ecosystem, which, according to him, is the total of interactions between living (biotic) and non-living (abiotic) components capable of independent existence.
• Biotic components include plants, animals, and bacteria, and abiotic components include light, temperature, rainfall, wind, and soil.
• An ecosystem is a self-sufficient unit.
• It may be a very small example, a freshwater pond, or a very large example, the Sahara desert.
• In an ecosystem, there is a cyclic exchange of materials between living beings and the environment. The only requirement is a constant input of energy.
• Desert grassland, forest, crop fields, etc., represent terrestrial ecosystems, whereas ponds, lakes, rivers, sea, etc., are aquatic ecosystems.
• Most of the ecosystems in the world are natural ones but some of them are man-made ecosystems such as aquariums, parks, etc.

Trophic Level

• Trophic means feeding, and hence trophic levels are the levels or positions at which species feed.
• In an ecosystem, producers represent the first trophic level; herbivores, the second trophic level; primary carnivores, the third trophic level; and so on.
• Mainly, the organisms are classified as producers, consumers, or decomposers depending on how they receive the food from the environment.

Producers-

• Those organisms that produce food are called producers.
• The green plants are the ultimate producers organisms in any ecosystem.
• They can prepare their food by using substances like carbon dioxide, water, and sunlight through the process of photosynthesis.

Consumers-

1. Those organisms that consume the food prepared by producers are called consumers.
2. All animals are consumers as they cannot prepare their food from simple inorganic substances.
3. There are mainly three types of consumers:

Primary consumers- Animals that feed on plants are called primary consumers. Example - cow, buffalo, goat etc.

Secondary consumers- Animals that eat the primary consumers are said to be secondary consumers. Example - Sparrow, crow, etc.

Tertiary consumers- Animals that feed on other carnivores are known as tertiary consumers. Wolf eating upon fox is an example of tertiary consumer.

Decomposers-

• The materials within the bodies of dead plants and animals are thus acted on by organisms of decay, known as decomposers.
• Bacteria and fungi are well-known examples of decomposers.

Food Chains and Food Webs

Some key points of the food chain and food web are explained below, along with clear diagrams.

Food Chain:

• The sequence of living organisms in an ecosystem in which one organism consumes another organism to transfer food energy is called a food chain.
• A food chain is made up of a sequence of organisms that participate at distinct biotic levels.
• A trophic level is formed at each level of the food chain.

• In the above diagram, the first trophic level is occupied by the producers (green plants).
• The second tropic level is occupied by primary consumers which are herbivores . In this diagram grasshopper occupies the second trophic level.
• The third tropic level is made up of secondary consumers that are small carnivores here bird.
• The fourth tropic level is made up of tertiary consumers known as larger carnivores such as fox.
• The number of people employed by producers is the highest.
• Example: Grass insects, frogs, snakes, and eagles
• Grasshopper eat grass, and bird eat the grasshopper, which are then eaten by fox, who are then devoured by eagles.

Food web:

• The interconnected food chains operating in an ecosystem that establish a network of relationships between various species is called a food web.
• It shows the pattern of energy or nutrient flow throughout an ecosystem.
• The energy flow in a food chain is one-way, once it reaches the next trophic level, it does not return.
• The complexity of food web depends upon the diversity of organisms in the system.

Ozone Layer and How it is Getting Depleted

• Ozone is a highly reactive molecule containing three oxygen atoms(O₃).

• A naturally occurring high altitude layer of ozone is important to life as it absorbs potentially damaging Ultraviolet radiation from sun.

UV rays break up molecular oxygen (O₂) into free oxygen (O) atoms, which mix with the molecular oxygen (O₂) to generate ozone (O₃).

O₂ →O + O

O+O₂ →O₃

Ozone layer depletion:

• Ozone layer in stratosphere protects us from the harmful Uv radiations from sun.
• The depletion of this ozone layer is due to human activities that has serious effects and this has become a subject of concern over the last few years.
• The depletion of ozone layer takes place due to reaction between ozone and chlorofluorocarbons(CFCs) which are released from sprays, air conditioners and refrigerators.
• One molecule of chlorofluorocarbons can damage 10,000 molecules of ozone.
• Although, ozone depletion is occuring widely in the stratosphere, the depletion is particularly marked over the Antarctic region. This has resulted in formation of large area of thinned ozone layer commonly known as ozone hole.

Effects of Ozone Depletion:

• Increased UV-radiation reaching the earth's surface due to ozone depletion in the stratosphere is harmful to human health, crop, forests, animals .
• It causes sunburn, skin cancer in humans. It also increased the acid production, global warming is also increased due to this.

NCERT Solutions Subject Wise

• NCERT Solutions for Class 10 Maths
• NCERT Solutions for Class 10 Science

Important Topics of Class 10 Biology Chapter 13: Our Environment

The following topics cover the essential concepts related to this chapter. These are important for the exam as well as for understanding ecological balance and environmental protection.

1. Ecosystem and Its Components

2. Biotic and Abiotic Factors

3. Food Chain and Food Web

4. Ozone layer and its depletion

Also, read Subject-Wise NCERT Exemplar Solutions

• NCERT Exemplar Class 10 Maths solutions
• NCERT Exemplar Class 10 Science solutions

Most Important Questions of Class 10 Science Chapter 13

Our Environment chapter helps you understand the balance of the ecosystems and the roles of biotic and abiotic components. It also covers the food chain, food web, and the importance of the ozone layer. Revise all key concepts with these important questions to increase your understanding of the chapter.

Question 1: UNEP stands for

A. Union Nations Environment Programme

B. United Nations Environment Position

C. United Nations Environment Programme

D. United Nations Emission Programme

Answer:

UNEP stands United Nations Environment Programme who succeeded in forging an agreement to freeze CFC production in the year 1987. Hence, the correct option is (c).

Question 2: Why is plastic called non-biodegradable?

Answer:

Plastic cannot be broken down into smaller particles by the action of bacteria, and hence it is called non-biodegradable.

Question 3: What is the sum total of plants, animals, and micro-organisms interacting with the non-living environment called?

Answer:

The environment is referred to as the sum total of all plants, animals and micro-organisms present along with all non-living factors.

Question 4: What is the major cause of the sharp drop of ozone in the atmosphere?

Answer:

Chlorofluorocarbons (CFCs) are the synthetic chemical used in refrigerators, air-conditioners or fire extinguishers has been observed as a major cause for the sharp drop of ozone in the atmosphere.

Question 5: In the given food chain, if the amount of energy at the first trophic level is 4000 kJ, what will be the energy available at the fourth trophic level?

Answer:

According to 10% law,

first trophic level --> second trophic level --> Third trophic level --> fourth trophic level

4000KJ --> 400KJ --> 40kJ -> 4KJ

So, 4KJ of energy is found at fourth trophic level.

NCERT Books and Syllabus

• NCERT Books for Class 10
• NCERT Syllabus for Class 10

Approach to solve questions of Class 10 Science Chapter 13 Our Environment

This is an interesting chapter as it allows students to explore and understand the functioning of the Earth and the Environment. To solve the questions from this chapter effectively, they can start by understanding the topic that how the ecosystem functions, including the importance of both biotic and abiotic components, along with the examples of each. Focus on the food chains and food webs that occur in our environment, and the specific function of each organism. They are advised to make a flow chart of both for quick revision and better retention. Prepare short notes on the importance of the ozone layer and what human activities are responsible for its depletion, as it helps you to understand the activities that need to be stopped. Go through the NCERT and Exemplar thoroughly and solve as many questions as you can to grasp the concepts easily.

Chapter-Wise NCERT Class 10 Notes Science

Given below are the chapter-wise links of class 10 notes: