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By rohit.pandey1
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Updated on 3 Jul 2026, 17:33 IST
Our Environment Class 10 Notes explain how living organisms interact with each other and with their surroundings. This chapter covers ecosystems, food chains, food webs, trophic levels, the 10 percent law, decomposers, biological magnification, ozone layer depletion, waste production, and biodegradable and non-biodegradable substances.
In the latest CBSE Class 10 Science Syllabus, Our Environment is included under Unit V: Natural Resources, which carries 5 marks in the theory paper. The official CBSE curriculum lists the topics as ecosystem, environmental problems, ozone depletion, waste production and their solutions, and biodegradable and non-biodegradable substances.
Our Environment Class 10 is a CBSE Science chapter that teaches students about ecosystems, food chains, energy flow, trophic levels, decomposers, biological magnification, ozone depletion, and waste management. It helps students understand how organisms depend on one another and how human activities affect the environment.
Students can use the Our Environment Class 10 Notes PDF for quick revision before school exams, pre-boards and board exams. The PDF should include definitions, comparison tables, diagrams, MCQs, assertion-reason questions, case-based questions and important board exam questions.
The chapter Our Environment explains the relationship between living organisms and their surroundings. It shows how plants, animals, microorganisms and non-living components work together in an ecosystem.
Students also learn how energy flows through food chains, why only a small amount of energy passes from one trophic level to the next, and why harmful chemicals can accumulate in organisms through biological magnification. The chapter also discusses ozone layer depletion, waste production, and the difference between biodegradable and non-biodegradable substances.
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CBSE question papers include objective questions, assertion-reason questions, short answers, long answers and source/case-based questions, so this page includes all those formats for practice.
The environment is everything that surrounds living organisms and affects their life. It includes both living and non-living components.
The environment includes:
In simple words, the environment is the natural world in which organisms live, grow, reproduce and interact.
An ecosystem is a self-sustaining unit where living organisms interact with each other and with non-living components of the environment.
Examples of ecosystems include:
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An ecosystem has two main components:
| Component | Meaning | Examples |
| Biotic components | Living components | Plants, animals, bacteria, fungi |
| Abiotic components | Non-living components | Air, water, soil, sunlight, temperature |
Abiotic components are the non-living parts of the environment. They affect the survival, growth and reproduction of organisms.
Important abiotic components include:
Biotic components are the living parts of an ecosystem. They are classified into three major groups:
Producers are organisms that prepare their own food using sunlight, carbon dioxide and water.
Green plants are the main producers in most ecosystems because they perform photosynthesis.
Examples:
Producers form the first trophic level in a food chain.
Consumers are organisms that depend directly or indirectly on producers for food.
Consumers may be herbivores, carnivores or omnivores.
| Type of Consumer | Meaning | Example |
| Herbivores | Eat plants | Deer, cow, goat |
| Carnivores | Eat other animals | Lion, tiger, snake |
| Omnivores | Eat plants and animals | Human, crow, bear |
Decomposers are microorganisms that break down dead plants, dead animals and organic waste into simpler substances.
Examples of decomposers:
Decomposers are important because they:
Decomposers are organisms such as bacteria and fungi that break down dead organic matter into simpler substances and recycle nutrients back into the ecosystem.
A food chain is a sequence of organisms in which one organism eats another organism and energy is transferred from one trophic level to the next.
Example:
Grass → Deer → Lion
In this food chain:
Another example:
Plants → Grasshopper → Frog → Snake → Eagle
| Organism | Trophic Level |
| Plants | Producer |
| Grasshopper | Primary consumer |
| Frog | Secondary consumer |
| Snake | Tertiary consumer |
| Eagle | Top carnivore |
Trophic levels are the different feeding levels in a food chain.
| Trophic Level | Organism Type | Example |
| First trophic level | Producers | Green plants |
| Second trophic level | Primary consumers | Deer, grasshopper |
| Third trophic level | Secondary consumers | Frog, small fish |
| Fourth trophic level | Tertiary consumers | Snake |
| Fifth trophic level | Top carnivores | Eagle, lion |
The 10 percent law states that only about 10% of energy is transferred from one trophic level to the next, while the remaining energy is lost as heat and used in life processes.
This law is also called Lindeman’s 10 percent law.
Assume plants have 10,000 J of energy.
| Trophic Level | Organism | Energy Available |
| First trophic level | Plants | 10,000 J |
| Second trophic level | Deer | 1,000 J |
| Third trophic level | Lion | 100 J |
| Fourth trophic level | Top carnivore | 10 J |
Only 10% of energy passes to the next level.
Food chains usually have only 3–4 trophic levels because energy decreases sharply at each level. Since only about 10% of energy is transferred to the next trophic level, very little energy remains after the third or fourth level. This makes it difficult to support more organisms at higher levels.
Energy flow in an ecosystem is unidirectional. It starts from the Sun, moves to producers, then to consumers, and finally to decomposers.
Flow of energy:
Sun → Producers → Herbivores → Carnivores → Decomposers
Energy flow is unidirectional because energy lost as heat cannot be reused by plants. The energy moves from one trophic level to the next but does not return to the previous level.
A food web is a network of interconnected food chains.
In nature, organisms usually depend on more than one food source. Therefore, food chains are interconnected to form a food web.
Example:
|  |
| Basis | Food Chain | Food Web |
| Meaning | Single pathway of food transfer | Network of many food chains |
| Complexity | Simple | Complex |
| Stability | Less stable | More stable |
| Energy flow | One direction through a chain | Multiple interconnected routes |
| Example | Grass → Deer → Lion | Many connected food chains in a forest |
A food chain shows one pathway of energy transfer, while a food web shows many interconnected food chains in an ecosystem. A food web is more realistic and stable than a food chain.
Biological magnification, or biomagnification, is the increase in the concentration of harmful chemicals at each successive trophic level of a food chain.
It usually occurs with toxic substances that do not break down easily and cannot be removed from the body quickly.
Examples of such substances:
DDT enters the food chain when it is sprayed on crops. It may enter water bodies through rainwater runoff. Small aquatic organisms absorb DDT. Fish eat those organisms, larger fish eat smaller fish, and birds or humans eat the larger fish.
At each trophic level, the concentration of DDT increases.
Example:
Water → Plankton → Small Fish → Large Fish → Bird
The top consumer receives the highest concentration of the chemical.
Biological magnification can:
Minamata disease is a disease caused by mercury poisoning. It occurred due to the release of mercury-containing industrial waste into water bodies. Mercury entered the aquatic food chain and became concentrated in fish, which affected people who consumed contaminated fish.
This is a real-life example of biological magnification.
Waste materials are classified into biodegradable and non-biodegradable substances.
Biodegradable substances are substances that can be broken down by microorganisms into simpler harmless substances.
Examples:
Non-biodegradable substances are substances that cannot be easily broken down by microorganisms.
Examples:
| Basis | Biodegradable | Non-Biodegradable |
| Breakdown | Broken down by microorganisms | Not easily broken down |
| Time taken | Shorter time | Very long time |
| Effect on environment | Less harmful if managed properly | Often causes pollution |
| Examples | Food waste, paper, leaves | Plastic, glass, metals |
| Disposal method | Composting, biogas | Recycling, reuse, safe disposal |
Human activities produce large amounts of waste. If waste is not managed properly, it pollutes air, water and soil.
| Type of Waste | Examples |
| Household waste | Food waste, paper, plastic |
| Industrial waste | Chemicals, metals, toxic gases |
| Agricultural waste | Pesticides, fertilisers, crop residue |
| E-waste | Old phones, batteries, computers |
| Biomedical waste | Syringes, medicines, hospital waste |
Effective waste management includes:
The 3Rs are important for environmental protection.
| 3R | Meaning | Example |
| Reduce | Use fewer resources | Carry a reusable water bottle |
| Reuse | Use items again | Reuse jars and bags |
| Recycle | Convert waste into useful products | Recycle paper, metal and plastic |
The ozone layer is a protective layer present in the stratosphere. It absorbs harmful ultraviolet radiation from the Sun and protects life on Earth.
Ozone layer depletion means the thinning of the ozone layer due to harmful chemicals such as chlorofluorocarbons, commonly called CFCs.
The ozone hole is a region where the ozone layer becomes extremely thin. It is not an actual hole, but a severe reduction in ozone concentration in a particular region of the atmosphere.
Major causes include:
Ozone layer depletion can lead to:
Ozone is formed when oxygen molecules absorb ultraviolet radiation and split into oxygen atoms. These oxygen atoms combine with oxygen molecules to form ozone.
Simple representation:
O₂ → O + O
O + O₂ → O₃
The Montreal Protocol is an international agreement made to reduce the use of ozone-depleting substances such as CFCs. Students should verify dates and treaty details from trusted sources such as UNEP or official environmental agencies when writing project work or updated reports.
The greenhouse effect is the process by which certain gases trap heat in the Earth’s atmosphere and keep the planet warm.
Important greenhouse gases include:
| Gas | Source |
| Carbon dioxide | Burning fossil fuels, deforestation |
| Methane | Paddy fields, cattle, landfills |
| Nitrous oxide | Fertilisers, industries |
| Water vapour | Natural evaporation |
| CFCs | Refrigerants and industrial sources |
| Basis | Natural Greenhouse Effect | Enhanced Greenhouse Effect |
| Meaning | Maintains Earth’s suitable temperature | Excess heat trapping due to pollution |
| Cause | Natural greenhouse gases | Human activities increase greenhouse gases |
| Effect | Supports life | Causes global warming |
Global warming is the gradual increase in Earth’s average temperature due to the excessive buildup of greenhouse gases in the atmosphere.
Global warming may cause:
Acid rain is rainwater that becomes acidic due to pollutants such as sulphur dioxide and nitrogen oxides.
Acid rain can:
A common example is the corrosion of marble monuments such as the Taj Mahal due to acidic pollutants.
A useful mind map for this chapter should include:
Suggested image alt text: our environment class 10 mind map ecosystem food chain ozone depletion
Students should practise these diagrams:
| Diagram | Why Important |
| Food chain diagram | Common 2-mark or 3-mark question |
| Food web diagram | Helps explain ecosystem stability |
| Trophic level pyramid | Useful for 10 percent law |
| Ozone layer depletion diagram | Helps explain CFC effect |
| Waste segregation chart | Useful for environment-based questions |
Use this quick revision section before exams:
A. Deer
B. Grass
C. Lion
D. Frog
Answer: B. Grass
A. Producers
B. Herbivores
C. Decomposers
D. Carnivores
Answer: C. Decomposers
A. Water cycle
B. Energy transfer
C. Ozone depletion
D. Waste management
Answer: B. Energy transfer
A. Paper
B. Vegetable peel
C. Plastic
D. Cotton cloth
Answer: C. Plastic
A. Producers
B. Primary consumers
C. Secondary consumers
D. Top consumers
Answer: D. Top consumers
A. Infrared rays
B. Ultraviolet rays
C. X-rays from soil
D. Sound waves
Answer: B. Ultraviolet rays
A. Oxygen
B. Nitrogen
C. CFCs
D. Water vapour
Answer: C. CFCs
A. A single food chain
B. A network of food chains
C. Only producers
D. Only decomposers
Answer: B. A network of food chains
A. Glass
B. Plastic bag
C. Metal can
D. Fruit peel
Answer: D. Fruit peel
A. Cyclic
B. Random
C. Unidirectional
D. Reversible
Answer: C. Unidirectional
Assertion: Food chains generally have only 3–4 trophic levels.
Reason: Only about 10% of energy is transferred from one trophic level to the next.
Answer: Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
Assertion: Decomposers are important for ecosystems.
Reason: They recycle nutrients by breaking down dead organic matter.
Answer: Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
Assertion: Biological magnification is highest in top consumers.
Reason: Non-biodegradable toxic substances increase at successive trophic levels.
Answer: Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
Assertion: Plastic waste creates long-term environmental problems.
Reason: Plastic is non-biodegradable and does not decompose easily.
Answer: Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
Assertion: Ozone layer depletion is harmful for living organisms.
Reason: The ozone layer absorbs harmful ultraviolet radiation.
Answer: Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
A grassland ecosystem includes grass, grasshoppers, frogs, snakes and eagles. Grass prepares food using sunlight. Grasshoppers feed on grass, frogs eat grasshoppers, snakes eat frogs, and eagles feed on snakes.
A pesticide is sprayed on crops near a water body. Rainwater carries the pesticide into the pond. Small aquatic organisms absorb it. Small fish eat these organisms, large fish eat small fish, and birds eat large fish.
A vegetarian diet is more energy efficient because it involves fewer trophic levels. When humans eat plants directly, they receive more energy than when they eat animals that have already used most of the energy obtained from plants. Due to the 10 percent law, energy decreases at each trophic level.
Single-use plastic should be avoided because it is non-biodegradable, remains in the environment for a long time, pollutes land and water, and harms animals when they accidentally consume it.
Decomposers are called nature’s cleaners because they break down dead plants, dead animals and organic waste. This prevents the accumulation of dead matter and recycles nutrients back into the ecosystem.
Our Environment Class 10 Notes help students understand ecosystems, food chains, food webs, trophic levels, decomposers, biological magnification, ozone layer depletion, waste production and biodegradable and non-biodegradable substances. This chapter is important because it connects Science with real environmental problems and teaches students how human activities affect nature.
For best exam preparation, revise the definitions, practise food chain diagrams, understand the 10 percent law, learn biological magnification with examples, and solve MCQs, assertion-reason and case-based questions.
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An ecosystem is a self-sustaining unit where living organisms interact with each other and with non-living components such as air, water, soil and sunlight.
A food chain is a sequence of organisms in which one organism eats another and energy is transferred from one trophic level to the next.
A food web is a network of interconnected food chains. It shows multiple feeding relationships in an ecosystem.
The 10 percent law states that only about 10% of energy is transferred from one trophic level to the next.
Biological magnification is the increase in concentration of harmful chemicals at each successive trophic level of a food chain.
Food chains have only 3–4 trophic levels because energy decreases at every level, and very little energy remains for higher trophic levels.
Decomposers are organisms such as bacteria and fungi that break down dead organic matter. They recycle nutrients and maintain soil fertility.
Biodegradable substances can be broken down by microorganisms, while non-biodegradable substances cannot be easily decomposed.
Ozone layer depletion is mainly caused by chemicals such as CFCs, halons and certain industrial gases.
Energy flow is unidirectional because energy lost as heat cannot be reused by producers and does not return to the previous trophic level.