Our Environment Class 10 Notes

These Notes for Class 10 Science Chapter 13 Our Environment give you a quick, concept-first revision of the whole chapter, built on the latest 2026-27 CBSE syllabus. They cover the ecosystem and its biotic and abiotic parts, food chains, food webs and trophic levels, the flow of energy and the ten per cent law, biological magnification, the ozone layer, and how we manage biodegradable and non-biodegradable waste.

• Every key term explained in one clean sentence, with simple diagrams and the exact way the CBSE board paper asks it.
• Full coverage of producers, consumers and decomposers, the 10% law, CFCs and ozone depletion, and the three Rs of waste management.
• Notes mapped to the 2026-27 CBSE Class 10 Science syllabus, written for the board exam, so students can revise the chapter in one sitting.

These Collegedunia revision notes are curated by Science subject experts, mapped to the 2026-27 NCERT textbook, and refined against the last five years of CBSE Class 10 Science board papers.

What the Notes for Class 10 Science Chapter 13 Our Environment Cover

This chapter answers one big question: how do the living and non-living things in an area work together as one unit? These Our Environment Class 10 notes compress the NCERT chapter into revision-ready blocks students can recall fast in the exam.

• Ecosystem, food chains and the 10% law: how food and energy pass from green plants up the trophic levels, and why food chains stay short.
• Environmental problems: biological magnification, ozone depletion by CFCs, and managing biodegradable and non-biodegradable waste.

The Ecosystem and Its Biotic and Abiotic Components

All the living things in an area, together with the non-living surroundings they live in, form a single working unit called an ecosystem. A pond, a forest or a school garden is one such unit. It always has two kinds of parts, which the board paper often asks students to name and sort: biotic components (all living organisms, such as plants, animals, fungi and bacteria) and abiotic components (non-living physical factors, such as temperature, rainfall, wind, soil and minerals).

Ecosystems are of two kinds. Natural ecosystems like forests, ponds and lakes form on their own. Artificial (human-made) ecosystems like gardens, crop fields and an aquarium are set up and looked after by people. The organisms and physical factors keep affecting each other, which keeps a balance in nature.

Producers, Consumers and Decomposers in an Ecosystem

The organisms of an ecosystem are grouped by how they get their food, because food is really energy on the move. The image below sums up the three groups: producers (autotrophs) like green plants make their own food by photosynthesis, consumers (heterotrophs) eat other organisms, and decomposers (saprophytes) like bacteria and fungi break dead remains into simple substances.

Producers are the gateway through which the Sun's energy enters the living world. Consumers cannot make their own food, so they feed on producers or on each other:

• Herbivores eat only plants (deer, goat, grasshopper).
• Carnivores eat only other animals (lion, frog, snake).
• Omnivores eat both plants and animals (crow, human, bear).
• Parasites live on or in a host and take food from it (ticks, lice).

Decomposers break down the dead bodies and waste of plants and animals into simple substances that return to the soil, where plants use them again. So decomposers complete the cycle of materials and keep the soil fertile.

Food Chain, Food Web and Trophic Levels in Class 10 Science

A food chain is a series of organisms, each feeding on the one before it, that shows how food and energy pass from one to the next. Each step is a trophic level: producers first (grass), then herbivores (deer), then small carnivores (frog), then large carnivores (snake). The arrow always points from the eaten to the eater, the direction food and energy travel. So grass to deer means the deer eats the grass, not the other way round. In real life an organism rarely eats only one kind of food, so the straight-line chains cross and link into a food web. This makes an ecosystem more stable, because if one prey species disappears, a predator can switch to another food in the web. Removing one whole trophic level still upsets the balance: remove the producers and the ecosystem starves, remove the herbivores and plants grow wild while carnivores starve, remove the top carnivores and herbivores multiply and overgraze.

Flow of Energy in an Ecosystem and the Ten Per Cent Law

Food chains are really pathways for energy. The Sun is the source, and producers capture only about 1% of the sunlight falling on their leaves, the entire energy budget of the ecosystem. The diagram below shows how the energy shrinks at each step.

Energy flow follows two rules. First, it is unidirectional: from the Sun to producers to consumers, never back. Second, energy decreases at each level, lost as heat. This is why food chains usually have only three or four steps. Note the contrast with nutrients like carbon and nitrogen, which are recycled round and round by the decomposers instead of being lost.

Biological Magnification in a Food Chain

The same food chains that carry energy can also carry poison. Farmers use pesticides to protect crops, which rain washes into soil, rivers and lakes, where plants and water organisms absorb them, so they enter the food chain. Many are not degradable, so bodies cannot break them down and the chemical stays stored in fat and tissues. When a higher animal eats many lower animals, it takes in all the chemical they had stored, so the concentration becomes higher and higher as we climb the trophic levels. This increase at each higher level is called biological magnification.

So along a pond chain the concentration climbs from lowest in the water plants, to higher in small fish, higher still in big fish, and highest in the human beings who eat them. Because human beings occupy the top level of most food chains, the maximum concentration of these non-degradable chemicals builds up in our bodies. This is why our food grains, vegetables, fruits and even meat may carry pesticide residue that washing cannot always remove.

The Ozone Layer and Its Depletion in Class 10 Science

Ozone (O₃) is a molecule of three oxygen atoms, and where it sits decides whether it helps or harms. Near the ground it is a deadly poison, but high in the atmosphere it forms a layer that shields the Earth from ultraviolet (UV) radiation. UV is highly damaging and causes skin cancer in humans, so the ozone shield protects our health. High up, ozone forms when UV rays split an oxygen molecule into free atoms, and each free atom joins another oxygen molecule:

Ozone began to fall sharply in the 1980s. The drop was traced to man-made chlorofluorocarbons (CFCs), released from refrigerators, air conditioners and aerosol sprays. They drift up to the upper atmosphere, break apart ozone molecules and thin the layer, so more harmful UV reaches the surface. In 1987 the world acted together: a UNEP agreement froze CFC production at 1986 levels, and CFC-free goods are now compulsory. Remember the two roles of ozone: up high it shields us from UV, near the ground it is a harmful pollutant.

Biodegradable and Non-biodegradable Waste Management

The second big problem is the mountain of waste our daily life throws away. We sort it into two groups by whether living things can break it down. Biodegradable waste is broken down by bacteria and fungi: kitchen waste, paper, cotton cloth, dead plants and animals. Non-biodegradable waste is not, and persists for a long time: plastics, glass, metals and many chemicals.

Living things break down some substances but not others because enzymes are specific: each acts on only one kind of substance, like one key for one lock. Decomposers have enzymes for natural materials but not for man-made ones such as plastic, which is why plastics last for years. Each kind of waste harms in its own way: biodegradable waste left in the open rots, smells foul, attracts flies and germs and can pollute water; non-biodegradable waste persists, chokes drains, kills animals that swallow it, and builds up through biological magnification.

We reduce the harm by handling waste wisely: turn biodegradable waste into compost or biogas, treat sewage before letting it into rivers, and follow the three Rs in order, Reduce (make less waste), then Reuse (use the same item again), then Recycle (remake the material into something new).

One-Glance Revision Strip and Common Exam Traps

These are the traps that cost students marks in Our Environment board answers every year. Read them in the last five minutes before the exam.

Other Resources for Class 10 Science Chapter 13 Our Environment

Pair these revision notes with the matching NCERT Solutions, handwritten notes, the formula and key-facts sheet and the official NCERT book chapter. All resources for Class 10 Science Chapter 13 Our Environment are linked below.

Notes for Class 10 Science: All Chapters

Related Links: Use the table below to open the revision notes for the other chapters of Class 10 Science. Every chapter ships with the same concept-first notes style, full PDF download, and revision FAQ.