{"slug":"cbse-class-10-science-our-environment","title":"Our Environment","description":"Ecosystems, food chains and energy flow, biological magnification, the ozone layer and waste disposal, weighted towards the biological magnification, crop field and waste disposal questions set in all three 2026 paper sets.","board":"CBSE","grade":"Class 10","subject":"Science","chapter":"Our Environment","url":"https://www.flipnlearn.app/deck/cbse-class-10-science-our-environment","studyUrl":"https://www.flipnlearn.app/deck/cbse-class-10-science-our-environment/study","cards":[{"id":"ecosystem","kind":"term-definition","front":"Ecosystem","back":"The living things of an area, all interacting, together with the non-living parts of their surroundings. It has biotic components, the living organisms, and abiotic components such as temperature, rainfall, wind, soil and minerals; forests, ponds and lakes occur naturally, whereas gardens and crop fields are made by people."},{"id":"why-crop-fields-are-artificial-ecosystems","kind":"concept-question","front":"Why are crop fields considered artificial ecosystems?","back":"They are made by human beings rather than arising naturally, in the same way as gardens and aquariums, and people decide what is grown in them and maintain them. Forests, ponds and lakes, by contrast, are natural ecosystems."},{"id":"producer","kind":"term-definition","front":"Producer","back":"An organism that builds organic compounds like sugar and starch out of inorganic materials, powered by sunlight and using chlorophyll. Green plants and some bacteria are producers, and they form the first trophic level."},{"id":"decomposer","kind":"term-definition","front":"Decomposer","back":"A microorganism, such as a bacterium or fungus, that decomposes the wastes and dead bodies of other organisms. It turns complex organic substances into simple inorganic ones that go into the soil and are used again by plants."},{"id":"what-if-decomposers-were-removed","kind":"concept-question","front":"What would happen to an ecosystem if all its decomposers were removed?","back":"Garbage, dead plants and animals and other wastes would not be broken down. The simple inorganic substances that decomposers return to the soil would no longer be released, so the natural replenishment of the soil for plants would stop."},{"id":"food-chain","kind":"term-definition","front":"Food chain","back":"A series of organisms each feeding on the one before it, from producers through successive levels of consumers. Each step is a trophic level, and the energy captured by the producers passes along the chain from one level to the next."},{"id":"trophic-level","kind":"term-definition","front":"Trophic level","back":"Each step or level of a food chain. Producers form the first level, herbivores or primary consumers the second, small carnivores or secondary consumers the third, and larger carnivores or tertiary consumers the fourth."},{"id":"food-web","kind":"term-definition","front":"Food web","back":"A network of branching food chains. Since most organisms are food for two or more other kinds, which in turn are eaten by several others, feeding relationships form a web rather than a single straight chain."},{"id":"why-food-chains-have-only-three-or-four-steps","kind":"concept-question","front":"Why do food chains generally consist of only three or four steps?","back":"Green plants capture only about 1% of the sunlight falling on their leaves, and on average only 10% of the food eaten at each level becomes available to the next, the rest being lost as heat and used in digestion and work. After four trophic levels very little usable energy remains."},{"id":"why-energy-flow-is-unidirectional","kind":"concept-question","front":"Why is the flow of energy in an ecosystem said to be unidirectional?","back":"Energy captured by autotrophs does not return to the solar input, and energy passed to herbivores does not come back to the autotrophs. Once energy has moved on to a higher trophic level, the level below cannot use it again, and it diminishes at every step."},{"id":"biological-magnification","kind":"term-definition","front":"Biological magnification","back":"The progressive accumulation of non-degradable chemicals, such as pesticides, at each trophic level of a food chain. Human beings occupy the top level, so the maximum concentration builds up in our bodies, which is why food grains, vegetables, fruits and even meat carry pesticide residues."},{"id":"ozone-layer","kind":"term-definition","front":"Ozone layer","back":"Ozone, O3, a molecule of three oxygen atoms, is a deadly poison at ground level. In the higher levels of the atmosphere, however, it shields the earth's surface from the Sun's ultraviolet radiation, which is highly damaging to organisms and can cause skin cancer."},{"id":"how-ozone-is-formed","kind":"concept-question","front":"How is ozone formed in the upper atmosphere?","back":"High-energy ultraviolet radiation splits some oxygen molecules into free oxygen atoms, which then combine with oxygen molecules to form ozone: O2 --UV--> O + O, followed by O + O2 --> O3."},{"id":"what-caused-ozone-depletion","kind":"concept-question","front":"What has caused the depletion of the ozone layer, and what was done about it?","back":"The sharp drop in ozone from the 1980s has been linked to synthetic chemicals such as chlorofluorocarbons (CFCs), used in refrigeration and fire extinguishers. In 1987 UNEP brokered a deal holding CFC production to its 1986 level, and CFC-free refrigerators are now mandatory worldwide."},{"id":"biodegradable-substance","kind":"term-definition","front":"Biodegradable substance","back":"A substance that is broken down by biological processes, such as the action of bacteria and other saprophytes. Non-biodegradable substances are not broken down in this way; they may linger in the environment for years or cause harm to living things in the ecosystem."},{"id":"why-some-substances-are-not-biodegradable","kind":"concept-question","front":"Why are some substances, such as many plastics, not biodegradable?","back":"Enzymes are specific in their action, so a substance is broken down only by the particular enzymes suited to it. Many human-made materials such as plastics are not acted on by bacteria or other saprophytes, and under ordinary conditions in the environment they persist for a long time."},{"id":"why-improper-waste-disposal-is-harmful","kind":"concept-question","front":"Why is improper disposal of the waste we generate harmful to the environment?","back":"Much of our waste, especially packaging and disposable items, is non-biodegradable, so instead of breaking down it persists in heaps or harms members of the ecosystem. Untreated sewage and industrial wastes can also pollute soil and water bodies."}]}