Summary
NCERT Class 10 Science Chapter 13 'Our Environment' explains how ecosystems function through food chains, energy flow, biological magnification of pesticides, ozone layer depletion by CFCs, and the environmental impact of biodegradable versus non-biodegradable waste.
Chapter 13 of NCERT Class 10 Science covers the structure and functioning of ecosystems, including biotic and abiotic components, producers, consumers, and decomposers. It explains food chains, trophic levels, and the 10% energy rule — only about 10% of energy transfers from one trophic level to the next, limiting food chains to three or four steps. The chapter also discusses biological magnification of pesticides, ozone layer depletion caused by CFCs, and the distinction between biodegradable and non-biodegradable waste and their environmental consequences.
Key points & formulas
- 01An ecosystem consists of biotic components (living organisms) and abiotic components (temperature, rainfall, wind, soil, minerals); examples include forests, ponds, gardens, and crop-fields.
- 02Organisms are classified as producers (green plants and certain bacteria using photosynthesis), consumers (herbivores, carnivores, omnivores, parasites), and decomposers (bacteria and fungi that break down dead matter).
- 03Only about 10% of energy at one trophic level is transferred to the next; green plants capture only about 1% of sunlight, which limits food chains to three or four trophic levels.
- 04Biological magnification occurs when non-degradable pesticide chemicals accumulate progressively at each trophic level, reaching maximum concentration in humans at the top of the food chain.
- 05The ozone layer (O₃) shields Earth from harmful UV radiation; synthetic chemicals called CFCs (used in refrigerants and fire extinguishers) caused a sharp drop in ozone levels from the 1980s, leading to a 1987 UNEP agreement to freeze CFC production.
- 06Waste is classified as biodegradable (broken down by biological processes) or non-biodegradable (persists in the environment and may harm ecosystems); increased use of disposable and plastic items has worsened non-biodegradable waste problems.
Frequently asked questions
01What is biological magnification in Class 10 Science Chapter 13?
Biological magnification is the progressive accumulation of non-degradable chemicals such as pesticides at each trophic level of a food chain. Because humans occupy the top trophic level, the maximum concentration of these chemicals gets accumulated in our bodies. These residues can be found in food grains, vegetables, fruits, and meat, and cannot always be removed by washing.
02Why are food chains generally limited to three or four trophic levels?
At each trophic level, only about 10% of the energy from food eaten is converted into body mass and made available to the next level. The remaining energy is lost as heat, in digestion, and in doing work. This rapid loss of energy means that very little usable energy remains after four trophic levels, making longer food chains unsustainable.
03How does CFC cause depletion of the ozone layer?
Chlorofluorocarbons (CFCs), used in refrigerants and fire extinguishers, are synthetic chemicals that react with and break down ozone (O₃) molecules in the upper atmosphere. The amount of ozone began dropping sharply in the 1980s due to CFC use. In 1987, the UNEP forged an agreement to freeze CFC production at 1986 levels, and it is now mandatory for all manufacturing companies to make CFC-free refrigerators worldwide.
04Is the NCERT Class 10 Science Chapter 13 PDF free to download?
Yes, the NCERT Class 10 Science Chapter 13 PDF is completely free to download on cbseprepmaster.com.
More chapters in Science
This is the complete Science Chapter 13 as published by NCERT — every diagram, solved example, and exercise included, free. Browse all CBSE Class 10 textbooks.
Read offline with notes, solutions & mock tests
CBSE Prepmaster — free on iOS & Android