Ch 14 covers major natural resources — air, water, and soil — and the biogeochemical cycles that keep them renewed. Students learn how human activities disrupt these cycles and what we can do to protect them.
Atmosphere is heated unevenly → winds, rain. Air pollution: fossil fuels, industries. Water pollution: sewage, chemicals. Soil is formed by weathering of rocks + organic matter. Soil erosion happens when trees are removed. These resources are interconnected through biogeochemical cycles.
Water cycle: evaporation + transpiration → clouds → precipitation → rivers/groundwater → ocean. Nitrogen cycle: atmospheric N₂ → fixed by bacteria/lightning → nitrates → absorbed by plants → animals eat plants → decomposition returns N₂. Carbon cycle: CO₂ absorbed by photosynthesis, released by respiration and burning. Oxygen cycle: linked to carbon cycle.
Ozone (O₃) in the stratosphere absorbs harmful UV radiation. CFCs (chlorofluorocarbons) from refrigerators/ACs break ozone molecules. Ozone depletion leads to skin cancer, cataracts, and harm to ecosystems. Montreal Protocol aims to phase out CFCs.
Download: https://ncert.nic.in/textbook/pdf/iesc114.pdf | Complete book: https://ncert.nic.in/textbook/pdf/iesc1ps.zip
Atmospheric nitrogen (N₂) cannot be used directly by plants. Nitrogen fixation converts N₂ into usable forms (NH₃, NO₃⁻) by: lightning, nitrogen-fixing bacteria (Rhizobium in legume root nodules), and industrial processes (Haber process). Without fixation, plants couldn't make proteins, and life would not survive.
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