Ch 15 covers ecosystems, food chains and webs, energy flow, the 10% rule, waste management (biodegradable vs non-biodegradable), and the ozone layer — connecting ecology to daily life.
Ecosystem: community of organisms + their physical environment. Components: abiotic (sunlight, water, soil, temp) + biotic (producers, consumers, decomposers). Food chain: linear sequence — producers → primary consumers (herbivores) → secondary (carnivores) → tertiary. Food web: interconnected food chains in an ecosystem.
10% law (Lindeman): only 10% of energy is transferred to the next trophic level; 90% is used/lost as heat. Maximum 4-5 trophic levels in a food chain. Biological magnification: concentration of non-biodegradable chemicals (DDT, heavy metals) increases at each trophic level — top predators most affected.
Biodegradable: broken down by microorganisms (food waste, paper, cotton). Non-biodegradable: persist in environment (plastics, pesticides, metals) — cause pollution. Ozone (O₃) layer: absorbs UV radiation. CFCs from refrigerators/ACs deplete it. UNEP succeeded in getting CFCs banned (Montreal Protocol, 1987).
Download: https://ncert.nic.in/textbook/pdf/jesc115.pdf | Complete book: https://ncert.nic.in/textbook/pdf/jesc1ps.zip
Because only 10% of energy transfers to the next trophic level (10% law). After 4-5 levels, the energy available is too little to sustain another level. For example, if producers capture 10,000 J, herbivores get 1,000 J, secondary consumers 100 J, tertiary 10 J — barely enough to survive.
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