Complete Concept Guide (100% Curriculum Coverage)
1. The 10% Law of Energy Flow
Energy flow in an ecosystem is strictly unidirectional. Green plants capture only $1\%$ of solar energy striking leaves. According to Raymond Lindeman's 10% Law, only about $10\%$ of the energy available at one trophic level is transferred to the next trophic level as biomass: $$\mathbf{10,000\text{ J (Plants)} \longrightarrow 1,000\text{ J (Deer)} \longrightarrow 100\text{ J (Tiger)}}$$ Because energy diminishes so rapidly, food chains rarely exceed 4 or 5 trophic levels!
2. Biological Magnification (Biomagnification)
Non-biodegradable toxic chemicals (like DDT and heavy metals) cannot be metabolized or excreted by living cells. As a result, their concentration multiplies progressively at each successive trophic level. Top carnivores (and humans) at the apex of the food chain accumulate the highest, lethal concentrations!
3. Ozone Depletion and Solid Waste
The stratospheric Ozone Layer ($\text{O}_3$) absorbs harmful solar UV rays ($3\text{O}_2 \xrightarrow{\text{UV}} 2\text{O}_3$). In 1985, a hole was discovered caused by CFCs from aerosol sprays and air conditioners. The global 1987 Montreal Protocol froze CFC production, allowing the ozone layer to heal!
Check Your Understanding (Diagnostic Practice Questions)
Diagnostic questions testing core conceptual clarity. Answers are hidden initially — solve each problem first, then click to reveal the step-by-step verified solution.
1
If $20,000\text{ J}$ of solar energy is captured by producers, how much energy will be available to tertiary consumers in a 4-step food chain?
Reveal Answer & Explanation
Answer: Producers: $20,000\text{ J}$ → Primary Consumer: $2,000\text{ J}$ → Secondary Consumer: $200\text{ J}$ → Tertiary Consumer: $20\text{ Joules}$.
10% law yields 20 Joules.
2
What is Biological Magnification? Why are humans most severely affected by it?
Reveal Answer & Explanation
Answer: It is the progressive increase in the concentration of non-biodegradable toxic chemicals (like pesticides) at each successive trophic level in a food chain. Humans occupy the apex of food chains and accumulate the highest toxic concentrations.
Toxin concentration rises up food chain.
3
What causes the depletion of the stratospheric ozone layer?
Reveal Answer & Explanation
Answer: Synthetic Chlorofluorocarbons (CFCs) used as refrigerants and aerosol propellants; UV rays break CFCs to release chlorine free radicals that destroy ozone molecules.
CFCs releasing chlorine radicals.
4
Why do food chains in an ecosystem rarely have more than four or five trophic levels?
Reveal Answer & Explanation
Answer: Because according to the 10% law, 90% of energy is lost as heat and metabolic maintenance at each transfer; after 4 or 5 levels, the remaining energy is too meager to sustain another organism.
Insufficient energy remains after 4-5 steps.
5
What is the difference between biodegradable and non-biodegradable substances? Give one example of each.
Reveal Answer & Explanation
Answer: Biodegradable substances can be broken down into simple harmless elements by natural microbial decomposers (e.g. vegetable peels); non-biodegradable substances cannot be decomposed and persist indefinitely (e.g. plastic bottles).
Broken down by microbes vs persistent plastics.
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