All organisms — plants, animals, micro-organisms, and human beings — interact with each other and with their physical surroundings to maintain balance in nature. Our Environment forms Chapter 15 of the CBSE Class 10 Biology curriculum.
This comprehensive guide covers ecosystem structure, food chains and food webs, Lindeman's 10% Law of energy flow, biological magnification of toxic pesticides, ozone layer formation and depletion by CFCs, and effective waste management strategies for biodegradable and non-biodegradable garbage.
- 1. Ecosystem & Its Components (Biotic & Abiotic)
- 2. Producers, Consumers & Role of Decomposers
- 3. Food Chains, Food Webs & Trophic Levels
- 4. Lindeman's 10% Law of Energy Transfer
- 5. Biological Magnification (Bioaccumulation of Toxins)
- 6. Ozone Layer Formation, UV Protection & CFC Depletion
- 7. Garbage Management: Biodegradable vs Non-Biodegradable Waste
- 8. Solved Board Exam Questions
- 9. Frequently Asked Questions (FAQ)
1. Ecosystem & Its Components (Biotic & Abiotic)
An Ecosystem is a self-sustaining structural and functional unit of biosphere where living organisms interact among themselves and with their non-living physical environment.
• Producers: Green plants & blue-green algae.
• Consumers: Animals depending on producers.
• Decomposers: Bacteria & fungi.
• Climatic Factors: Sunlight, temperature, rainfall, wind, humidity.
• Edaphic Factors: Soil texture, pH, water, minerals, inorganic nutrients (N, P, K).
2. Producers, Consumers & Role of Decomposers
| Category | Biological Definition & Function | Examples |
|---|---|---|
| Producers (Autotrophs) | Organisms that manufacture their own organic food from simple inorganic substances (CO₂ & H₂O) using solar light energy via photosynthesis. | Green plants, Phytoplankton, Cyanobacteria |
| Consumers (Heterotrophs) | Organisms that consume food produced by autotrophs directly or indirectly. • Herbivores (Primary Consumers): Feed directly on plants. • Carnivores (Secondary/Tertiary Consumers): Feed on other animals. • Omnivores: Feed on both plants and animals. • Parasites: Live on/in host body for nutrition without killing immediately. |
Cow, Deer (Herbivores) Lion, Tiger, Snake (Carnivores) Humans, Bear, Crow (Omnivores) Cuscuta (Amarbel), Tapeworm, Leech (Parasites) |
| Decomposers (Saprophytes) | Micro-organisms that break down complex organic substances of dead plants and animal wastes into simple inorganic nutrients. | Bacteria, Fungi (Bread mould, Mushrooms) |
2. Cleansing the Environment: In the absence of decomposers, dead bodies of plants and animals would pile up, creating foul odors and spreading deadly diseases!
3. Food Chains, Food Webs & Trophic Levels
A Food Chain is a linear sequence of organisms where each organism feeds on the one below it to transfer food energy.
• T₁ (1st Trophic Level): Autotrophs / Producers (Green Plants).
• T₂ (2nd Trophic Level): Primary Consumers (Herbivores — Grasshopper, Deer).
• T₃ (3rd Trophic Level): Secondary Consumers (Small Carnivores — Frog, Jackal).
• T₄ (4th Trophic Level): Tertiary Consumers (Top Carnivores — Eagle, Lion, Human).
Food Web: In nature, food chains are not isolated straight lines. Instead, multiple interconnected food chains form a complex network called a Food Web.
4. Lindeman's 10% Law of Energy Transfer
Energy flow in an ecosystem is UNIDIRECTIONAL (Sun → Producers → Herbivores → Carnivores). Energy once lost as heat cannot return to the Sun!
2. When green plants are eaten by primary consumers, a huge amount of energy is lost as heat to surroundings, digestions, and work.
3. Only 10% of the energy present at one trophic level is transferred and converted into organic biomass at the next higher trophic level.
4. Why food chains have only 3 to 4 steps: Because after 3-4 trophic levels, the amount of remaining energy becomes so minuscule that it is insufficient to support another higher organism!
Solution:
• Energy captured by Green Plants (1% of solar energy) = 20,000 J × 1% = 200 J.
• Energy transferred to Deer (10% of Producers) = 200 J × 10% = 20 J.
• Energy transferred to Lion (10% of Deer) = 20 J × 10% = 2 J.
5. Biological Magnification (Bioaccumulation of Toxins)
Biological Magnification is the phenomenon of progressive increase in the concentration of non-biodegradable toxic chemicals (such as pesticides, DDT, heavy metals) at successive trophic levels of a food chain.
2. These chemicals are washed into soil and water bodies, where they are absorbed by plants/phytoplankton.
3. Since these chemicals are non-biodegradable, they cannot be digested or excreted by living organisms — accumulating inside body tissues.
4. Herbivores eat many plants, concentrating the pesticide. Carnivores eat many herbivores, further magnifying toxin levels.
5. Why Humans Have Maximum Concentration: As humans occupy the topmost trophic level in almost all food chains, non-biodegradable pesticides accumulate in maximum concentration inside human bodies, leading to health hazards (cancer, organ failure)!
6. Ozone Layer Formation, UV Protection & CFC Depletion
Ozone (O₃) is a deadly poison at ground level, but in the upper atmosphere (Stratosphere, 15-30 km high), it forms a vital protective shield that absorbs harmful Ultraviolet (UV-B) radiation from the Sun.
O₂ + High UV Radiation → O + O
These reactive free oxygen atoms combine with molecular oxygen to form Ozone:
O + O₂ → O₃ [Ozone]
• Effects of UV Exposure: Skin cancer, eye cataracts, damage to immune system, and reduced crop yield.
• Montreal Protocol (1987): International agreement signed by UNEP to freeze CFC production at 1986 levels.
7. Garbage Management: Biodegradable vs Non-Biodegradable Waste
Human activities generate massive quantities of waste (garbage) daily. Proper waste segregation and disposal are crucial to prevent environmental pollution.
| Property | Biodegradable Waste | Non-Biodegradable Waste |
|---|---|---|
| Decomposition | Broken down into simple harmless substances by biological action of micro-organisms (bacteria & fungi). | CANNOT be broken down by biological action of micro-organisms; persist indefinitely in the environment. |
| Environmental Impact | Safe for environment if disposed properly; can be converted into natural manure/compost. | Major cause of soil, water, and air pollution; chokes drains and harms animals. |
| Examples | Fruit peels, vegetable scraps, leftover food, paper, cotton cloth, wood, cow dung, jute. | Plastics, polythene bags, glass bottles, nylon, DDT, synthetic rubber, heavy metals (Lead, Mercury). |
2. Composting / Vermicomposting: Organic kitchen waste converted into rich humus manure using earthworms.
3. Recycling: Waste plastics, glass, metals, and paper processed to manufacture new useful products.
4. Incineration: Burning hazardous hospital and toxic chemical waste at very high temperatures (>1000°C) to reduce volume to ash.
5. Landfills: Low-lying urban areas filled with non-hazardous solid garbage and compacted under soil layers.
6. Sewage Treatment Plant (STP): Municipal drain water filtered and treated biologically before discharging into rivers.
8. Solved Board Exam Questions
Calculation:
• T₁ Producers = 10,000 J
• T₂ Primary Consumers = 10,000 J × 10% = 1,000 J
• T₃ Secondary Consumers = 1,000 J × 10% = 100 J
• T₄ Tertiary Consumers = 100 J × 10% = 10 J.
Difference at levels: Yes! The concentration of toxic chemicals increases at each higher trophic level. Organisms at the highest trophic level (top carnivores/humans) accumulate the maximum concentration of the chemical toxin.
Formation: Solar UV radiation splits molecular oxygen into free oxygen atoms: O₂ + UV → O + O. Free O atom combines with O₂ molecule: O + O₂ → O₃.
Main cause of depletion: Synthetic chemicals called Chlorofluorocarbons (CFCs) used in refrigerators, ACs, and aerosol sprays.
If eliminated: (1) Dead bodies of plants and animals would accumulate indefinitely, polluting soil and water. (2) Mineral nutrient cycling would stop, leaving soil infertile, which would eventually destroy all plant life and the entire ecosystem!
(2) Non-Biodegradable Wastes: Wastes that cannot be broken down by micro-organisms and persist in the environment for long periods. Examples: Plastic bags, DDT.
Explore Related CBSE Class 9 & 10 Science Guides
9. Frequently Asked Questions (FAQ)
Lindeman's 10% law states that only 10% of the energy stored in organic biomass at one trophic level is transferred to the next higher trophic level during feeding. The remaining 90% is lost as metabolic heat, digestion, and bodily functions.
Biological magnification is the progressive accumulation of non-biodegradable toxic chemicals (like DDT or mercury) in increasing concentrations at higher trophic levels. For example, DDT sprayed on crops accumulates in water, phytoplankton, small fish, large fish, and reaches maximum dangerous concentration in top consumers like humans or eagles.
The Montreal Protocol (1987) is an international environmental treaty established by UNEP to freeze and phase out the production of Chlorofluorocarbons (CFCs) worldwide in order to stop the depletion of the stratospheric ozone layer.
Energy flow is unidirectional because solar energy captured by green plants (producers) cannot pass back to the Sun, and energy transferred to herbivores cannot be reclaimed by producers. Energy lost as metabolic heat at each trophic level is dissipated permanently into the environment.
A Food Chain is a simple linear sequence of organisms showing one-way transfer of food energy (e.g., Grass → Deer → Lion). A Food Web is a complex interconnected network of multiple food chains existing in a natural ecosystem.
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