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Our Environment

Created by Team Vardaan with ❤️

1. Ecosystem and its Components

Ecosystem: A self-sustaining system where biotic (living) and abiotic (non-living) components interact with each other. (e.g., Garden, Forest, Pond).

Component	Examples & Role
Abiotic	Temperature, Rainfall, Soil, Air, Light.
Biotic	1. Producers: Green plants/Blue-green algae (Make food). 2. Consumers: Herbivores, Carnivores, Omnivores, Parasites. 3. Decomposers: Bacteria, Fungi (Break down dead matter).

What is the role of Decomposers?
They break down complex organic matter (dead plants/animals) into simple inorganic substances that go into the soil and are used up once more by the plants. They act as natural cleansing agents of the environment.

2. Food Chain & Energy Flow

Food Chain: A series of organisms where one eats another to transfer energy. (Grass → Deer → Tiger).

Food Web vs Food Chain:
In nature, food chains are not isolated. One organism may be eaten by many others (e.g., a Frog eaten by Snake or Bird). This interconnected network is a Food Web. It provides stability to the ecosystem.

A. The 10% Law (Lindeman)

            Statement: Only 10% of energy entering a particular trophic level is
            available for transfer to the next higher trophic level. The remaining 90% is lost as
            heat/digestion/growth.

            *Note: Plants capture only 1% of Solar Energy.
        

Numerical Example (PYQ):
Sun (100,000 J) → Plant (1% = 1000 J) → Deer (10% = 100 J) → Lion (10% = 10 J).
Conclusion: Food chains generally consist of only 3 or 4 steps because very little energy is left for a 5th level.

B. Flow of Energy is Unidirectional

Energy captured by autotrophs does not revert back to the sun. Energy passed to herbivores does not come back to autotrophs. It moves progressively through trophic levels.

Figure 5.1: Trophic Levels Pyramid

3. Biological Magnification

Mechanism:
1. Harmful chemicals (Pesticides/DDT) are sprayed on crops.
2. They enter the soil/water bodies.
3. Absorbed by plants (Producers).
4. Passed on to Herbivores and then Carnivores.
5. Since these are non-biodegradable, they accumulate at each level.
Result: Concentration is maximum in Humans (Top level).

4. Ozone Layer Depletion

Ozone (O₃): A deadly poison at ground level, but a shield in the stratosphere. It protects earth from harmful UV radiation (causes skin cancer, cataracts).

A. Formation of Ozone

            UV splits Oxygen molecule: O2 —(UV)→ O + O
Free oxygen combines with Oxygen molecule: O + O2 → O3
                        (Ozone)

        

B. Depletion Cause

Synthetic chemicals like CFCs (Chlorofluorocarbons) used in Refrigerators and Fire Extinguishers reach the upper atmosphere and break down Ozone.
UNEP (1987): Forged an agreement to freeze CFC production at 1986 levels (Montreal Protocol).

5. Managing Garbage

Biodegradable	Non-Biodegradable
Broken down by biological processes (Bacteria/Enzymes).	Cannot be broken down biologically. Persist for long.
Example: Fruit peels, Paper, Wood, Cotton.	Example: Plastic, Glass, Metals, DDT.

Why replaced plastic cups with Kulhads (Clay cups) and then Paper cups?
• Plastic: Non-biodegradable waste.
• Kulhads: Biodegradable, but caused loss of fertile topsoil (to make clay).
• Paper Cups: Biodegradable and can be recycled. Best option.

🎯 TRICKY PRACTICE ZONE (Environment)

Calculate the energy available to the Tiger if the Plants absorb 20,000 J of energy from the Sun. Hint: Don't forget Plants take only 1% from Sun (200 J), then 10% passes to Deer (20 J), then 10% to Tiger (2 J).
Why do we find maximum chemical accumulation in Humans in a food chain? Hint: Humans are at the top trophic level. Chemicals are non-biodegradable and accumulate at every step (Biomagnification).
"Damage to the Ozone layer is a cause for concern." Justify this statement. Hint: Ozone protects from UV rays. UV rays cause Skin Cancer, Cataracts in humans, and damage to crops/ecosystems.