Environment and Ecosystem is a foundational topic in the Science section of CG TET Paper II, bridging biology with real-world environmental concerns. This topic tests your understanding of how living organisms interact with each other and their physical surroundings, forming functional units called ecosystems.
For CG TET, expect questions on ecosystem components, energy flow through food chains and food webs, ecological pyramids, and types of pollution with their causes and effects. Chhattisgarh's rich forest cover (over 41% of the state) and industrial zones like Bhilai make local environmental issues particularly relevant. Questions often connect textbook concepts to practical scenarios—identifying producers in a food chain, explaining biomagnification, or linking industrial activities to specific pollution types.
Mastering this topic requires understanding the interconnectedness of living and non-living components. Focus on classification of ecosystem components, energy transfer mechanisms, and the three major types of pollution with their sources and control measures.
Key Concepts
**Ecosystem** is a self-sustaining functional unit where living organisms (biotic) interact with non-living components (abiotic) through energy flow and nutrient cycling.
**Biotic components** include producers (green plants), consumers (herbivores, carnivores, omnivores), and decomposers (bacteria, fungi). **Abiotic components** include sunlight, temperature, water, soil, and air.
**Food chain** represents a linear sequence of energy transfer: Producer → Primary Consumer → Secondary Consumer → Tertiary Consumer. Energy decreases at each level (10% rule).
**Food web** is an interconnected network of multiple food chains in an ecosystem, showing realistic feeding relationships and ecosystem stability.
**Ecological pyramids** represent trophic levels graphically—pyramid of numbers, pyramid of biomass, and pyramid of energy (always upright).
**Biomagnification** is the progressive increase in concentration of non-biodegradable substances (like DDT, mercury) as we move up the food chain.
**Pollution** is the introduction of harmful substances into the environment that cause adverse changes. Three main types: air, water, and soil pollution.
**Biodegradable substances** (paper, food waste) can be broken down by decomposers, while **non-biodegradable substances** (plastic, glass, pesticides) persist in the environment.
Formulas / Key Facts
**10% Law of Energy Transfer**: Only 10% of energy passes from one trophic level to the next; 90% is lost as heat during respiration.
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**Ozone Layer**: Found in stratosphere (15-35 km altitude); absorbs harmful UV radiation; depleted by CFCs
**Greenhouse Gases**: CO₂, methane (CH₄), nitrous oxide (N₂O), water vapour—cause global warming
Worked Examples
**Example 1**: In a grassland ecosystem, grass is eaten by grasshoppers, grasshoppers are eaten by frogs, frogs are eaten by snakes, and snakes are eaten by hawks. Construct the food chain and identify each trophic level.
**Example 2**: If 10,000 joules of energy is available at the producer level, calculate the energy available to the secondary consumer.
*Solution*: Using 10% rule:
Energy at producer level = 10,000 J
Energy at primary consumer = 10% of 10,000 = 1,000 J
Energy at secondary consumer = 10% of 1,000 = 100 J
**Example 3**: A factory releases hot water into a river. What type of pollution is this, and what are its effects?
*Solution*: This is **thermal pollution** (a type of water pollution).
Effects:
Decreases dissolved oxygen in water (warm water holds less oxygen)
Affects aquatic life—fish and other organisms may die or migrate
Disrupts breeding cycles of aquatic animals
Promotes growth of harmful algae (algal bloom)
Common Mistakes
**Confusing food chain with food web** → A food chain is a single linear pathway; a food web is multiple interconnected food chains. In nature, most organisms have multiple food sources, so food webs represent reality better.
**Thinking decomposers are consumers** → While decomposers do obtain energy from dead matter, they form a separate category. They break down organic matter and return nutrients to soil (nutrient cycling), unlike consumers who pass energy up trophic levels.
**Assuming pyramid of numbers is always upright** → Pyramid of numbers can be inverted (e.g., tree ecosystem: one tree supports many insects). Only pyramid of energy is always upright because energy continuously decreases at higher levels.
**Mixing up biodegradable and non-biodegradable** → Students often misclassify items. Remember: if microorganisms can break it down naturally in reasonable time, it's biodegradable. Plastics, heavy metals, and synthetic pesticides are non-biodegradable.
**Forgetting that pollution has natural sources too** → While exam questions focus on human-caused pollution, remember that volcanic eruptions (air pollution), forest fires, and natural mineral leaching also cause pollution.
Quick Reference
Ecosystem = Biotic (living) + Abiotic (non-living) components interacting together
Food chain energy flow: always unidirectional, always decreasing (10% rule)
Decomposers: bacteria and fungi that recycle nutrients back to soil
Biomagnification: DDT concentration increases from water → fish → birds
Three pollution types: Air (gases, SPM), Water (effluents, sewage), Soil (pesticides, plastic)
Ozone depletion caused by CFCs; global warming caused by greenhouse gases (CO₂, CH₄)