Environment and Ecosystem

Overview

Environment and Ecosystem is a foundational topic in the Science section of MP TET Varg-2, bridging biology with environmental awareness. Questions typically test your understanding of ecological relationships, energy flow through food chains and webs, types of biodiversity, and the causes and effects of pollution.

This topic carries moderate weightage but is conceptually interconnected with other chapters like Natural Resources and Agriculture. Examiners often frame application-based questions—identifying trophic levels, explaining bioaccumulation, or linking human activities to environmental degradation. Mastery here also supports the pedagogy component, as environmental education is emphasised in NCF 2005 and NEP 2020.

Students must clearly distinguish between related terms (environment vs ecosystem, food chain vs food web), understand energy flow principles, and recognise local examples from Madhya Pradesh's rich biodiversity.

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Key Concepts

• **Environment** refers to all living (biotic) and non-living (abiotic) factors surrounding an organism, while an **ecosystem** is a functional unit where biotic and abiotic components interact through energy flow and nutrient cycling.

• **Biotic components** include producers (green plants), consumers (herbivores, carnivores, omnivores), and decomposers (bacteria, fungi). **Abiotic components** include sunlight, water, temperature, soil, and air.

• **Food chain** is a linear sequence showing "who eats whom" (e.g., Grass → Grasshopper → Frog → Snake → Eagle). **Food web** is an interconnected network of multiple food chains in an ecosystem.

• **Trophic levels** are feeding positions: T1 = Producers, T2 = Primary consumers (herbivores), T3 = Secondary consumers (carnivores), T4 = Tertiary consumers, and so on.

• **10% Law (Lindeman's Law)**: Only about 10% of energy is transferred from one trophic level to the next; the rest is lost as heat through respiration.

• **Biodiversity** refers to the variety of life at three levels: genetic diversity (within species), species diversity (between species), and ecosystem diversity (variety of habitats).

• **Pollution** is the introduction of harmful substances (pollutants) into the environment, classified as air, water, soil, and noise pollution based on the medium affected.

• **Bioaccumulation** is the build-up of toxins in an organism over time; **biomagnification** is the increasing concentration of toxins at higher trophic levels.

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Formulas / Key Facts

| Concept | Key Fact | |---------|----------| | Energy flow | Unidirectional — from sun → producers → consumers → decomposers | | 10% Rule | Only 10% energy passes to the next trophic level | | Pyramids of energy | Always upright (energy decreases at higher levels) | | Pyramid of biomass | Usually upright; inverted in aquatic ecosystems | | Pyramid of numbers | Can be upright, inverted (tree ecosystem), or spindle-shaped | | Hotspots in India | 4 biodiversity hotspots — Western Ghats, Himalayas, Indo-Burma, Sundaland | | MP's biodiversity | Major national parks: Kanha, Bandhavgarh, Pench, Satpura; State animal: Barasingha | | Air pollutants | CO, SO₂, NO₂, particulate matter, CFCs (ozone depletion) | | Water pollutants | Industrial effluents, sewage, pesticides, heavy metals | | Soil pollutants | Pesticides, plastic, industrial waste, excessive fertilisers | | Noise pollution | Sound above 80 dB is harmful; traffic, industries are major sources |

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Worked Examples

### Example 1: Constructing a Food Chain **Question**: Arrange in correct food chain order: Snake, Grass, Eagle, Grasshopper, Frog

**Solution**:

• Identify the producer (makes its own food) → Grass
• Primary consumer (eats producer) → Grasshopper
• Secondary consumer (eats herbivore) → Frog
• Tertiary consumer → Snake
• Top consumer → Eagle

**Answer**: Grass → Grasshopper → Frog → Snake → Eagle

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### Example 2: Applying the 10% Law **Question**: If producers in an ecosystem have 10,000 J of energy, how much energy is available to tertiary consumers?

**Solution**:

• Producers (T1) = 10,000 J
• Primary consumers (T2) = 10% of 10,000 = 1,000 J
• Secondary consumers (T3) = 10% of 1,000 = 100 J
• Tertiary consumers (T4) = 10% of 100 = **10 J**

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### Example 3: Biomagnification **Question**: Why do top predators like eagles have higher DDT concentration than herbivores?

**Solution**:

• DDT (a pesticide) enters the food chain through plants.
• Herbivores consume many plants, accumulating DDT in their tissues.
• Carnivores eat many herbivores, further concentrating DDT.
• At each trophic level, DDT concentration increases because it is not excreted or broken down easily.
• Result: Top predators accumulate the highest concentration — this is **biomagnification**.

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Common Mistakes

| Wrong Thinking | Correct Fix | |----------------|-------------| | Confusing food chain with food web | Food chain is a single linear pathway; food web is multiple interconnected chains in an ecosystem. | | Thinking energy cycles like nutrients | Energy flows unidirectionally and is lost as heat; only nutrients (carbon, nitrogen) cycle. | | Believing pyramid of numbers is always upright | It can be inverted (e.g., one tree supporting many insects) or spindle-shaped. | | Mixing bioaccumulation and biomagnification | Bioaccumulation = build-up in one organism; biomagnification = increase across trophic levels. | | Assuming decomposers are consumers | Decomposers are a separate category (saprotrophs); they break down dead matter, not hunt prey. |

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Quick Reference

• **Ecosystem = Biotic + Abiotic components interacting through energy flow and nutrient cycling**

• **Energy flow is unidirectional; 10% rule governs transfer between trophic levels**

• **Biodiversity = Genetic + Species + Ecosystem diversity**

• **India has 4 biodiversity hotspots; MP is home to Kanha, Bandhavgarh, Pench**

• **Biomagnification causes top predators to have highest toxin concentration**

• **Types of pollution: Air (CO, SO₂), Water (sewage, effluents), Soil (pesticides), Noise (>80 dB harmful)**