Environment and Ecology
Overview
Environment and Ecology is a high-scoring topic in GTET Paper-2 Science section that connects biological concepts with real-world environmental issues. This topic tests your understanding of how living organisms interact with each other and their physical surroundings, forming complex systems that sustain life on Earth.
For GTET, you must understand ecosystem structure and function, levels of biodiversity, types and effects of pollution, and conservation strategies. Questions often link theoretical concepts to practical examples—particularly those relevant to Gujarat's unique ecosystems like the Gir forest, Rann of Kutch, and Gulf of Khambhat.
Mastery requires understanding ecological relationships, memorising key terms and examples, and applying conservation principles to classroom teaching contexts.
Key Concepts
- Ecosystem is a functional unit comprising living organisms (biotic) and non-living environment (abiotic) interacting through energy flow and nutrient cycling. Examples: pond, forest, desert.
- Food chain shows linear transfer of energy from producers → primary consumers → secondary consumers → tertiary consumers. Only 10% energy transfers to the next level (10% Law by Lindeman).
- Food web is an interconnected network of multiple food chains in an ecosystem, showing complex feeding relationships and ecosystem stability.
- Biodiversity refers to variety of life at three levels: genetic diversity (within species), species diversity (between species), and ecosystem diversity (variety of habitats).
- Biogeochemical cycles are pathways through which nutrients like carbon, nitrogen, and water circulate between biotic and abiotic components.
- Ecological succession is the gradual replacement of one community by another until a stable climax community is reached. Primary succession starts on bare rock; secondary succession occurs after disturbance.
- Pollution is the introduction of harmful substances into the environment causing adverse changes. Classified as air, water, soil, and noise pollution.
- Conservation includes all measures to protect, preserve, and sustainably manage natural resources and biodiversity for present and future generations.
Formulas / Key Facts
| Concept | Key Fact |
|---|---|
| Energy flow | Unidirectional; only 10% energy passes to next trophic level |
| Biomass pyramid | Always upright in terrestrial ecosystems; inverted in aquatic (pond) ecosystems |
| Number pyramid | Inverted in parasitic food chain and tree ecosystem |
| Biodiversity hotspots | India has 4 hotspots: Western Ghats, Himalayas, Indo-Burma, Sundaland |
| Endemic species | Species found only in one geographical area (e.g., Asiatic Lion in Gir) |
| Ozone layer | Found in stratosphere (15-35 km); depleted by CFCs |
| Greenhouse gases | CO₂, CH₄, N₂O, CFCs cause global warming |
| BOD | Biological Oxygen Demand—higher BOD indicates more polluted water |
| Protected areas in Gujarat | Gir National Park, Marine National Park (Gulf of Kutch), Wild Ass Sanctuary (Little Rann) |
| Ramsar sites in Gujarat | Nalsarovar Bird Sanctuary, Khijadiya Bird Sanctuary |
Worked Examples
Example 1: Food Chain Construction
Question: Construct a food chain in a grassland ecosystem with grass, grasshopper, frog, snake, and eagle.
Solution:
- Producer: Grass (makes food through photosynthesis)
- Primary consumer (herbivore): Grasshopper (eats grass)
- Secondary consumer: Frog (eats grasshopper)
- Tertiary consumer: Snake (eats frog)
- Quaternary consumer: Eagle (eats snake)
Food chain: Grass → Grasshopper → Frog → Snake → Eagle
Energy available decreases at each level. If grass has 10,000 J, grasshopper gets 1,000 J, frog gets 100 J, snake gets 10 J, eagle gets 1 J.
Example 2: Identifying Pollution Type
Question: A factory releases untreated effluents containing mercury into a river. Fish in the river show high mercury concentration. What type of pollution is this, and what phenomenon causes mercury accumulation in fish?
Solution:
- Type: Water pollution (industrial effluent discharge)
- Phenomenon: Biomagnification—concentration of non-biodegradable toxins increases at each trophic level
- Mercury enters water → absorbed by algae → eaten by small fish → eaten by large fish
- Top predators (including humans eating fish) receive highest concentration
- This is why Minamata disease occurred in Japan from mercury-contaminated fish
Example 3: Conservation Strategy
Question: Differentiate between in-situ and ex-situ conservation with examples from Gujarat.
Solution:
| Feature | In-situ Conservation | Ex-situ Conservation |
|---|---|---|
| Meaning | Conservation in natural habitat | Conservation outside natural habitat |
| Examples | National parks, wildlife sanctuaries, biosphere reserves | Zoos, botanical gardens, seed banks, gene banks |
| Gujarat examples | Gir National Park (Asiatic Lion), Wild Ass Sanctuary | Sakkarbaug Zoo (Junagadh), Botanical Garden Vadodara |
| Advantage | Preserves entire ecosystem | Protects critically endangered species |
| Limitation | Requires large protected areas | Cannot maintain natural behaviour fully |
Common Mistakes
- Confusing food chain with food web → Food chain is single linear pathway; food web is network of interconnected chains. Questions may ask specifically for one—read carefully.
- Thinking energy cycles in ecosystem → Energy flows unidirectionally (sun → producers → consumers → decomposers → heat lost). Only nutrients cycle; energy does not.
- Mixing up biodegradable and non-biodegradable pollutants → Biodegradable (sewage, paper) can be broken down by microorganisms. Non-biodegradable (plastic, DDT, mercury) persist and biomagnify. DDT and mercury show biomagnification, not sewage.
- Assuming all pyramids are upright → Pyramid of energy is always upright. Pyramid of biomass is inverted in pond ecosystem (small phytoplankton support large fish biomass at any moment). Pyramid of numbers is inverted in tree ecosystem (one tree supports many insects).
- Confusing national park and wildlife sanctuary → In national parks, no human activity (grazing, forestry) is permitted. In wildlife sanctuaries, limited human activities may be allowed. Both are in-situ conservation.
Quick Reference
- Ecosystem = Biotic + Abiotic + Energy flow + Nutrient cycling
- 10% Law: Only 10% energy transfers to next trophic level
- Biodiversity levels: Genetic → Species → Ecosystem
- India's biodiversity hotspots: Western Ghats, Himalayas, Indo-Burma, Sundaland
- Biomagnification: Toxin concentration increases up the food chain (DDT, mercury)
- Gujarat's pride: Gir (Asiatic Lion), Little Rann (Wild Ass), Gulf of Kutch (Marine NP)
- In-situ = in habitat; Ex-situ = outside habitat