Environment and Natural Resources

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision.

Ecosystem — The Basics

An ecosystem is a community of living organisms interacting with their physical environment.

Components of an Ecosystem:

Component	Role	Examples
Producers	Make their own food via photosynthesis	Green plants, algae
Consumers	Cannot make their own food; eat others	Herbivores (cow), Carnivores (lion), Omnivores (human)
Decomposers	Break down dead organic matter	Bacteria, fungi

Food Chain and Food Web

• A food chain is a linear sequence: Grass → Grasshopper → Frog → Snake → Hawk. Energy flows from one trophic level to the next. About 10% of energy is transferred at each step — the rest is lost as heat.

• A food web is a network of overlapping food chains. More realistic — if one species declines, others can still get energy from different sources.

Natural Resources

Renewable Resources	Non-renewable Resources
Solar energy, wind, water	Coal, petroleum, natural gas
Forests, wildlife	Minerals, metals
Can be replenished naturally	Fixed amounts, take millions of years to form

Environmental Pollution

• Air pollution: SO₂, NO₂, CO from vehicles/industry → causes acid rain, respiratory problems.
• Water pollution: Industrial waste, agricultural runoff (fertilisers, pesticides) → eutrophication.
• Soil pollution: Plastic waste, heavy metals, chemical pesticides.

⚡ Exam Tip: UPTET frequently asks about the 10% energy transfer rule in food chains. A common question: “If grass captures 1000 kJ of energy from sunlight, how much energy is available to the grasshopper?” Answer: approximately 100 kJ (10% of 1000). The rest is lost as heat through respiration.

⚡ Common Mistake: Confusing “decomposers” with “detritivores.” Decomposers (bacteria, fungi) break down organic matter at the molecular level. Detritivores (earthworms, beetles) break down detritus mechanically.

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🟡 Standard — Regular Study (2d–2mo)

For students who want genuine understanding.

Biogeochemical Cycles

1. Water Cycle (Hydrological Cycle)

The continuous movement of water between the atmosphere, land, and oceans:

• Evaporation: Water from oceans, lakes, rivers changes to water vapour (powered by solar energy).
• Transpiration: Plants release water vapour through stomata.
• Condensation: Water vapour cools and forms clouds.
• Precipitation: Rain, snow, hail fall back to Earth.
• Runoff: Water flows back to oceans through rivers.

Approximate cycle time for water: 9 days in the atmosphere, 20–50 years in lakes, 1000 years in oceans.

2. Carbon Cycle

Carbon circulates through living organisms and the environment:

• Photosynthesis: CO₂ + H₂O → C₆H₁₂O₆ + O₂ (plants fix carbon as glucose).
• Respiration: C₆H₁₂O₆ + O₂ → CO₂ + H₂O + energy (all living organisms release carbon).
• Decomposition: Decomposers break down dead organisms, releasing CO₂.
• Combustion: Burning fossil fuels and wood releases stored carbon as CO₂.
• Carbon sink: Forests and oceans absorb CO₂. Deforestation reduces this sink.

The carbon cycle takes 100–200 years to cycle carbon through the ocean, and seconds to minutes through organisms.

3. Nitrogen Cycle

Nitrogen is 78% of the atmosphere but cannot be used directly by most organisms. It must be “fixed”:

• Nitrogen fixation: Atmospheric N₂ → NH₃ (ammonia) by bacteria (Rhizobium in legume root nodules) or lightning.
• Nitrification: NH₃ → NO₂⁻ (nitrite) → NO₃⁻ (nitrate) by nitrifying bacteria.
• Assimilation: Plants absorb nitrates from soil.
• Ammonification: Decomposers break down dead organisms, releasing ammonia back to soil.
• Denitrification: Anaerobic bacteria convert nitrates back to N₂ gas (released to atmosphere).

Food Chains — Detailed Analysis

Trophic levels:

• Producers (1st trophic level): Green plants — autotrophs.
• Primary consumers (2nd trophic level): Herbivores — eat producers.
• Secondary consumers (3rd trophic level): Small carnivores — eat herbivores.
• Tertiary consumers (4th trophic level): Top predators — eat other carnivores.

Energy pyramid: Energy decreases at each trophic level. 10% is passed on; 90% is lost as heat, in respiration, and through incomplete digestion.

Biomagnification: Some toxic substances (DDT, mercury) become more concentrated at higher trophic levels. Example: DDT in water → algae → small fish → large fish → birds. Birds at the top have the highest concentration.

Environmental Pollution — Types and Effects

Air Pollution:

• Smog: Photochemical smog (formed by NO₂ and hydrocarbons in sunlight) causes eye irritation, respiratory problems.
• Greenhouse effect: CO₂, CH₄, water vapour trap infrared radiation → global warming. CO₂ is the largest contributor.
• ** Ozone depletion:** CFCs (chlorofluorocarbons) break down stratospheric O₃ → more UV radiation reaches Earth → skin cancer, crop damage.

Water Pollution:

• BOD (Biochemical Oxygen Demand): Amount of oxygen needed by microorganisms to decompose organic matter. High BOD indicates heavy pollution.
• Eutrophication: Excess nutrients in water bodies cause algal bloom → algae die → decomposers consume oxygen → fish die.
• Biomagnification of mercury (Minamata disease) and arsenic in water.

Soil Pollution:

• Plastic waste: takes 100–500 years to decompose.
• Heavy metals: lead, cadmium, mercury from industrial waste.
• Excessive use of chemical fertilisers: degrades soil structure, reduces microbial diversity.

⚡ UPTET Common Mistakes:

1. Confusing the carbon cycle with the oxygen cycle — they are linked (photosynthesis produces O₂, respiration produces CO₂), but the cycles operate on different timescales.
2. Mixing up the roles of nitrifying bacteria and denitrifying bacteria in the nitrogen cycle.
3. Forgetting that energy is NEVER recycled — it flows in one direction (sun → producers → consumers → decomposers → lost as heat). Matter is recycled.
4. Thinking all pollutants are visible — CO and SO₂ are invisible gases, very dangerous.

Conservation Efforts in India

• Wildlife Protection Act (1972): Established national parks and sanctuaries.
• Project Tiger (1973): Conservation of Bengal tigers. India has 50+ tiger reserves.
• Project Elephant (1991): Protection of elephant habitats.
• Forest Conservation Act (1980): Regulates forest clearing.
• National Green Tribunal (2010): Handles environmental disputes.
• Swachh Bharat Abhiyan: Waste management, clean India.
• Compensatory Afforestation: When forest land is used for development, equal area must be afforested elsewhere.

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🔴 Extended — Deep Study (3mo+)

Comprehensive theory for students with extended preparation time.

Ecosystem Structure and Functions

Abiotic and Biotic Factors:

Abiotic (non-living): Sunlight, temperature, water, soil, air, pH, minerals, atmospheric gases.

Biotic (living): All living organisms, their interactions, and their byproducts.

Ecological Interactions:

• Predation: One organism kills and eats another (lion → zebra).
• Competition: Two organisms fight for the same limited resource (two hawks fighting over a rabbit).
• Parasitism: One benefits, one is harmed (tapeworm in human intestine).
• Commensalism: One benefits, one is unaffected (barnacle on whale).
• Mutualism: Both benefit (rhino and egrets — egrets eat parasites, rhino gets cleaning).

Ecological Niche: The role a species plays in its ecosystem (what it eats, where it lives, when it’s active). No two species can occupy the same niche in the same habitat indefinitely (Competitive Exclusion Principle).

Biomes:

Biome	Climate	Vegetation	Example
Tropical rainforest	Hot, wet year-round	Dense,多层 canopy, high biodiversity	Amazon, Western Ghats
Desert	Hot/dry or cold/dry	Xerophytic plants, cacti	Thar Desert, Rajasthan
Tundra	Extremely cold	Mosses, lichens, no trees	Himalayas above 4000m
Savanna	Warm, seasonal rainfall	Grasses, scattered trees	African savanna
Temperate forest	Mild, distinct seasons	Deciduous trees	Eastern Himalayas

Water Cycle — Deep Dive

Water covers 71% of Earth’s surface. The hydrological cycle:

• Evapotranspiration: 425 × 10¹² kg/year evaporates from oceans; 70 × 10¹² kg from land.
• Precipitation: Ocean gets ~398 × 10¹² kg/year; land gets ~111 × 10¹² kg/year.
• Runoff: Rivers carry ~40 × 10¹² kg/year from land to ocean.

Groundwater: Recharged by infiltration through soil. Aquifers are underground water reservoirs. Over-extraction leads to falling water tables — a major issue in Punjab, Rajasthan, and Tamil Nadu.

Carbon Cycle — Deep Dive

• Reservoirs: Atmosphere (~750 Gt C), oceans (~38,000 Gt), terrestrial biosphere (~2,000 Gt), fossil fuels (~5,000 Gt).
• The atmosphere contains ~800 Gt of carbon. Human activities add ~9 Gt/year (fossil fuels + deforestation).
• CO₂ concentration has risen from ~280 ppm (pre-industrial) to ~420 ppm (2024).
• The ocean absorbs ~25% of human CO₂ emissions. This causes ocean acidification (pH decreasing from ~8.2 to ~8.1) — affects coral reefs and shellfish.

Nitrogen Cycle — Deep Dive

• N₂ fixation: Haber-Bosch process (industrial, produces ammonia for fertilisers) and biological fixation (Rhizobium bacteria).
• The nitrogen cycle is the most complex of the major biogeochemical cycles.
• Over-fertilisation leads to: runoff → eutrophication → dead zones (e.g., Gulf of Mexico dead zone).
• Nitrous oxide (N₂O) is a greenhouse gas 300× more potent than CO₂.

Ozone Layer and Depletion

• Ozone (O₃): UV absorber in the stratosphere (20–35 km above Earth).
• Ozone hole: Seasonal depletion over Antarctica (spring, September–November).
• Causes: CFCs (refrigerants, aerosols), halons, bromomethane.
• Effects: UVB radiation causes skin cancer, cataracts, suppresses immune system; damages plankton (base of marine food chains); reduces crop yields.

Climate Change — Science and Impact

Greenhouse gases: CO₂ (76%), CH₄ (16%), N₂O (6%), F-gases (2%).

Evidence of climate change:

• Global average temperature risen ~1.1°C since pre-industrial era.
• Arctic sea ice declining ~13% per decade.
• Sea level rising ~3.3 mm/year.
• Increased frequency of extreme weather events (cyclones, floods, droughts).

India-specific impacts:

• Himalayan glaciers melting → threat to rivers (Ganges, Brahmaputra).
• Sea-level rise threatens coastal areas (Mumbai, Kolkata, Chennai).
• Monsoon patterns becoming more erratic.
• Heat waves: India recorded 50°C+ in Rajasthan (2024).

Mitigation and Adaptation:

• Kyoto Protocol (1997): Legally binding emission reductions for developed countries.
• Paris Agreement (2015): Limit warming to 1.5–2°C.
• India’s commitments: 50% electricity from renewable sources by 2030; Net-zero by 2070.
• Carbon credits: Tradable permits to emit CO₂.

Biodiversity in India

• Biodiversity hotspots: Western Ghats, Himalayas, Sundarbans, Indo-Burma region.
• Endangered species: Bengal tiger, Asiatic lion, snow leopard, Ganges river dolphin, great Indian bustard.
• Causes of biodiversity loss: Habitat destruction, overexploitation, pollution, invasive species, climate change.
• Conservation methods: In-situ (national parks, sanctuaries, biosphere reserves) and ex-situ (zoos, botanical gardens, seed banks). The Conservation Reserve and Community Reserve categories were added in 2003.

⚡ Previous Year UPTET Focus: Questions on biogeochemical cycles and ecological interactions appear frequently in the science section. A typical UPTET question: “Which bacteria are responsible for nitrogen fixation in leguminous plants?” Answer: Rhizobium. Another common question: “Name the process by which CO₂ is returned to the atmosphere from dead organisms.” Answer: Decomposition/respiration.

⚡ NEET/JEE Relevance: Biomagnification of DDT, eutrophication processes, and carbon cycle numericals (calculating CO₂ levels) appear in NEET. For NEET preparation, note that the BOD value increases as pollution increases — water with high BOD is heavily polluted.

⚡ Common Errors to Flag:

1. Confusing “stratospheric ozone depletion” (good thing) with “ground-level ozone pollution” (bad thing) — stratospheric ozone is protective; ground-level ozone is a pollutant.
2. Thinking natural resources are unlimited — even renewable resources can be depleted faster than they regenerate.
3. Confusing “weather” (day-to-day atmospheric condition) with “climate” (long-term average over 30+ years).
4. Forgetting that decomposers are essential — without them, nutrients would stay locked in dead organisms and life would cease.