Renewable Resources: Resources that can be replenished naturally over time.

• Examples: Sunlight, wind, water, forests, soil
• These are infinite or can be regenerated if properly managed

Non-Renewable Resources: Resources that cannot be regenerated once used up.

• Examples: Coal, petroleum, natural gas, minerals
• Formed over millions of years; once exhausted, cannot be replaced

Key Difference: Renewable resources are sustainable; non-renewable resources will eventually run out and cause environmental damage when over-exploited.

Definition: Deforestation is the large-scale removal of trees and forests for other land uses.

Causes:

• Agricultural expansion – forests cleared for farming
• Timber extraction – commercial logging
• Mining activities – forest land cleared for mines
• Construction of dams, roads, and urban areas
• Fuel wood collection by local communities

Effects:

• Loss of biodiversity – animals and plants lose habitat
• Soil erosion – tree roots hold soil; without them, soil washes away
• Climate change – forests absorb CO₂; deforestation releases it
• Floods and drought – trees regulate water cycle
• Desertification – land becomes barren

Control Measures:

• Afforestation – planting new trees
• Reforestation – replanting in deforested areas
• Strict legal protection of forests
• Use of alternative fuels instead of firewood
• Promoting sustainable agriculture (agroforestry)

Problems:

• Over-utilization: Excess withdrawal of surface and groundwater for agriculture, industry
• Floods: Caused by heavy rain, deforestation, and poor drainage
• Drought: Shortage of water due to low rainfall or over-extraction
• Water Conflicts: Disputes between states/countries over shared rivers
• Dam problems: Dams displace communities, affect ecosystems downstream

Conservation Methods:

• Rainwater harvesting
• Drip irrigation in agriculture
• Recharge of groundwater
• Treating and reusing wastewater

Conventional (Non-Renewable) Energy Sources:

• Coal, Petroleum, Natural Gas – fossil fuels
• Nuclear energy – uses uranium
• Cause pollution and greenhouse gas emissions
• Finite resources – will run out

Non-Conventional (Renewable) Energy Sources:

• Solar Energy: From sunlight using solar panels – clean and abundant
• Wind Energy: Wind turbines convert wind to electricity
• Hydropower: Energy from flowing water in rivers/dams
• Geothermal Energy: Heat from inside the Earth
• Biomass Energy: From organic waste, wood, crop residue
• Tidal Energy: From ocean tides

Why Alternative Energy?

• Fossil fuels are depleting fast
• Growing energy demand worldwide
• Need to reduce carbon emissions and climate change

Land Degradation: Decline in quality and productivity of land due to human activities.

• Causes: Deforestation, overgrazing, mining, improper farming

Soil Erosion: Removal of topsoil by wind or water.

• Types: Wind erosion (arid regions), Water erosion (rain/rivers)
• Effects: Loss of fertile land, sedimentation in rivers

Desertification: Fertile land turns into desert due to drought, deforestation, and overuse.

• India's problem: Rajasthan, parts of Maharashtra and Gujarat affected
• Prevention: Shelter belts of trees, proper irrigation, reducing overgrazing

Definition: An ecosystem is a community of living organisms (biotic) interacting with their non-living environment (abiotic) as a system.

Structure of Ecosystem:

• Abiotic Components: Sunlight, water, soil, temperature, minerals
• Biotic Components:
  • Producers – plants that make food through photosynthesis
  • Consumers – animals (Primary, Secondary, Tertiary)
  • Decomposers – bacteria and fungi that break down dead matter

Functions of Ecosystem:

• Energy flow – from sun → producers → consumers → decomposers
• Nutrient cycling – nutrients recycled through biogeochemical cycles
• Productivity – primary production by plants; secondary by animals
• Decomposition – breaking down dead organic matter
• Regulation of climate, water cycle, gas composition

Types: Forest, Grassland, Desert, Aquatic (pond, lake, river, ocean)

Definition: Energy flows in one direction through the ecosystem – from Sun → Producers → Consumers.

Trophic Levels:

• T1 – Producers: Plants absorb solar energy (photosynthesis)
• T2 – Primary Consumers: Herbivores (e.g., grasshopper, rabbit)
• T3 – Secondary Consumers: Carnivores that eat herbivores (e.g., frog, fox)
• T4 – Tertiary Consumers: Top predators (e.g., eagle, tiger)
• Decomposers: Break down dead matter, return nutrients to soil

10% Law (Lindeman's Law):

• Only 10% of energy is transferred from one trophic level to the next
• 90% is lost as heat during respiration and other activities
• Example: 1000 kcal in plants → 100 kcal in herbivores → 10 kcal in carnivores

Importance: Explains why food chains are short (usually 4–5 levels) and why fewer top predators exist in nature.

Food Chain: A linear sequence of organisms where each is eaten by the next.

• Example: Grass → Grasshopper → Frog → Snake → Eagle
• Types: Grazing food chain (starts with plants), Detritus food chain (starts with dead matter)

Food Web: An interconnected network of many food chains in an ecosystem.

• More realistic than food chain
• Provides stability – if one species disappears, others can compensate
• Example: In a forest, a deer is eaten by tigers AND leopards AND wolves

Key Difference: Food chain is simple and linear; food web is complex and shows real relationships in nature.

Definition: A graphical representation of the number, biomass, or energy at each trophic level.

Types:

• Pyramid of Numbers: Shows number of organisms at each level. Usually upright (many plants, few predators). Can be inverted (e.g., one tree supporting many insects).
• Pyramid of Biomass: Shows total mass of living material at each level. Usually upright in terrestrial ecosystems. Inverted in aquatic ecosystems.
• Pyramid of Energy: Shows energy at each trophic level. Always upright – energy always decreases as you go up. Most accurate pyramid.

Definition: The gradual and orderly change in the composition of species in an ecosystem over time.

Types:

• Primary Succession: Begins on bare, lifeless land (e.g., new volcanic island, bare rock). Pioneer species (lichens, mosses) first colonize.
• Secondary Succession: Occurs where ecosystem was disturbed but soil remains (e.g., after a fire or flood). Faster than primary succession.

Stages: Pioneer community → Intermediate communities → Climax community (stable, final stage)
Importance: Helps restore degraded ecosystems; explains how forests develop over time.

Definition: Biodiversity is the variety of life on Earth – including all plants, animals, microorganisms, and the ecosystems they form.

Levels of Biodiversity:

• Genetic Diversity: Variation in genes within a species (e.g., different rice varieties)
• Species Diversity: Variety of different species in an area (e.g., a rainforest has thousands of species)
• Ecosystem Diversity: Variety of ecosystems – forests, grasslands, wetlands, deserts, oceans

Values of Biodiversity:

• Direct Values: Food, medicine, timber, fiber – economic uses
• Indirect Values: Ecosystem services – clean air/water, soil fertility, climate regulation
• Option Values: Future potential for medicines and discoveries
• Existence Values: Ethical and aesthetic – every species has right to exist

India's Biodiversity: One of 17 mega-diverse countries. Rich in species of plants, animals, and microbes.

Main Threats:

• Habitat Loss: Most serious threat – forests cleared for agriculture, urban growth, mining
• Poaching of Wildlife: Illegal hunting for skin, bones, horns, tusks (tiger, elephant, rhino)
• Man-Wildlife Conflict: As forests shrink, animals enter human areas – both sides harmed
• Invasive Species: Non-native species introduced and destroy native species
• Pollution: Air, water, and soil pollution kills species
• Climate Change: Temperature rise, changing rainfall – species cannot adapt fast enough
• Over-exploitation: Over-fishing, over-harvesting beyond sustainable limits

IUCN Categories of Threat: Extinct → Extinct in Wild → Critically Endangered → Endangered → Vulnerable → Near Threatened → Least Concern