Understanding Earth's precious gifts - Air, Water, Soil, and their cycles
Natural resources are materials or substances that occur naturally in the environment and are essential for the survival of living organisms. They are provided by nature and cannot be made by humans.
Natural resources are like gifts from Mother Nature! Just like parents provide everything we need at home (food, shelter, water), Earth provides everything living things need to survive - air to breathe, water to drink, soil to grow food, and sunlight for energy. We didn't make these; nature gave them to us!
• Essential for survival of all living organisms
• Provide basic necessities: air, water, food, shelter
• Support all life processes
• Maintain ecological balance
• Source of energy and raw materials
• Cannot be created by humans - must be conserved!
The atmosphere is the blanket of air that surrounds the Earth. It extends up to many kilometers above Earth's surface and contains various gases essential for life.
Nitrogen (N₂): 78% - Most abundant, used by
plants after fixation
Oxygen (O₂): 21% - Essential for respiration and
burning
Carbon dioxide (CO₂): 0.03% - Used by plants for
photosynthesis
Water vapor: Variable - Forms clouds and rain
Other gases: Argon, ozone, etc. (less than 1%)
Air is like a protective blanket wrapped around Earth! It keeps us warm (like a blanket), protects us from harmful sun rays (like an umbrella), and provides oxygen to breathe (like a life support system). Without it, Earth would be as lifeless as the Moon!
Wind is the movement of air from one place to another. It is caused by unequal heating of Earth's surface by the Sun.
Step 1: Sun heats Earth's surface unevenly
Step 2: Some areas get hotter than others
Step 3: Hot air becomes lighter and rises up (low
pressure)
Step 4: Cool air from surrounding areas rushes in
to fill the space
Step 5: This movement of air is WIND!
Simple rule: Air moves from high pressure (cool)
to low pressure (hot) areas.
Remember standing near an open fridge on a hot day? You feel cool
air coming towards you. That's because:
• Fridge = Cool air (high pressure)
• Room = Hot air (low pressure)
• Cool air moves from fridge to room = Wind!
Same thing happens in nature on a massive scale!
Air carries water vapor! When this water vapor cools down, it forms clouds and eventually falls as rain. Without air, there would be no rain, and without rain, there would be no life!
Air pollution is the presence of harmful substances in the air that make it impure and unhealthy. These pollutants can harm living organisms and the environment.
Natural sources:
• Volcanic eruptions
• Forest fires
• Dust storms
Human-made sources:
• Vehicle exhaust (major polluter!)
• Factory smoke and industrial emissions
• Burning of fossil fuels (coal, petrol, diesel)
• Burning crop residues and garbage
• Construction activities (dust)
• Firecrackers
On Human Health:
• Breathing problems, asthma, bronchitis
• Eye irritation, skin problems
• Heart diseases
• Lung cancer (long-term exposure)
On Environment:
• Global warming (greenhouse effect)
• Acid rain (damages plants, buildings, water bodies)
• Ozone layer depletion
• Smog formation (reduced visibility)
• Damage to plants and crops
✓ Use public transport, carpool, or bicycle
✓ Plant more trees (they absorb CO₂)
✓ Use CNG/electric vehicles
✓ Reduce use of fossil fuels
✓ Don't burn garbage or leaves
✓ Use cleaner fuels (solar, wind energy)
✓ Don't burst firecrackers
✓ Regular vehicle maintenance
✓ Use energy-efficient appliances
✓ Create awareness about pollution
The hydrosphere includes all water on Earth - oceans, rivers, lakes, glaciers, groundwater, and water vapor in the atmosphere.
• Earth's surface is 71% water (that's why it's called "Blue
Planet")
• 97% is salt water (oceans) - NOT drinkable
• 3% is fresh water
• Of this 3%, most is frozen in glaciers and ice caps
• Only 1% of Earth's water is easily available as
fresh water!
Shocking fact: Out of all water on Earth, less
than 1% is available for drinking!
The water cycle is the continuous movement of water between Earth's surface and atmosphere through evaporation, condensation, precipitation, and collection.
1. Evaporation:
• Sun heats water in oceans, rivers, lakes
• Water turns into water vapor (gas) and rises up
• Also happens from soil, plants (transpiration)
2. Condensation:
• Water vapor rises high and cools down
• Turns back into tiny water droplets
• These droplets form clouds
3. Precipitation:
• When clouds become heavy with water
• Water falls back to Earth as rain, snow, or hail
4. Collection:
• Rain water collects in rivers, lakes, oceans
• Some water seeps into ground (groundwater)
• Some is absorbed by plants
• Cycle continues forever!
Water cycle is like a washing machine that never stops!
• Evaporation = Picking up dirty clothes (water going up)
• Condensation = Washing in machine (forming clouds)
• Precipitation = Clean clothes coming out (rain falling)
• Collection = Putting clothes in wardrobe (water in
rivers/oceans)
• Process repeats = Cycle continues!
Nature constantly recycles the same water - the water you drink
today might have been drunk by dinosaurs millions of years ago!
Ever noticed these?
• Wet clothes dry in sun → Evaporation
• Bathroom mirror fogs up → Condensation
• Clouds in sky → Condensed water vapor
• Rain from clouds → Precipitation
• Puddles after rain → Collection
These are all parts of the water cycle happening around you every
day!
Water pollution is the contamination of water bodies (rivers, lakes, oceans, groundwater) with harmful substances that make water unsafe for drinking and harmful to aquatic life.
Industrial waste:
• Factories discharge chemicals, heavy metals into rivers
• Oil spills from tankers
Sewage and domestic waste:
• Household waste water
• Detergents and soaps
• Plastic garbage
Agricultural waste:
• Pesticides and fertilizers wash into water bodies
• Animal waste from farms
Religious activities:
• Immersion of idols
• Throwing flowers, waste in rivers
Other sources:
• Littering plastic in water bodies
• Oil and grease from vehicles
• Mining activities
On Human Health:
• Waterborne diseases: Cholera, typhoid, dysentery, hepatitis
• Heavy metal poisoning (lead, mercury)
• Skin diseases and allergies
On Aquatic Life:
• Fish and other animals die (oxygen depletion)
• Disrupts food chain
• Loss of biodiversity
On Environment:
• Eutrophication (excess nutrients cause algae growth)
• Death of water bodies
• Bad smell and appearance
• Not usable for agriculture or industry
✓ Don't throw garbage in rivers, lakes, or oceans
✓ Treat sewage and industrial waste before releasing
✓ Reduce use of chemical fertilizers and pesticides
✓ Don't wash vehicles near water bodies
✓ Proper disposal of plastic waste
✓ Use biodegradable products
✓ Save water - don't waste it!
✓ Rainwater harvesting
✓ Create awareness about water conservation
✓ Participate in river/beach cleaning drives
Soil is the upper layer of Earth's crust that supports plant life. It is formed by the weathering of rocks over thousands of years and contains minerals, organic matter, air, and water.
Soil formation is a very slow process that takes thousands of
years!
Step 1: Big rocks break into smaller pieces
Step 2: Broken by: Sun's heat, rain, wind, ice,
plant roots
Step 3: Small rock particles mix with decayed
plants and animals (humus)
Step 4: This mixture becomes SOIL!
Main factors:
• Climate (temperature, rainfall)
• Parent rock type
• Time (thousands of years)
• Living organisms (bacteria, earthworms)
• Topography (slope of land)
Imagine a chocolate bar left in sun, rain, and wind for years! It
would break into pieces, mix with dust and leaves, and become
something new. Similarly, hard rocks break down over thousands of
years and become soft soil!
It takes nature 1000 years to make just 1 inch of soil! That's why
soil is precious and must be conserved.
Soil pollution is the presence of toxic chemicals and substances in soil that reduce its quality and harm plants, animals, and humans.
• Excessive use of chemical fertilizers and pesticides
• Dumping of industrial waste
• Plastic and non-biodegradable waste
• Acid rain
• Mining activities
• Deforestation
• Oil spills
Soil erosion is the removal or washing away of top fertile soil by water, wind, or human activities. The top layer of soil is most fertile and important for plants!
• Deforestation: Cutting trees (roots hold
soil)
• Overgrazing: Animals eat all grass, leaving
soil exposed
• Heavy rainfall: Washes away soil
• Strong winds: Blow away dry soil
• Wrong farming practices: Ploughing up and down
slopes
• Mining and construction: Remove vegetation
Have you seen muddy water flowing on roads after heavy rain?
That's soil erosion happening! The fertile topsoil is being washed
away, which is very bad for agriculture.
In hilly areas, landslides occur due to soil erosion - entire
hills slide down because there are no tree roots to hold the soil!
✓ Afforestation: Plant more trees (roots bind
soil)
✓ Contour ploughing: Plough along slopes, not
up-down
✓ Terrace farming: Make steps on hills
✓ Mulching: Cover soil with leaves/grass
✓ Crop rotation: Change crops each season
✓ Build windbreaks: Plant trees to stop wind
✓ Control overgrazing
✓ Reduce deforestation
Biogeochemical cycles are the pathways through which essential elements (like carbon, nitrogen, oxygen) circulate in nature between living organisms and the environment. "Bio" = living, "geo" = earth, "chemical" = elements.
These cycles are like a recycling system that never stops! Just like we recycle paper and plastic, nature recycles important elements. The same carbon atoms in your body might have been in a dinosaur millions of years ago, then in a tree, then in air, and now in you! Nature wastes nothing - everything is reused!
Oxygen goes into atmosphere:
• Plants release oxygen during photosynthesis
• Decomposition of water also releases oxygen
Oxygen is removed from atmosphere:
• Animals and humans breathe in oxygen (respiration)
• Burning (combustion) uses oxygen
• Decomposition of organic matter uses oxygen
• Oxygen combines with other elements (oxidation)
Balance: Plants produce oxygen → Animals use
oxygen → Carbon dioxide released → Plants use CO₂ and produce
oxygen again!
Carbon goes into atmosphere (as CO₂):
• Animals and humans breathe out CO₂ (respiration)
• Burning of fuels releases CO₂ (combustion)
• Decomposition releases CO₂
• Volcanic eruptions
Carbon is removed from atmosphere:
• Plants absorb CO₂ for photosynthesis
• Dissolves in ocean water
• Used by marine organisms to make shells
How it moves:
Air (CO₂) → Plants → Animals eat plants → Animals breathe out CO₂
→ Back to air!
When you breathe out, you release carbon dioxide. A nearby plant
absorbs this CO₂ and makes food (glucose - contains carbon). You
eat fruits/vegetables. Carbon enters your body. You breathe out
CO₂ again. Carbon returns to air!
Same carbon keeps cycling - from air to plants to animals and back
to air!
Problem: Humans are burning too much fossil fuels (coal, oil,
gas)!
• This releases extra CO₂ into atmosphere
• Plants can't absorb all this extra CO₂
• CO₂ accumulates in atmosphere
• Causes global warming (greenhouse effect)
• Earth's temperature is rising!
Solution: Reduce fossil fuel use, plant more
trees, use renewable energy!
Nitrogen is very important for living things (needed for
proteins), but there's a problem:
• Air has 78% nitrogen gas (N₂)
• But plants and animals CANNOT use nitrogen gas directly!
• Nitrogen gas must be "fixed" (converted) into usable forms
• This is done by special bacteria and natural processes
1. Nitrogen Fixation:
Converting nitrogen gas (N₂) into usable forms (nitrates,
ammonia):
• By bacteria: Rhizobium (in root nodules of
legumes), Azotobacter (in soil)
• By lightning: Converts N₂ to nitrogen oxides
• By industry: Making fertilizers
2. Assimilation:
• Plants absorb nitrates from soil
• Make proteins
• Animals eat plants and get nitrogen
3. Ammonification:
• When plants and animals die
• Decomposers convert their proteins to ammonia
4. Nitrification:
• Soil bacteria convert ammonia to nitrites, then nitrates
• Plants can use these nitrates
5. Denitrification:
• Some bacteria convert nitrates back to nitrogen gas
• Nitrogen returns to atmosphere
• Cycle completes!
Imagine nitrogen as money in a bank (atmosphere). You can't use
money directly from the bank - you need to withdraw it (fixation
by bacteria). Then you can spend it (plants use it). When you die,
money goes back to bank through other people (decomposition and
denitrification)!
Bacteria are like ATM machines that convert atmospheric nitrogen
into a form living things can use!
Farmers plant legumes (peas, beans, gram) because:
• These plants have Rhizobium bacteria in their roots
• These bacteria fix atmospheric nitrogen
• Add nitrogen to soil naturally (free fertilizer!)
• Next crop planted gets nitrogen-rich soil
This is why farmers rotate crops - it maintains soil fertility
naturally!
The greenhouse effect is the warming of Earth's surface due to the trapping of heat by certain gases (greenhouse gases) in the atmosphere. These gases act like glass walls of a greenhouse!
Ever sat in a closed car in summer? It gets very hot inside even
though windows are transparent! This is because:
• Sunlight enters through windows
• Gets absorbed and converts to heat
• Heat cannot escape easily
• Car becomes hot!
Same happens with Earth! Greenhouse gases in atmosphere trap heat
like car windows, making Earth warmer!
• Carbon dioxide (CO₂) - Main culprit!
• Methane (CH₄) - From cattle, rice fields, landfills
• Water vapor (H₂O)
• Nitrous oxide (N₂O)
• CFCs (Chlorofluorocarbons) - From refrigerators, ACs
• Ozone (O₃)
Natural greenhouse effect is GOOD!
• Without it, Earth would be too cold (about -18°C)
• It maintains Earth's temperature suitable for life
• Like a blanket that keeps Earth warm
Enhanced greenhouse effect is BAD!
• Humans are adding too many greenhouse gases
• Too much trapping of heat
• Earth is getting too warm
• This is called GLOBAL WARMING!
Global warming is the gradual increase in Earth's average temperature due to enhanced greenhouse effect caused by human activities.
1. Melting of ice caps and glaciers:
• Polar ice is melting
• Sea level rising
• Coastal cities may flood!
2. Climate change:
• Unpredictable weather patterns
• More droughts, floods, storms
• Heat waves
3. Impact on wildlife:
• Animals losing habitat (polar bears!)
• Species extinction
• Coral reefs dying
4. Impact on agriculture:
• Crop failures
• Food shortage
• Water scarcity
5. Health issues:
• Spread of diseases
• Heat-related deaths
✓ Reduce use of fossil fuels
✓ Use renewable energy (solar, wind)
✓ Plant more trees (they absorb CO₂)
✓ Use energy-efficient appliances
✓ Reduce, reuse, recycle waste
✓ Use public transport
✓ Save electricity (switch off when not needed)
✓ Reduce meat consumption (less methane from cattle)
✓ Support environmental policies
✓ Spread awareness
The ozone layer is a protective layer of ozone gas (O₃) present in the upper atmosphere (stratosphere, 15-35 km above Earth). It acts as a shield protecting life on Earth from harmful ultraviolet (UV) radiation from the Sun.
Ozone layer is like a sunscreen or umbrella for Earth! Just like sunscreen protects your skin from harmful sun rays, the ozone layer protects all life on Earth from dangerous UV radiation that can cause skin cancer, eye damage, and harm plants!
Problem: The protective ozone layer is getting
thinner!
Main culprit: CFCs (Chlorofluorocarbons)
• Used in refrigerators, ACs, aerosol sprays
• When released, they rise to stratosphere
• Break down ozone molecules (O₃)
• Create "holes" in ozone layer
Biggest hole: Over Antarctica!
If ozone layer gets thinner, more UV rays reach Earth:
• Skin cancer increases
• Eye cataracts (blindness)
• Weakened immune system
• Damage to plants and crops
• Harm to marine life (phytoplankton dies)
• Disrupts food chains
✓ Ban CFCs (Montreal Protocol 1987 - international agreement)
✓ Use CFC-free refrigerators and ACs
✓ Don't use aerosol sprays with CFCs
✓ Repair old refrigerators/ACs (don't let CFCs leak)
✓ Use eco-friendly alternatives
✓ Support ozone-friendly products
REDUCE - Use less (save electricity, water,
fuel)
REUSE - Use things again (bags, bottles,
paper)
RECYCLE - Convert waste to useful products
Small actions by millions of people can save our planet!
Q1. Why is water cycle important for life on
Earth?
Answer: Water cycle ensures continuous
availability of fresh water on Earth. It distributes water from
oceans to land through rain, which is essential for drinking,
agriculture, and survival of all living organisms.
Q2. How do forests help in reducing air
pollution?
Answer: Trees absorb carbon dioxide during
photosynthesis and release oxygen. They also trap dust particles
and absorb harmful gases, thus purifying air and reducing
pollution.
Q3. Why are leguminous plants beneficial for
soil?
Answer: Leguminous plants (peas, beans) have
Rhizobium bacteria in their root nodules that fix atmospheric
nitrogen into the soil, naturally enriching soil with nitrogen
without need for chemical fertilizers.