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chapter-13-Earth-as-a-System-Energy-Matter-and-Life (1).pdf// Grade 9 Science (Curiosity) Prepared by K Sandeep Swamy (M.Sc, B.Ed) · For online classes contact 9491878325 · Subscribe Samyans EduHub on YouTube

Earth as a System: Energy, Matter, and Life Chapter 13 — Grade 9 Science (Curiosity) Prepared by K Sandeep Swamy (M.Sc, B.Ed) · For online classes contact 9491878325 · Subscribe Samyans EduHub on YouTube Chapter Overview Part 1: Earth's Spheres & Solar Energy Discover how the Sun powers our planet and how Earth's five great spheres interact to create the conditions for life. Spheres Five interconnected layers of Earth Solar Energy The Sun as Earth's primary energy source Albedo & Atmosphere How energy is reflected and trapped Earth's Five Interconnected Spheres Geosphere Solid rocks, soil, landforms — e.g. Deccan Plateau, Thar Desert Hydrosphere All surface water — oceans, rivers, lakes, and groundwater Cryosphere Ice and snow — Himalayan Solar Radiation: Earth's Main Energy Source EM Waves Sun's energy travels as electromagnetic waves at 3 × 10⁸ m/s — the speed of light 99% Spectrum Nearly all solar energy falls in the UV, visible, and infrared (IR) range Solar Constant ~1.4 kW/m² at the top of the atmosphere Surface Max Up to ~1 kW/m² reaches Earth's surface under clear skies How Solar Radiation Warms the Earth UV Rays Mostly absorbed by the ozone layer in the stratosphere — protecting life below Visible Light Reaches the surface; powers photosynthesis and warms land and water Infrared (IR) Warms the surface; re-radiated heat is trapped by greenhouse gases — CO₂, CH₄, and water vapour Without the atmosphere, Earth would be far too cold to support any life at all. Albedo: Why Some Surfaces Stay Cooler What is Albedo? The fraction of solar radiation reflected by a surface — ranges from 0 (none) to 1 (all) High Albedo Snow: 0.80–0.90 · Ice: 0.50–0.70 → reflects more sunlight → stays cool Low Albedo Black soil, ocean water → absorbs more radiation → heats up faster Urban Heat Island Cities are warmer than rural areas — concrete and asphalt absorb and re-radiate more heat Layers of the Atmosphere Troposphere (0–12 km) All weather occurs here; temperature drops ~6.5°C per km as you go higher Stratosphere (12–50 km) Ozone layer absorbs harmful UV; temperature actually increases with height here Upper Layers Mesosphere, Thermosphere, Exosphere — play a minor role in surface climate Excess CO₂ from human activities enhances the greenhouse effect — leading to global warming. Chapter Overview Part 2: Winds & Ocean Currents Explore how uneven solar heating sets the atmosphere and oceans into motion — shaping climates across the globe. Local Winds Valley and mountain breezes Planetary Winds Global pressure belts and the Coriolis effect Ocean Currents Earth's great heat conveyor belts Local Winds: Valley & Mountain Breezes These breezes are experienced in Shimla, Dehradun, and other Himalayan valleys. They regulate temperature, moisture, and support local agriculture. Valley Breeze (Day) Slopes heat up faster than valleys → warm air rises → cooler valley air flows up the slope to replace it

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Eart a a Sy te : E ergy, Matter, a d Life Chapter 13 — Grade 9 Science (Curiosity) Prepared by K Sandeep Swamy (M.Sc, B.Ed) · For online classes contact 9491878325 · Subscribe Samyans EduHub on YouTube
CHAPTER OVERVIEW Part 1: Eart ' Sp ere Solar E ergy Discover how the Sun powers our planet and how Earth's five great spheres interact to create the conditions for life. 1 Sp ere Five interconnected layers of Earth 2 Solar E ergy The Sun as Earth's primary energy source 3 Albedo At o p ere How energy is reflected and trapped
Earth's Five Interconnected Spheres 🪨Geosphere Solid rocks, soil, landforms — e.g. Deccan Plateau, Thar Desert 💧 Hydrosphere All surface water — oceans, rivers, lakes, and groundwater 🧊Cryosphere Ice and snow — Himalayan
Solar Radiatio : Eart ' Mai E ergy Source EM Wave Sun's energy travels as electromagnetic waves at 3 × 10⁸ m/s — the speed of light 99% Spectru Nearly all solar energy falls in the UV, visible, and infrared (IR) range Solar Co ta t ~1.4 kW/m² at the top of the atmosphere Surface Max Up to ~1 kW/m² reaches Earth's surface under clear skies
How Solar Radiatio War t e Eart 1 UV Ray Mostly absorbed by the ozone layer in the stratosphere — protecting life below 2 Vi ible Lig t Reaches the surface; powers photosynthesis and warms land and water 3 I frared (IR) Warms the surface; re-radiated heat is trapped by greenhouse gases — CO₂, CH₄, and water vapour Without the atmosphere, Earth would be far too cold to support any life at all.
Albedo: Why Some Surfaces Stay Cooler What is Albedo? The fraction of solar radiation reflected by a surface — ranges from 0 (none) to 1 (all) High Albedo Snow: 0.80–0.90 · Ice: 0.50–0.70 →reflects more sunlight →stays cool Low Albedo Black soil, ocean water →absorbs more radiation →heats up faster Urban Heat Island Cities are warmer than rural areas — concrete and asphalt absorb and re-radiate more heat
Layer of t e At o p ere 1 Tropo p ere (0–12 k ) All weather occurs here; temperature drops ~6.5°C per km as you go higher 2 Strato p ere (12–50 k ) Ozone layer absorbs harmful UV; temperature actually increases with height here 3 Upper Layer Mesosphere, Thermosphere, Exosphere — play a minor role in surface climate Excess CO₂ from human activities enhances the greenhouse effect — leading to global warming.
CHAPTER OVERVIEW Part 2: Wi d Ocea Curre t Explore how uneven solar heating sets the atmosphere and oceans into motion — shaping climates across the globe. 1 Local Wi d Valley and mountain breezes 2 Pla etary Wi d Global pressure belts and the Coriolis effect 3 Ocea Curre t Earth's great heat conveyor belts
Local Winds: Valley & Mountain Breezes These breezes are experienced in Shimla, Dehradun, and other Himalayan valleys. They regulate temperature, moisture, and support local agriculture. ☀️Valley Breeze (Day) Slopes heat up faster than valleys →warm air rises → cooler valley air flows up the slope to replace it 🌙Mountain Breeze (Night) Slopes cool faster →cold, dense air sinks →flows down into the warmer valley below
Planetary Winds & Pressure Belts 01 Equatorial Low Pressure Intense heating at the equator →warm air rises →creating a belt of low pressure and heavy rainfall 02 Sub-Tropical High Pressure Rising air cools and sinks at about 30°N and 30°S →forming high pressure belts and dry zones 03 Coriolis Effect Earth's rotation deflects winds — to the right in the Northern Hemisphere, left in the Southern Hemisphere 04 Global Impact These planetary wind patterns drive weather systems, monsoons, and distribute heat around the globe
Ocea Curre t : Eart ' Heat Co veyor Driven by planetary winds, temperature and salinity differences, Earth's rotation, and landmass shapes Form large circular gyres — clockwise in the Northern Hemisphere, counter- clockwise in the Southern Hemisphere The North Atlantic Drift (extension of the Gulf Stream) keeps European ports ice-free in winter Transport heat from the equator to the poles, reducing global temperature extremes Ocean currents act like a global thermostat — moving warm water to cold regions and vice versa.
CHAPTER OVERVIEW Part 3: Biogeochemical Cycles Understand how matter — water, carbon, nitrogen, and oxygen — moves endlessly between living and non-living parts of Earth, sustaining all life. 💧Water Cycle Evaporation, condensation, precipitation, runoff 🌿Carbon Cycle Fast and slow pathways through life, soil, and atmosphere 🔬Nitrogen Cycle Fixation, nitrification, denitrification 🌬️Oxygen Cycle Photosynthesis, respiration, and combustion
What Are Biogeochemical Cycles? The cyclic movement of matter and energy between the abiotic (non-living) and biotic (living) components of Earth. Key cycles: Water, Carbon, Nitrogen, Oxygen. Nutrient Availability Make essential nutrients available to living organisms so they can grow, reproduce, and survive Climate Regulation Regulate the climate and maintain the energy balance of the entire planet Sphere Connections Connect all five spheres of Earth — linking the geosphere, hydrosphere, cryosphere, atmosphere, and biosphere
T e Water Cycle Evaporatio Co de atio Precipitatio Ru off Grou dwater Climate change intensifies this cycle — producing heavier rains in some areas and severe droughts in others. Melting glaciers raise river levels and threaten coastal cities like Mumbai and Chennai.
The Carbon Cycle ⚡Fast Cycle (Days– Years) Photosynthesis absorbs CO₂; respiration and decomposition release it back into the atmosphere 🐌Slow Cycle (Millions of Years) Dead organisms →fossil fuels buried underground →burned by humans →CO₂ released rapidly Human activities raised atmospheric CO₂ by ~35% since 1960 (315 ppm →420 ppm). Excess CO₂ intensifies the greenhouse effect →global warming and rising sea levels.
The Nitrogen Cycle 1 N₂ in Atmosphere Nitrogen gas = 78% of air, but plants and animals cannot use it directly 2 Nitrogen Fixation Bacteria like Rhizobium convert N₂ →ammonia (NH₃) in the soil 3 Nitrification Bacteria convert NH₃ →nitrite →nitrate, which plants absorb through their roots 4 Denitrification Other bacteria convert nitrates back to N₂ gas, completing the cycle
The Oxygen Cycle Oxygen (O₂) makes up approximately 21% of Earth's atmosphere — and it is constantly being consumed and replenished. The balance between consumption and production of oxygen sustains life across all five spheres. O₂ Consumed By Respiration by plants and animals · Combustion of fossil fuels and biomass O₂ Restored By Photosynthesis — plants use sunlight + CO₂ + water → glucose + O₂
CHAPTER OVERVIEW Part 4: Hu a I pact Solutio Human activities are disrupting Earth's finely balanced cycles — but with knowledge and action, we can restore balance and protect our planet. 1 Di ruptio How humans break Earth's cycles 2 Co eque ce Global warming, ocean acidification, eutrophication 3 Solutio Renewables, reforestation, global cooperation
How Humans Disrupt Earth's Cycles 🏭Burning Fossil Fuels Raises atmospheric CO₂ → intensifies the greenhouse effect →global warming and rising sea levels 🌲Deforestation Less photosynthesis, less transpiration, more soil erosion, and reduced rainfall 🌾Fertiliser Overuse Excess nitrates leak into water bodies →algal blooms → eutrophication →fish die-offs 🌊Ocean Acidification Excess CO₂ absorbed by oceans →threatens coral reefs and plankton that support entire food chains
Re tori g t e Bala ce: W at We Ca Do Switc to Re ewable India is rapidly expanding solar and wind energy to cut fossil fuel dependence Pla t Tree India has planted billions of trees to restore carbon sinks and reverse deforestation Global Cooperatio The Montreal Protocol successfully reduced CFCs — the ozone layer is now recovering I dividual Actio Save water, reduce waste, reuse and recycle, practise sustainable farming
Key Takeaways: Chapter 13 at a Glance 1 Five Spheres Are One System Earth's geosphere, hydrosphere, cryosphere, atmosphere, and biosphere are deeply interconnected — a change in one affects all others 2 Solar Energy Drives Everything Uneven solar heating drives winds, ocean currents, and the water cycle — shaping climates across the entire planet 3 Cycles Sustain Life Biogeochemical cycles — water, carbon, nitrogen, and oxygen — continuously recycle matter and sustain all living things 4 We Have the Power to Act Human activities disrupt these cycles — but individual choices and collective global action can and do restore balance 🌍Remember: Earth is one giant, interconnected system. Understanding it is the first step to protecting it.