Cheat Sheet: Energy Matter And Life

1. Earth as a System: Energy, Matter, and Life

1.1 Earth System and Spheres

1.2 Solar Energy and Electromagnetic Radiation

1.3 Interaction of Solar Radiation on Earth's Surface

• Dark surfaces absorb more sunlight; light surfaces reflect more and remain cooler
• Urban heat island effect: built materials absorb and retain heat, raising city temperatures relative to rural areas

1.4 Latitude and Earth's Shape

• Sunlight concentrated at equator; spread over larger area at poles
• Uneven heating causes temperature differences between equator and poles
• Axial tilt and Earth's shape produce seasons and varying day lengths
• Uneven insolation drives global winds and ocean currents

1.5 Role and Structure of the Atmosphere

• Atmosphere partly absorbs incoming solar radiation (ozone blocks harmful UV)
• Atmosphere traps outgoing heat via greenhouse effect, keeping Earth warm enough for life
• Outer space begins at about 100 km above Earth

2. Uneven Heating Causes Wind and Ocean Currents

2.1 Local Winds

• Valley breeze (daytime): mountain slopes heat faster than valley floor; warm air rises along slopes; cooler valley air moves up
• Mountain breeze (after sunset): slopes cool faster; cooler dense air flows down into the valley

2.2 Planetary Winds

• Equatorial low: warm air rises near equator and moves poleward aloft
• Sub-tropical highs (~30° N/S): sinking cooled air creates high pressure belts
• Sub-polar lows (~60° N/S): rising air where polar and mid-latitude air converge
• Polar highs (~90° N/S): cold sinking air produces polar high pressure belts
• Coriolis effect: winds curve to the right in Northern Hemisphere and to the left in Southern Hemisphere

2.3 Ocean Currents

• Temperature and salinity: warm equatorial waters move poleward at surface; cold denser waters return toward equator at depth
• Low salinity water stays near surface; high salinity water sinks
• Gyres: large circular current patterns; clockwise in Northern Hemisphere; counterclockwise in Southern Hemisphere
• Role: redistribute heat from equator to poles and transport nutrients, regulating climate and supporting marine ecosystems
• North Atlantic Drift: carries warm water from the southern North American east coast to northwestern Europe, keeping many ports ice-free in winter

3. Biogeochemical Cycles

3.1 Water Cycle

• Process sequence: evaporation from water bodies → condensation to clouds → precipitation → surface flow back to oceans → infiltration into ground
• Water dissolves minerals during movement, transporting nutrients to terrestrial and marine organisms
• Climate change effects: warmer atmosphere holds more moisture, causing heavier rainfall in some regions and droughts in others
• Melting glaciers increase river water and sea level, threatening coastal cities such as Mumbai and Chennai
• Intense rainfall increases runoff and soil erosion
• Reduced infiltration decreases groundwater recharge and complicates agriculture during dry periods
• Water cycle links cryosphere, hydrosphere, atmosphere, geosphere and biosphere; all affected by global warming

3.2 Carbon Cycle

3.3 Nitrogen Cycle

3.4 Oxygen Cycle

4. Human Impact on Earth's Processes

4.1 Carbon and Ocean Impacts

• Burning fossil fuels and deforestation raise atmospheric CO₂, intensifying the greenhouse effect and causing extreme weather and biodiversity loss
• Increased atmospheric CO₂ leads to greater ocean CO₂ absorption, causing ocean acidification that threatens plankton and coral reefs
• Warmer ocean water reduces the ocean's capacity to absorb CO₂
• Natural carbon sinks (forests and oceans) become saturated by continued emissions

4.2 Nitrogen and Water Impacts

• Overuse of fertilisers adds excessive nitrates to rivers and lakes causing eutrophication and fish kills

4.3 Land Use, Air Pollution and Restoration Steps

• Deforestation reduces photosynthesis and transpiration, can decrease local rainfall, alters surface albedo, increases soil erosion and destroys habitats causing biodiversity decline
• Vehicular emissions react with sunlight to form ground-level smog and ground-level ozone, which is harmful to health
• Montreal Protocol initiated ozone-layer recovery by reducing CFCs
• Kyoto Protocol and Paris Agreement aimed to reduce CO₂ emissions but have been less successful
• Restoration measures: conserve energy; switch to renewable energy (solar, wind); plant trees; save water; practice sustainable farming
• India actions: large-scale tree planting and expansion of solar and renewable energy; Mission LiFE introduced at the UN Climate Change Conference in 2021 to promote mindful, eco-friendly lifestyles