(ii) To recycle essential nutrients between biotic and abiotic components.
(iii) The Earth’s surface absorbs solar radiation, which is then re-radiated and trapped by greenhouse gases.
Climate change intensifies the water cycle by increasing evaporation and changing cloud and rainfall patterns. Some regions may face heavier rain and floods, while others face drought. Melting glaciers and altered monsoon patterns also change river flow and groundwater recharge.
Albedo is the fraction of sunlight reflected by a surface. Snow and ice have high albedo and keep surfaces cooler; dark oceans, forests and rocks have lower albedo and absorb more heat. Changes in albedo affect temperature and climate.
During the day, heated mountain slopes warm air, which rises and draws air up from valleys as valley breeze. At night, slopes cool and dense air flows downward as mountain breeze. A barren rocky mountain breeze may be warmer by day than a grass-covered one because rocks heat faster and vegetation cools by evaporation.
The troposphere is mainly responsible. It contains most water vapour and is heated from Earth’s surface, causing convection, clouds, winds, storms and rainfall.
Nitrogen fixation converts atmospheric nitrogen into usable compounds; plants absorb nitrates/ammonium; animals get nitrogen through food; decomposers return nitrogen to soil; denitrifying bacteria return nitrogen gas to air. Without cycling, usable nitrogen would be depleted, harming proteins, DNA, plant growth and food webs.
Deforestation reduces photosynthesis, so less CO₂ is removed and less O₂ is released; burning/decay of trees adds CO₂. It also causes habitat loss, biodiversity decline, soil erosion, disturbed rainfall, floods and climate warming.
Carbon path: atmospheric CO₂ → plants by photosynthesis → animals through food → CO₂ returned by respiration; dead matter and wastes → decomposers → CO₂; some carbon becomes fossil fuels over long periods and returns to air by combustion. A diagram should show these arrows.
Plants need CO₂, but excess CO₂ strengthens the greenhouse effect, causing global warming and climate change, which can disturb rainfall, melt ice, raise sea level and stress ecosystems.
Earth loses heat mainly by emitting infrared radiation to the atmosphere and space; heat is also transferred by convection, conduction and evaporation. This maintains Earth’s energy balance and suitable temperatures.
A flat disc would not receive sunlight with the same gradual latitude-based angles as a sphere. Present equator-to-pole temperature zones, wind patterns and seasons would be drastically different.
Cryosphere: snow, glaciers and sea ice melt, lowering albedo and raising sea level. Hydrosphere: evaporation, ocean warming and rainfall extremes increase. Biosphere: habitats shift, species face heat stress, and agriculture/food webs are disrupted.
The atmosphere lets sunlight in but absorbs and re-emits some outgoing infrared radiation through greenhouse gases, reducing extreme cooling. Winds and water vapour also redistribute heat.
Earth’s atmosphere, hydrosphere, geosphere/lithosphere, biosphere and cryosphere exchange matter and energy. For example, plants use atmospheric CO₂, water and soil minerals, release oxygen and support animals. Removing forests alters carbon balance, rainfall, soil stability and biodiversity, showing the delicate balance.