Class 9 Science Chapter 13 Earth as a System: Energy, Matter and Life – Revision Notes

Earth functions as a single interconnected system of five spheres, driven by solar energy and tied together by cycles like the water and carbon cycle — this chapter maps out how each piece fits.

Last Updated: September 23, 2026

Five Spheres

• Geosphere: solid Earth (rocks, minerals).
• Hydrosphere: all water (oceans, rivers, groundwater).
• Atmosphere: gases surrounding Earth.
• Cryosphere: frozen water (ice, glaciers, permafrost).
• Biosphere: all living organisms.

Solar Radiation

• Sun’s energy (electromagnetic spectrum) drives weather, climate, photosynthesis.

Differential Heating & Wind

• Uneven surface heating → pressure differences → wind (high → low pressure).

Biogeochemical Cycles

• Water cycle: evaporation → condensation → precipitation → collection.
• Carbon cycle: atmosphere ↔ organisms (photosynthesis/respiration) ↔ oceans/fossil fuels.
• Nitrogen cycle: atmosphere (N2) ↔ soil (fixation) ↔ organisms ↔ atmosphere (denitrification).
• Oxygen cycle: released by photosynthesis, consumed by respiration/combustion.

Human Impact

• Fossil fuels → excess CO2 (carbon cycle disruption).
• Fertiliser overuse → nitrogen cycle disruption.

One-Line Summary

Earth functions as one interconnected system of five spheres, powered by solar radiation, with differential heating driving winds and matter continuously recycled through the water, carbon, nitrogen, and oxygen cycles — cycles that human activity increasingly disrupts.

Frequently Asked Questions

Why is the Earth described as a system with interacting components in this chapter?
The Earth is described as a system because its different components, such as the atmosphere, hydrosphere, lithosphere, and biosphere, continuously interact with and influence one another rather than functioning as isolated, independent parts.

What role does energy from the Sun play in Earth processes according to this chapter?
Solar energy drives most Earth processes, including weather patterns, ocean currents, and the water cycle, and it is also the ultimate source of energy that sustains life through photosynthesis in the biosphere.

Written by Satish

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