NSCI 111

• The Earth's life-support system consists of four main spherical systems that interact with one another:
• Atmosphere (air)
• Hydrosphere (water)
• Geosphere (rock, soil, sediment)
• Biosphere (living things)
• The Atmosphere has five layers:
• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere
• The Geosphere has three layers:
• Core (Inner and Outer)
• Mantle
• Crust
• Life on Earth depends on three interconnected factors:
• The one-way flow of high-quality energy from the sun through living things into the environment as low-quality energy and eventually back into space as heat
• The cycling of matter or nutrients through parts of the biosphere
• Gravity, which allows the planet to hold onto its atmosphere
• Four types of nutrient cycles:
• Water / Hydrologic cycle
• Carbon Cycle
• Nitrogen Cycle
• Phosphorus Cycle