Overview
This lecture explains Earth's four subsystems—atmosphere, geosphere, hydrosphere, and biosphere—their characteristics, interactions, and how matter and energy flow between them to support life.
Factors That Make Earth Habitable
- The acronym "TWEEN" stands for Temperature, Water, Energy, Atmosphere, and Nutrients.
- Earth's optimal distance from the Sun provides suitable temperature for life.
- Liquid water is essential for organisms to survive.
- Energy from the Sun or chemicals drives life processes.
- The atmosphere keeps Earth warm and shields it from harmful radiation.
- Nutrients are necessary to build and maintain living organisms.
Earth’s Subsystems Overview
- Earth is a closed system with interconnected subsystems that support life.
- Subsystems are called "spheres": atmosphere, geosphere, hydrosphere, biosphere.
- Subsystems interact through physical, chemical, and biological processes.
The Four Subsystems ("Spheres")
- Atmosphere: Gaseous layer, made of 78% nitrogen, 21% oxygen, and protects Earth from UV rays.
- Geosphere: Solid part of Earth; includes crust, mantle, and core; composed of rocks, soil, and minerals.
- Hydrosphere: All water on Earth in all forms, including the cryosphere (frozen parts); moves and redistributes solar energy.
- Biosphere: All living things and where they exist, including land, water, and air; highly interactive with other spheres.
Interaction and Flow of Matter & Energy
- Matter and energy flow among all four subsystems, supporting life.
- Biogeochemical cycles (carbon, nitrogen, water, etc.) transfer substances across spheres.
- Disturbances in one sphere can impact the others due to their interconnectedness.
Comprehension Check (Sample Q&A)
- The geosphere contains landforms like mountains and hills.
- Biotic factors are living things (e.g., bees); abiotic factors are non-living (e.g., air).
- Oceans (hydrosphere) absorb and redistribute solar energy.
- The biosphere includes all living organisms on Earth.
- Water evaporation from soil shows geosphere–atmosphere interaction.
Key Terms & Definitions
- System — A set of interconnected components forming a unified whole.
- Atmosphere — The gaseous sphere surrounding Earth.
- Geosphere — The solid, rocky part of the planet.
- Hydrosphere — All of Earth's water in any state.
- Biosphere — All living organisms and their habitats.
- Biogeochemical Cycle — Circulation of elements through Earth's spheres.
Action Items / Next Steps
- Prepare for the next lesson on Earth materials, resources, and properties of minerals.
- Review notes on the characteristics and interactions of the four subsystems.