1. KEY CONCEPT The biosphere is one of Earth’s four interconnected systems.

2. The biosphere is the portion of Earth that is inhabited by life.
The biosphere includes all ecosystems.
one of Earth’s systems
includes the biota, all the living things in the biosphere

3. There are three other Earth systems.
hydrosphere—water, ice, and water vapor
atmosphere—air blanketing Earth’s solid and liquid surface
geosphere—geologic features above and below Earth’s surface

4. Biotic and abiotic factors interact in the biosphere.
All four Earth systems are interconnected.
The Gaia hypothesis considers Earth as a kind of living organism.
Earth systems interact to yield a biosphere capable of supporting life.
It was developed by James Lovelock and Lynn Margulis.