Overview
This lecture covers the definition, origin, extent, and concepts of the biosphere, including its interactions with Earth's other spheres and specific experimental biospheres.
Definition and Concepts of the Biosphere
- The biosphere is the part of Earth where living organisms exist, overlapping atmosphere, geosphere, and hydrosphere.
- Some define the biosphere as all living things on Earth, while others include both organisms and their environments.
- The biosphere is one of Earth's four main spheres: biosphere, atmosphere, geosphere (lithosphere), and hydrosphere.
- The biosphere constitutes a very small fraction of Earth's mass and volume.
- Interactions between the biosphere and other spheres are vital, as seen in biogeochemical cycles.
Origin and Use of the Term
- The term "biosphere" was coined by Eduard Suess in 1875, meaning the place where life exists on Earth's surface.
- Biosphere is an interdisciplinary concept, linking many earth and life sciences.
- Vladimir Vernadsky popularized the term and viewed life as a geological force shaping Earth.
Alternative Concepts and the Gaia Hypothesis
- Some scientists use "biosphere" to mean only living organisms ("biomass" or "biota").
- The broader sense includes environments capable of supporting life (sometimes called the "ecosphere").
- The Gaia hypothesis proposes that Earth acts as a living organism, with biosphere and other spheres cooperating.
Extent and Features of Earth's Biosphere
- Life exists in almost all parts of the hydrosphere, upper lithosphere, and lower atmosphere.
- Microbes live in extreme environments, from deep within Earth's crust to high altitudes and ocean trenches.
- The biosphere is estimated to form a hollow sphere about 23 km thick, about 0.0007% of Earth's volume.
- Biomass averages 3.7 kg carbon per m², totaling about 1900 gigatonnes.
- The biosphere is divided into biomes, broad regions with similar plants and animals, often determined by latitude.
Specific Biosphere Projects
- Biosphere 1: The planet Earth.
- Biosphere 2: Closed ecosystem laboratory in Arizona.
- BIOS-3: Closed ecosystem in Krasnoyarsk, Siberia.
- Biosphere J (CEEF): Closed ecology experiment facility in Japan.
Key Terms & Definitions
- Biosphere — Earth's zone where life exists, including parts of the atmosphere, hydrosphere, and lithosphere.
- Biogeochemical cycles — Natural cycles (e.g., water, carbon) involving interactions among Earth's spheres.
- Ecosphere — All living organisms and their environment; sometimes synonymous with biosphere.
- Biome — Large ecological regions with similar climate, plants, and animals.
- Gaia hypothesis — Theory that Earth and its biosphere function as a living organism.
Action Items / Next Steps
- Review the definitions and concepts related to the biosphere.
- Understand key examples of extreme life in the biosphere for discussion or exam preparation.