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Describes the part of Earth, including the air, land, surface rocks, and water, where life is found.

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The Biosphere (SE)

Is Earth a living organism?

Most scientists agree that the Earth itself is not a living thing. However, the Earth does have some aspects of life. Some scientists argue that the Earth maintains homeostasis, a stable state, just like a living organisms.

The Biosphere

The highest level of ecological organization is the biosphere. It is the part of the earth, including the air, land, surface rocks, and water, where life is found. Parts of the lithosphere, hydrosphere, and atmosphere make up the biosphere. The lithosphere is the outermost layer of the earth's crust; essentially land is part of the lithosphere. The hydrosphere is composed of all the areas that contain water, which can be found on, under, and over the surface of Earth. The atmosphere is the layer of gas that surrounds the planet. The biosphere includes the area from about 11,000 meters below sea level to 15,000 meters above sea level. It overlaps with the lithosphere, hydrosphere, and atmosphere. Land plants and animals are found on the lithosphere, marine plants and animals are found in the hydrosphere, and birds and other flying animals are found in the atmosphere. Of course, there are countless bacteria, protists, and fungi that are also found in the biosphere.

Is the Biosphere Living?

The Gaia hypothesis states that the biosphere is its own living organism. The hypothesis suggests that the earth is self-regulating and tends to achieve a stable state, known as homeostasis. For example the composition of our atmosphere stays fairly consistent, providing the ideal conditions for life. When carbon dioxide levels increase in the atmosphere, plants grow more quickly. As their growth continues, they remove more carbon dioxide from the atmosphere. In this way, the amount of carbon dioxide stays fairly constant without human intervention.

For a better understanding of how the biosphere works and various dysfunctions related to human activity, scientists have simulated the biosphere in small-scale models. Biosphere 2 (Figure below) is a laboratory in Arizona that contains 3.15 acres of closed ecosystems. Ecosystems of Biosphere 2 are an ocean ecosystem with a coral reef, mangrove wetlands, a tropical rainforest, a savannah grassland and a fog desert. See http://www.b2science.org/ for additional information.

Additional biosphere projects include BIOS-3, a closed ecosystem in Siberia, and Biosphere J, located in Japan.

Biosphere 2, in Arizona, contains 3.15 acres of closed ecosystem and is a small-scale model of the biosphere.


  • atmosphere: Layer of gases that surrounds a planet; held in place by gravity.
  • biosphere: Part of Earth that supports life, including the crust, water, and atmosphere.
  • homeostasis: Tendency of a system to maintain a stable internal environment.
  • hydrosphere: Combined mass of water found on, under, and over the surface of a planet.
  • Gaia hypothesis: Concept of Earth as a self-regulating living thing.
  • lithosphere: Rigid outermost shell or layer of a rocky planet; land is part of the lithosphere.


  • The biosphere is the part of the Earth, including the air, land, surface rocks, and water, where you can find life.
  • The Gaia hypothesis states that the biosphere is its own living organism


Use the resource below to answer the questions that follow.

  1. How is biomass in the deep biosphere thought to compare to biomass in tropical rainforests?
  2. How do the number of individual organisms compare between the deep biosphere and the tropical rainforests? What does this suggest about the rate of evolution between these two areas?
  3. How does the deep biosphere contribute to overall global diversity?
  4. How deep into the Earth have researchers at MARUM found living organisms? What do they expect to find as technologies are developed to drill even deeper? Do we know how deep into the Earth the biosphere extends?
  5. What implications do you think research into the deep biosphere has to the search for life on other planets?


  1. What is the biosphere?
  2. Give an example of how Earth is self-regulating.

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