The Earth's Biosphere | Science

August 18, 2015 thetasctest

You’ve been hard at work learning about Earth’s ecosystems and geosphere. The TASC Test Assessing Secondary Completion™ Science subtest also highlights Earth’s four spheres: the hydrosphere, atmosphere, lithosphere, and biosphere. All life on Earth is contained and supported within the biosphere.

Biosphere Crossroads 

Since life can stretch from the deepest parts of the ocean to the darkest corners of caves, it’s easy to see how the biosphere is the main crossroads to other spheres:  

  • Lithosphere (land). The lithosphere is the solid layer on Earth’s surface. Life in this sphere consists of all land animals and plants.
  • Atmosphere (air). The atmosphere is the layer of air that extends above the lithosphere. Life in this sphere consists of all creatures that fly.
  • Hydrosphere (water). The hydrosphere makes up any portion of Earth where water is found (on the surface, in the ground, and in the air). Life in this sphere consists of all oceanic and fresh water species.

The Biosphere: Then and Now

Earth’s biosphere surfaced roughly 3.5 billion years ago as prokaryotes evolved. These single-celled organisms survived without oxygen, but progressed to use sunlight to make oxygen from water and carbon dioxide. You may know this process as photosynthesis. According to National Geographic, new life forms began to emerge as oxygen became present in the biosphere.

The Encyclopedia of Earth notes that as more plant and photosynthetic species evolved, animals capable of sustaining life by eating plants advanced. Bacteria also began to evolve, allowing for the decomposition of dead plants and animals.

The Biosphere and Us 

The future of the biosphere will depend on how humans interact with other living things. The biosphere is threatened when:

  • Rain forests are diminished, decreasing the oxygen level in the atmosphere.
  • Industrial waste flows from manufacturing plants and mixes with the lithosphere.
  • Oil spills contaminate the hydrosphere.
  • Vehicle exhaust pollutes the atmosphere.

Animal and insect populations decrease as the biosphere changes, further threatening its stability. And discover how you can help conserve the biosphere and help life on Earth continue to thrive at

Conquer the biosphere! Test your mastery of the biosphere by taking this quiz.

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