How far does the biosphere extend above and below the Earth's surface?

The biosphere is defined as the global sum of all ecosystems and represents the zone of life on Earth. It extends where life can exist, influenced by factors such as temperature, pressure, and the availability of water. Typically, the biosphere extends about 8 kilometers above sea level, where the atmosphere is still dense enough to support life. This upper limit includes the peaks of high mountains where organisms can be found, such as in high-altitude ecosystems.

Below the Earth's surface, life extends down to approximately 11 kilometers. This includes environments like deep-sea hydrothermal vents and underground aquifers where microorganisms have been discovered thriving in extreme conditions. This depth is generally associated with the range of life forms that can withstand intense pressure and varying temperatures.

The chosen answer accurately reflects these limits, thus providing a comprehensive understanding of how far the biosphere extends above and below the Earth's surface.