Recycling in the Biosphere

Matter, unlike energy, is recycled within and between ecosystems. Elements pass from one organism to another and from one part of the biosphere to another through biogeochemical cycles, which are closed loops powered by the flow of energy.

Water Cycle

Water moves between the ocean, the atmosphere, and land--sometimes outside living organisms and sometime inside them.

• Evaporation is the process in which water changes from a liquid to a gas.

• Transpiration is the process in which water evaporates from the leaves of plants.

​Nutrient Cycles

The chemical substances that an organism needs to survive are called nutrients. Like water, nutrients pass through organisms and the environment.

Carbon Cycle: Carbon is a key ingredient of all organic compounds. Processes involved in the carbon cycle include photosynthesis and human activities such as burning.

Nitrogen Cycle: Nitrogen is needed by all organisms to build proteins. Processes involved in the nitrogen cycle include nitrogen fixation and denitrification.

·    In nitrogen fixation, certain bacteria convert nitrogen gas into ammonia.

·   In denitrification, other soil bacteria convert nitrogen compounds called nitrates back into nitrogen gas.

​Phosphorus Cycle: Phosphorus is needed for molecules such as DNA and RNA. Most of the phosphorus in the biosphere is stored in rocks and ocean sediments. Stored phosphorus is gradually released into water and soil, where it is used by organisms.

Nutrient Limitation

A nutrient that, in short supply, can limit the productivity of an ecosystem is called a limiting nutrient.