Understanding Eco-Chemical Cycles

Precipitation is when condensed water vapor falls to Earth. Common types of precipitation include rain, sleet, and snow. In contrast, runoff is water flow across the Earth’s surface.

The burning of fossil fuels has increased the amount of carbon in the atmosphere, contributing to the greenhouse effect and global warming. Burning fossil fuels mainly involves combustion reactions in which the fuel is oxidized, producing carbon dioxide and water. While the other answer choices may add to the carbon dioxide levels of the atmosphere, the question asks for a direct cause.

Water, carbon, nitrogen, sulfur, and phosphorus have cyclic pathways that allowing them to flow within an ecosystem. Iron is not involved in very many ecological processes, and does not follow a defined chemical cycle.

In the process of assimilation, organic nitrogen is incorporated into plants through the roots. The type of nitrogen incorporated may be nitrate ions, nitrite ions, or ammonium ions. Symbiotic bacteria may assist this process.

The marine nitrogen cycle is very similar to the terrestrial nitrogen cycle. In marine ecosystems, atmospheric nitrogen enters the cycle through precipitation.

Nitrogen is necessary for all life; therefore, it is present in the territorial biosphere in living organisms, humus, and decomposing matter.

Transpiration is defined as the release of water vapor from plants and soil.

Percolation is defined as the vertical flow of water through subsurface soil and rocks. Percolation is influenced by gravity.

Advection can be described as the movement of water through the atmosphere and it is critical to the water cycle.

Deposition is the conversion of water from a gaseous to a solid phase; therefore, deposition is the opposite process of sublimation.