What is the pathway of water from the atmosphere to Earth's surface, below ground, and back to the atmosphere?

• A. Biogeochemical cycle
• B. Hydrologic cycle
• C. Energy pyramid
• D. Population density

Answer: (B)

The hydrologic cycle describes how water moves through the atmosphere, the surface, and below ground, and back into the atmosphere. Water is lifted from bodies of water by evaporation and from plants by transpiration, then it condenses into clouds and falls as precipitation. Once on land, water can infiltrate soil and rock to become groundwater or flow over the surface as runoff into rivers and lakes. This liquid water at the surface can evaporate again, continuing the cycle. This pathway specifically tracks water’s journey through air, land, and underground back to air. Biogeochemical cycles involve multiple elements, not just water; the energy pyramid maps energy transfer among trophic levels; population density is a measure of how many organisms live in a given area.