4.3 Cycling Of Matter I. Water Cycle A. Water moves between the atmosphere, the land, & the oceans B. Water vapor condenses & falls to Earth as precipitation (rain, snow, hail, sleet, etc.) 1. Some percolates into the soil as groundwater 2. Some runs off into rivers, lakes, & streams C. Water evaporates when heated back to the atmosphere D. Evaporation from plants is called transpiration

II. Carbon & oxygen cycles A. Movement of carbon from the nonliving environment into living things & back B. Plants use CO2 in air to build organic molecules during photosynthesis 1. Oxygen is released during this process 2. Most animals use oxygen a. they then release CO2 C. Respiration 1. process of exchanging oxygen & CO2 between organisms & their surroundings

D. Combustion 1. The burning of living or once living things releases CO2 into the atmosphere 2. Burning trees & fossil fuels (oil, coal, etc.) III. Nitrogen Cycle A. Process which circulates nitrogen between the air, soil, water, and organisms B. 78% of the atmosphere is nitrogen C. Nitrogen fixation 1. Bacteria in the soil change nitrogen in the air into a useable form

D. Assimilation 1. process in which plants absorb nitrogen E. Ammonification 1. nitrogen from animal waste is returned to the soil by bacteria F. Denitrification 1. nitrate is changed to nitrogen gas IV. Phosphorus Cycle A. The movement of phosphorus from surroundings to organisms & back B. ATP & DNA need phosphorus to support life