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13.5 Cycling of Matter A biogeochemical cycle is the movement of a particular chemical through the biological and geological parts of an ecosystem. Matter (elements) cycles in and out of an ecosystem. 13.5 Cycling of Matter • Oxygen cycles indirectly through an ecosystem by the cycling of other nutrients. The main processes involved in the oxygen cycle are photosynthesis and respiration. oxygen photosynthesis respiration carbon dioxide 13.5 Cycling of Matter Water cycles through the environment. • The hydrologic, or water cycle is the circular pathway of water on Earth. • Organisms all have bodies made mostly of water. precipitation condensation transpiration evaporation lake groundwater surface runoff water storage in ocean 13.5 Cycling of Matter • Carbon is the building block of life. – The carbon cycle moves carbon from the atmosphere, through the food web, and returns to the atmosphere. – Carbon is emitted by the burning of fossil fuels. – Some carbon is stored for long periods of time in areas called carbon sinks. carbon dioxide in air combustion respiration photosynthesis respiration decomposition of organisms fossil fuels photosynthesis carbon dioxide dissolved in water 13.5 Cycling of Matter • The nitrogen cycle mostly takes place underground. – Some bacteria convert gaseous nitrogen into ammonia through a process called nitrogen fixation. – Some nitrogen-fixing bacteria live in nodules on the nitrogen in atmosphere roots of plants; animals others live freely in the soil. plant nitrogen-fixing bacteria in decomposers roots ammonification nitrogen-fixing ammonium bacteria in soil nitrifying bacteria nitrates nitrifying bacteria nitrites denitrifying bacteria 13.5 Cycling of Matter – Ammonia released into the soil is transformed into ammonium. – Nitrifying bacteria change the ammonium into nitrate. – Nitrogen moves through the food web and returns nitrogen in atmosphere to the soil during animals decomposition. plant nitrogen-fixing bacteria in decomposers roots ammonification nitrogen-fixing ammonium bacteria in soil nitrifying bacteria nitrates nitrifying bacteria nitrites denitrifying bacteria 13.5 Cycling of Matter • The phosphorus cycle takes place at and below ground level. – Phosphate is released by the weathering of rocks. – Phosphorus moves through the food web and returns to the soil during decomposition. rain geologic uplifting – Phosphorus leaches into groundwater weathering of phosphate from rocks from the soil and runoff plants is locked in sediments. animalsphosphate phosphate in solution in soil – Both mining and leaching agriculture add sedimentation phosphorus into decomposers forms new rocks the environment.
