KEY CONCEPT Matter cycles in and out of an ecosystem.

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 water storage in ocean surface runoff lake groundwater seepage

Elements essential for life also cycle through ecosystems. A biogeochemical cycle is the movement of a particular chemical through the biological and geological parts of an ecosystem. The main processes involved in the oxygen cycle are photosynthesis and respiration.

Oxygen cycles indirectly through an ecosystem by the cycling of other nutrients. respiration carbon dioxide photosynthesis Fig. In the oxygen cycle, oxygen flows into the atmosphere as a byproduct of photosynthesis. Organisms take in this oxygen and release it as carbon dioxide through respiration.

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. fossil fuels photosynthesis carbon dioxide dissolved in water decomposition of organisms respiration carbon dioxide in air combustion Fig. Photosynthesis and respiration account for much of the transformation and movement of carbon.

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 roots of legumes; others live freely in the soil. nitrogen in atmosphere animals denitrifying bacteria nitrifying ammonium ammonification decomposers plant nitrogen-fixing bacteria in soil bacteria in roots nitrates nitrites Fig. Much of the nitrogen cycle occurs underground, where bacteria transform ammonium into nitrates, which are used by plants to make amino acids.

Ammonia released into the soil is transformed into ammonium. Nitrifying bacteria change the ammonium into nitrate. Nitrogen moves through the food web and returns to the soil during decomposition. nitrogen in atmosphere animals denitrifying bacteria nitrifying ammonium ammonification decomposers plant nitrogen-fixing bacteria in soil bacteria in roots nitrates nitrites Fig. Much of the nitrogen cycle occurs underground, where bacteria transform ammonium into nitrates, which are used by plants to make amino acids.

Eutrophication When excessive inorganic nutrients (like nitrogen or phosphorus) build up in a lake or other body of water algal blooms occur. This is usually caused by excessive use of fertilizers that run off from land into the water system. Once the algae and plants die off, decomposers deplete the water of oxygen while breaking down the dead plant and algae matter. Once oxygen levels drop too low, fish and other animals that live in the water suffocate and die. Fig. Red tide is a phenomenon caused by algal blooms (Wikipedia definition) during which algae become so numerous that they discolor coastal waters (hence the name "red tide"). The algal bloom may also deplete oxygen in the waters and/or release toxins that may cause illness in humans and other animals. Jun 14, 2015

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 of organic matter. Phosphorus leaches into groundwater from the soil and is locked in sediments. Both mining and agriculture add phosphorus into the environment. geologic uplifting rain weathering of phosphate from rocks runoff sedimentation forms new rocks leaching phosphate in solution animals plants decomposers phosphate in soil