1. KEY CONCEPT Matter cycles in and out of an ecosystem.

2. 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

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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

9. 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