Cycles

Unit 4 Section 3

Water Cycle

• Water constantly moves between the oceans, atmosphere and the land

• It can be inside or outside of living organisms

Steps of the water cycle

• Evaporation:– Water evaporates or enters the atmosphere as a

gas called water vapor from bodies of water or plants

• Condensation:– The water vapor in the atmosphere condenses

into tiny droplets that form clouds

Steps of the water cycle continued…..

• Precipitation:– When the droplets in the clouds become large

enough they fall to the earth as precipitation– Example: rain, sleet, snow

• Runoff:– Precipitation that flows along the surface of the

land into a river or stream

Steps of the water cycle continued…..

• Groundwater:– Precipitation can be absorbed into the ground

becoming groundwater– If groundwater goes deep enough it can become

part of the underground reservoirs– Groundwater enters plants through their roots or

flows into bodies of water• Water re-enters the atmosphere through evaporation

and the process starts again

Carbon cycle

• Carbon is a major component of all organic (relating to an organism) compounds– Example: carbohydrates, lipids, proteins and

nucleic acids

Steps of the Carbon Cycle

• Geological activity:– Carbon is found in reservoirs in the biosphere– A mineral found in animal skeletons and rocks– Marine sediments that have animal skeletons in

them are turned into rocks– This releases carbon dioxide into the atmosphere

Steps of the carbon cycle continued…..

• Photosynthesis:– Carbon dioxide from the atmosphere is taken up

by producers to make food– Consumers eat producers and release carbon

dioxide into the atmosphere through cellular respiration

Steps of the carbon cycle continued…..

• Fossil fuels:– Examples: coal, oil and natural gas– When they are burned they give us energy they

release carbon dioxide into the atmosphere– Dead matter eventually decomposes into fossil

fuels• Ocean and rainwater– Dissolved carbon dioxide is found in the ocean and

rainwater

Nitrogen Cycle

• All organisms need nitrogen to make amino acids (proteins) and nucleic acids (DNA and RNA)

• Nitrogen exists as a gas in the atmosphere (N2)

• Nitrogen compounds such as ammonia (NH3), nitrate ions (NO3

-) and nitrite ions (NH2-) are

found in the soil • They can also be found in wastes and decomposing

organisms

Nitrogen cycle continued……

• Dissolved nitrogen can be found in oceans and large bodies of water

• Steps of the nitrogen cycle:– Atmospheric nitrogen: nitrogen gas in the

atmosphere is the most common kind of nitrogen– Only certain kinds of bacteria can use this gas– These bacteria convert the nitrogen gas to ammonia so that

producers can use it– Some nitrogen gas can be changed by lightning

Steps of the nitrogen cycle continued……

• Producers use nitrogen in the soil to make proteins and nucleic acids

• Consumers eat producers and use nitrogen to make their own proteins and nucleic acids

• Decomposers release ammonia, nitrates and nitrites from wastes and dead organisms– Producers then use these compounds

Steps of the nitrogen cycle continued…..

• Nitrogen fixation – bacteria convert nitrates into nitrogen gas

• These bacteria live in the soil

• Humans add nitrogen to the cycle by using fertilizers

• Runoff carries excess fertilizer into surface water or groundwater