1. Biogeochemical Cycles
Biology I

2. Lesson Objectives
Describe how nutrients move through the biotic and abiotic parts of an ecosystem.
Explain the importance of nutrients to living organisms.
Compare the biogeochemical cycles of nutrients.

3. Main Idea
Essential nutrients are cycled through biogeochemical processes.

4. Cycles in the Biosphere
Energy is transformed into usable forms to support the functions of an ecosystem.
A constant supply of usable energy is needed for the biosphere, but this is not true of matter.
The law of conservation of mass states that matter is not created or destroyed.
Matter cannot be replenished like the sun’s energy. Instead it is constantly recycled.

5. Cycles in the Biosphere
Matter is defined as anything that has mass and takes up space.
Matter provides the nutrients needed for organisms to function.
Matter moves through the organisms at each trophic level.

6. Cycles in the Biosphere
A nutrient is a chemical substance that an organism must obtain from its environment to sustain life.
The bodies of all organisms are built from water and nutrients such as carbon, nitrogen, and phosphorous.
In most ecosystems, plants obtain the nutrients first and then cycle the nutrients to consumers and eventually decomposers.

7. Cycles in the Biosphere
The cycling of nutrients in the biosphere involves both matter and living organisms and physical processes found in the environment.
The exchange of matter through the biosphere is called the biogeochemical cycle.

8. The Water Cycle Organisms cannot live without water.
Water is constantly evaporating into the atmosphere from bodies of water, soil, and organisms.
Water in the atmosphere is called water vapor, which rises and begins to cool in the atmosphere.
Clouds form when the cooling water vapor condenses into droplets around dust particles in the atmosphere.

9. The Water Cycle
Water falls from the clouds as precipitation (rain, snow, sleet, or hail) transferring water to the Earth’s surface.
Groundwater and runoff from land surfaces flow into streams, rivers, lakes, and oceans, where the water is evaporated.
Approximately 90% of water vapor evaporates from oceans, lakes, and rivers.
10% evaporates from the surface of plants through transpiration.

11. The Water Cycle All living organisms rely on freshwater.
Freshwater constitutes about only 3% of all water on earth.
69% of all freshwater is found in ice caps and glaciers, which is unavailable for use by living organisms.

12. The Carbon and Oxygen Cycles
All life on Earth is based on carbon molecules.
Carbon forms the framework for proteins, carbohydrates, fats (lipids), and can be found in nucleic acids.
Oxygen is another element that is important to many life processes.
Together, carbon and oxygen make up molecules essential for life, including carbon dioxide and simple sugars.

13. The Carbon and Oxygen Cycles
During photosynthesis, green plants and algae convert carbon dioxide and water into carbohydrates and release oxygen back into the air.
The carbohydrates are used as source of energy for all organisms in the food web.
Carbon dioxide is recycled when autotrophs and heterotrophs release it back into the air during cellular respiration.

14. The Carbon and Oxygen Cycles
Carbon enters a long term cycle when organic matter is buried underground and converted to peat, coal, oil, or gas deposits.
Carbon is released in the form of carbon dioxide when these fossil fuels are burned.

15. The Carbon and Oxygen Cycles
Carbon and oxygen can also enter a long term cycle in the form of calcium carbonate.
Calcium carbonate is found in the shells of plankton and animals such as coral, clams, and oysters.
Carbon and oxygen remain trapped in these deposits until weathering and erosion release these elements to the short-term cycle.

17. The Nitrogen Cycle
The largest concentration of nitrogen is found in the atmosphere.
Plants and animals cannot use this nitrogen directly.
Nitrogen gas is captured from the air by species of bacteria that live in water, soil, or grow on the roots of some plants.

18. The Nitrogen Cycle
The process of capture and conversion of nitrogen into a form that is useable by plants is called nitrogen fixation.
Nitrogen can also be fixed during an electrical storm (by the lightning).
Nitrogen enters the food web when plants absorb nitrogen compounds from the soil and convert it into proteins.

19. The Nitrogen Cycle
Consumers get the nitrogen by eating plants or animals that have the nitrogen.
They reuse the nitrogen to form their own proteins.
Nitrogen in the food web is dependent upon how much can be fixed, therefore limiting the growth of producers.

20. The Nitrogen Cycle
Nitrogen is returned to the soil when animals urinate or die.
In a process called denitrification, some of the bacteria convert fixed nitrogen compounds back into nitrogen gas, which returns to the atmosphere.

22. The Phosphorous Cycle
Phosphorous is an element that is essential for the growth and development of organisms.
2 cycles: short-term and long term
In the short term cycle, phosphorous is cycled from the soil to producers then to consumers.
When organisms die, decomposers will return the phosphorous to the soil.

23. The Phosphorous Cycle
Phosphorous moves from the short term cycle to the long term cycle through precipitation and sedimentation to form rocks.
In the long term cycle, weathering or erosion of rocks that contain phosphorous slowly adds phosphorous to the soil.
Phosphorous is a factor that limits the growth of producers.

24. The Phosphorous Cycle