Online College Courses for Credit

Biogeochemical Cycles

Biogeochemical Cycles

Author: Emma Scanlon



Objective:  Describe the events which occur during the major biogeochemical cycles in which matter is recycled.



Biogeochemical Cycles:

1.) Water Cycle

a. What are some biotic and abiotic reservoirs of water?

b. How do humans depend on the water cycle?

c. How do humans impact the water cycle?

2.) Carbon Cycle

What is the role of photosynthesis and cell respiration?

What are some abiotic and biotic reservoirs of carbon?

How do humans impact the carbon cycle? 

3.) Phosphorus Cycle

a. How is phosphorus used in living things?

b. What are some biotic and abiotic reservoirs of phosphorus?

4.) Nitrogen Cycle

 a. What is "fixed" nitrogen?  What is nitrogen fixation and denitrification?  What is the role of nitrogen fixing bacteria?

b. What are some biotic and abiotic reservoirs of nitrogen?

c. How is nitrogen used in living things?


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Key Vocabulary and Background Information for Biogeochemical Cycles

biogeochemical cycle shows us how a certain element or molecule moves throughout the biotic and abiotic parts of an ecosystem.  

The four biogeochemical cycles we will study are: the water cycle, the carbon cycle, the nitrogen cycle and the phosphorus cycle.

Key Vocab:

Abiotic:  Nonliving (e.g. rocks, clouds, and soil are all abiotic factors of an ecosystem)

Biotic: Living: (e.g. trees, humans, animals, bacteria and fungi are all biotic factors of an ecosystem).

Reservoir:  A place where the element or molecule is stored for a long period of time (e.g. in the water cycle, clouds are consider reservoirs of water).


Big Idea:

Matter cannot be created or destroyed, it can only change form.  This is true for living things as well.  Every single atom that makes up your body came from something else (your food and the air you breathed).  Before it was an atom that made up your food (let's say a hamburger) , it was an atom that made up something else (the grass that the cow ate).  When we study biogeochemical cycles, we are trying to figure out where the atoms that make up a certain thing (a rock, an organism, a cloud, etc) came from and where they will go.


The Water Cycle

Source: Discovery Education

The Carbon Cycle

Source: Discovery Education

The Nitrogen Cycle

Source: Discovery Education

The Phosphorus Cycle

Source: Discovery Education

Biogeochemical Cycles

This slideshow contains diagrams of each of the four cycles as well as descriptions and definitions of key vocabulary.