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By the end of this section, you will be able to:
  • Discuss the biogeochemical cycles of water, carbon, nitrogen, phosphorus, and sulfur
  • Explain how human activities have impacted these cycles and the resulting potential consequences for Earth

Energy flows directionally through ecosystems, entering as sunlight (or inorganic molecules for chemoautotrophs) and leaving as heat during the transfers between trophic levels. Rather than flowing through an ecosystem, the matter that makes up living organisms is conserved and recycled. The six most common elements associated with organic molecules—carbon, nitrogen, hydrogen, oxygen, phosphorus, and sulfur—take a variety of chemical forms and may exist for long periods in the atmosphere, on land, in water, or beneath Earth’s surface. Geologic processes, such as weathering, erosion, water drainage, and the subduction of the continental plates, all play a role in the cycling of elements on Earth. Because geology and chemistry have major roles in the study of this process, the recycling of inorganic matter between living organisms and their nonliving environment is called a biogeochemical cycle    .

Water, which contains hydrogen and oxygen, is essential to all living processes. The hydrosphere    is the area of Earth where water movement and storage occurs: as liquid water on the surface (rivers, lakes, oceans) and beneath the surface (groundwater) or ice, (polar ice caps and glaciers), and as water vapor in the atmosphere. Carbon is found in all organic macromolecules and is an important constituent of fossil fuels. Nitrogen is a major component of our nucleic acids and proteins and is critical to human agriculture. Phosphorus, a major component of nucleic acids, is one of the main ingredients (along with nitrogen) in artificial fertilizers used in agriculture, which has environmental impacts on our surface water. Sulfur, critical to the three-dimensional folding of proteins (as in disulfide binding), is released into the atmosphere by the burning of fossil fuels.

The cycling of these elements is interconnected. For example, the movement of water is critical for the leaching of nitrogen and phosphate into rivers, lakes, and oceans. The ocean is also a major reservoir for carbon. Thus, mineral nutrients are cycled, either rapidly or slowly, through the entire biosphere between the biotic and abiotic world and from one living organism to another.

Concept in action

Head to this website to learn more about biogeochemical cycles.

The water cycle

Water is essential for all living processes. The human body is more than one-half water and human cells are more than 70 percent water. Thus, most land animals need a supply of fresh water to survive. Of the stores of water on Earth, 97.5 percent is salt water ( [link] ). Of the remaining water, 99 percent is locked as underground water or ice. Thus, less than one percent of fresh water is present in lakes and rivers. Many living things are dependent on this small amount of surface fresh water supply, a lack of which can have important effects on ecosystem dynamics. Humans, of course, have developed technologies to increase water availability, such as digging wells to harvest groundwater, storing rainwater, and using desalination to obtain drinkable water from the ocean. Although this pursuit of drinkable water has been ongoing throughout human history, the supply of fresh water continues to be a major issue in modern times.

Questions & Answers

why do humans enhale oxygen and exhale carbondioxide?
Maryam Reply
why do humans enhale oxygen and exhale carbondioxide? For the purpose of breaking down the food
dil
what is allele
uzoka Reply
process of protein synthesis
SANTOSH Reply
what is cell
Zulf Reply
what is cytoplasm
uzoka Reply
cytoplasm is fluid of cell.
Deepak
how many major types of Cloning
Saeed Reply
two
amir
two
Zulf
comparative anatomy of gymnosperms?
Meenakshi Reply
anatomy of gymnosperms
Meenakshi
how genes are regulated
Ainjue Reply
what is storage of glycogen
Student Reply
glycogen is a protein content
Najeem
how many times breathing a day normally does a person have
Vernalyn Reply
100
Aadil
on average 18000 times a day when resting.
gagan
the -10 and -35 regions of prokaryotic promoters are called consensus sequences because
Michelle Reply
Oogenesis is the process that produces sperm
Kelly Reply
no... thats is egg production
uzoka
that is egg production
uzoka
what is the nephrons
Kalim Reply
what is the DNA and how to work
Kalim
nephrons are functional units of kidney.
gagan
a picture of a diktiosoom
Zandri Reply
How so you understand Darwin's theory when this is not what you believe?
Jessica Reply

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Source:  OpenStax, Concepts of biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11487/1.9
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