Unit A

Module 1 ~ Lesson 4


  Nutrient cycling


The dark green lines represent the movement of nutrients and the dashed lines represent the movement of energy. Nutrients are not depleted, whereas energy is depleted, so a constant supply of solar radiation is required to sustain the biosphere.  Image Credit: Horne, E. and Bear, R.A. Biogeochemical cycles. CC BY 4.0

The biosphere is a closed system in relation to the matter


The biosphere is an open system in relation to energy


Since nutrients are not replenished in the biosphere, they are finite and cycle through the biosphere. The biogeochemical cycles are the pathways through which all nutrients cycle.

Nutrients cycle through both slow and rapid cycling. When nutrients move relatively quickly between organisms or abiotic components, this is called rapid cycling. Photosynthesis and cellular respiration are rapid cycles. When nutrients become unavailable for long periods of time (e.g., deep in the ocean or deposited in rocks) they are slow cycling.   


Carbon


Carbon composes almost 20% of the human body. It is also important in carbohydrates, fat, proteins, hormones, and vitamins.  Life on Earth is carbon-based since carbon provides the framework to all molecules important in biological systems.

Oxygen


Oxygen is the most common element found in the human body. It is an important building block in carbohydrates, fat, proteins, hormones, and vitamins.

Phosphorus, Nitrogen and Sulfur


Phosphorus, nitrogen, and sulfur are found in proteins and vitamins. Nitrogen is also an important building block in DNA.

 Read 

Read "Biogeochemical Cycles" on pages 42 to 52 in your textbook.