Phosphorus Cycle: Steps, Definition & Diagram

Lesson Transcript
Instructor: Kelly Robson

Kelly has taught High School Science and Applied Communications. She holds an Education Specialist Degree in Ed. Leadership.

The phosphorus cycle is vital to life. Define the phosphorus cycle, understand the importance of the cycle to all life on Earth, examine the diagram of the steps in the cycle, and understand that the phosphorus cycle is not a complete cycle. Updated: 09/07/2021

The Phosphorus Cycle - Definition

Phosphorus is an essential element to all life. It is an important part of the ATP molecule that stores and gives every cell its energy. It is also found in DNA and RNA, which tell the cells how to look and act. Needless to say, phosphorus is needed for every living organism to grow and function. The phosphorus cycle is the process in which phosphorus travels from its main source of rocks through ecosystems to living organisms.

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  • 0:01 The Phosphorous Cycle
  • 0:32 Steps of the Phosphorous Cycle
  • 2:35 Lesson Summary
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Steps to the Phosphorus Cycle

The phosphorus cycle begins its journey in the crust of the Earth as phosphorous is found in rocks. Weathering causes it to break free from the rocks and wash away into the ground. At this time, the phosphorus gets mixed in the soil. Land plants are now able to soak up the phosphorus from the ground. Animals obtain the phosphorus by eating the plants.

Sometimes the phosphorus just gets washed up into the water supply. Aquatic plants and other producers are able to obtain phosphorus directly from the water. Animals, too, can get phosphorus from drinking the water.

The phosphorus is returned to the Earth in different ways. Plants and producers that are not eaten will die, and their phosphorus will be broken down when they decay. This will return the phosphorus back to the earth to mix with the soil or water. Then new producers that use the soil or water will be able to use the phosphorus. Humans and other animals return phosphorus through our waste. When our waste gets broken down, the phosphorus goes into the water system.

Even though phosphorus gets passed on from the ground to producer to animal and then returns back to the land or water, the phosphorus cycle is still not a true cycle. In a true cycle, all the phosphorus will continue to circulate through the cycle. However, in the actual phosphorus cycle, some of the phosphorus will get lost. The phosphorus that is returned to the ocean may sink to the bottom and become inaccessible and unusable. The only usable phosphorus will remain at the surface of the water.

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