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Water and Nitrogen Cycles

Water and Nitrogen Cycles

Author: Sophia Tutorial

Recognize key aspects of the nitrogen cycle.

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what's covered
This tutorial will cover the topic of water and nitrogen cycles. We will explore how water cycles between the ocean, atmosphere, and land, as well as the movement of nitrogen through living things and the atmosphere. We will also discuss the human impact on the nitrogen cycle.

Our discussion breaks down as follows:

  1. Water Cycle
  2. Nitrogen Cycle
  3. Human Impact on Nitrogen Cycle

1. Water Cycle

The water cycle, illustrated in the diagram below, is comprised of the cycling of water between three areas: ocean, atmosphere, and land.

Water Cycle

The sun causes evaporation from things like rivers, lakes, oceans, swamps, mud puddles, and ditches, adding water to the atmosphere. Water can also enter the atmosphere through transpiration, which is the release of water vapor from plants.

did you know
The evaporation process naturally cleanses water.

Once water is in the atmosphere, it condenses and creates clouds in what is called condensation. Once the condensation has reached a certain point, water will fall as precipitation. This water will join lakes and streams, which eventually return to the ocean, completing the cycle. Some precipitation will fall as snow and become compacted into a glacier, which takes the water out of the cycle until the glacier eventually melts.

big idea
The water cycle recycles water, providing an ongoing supply of fresh water for life on land.

2. Nitrogen Cycle

The nitrogen cycle, illustrated below, is the movement of nitrogen through living things and the atmosphere. Nitrogen is a gas that is found in the atmosphere, and it is also an important biological compound that is found in DNA and amino acids that make up proteins.

Nitrogen Cycle

Atmospheric nitrogen is not usable by life forms, so it needs to be fixed in the form that is usable. Nitrogen fixation is a process where atmospheric nitrogen, which makes up 78% of our atmosphere's composition, is converted into usable forms by microorganisms like bacteria. This type of bacteria lives on the roots of plants, such as legumes like clover, alfalfa, soybeans, and peanuts.

Animals get this nitrogen by consuming plants, and then building DNA, proteins, and muscle. In turn, they pass it on in the cycle through their urine, or when they die.

Microorganisms then break down the nitrogen in the body into usable forms again.

3. Human Impact on Nitrogen Cycle

It is important to note that humans contribute to extra nitrogen in the cycle through the runoff from fertilizer use and animal waste. This extra nitrogen can cause harm to humans, animals, and various aquatic species. The excess nitrogen is primarily a problem in water systems where it can cause large algae blooms, which disrupt these aquatic ecosystems.

Most of the nitrogen used for fertilizer is created by an industrial chemical process, which uses natural gas and air to create usable nitrogen compounds. Agricultural nitrogen can be considered a pollutant.

Today we learned about the water cycle, which cycles between the oceans, atmosphere, and land, providing an ongoing supply of fresh water for life on land. We also learned about the nitrogen cycle, which cycles nitrogen — a gas found in the atmosphere — through living things and the atmosphere. We also learned about the human impact on the nitrogen cycle.

Source: Adapted from Sophia instructor Jensen Morgan, WATER CYCLE CC HTTP://BIT.LY/1XC3O4X NITROGEN CYCLE CC HTTP://BIT.LY/19IKBOC