The Water Cycle

My AP Biology ThoughtsEpisode #39

Welcome to My AP Biology Thoughts podcast, my name is Corrinna and I am your host for episode 39 called Unit 1 macromolecules: the water cycle. Today we will be discussing the water cycle.

Segment #1: Intro to the Water Cycle

The water cycle is one of a few biogeochemical cycles which also include the nitrogen and carbon cycles. Each cycle is unique but plays an important role in sustaining life. In the water cycle, water vapor is made when the sun causes evaporation in bodies of water such as the ocean by heating the water into vapor. Snow can also be vaporized in the process called sublimation. This vapor is moved by the winds to other parts of the world. When it reaches air that is cooler, it condenses into precipitation (which is seen as rain or snow). It then returns to the ocean or the land. If it returns to the land, it eventually travels tco plants or other bodies of water that will eventually get it back to the ocean. If it is absorbed by plants, the water is used for photosynthesis or can be lost in transpiration.

Segment #2: Digging Deeper into the Water Cycle

Since the water cycle is a cycle, it is difficult to find examples of it. However, we can provide examples for the different steps of the cycle. An example of evaporation would be when the sun warms water in a pond enough to change its state from liquid to gas. This can happen in any body of water, such as oceans, as previously mentioned, lakes, or rivers. After evaporation, the water molecules are in the sky. Precipitation takes many forms, but its most recognizable form is rain. Precipitation is any type of water that falls from the sky, so It can also be in the form of snow, hail, freezing rain, or sleet. The last step of the water cycle is collection, which is when water goes back to its original source. One example of this is if it rains on a lake that leads to an ocean. This would carry the water back to the ocean, its original source, to be evaporated as the cycle continues. The water cycle is constant, which means that as some water particles are being evaporated, others are in the form of precipitation, and still others are being collected.

Segment #3: Making larger Connections with the Water Cycle

The water cycle helps to regulate temperatures in both organisms and on earth. One example of this is when oceans heat up more slowly than air since the water absorbs the light energy. Hydrogen bonds make this possible because it takes more energy to break the hydrogen in water to convert the liquid into a gas than to heat up gas that is already a gas. This property keeps the temperature on the earth more stable. Evaporation also helps animals and plants too cool down. Evaporation carries heat energy away from the organism which provides cooling. Additionally, water’s expansion when it freezes is also caused by hydrogen bonds. When water freezes the hydrogen bonds move outward to 90 degree angles which causes the water molecules to be further apart. This also makes it less dense which is why ice floats on water. Because of this, life is still able to survive under ice in the ocean since the ice is only on the top.

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