For more information about the understandings, essential questions, and alignment of this lesson to National Health Education Standards, State Standards, please visit our website, www.roadoflife.org



In order to survive humans need water, food and shelter. These three basic elements provide a foundation for humans to sustain life. Since the earth is composed of 70% water, it has been argued that water is the most important of these elements. Without clean water to drink, a person cannot live longer than a couple of days. In comparison, a person can live for weeks without food and shelter. One major component of a functioning society in ancient times involved clean drinking water, and today some third world countries still are not afforded this necessity.


Invite students to brainstorm ideas about the composition of the earth and the human body. After students have discussed the different components of the earth and the human body, explain to the students that the body and the earth are mostly made of water.

Human Body: More than half of the human body consists of water.

Earth: 70% of the earth is made of water.

Note to Teacher: Students may find it difficult to understand that the human body is made mostly of water when humans have an epithelial (skin) outer covering. In order to illustrate this point you may choose to do the Fruit Demonstration Activity.

Ask students to identify the purpose of water. What do humans use water for and how does water benefit the human race? Humans need water to drink, and to clean their bodies as well as other objects. Water also serves as a tool to prevent dental cavities through fluoridation.

Learning Activity: Research Project

Divide the class into groups of five students. Each group is responsible for researching water as it relates to different cultures around the world and giving a brief presentation about their results. The students are allowed to use the library and the internet to gain useful information.

Within the group, have each student volunteer to complete a portion of the research project and presentation. The five duties include examining the culture, identifying the problem, discovering the impact of the water-health issue, recognizing the solution, and the references used for research.

1. Culture: background and history including population, location or region of the world, and land composition

2. Problem: water related health issue that affects the population

3. Impact: How does this health issue affect humans?

4. Solution: explain how technology from different area (transportation, communication, nutrition, healthcare, agriculture, entertainment, and manufacturing) could solve the problem

5. References: books, articles, and websites used in research and other suggestions to learn more about the topic

If students are having trouble identifying topics to research some, some examples include the lack of fluoridation in third world countries, clean drinking water, sewer systems, and polluted lakes, rivers, and streams.

Fruit Demonstration

•This demonstration further explains the somewhat abstract concept that the human body is composed mainly of water, despite the fact that it is not seen due to our skin.



•Sharp knife

Directions and Debrief:

  1. (Cut open the fruit) Inform students that this grapefruit is like our bodies. On the outside, it is firm, solid, and can sit up on its own, but on the inside it is filled with water.
  2. Slice the fruit and give a piece to each student, allowing them to feel the outside and the inside of the fruit. Discuss the structure of the fruit and how the peel or the outer covering of the fruit aids in protecting the more vulnerable parts inside of the fruit. Discuss how this concept relates to the human body and how the skin helps to protect the inner parts of the body.
  3. Conclude by explaining to the students that the water that gives us shape and form is inside our body. If possible, dissect the grapefruit and extract the tiny bits of the grapefruit that actually hold the water and juices. These tiny pieces of the grapefruit illustrate how the water in the human body is encapsulated in the organs. In fact, that is the reason why we as humans are not like huge puddles or all wet and soggy.

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