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Origins: How Life Began

Classroom Activities

What is It?


To learn about what characteristics define an organism.

Part I

Materials for teacher
  • dropper bottle with at least 100 ml of water dyed with green food coloring
  • towels, cloths, or sponges for clean-up
Materials for students
  • 1 cm square of wax paper (15 cm by 15 cm)
  • 2 toothpicks
Materials for each team
  • copy of the "Life's Characteristics" student handout (PDF or HTML)
  • copy of the "What Is Life?" student handout (PDF or HTML)

Part II

Materials for each team
  • copy of the "What Is It?" student handout (PDF or HTML)
  • hand lens
  • 1 packet of Mystery Matter (regular baker's yeast repackaged in a plastic bag to conceal its identity)
  • 1 tablespoon sugar
  • 1/2 cup hot tap water (roughly 43 degrees C)
  • 4 clear plastic bottles (4 oz.-16 oz.) with labels removed
  • 4 balloons (15-inch required)
  • measuring spoons (1/4 teaspoon, 1/2 teaspoon, 1 teaspoon)
  • measuring cup (1/2 cup)
  • funnel
  • glucose strips


Part I

  1. Life is ubiquitous on Earth and appears in a diversity of forms. But what characteristics do organisms have? What makes them alive? This activity explores that question.

  2. In the first part of the activity, announce to students that you have just received a supply of mysterious matter that you would like them to examine for you. Tell them that scientists are trying to determine if these are organisms and that you would like to know what students think.

  3. Review with students the meaning of "organism" (living thing). For the purposes of this activity, a living thing is something that is currently alive or has once been alive, like a plant. A nonliving thing is something that is not alive and has never lived, like a rock.

  4. Distribute the wax paper and toothpicks to each student. Create five to ten mounds of water (i.e., mysterious matter) on each student's sheet of wax paper by squeezing drops from a supply bottle. Make a variety of sizes—the smallest mound being one drop and the biggest five drops. Do not reveal that the matter is just colored water.

  5. Ask students to investigate the droplets with their toothpicks. Have them list characteristics and behaviors they think could be found in organisms and those that seem non-lifelike. (See Activity Answer for some examples of mysterious matter characteristics.)

  6. Create a class list of lifelike and non-lifelike characteristics.

  7. Organize students into teams. Distribute the "Life's Characteristics" student handout to each team. Have teams study the forest scene for organisms and further develop their list of characteristics of living things. As a class, expand the list of life characteristics begun earlier. You may need to help students understand that while some things (such as crystals, icicles, or fire) may seem to be alive according to a very simple set of characteristics (it moves, it reproduces), that life comprises a far more complex set of traits.

  8. Distribute the "What Is Life?" handout. After having students read the handout, discuss how the mystery matter they studied and each of the organisms illustrated on the "Life's Characteristics" handout manifest the characteristics listed.

  9. Now tell students you are going to give them a different type of mysterious matter that you also need categorized as living or nonliving. Distribute the Mystery Matter (yeast) and hand lenses to each team.

  10. Ask students to examine a small sample of the matter with the hand lenses and record their observations.

  11. Have students apply what they currently know about the characteristics of life to the matter to determine whether the Mystery Matter is alive. (As the yeast is dormant, it is likely that many students will say it is not an organism, that it is a dead organism, or that they do not know without further testing.) Ask students what other ways they can determine whether the matter is an organism. Some students might mention that organisms need food and water. Follow up by telling students they will test the matter to help determine if it is alive by providing it with water and an energy source and seeing what occurs.

Part II

  1. To test the idea that yeast will grow and reproduce under the right conditions, have students conduct the experiment as listed on their "What Is It?" student handout.Make sure you refer to the yeast as "Mystery Matter"until you reveal its identity in Step 5 below.

  2. Distribute Part II materials listed to each team. (Note that you must use 15-inch balloons because the carbon dioxide produced by the yeast will quickly f ill smaller balloons. Once the gas makes several balloons equally taut, it becomes impossible to tell which bottle produced the most gas. The 15-inch balloons have enough capacity so that only the most active yeast will completely inflate the balloons.) Review the activity procedure with students as outlined on their handouts. Have students conduct the activity, observing the bottles once they have prepared them and again after 24 hours. (The hot water, which is necessary to stimulate yeast growth, may initially inflate the balloons. This should dissipate when the water cools and further inflation will be caused by yeast respiration.)

  3. After two days, have the class retest the two bottles using the glucose strips. Discuss students'observations. What did they see to indicate that the matter might be alive? (Bottles 2-4 had foam and inflated balloons, which could indicate respiration. The sugar depletion could signal energy uptake.) Based on what they have learned, what are students' final conclusions about whether the matter is alive?

  4. Ask students if, based on the results of their experiment, there is anything else they would add to their list of life's characteristics. (They might mention that signs of life or past life are not always easy to recognize and that dormant and/or slow-growing organisms may appear to be nonliving unless observed under the right conditions or over long periods of time.) Many of the characteristics of life do not lend themselves to quick, one-time tests. Instead, they require multiple observations over a period of time. Earth's organisms exhibit many different ways to survive stressful conditions, such as periods with no food or water. Ask students what other tests they might conduct to determine whether the Mystery Matter is an organism.

  5. Reveal that the Mystery Matter is yeast. Remind students that yeast is a kind of organism. Different members of this large group live in nearly every environment on Earth, including in and on humans.

  6. As an extension, have students research definitions of life and try to establish a definition of life.

Related Activities

Looking for Life in the School
Test different locations in school for the existence of bacteria.

Microbial Survival!
Expose bacteria to extreme environments to see how they survive.

Discover how life survives in extreme environments and follow scientists who retrieve a stromatalite from the Saharan Desert in this American Museum of Natural History site that offers articles and student materials related to NOVA's "How Life Began" program.

Activity Answer

Part I
Mystery Matter Organism Characteristics

Lifelike Behaviors

Non-lifelike Behaviors

  • follow a toothpick
  • eat by consuming one another
  • grow by merging together
  • reproduce by breaking into little potential organisms
  • have a firm, cell-like structure
  • are green, like plants
  • are shaped like cells
  • have a tough outer skin/membrane
  • move easily across the surface
  • contain water
  • do not respond to the environment
  • lack internal structures
  • cannot move on their own
  • can become any size with no apparent consequence beyond size change
  • behave differently when not on a wax-paper surface (e.g., on the table)

Part II
Sample Results




Balloon Inflation



turbid after agitation



Bottle 1: none
B2-4: present

30 minutes

turbid after agitation

Bottle 1: little/none
B2-4: froth

Bottle 1: none
B2-4: little/none

B1: none
B2-4: present

60 minutes

solids settle out

B1: little/none
B2-4: froth

B1: none
B2: slight
B3: medium
B4: substantial

B1: none
B2: depleted
B3-4: present

24 hours

solids settle out

B1: little/none
B2-4: froth

B1: none
B2: slight
B3: medium
B4: substantial

B1-4: none

Links and Books

Web Sites

NOVA Web Site—Origins
In this companion Web site to the program, find out how life could have started and why water is needed for life; read about the latest discoveries in origins research; use raw data to assemble the famous Eagle Nebula image; insert your own values into the Drake Equation; decode cosmic spectra; and more.

Astrobiology Education Poster: What Is Life?
Includes three poster activities that address what life is, where it is found, and how to look for it.

Links to articles about extremophiles that thrive in cold, heat, metallic, methane-rich, radioactive, and salty environments.

Life on Earth ...and elsewhere?
Links to a 60-page PDF that explores what life is, what it needs to live, what makes a world habitable, what extremes life can tolerate, and whether there might be life on other worlds.


Breidahl, Harry. Extremophiles: Life in Extreme Environments. Broomall, PA: Chelsea House Publishers,2001.
Details extremophiles, their environments, and the technology used to research them. Presentation caters to younger audiences.

Raymo, Chet. Biography of a Planet: Geology, Astronomy, and the Evolution of Life on Earth. Englewood Cliffs, NJ: Prentice-Hall, Inc.,1984.
Takes the reader on an illustrated and comprehensive journey across 4 billion years of life on Earth. Includes informational graphics.


The "The Hunt for Micrometeorites" activity aligns with the following National Science Education Standards:

Grades 5-8

Life Science

Science Standard C:
Life Science

Structure and function in living systems:

  • Cells carry on the many functions needed to sustain life. They grow and divide, thereby producing more cells. This requires that they take in nutrients, which they use to provide energy for the work that cells do and to make the materials that a cell or an organism needs.

Reproduction and heredity:

  • Reproduction is a characteristic of all living systems; because no individual organism lives forever, reproduction is essential to the continuation of every species. Some organisms reproduce asexually. Other organisms reproduce sexually.

Regulation and behavior:

  • All organisms must be able to obtain and use resources, grow, reproduce, and maintain stable internal conditions while living in a constantly changing external environment.

Diversity and adaptations of organisms:

  • Millions of species of animals, plants, and microorganisms are alive today. Although different species might look dissimilar, the unity among organisms becomes apparent from an analysis of internal structures, the similarity of their chemical processes, and the evidence of common ancestry.

Grades 9-12

Life Science

Science Standard C:
Life Science

Matter, energy, and organization in living systems:

  • All matter tends toward more disorganized states. Living systems require a continuous input of energy to maintain their chemical and physical organizations. With death, the cessation of energy input, living systems rapidly disintegrate.

  • The complexity and organization of organisms accommodates the need for obtaining, transforming, transporting, releasing, and eliminating the matter and energy used to sustain the organism.

Classroom Activity Author

Chris Randall is a senior curriculum developer and project director at TERC in Cambridge, Massachusetts. He has taught for 10 years. At TERC, he has developed Web sites, curriculum materials for K-14 classrooms, textbooks, teacher training programs, and museum exhibits.

Teacher's Guide
Origins: How Life Began

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