Photosynthesis and Respiration (page 2)

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Author: Janice VanCleave

Try New Approaches

  1. Does the amount of light affect the results? Repeat the experiment two times, first placing the jars closer to the light source and then placing them farther away.
  2. Does the source of light affect the results? Repeat the original experiment using various light sources, such as sunlight, incandescent bulbs, fluorescent lighting, and plant grow-lights. Compare the results.
  3. How do different colors of light affect the results? Repeat the original experiment several times, and with each test cover the jars with a different color of cellophane.

Design Your Own Experiment

CAUTION: Perform the exercise section only if your health permits such an activity.

Photosynthesis and Respiration

  1. Respiration in animals and plants is generally the same. Gases are exchanged between the atmosphere and the bodies of the organisms. Check for the presence of carbon dioxide in your exhaled breath by breathing through a drinking straw into a small glass soda bottle half filled with a solution of brom thymol blue indicator. Count the number of exhaled breaths needed to produce a yellow color. Repeat the experiment two times, first after sitting and resting for five minutes, and then after exercise (such as climbing stairs) for one minute. Prepare a bar graph to compare the results.
  2. Seeds do not need light to germinate. Find out whether germinating seeds release carbon dioxide and thus produce energy by respiration. Fill a small glass soda bottle one-third full with pinto beans and pour water over the beans. Let the beans soak overnight and then pour off the water. Insert the end of a flexible drinking straw into the mouth of the bottle. Use modeling clay to secure the straw and close off the bottle. Insert the free end of the straw into a glass of brom thymol blue indicator (see Figure 16.2). Observe the color of the solution to determine whether carbon dioxide is present.
  3. Aerobic means "in the presence of oxygen." Anaerobic means without the presence of oxygen. In aerobic respiration, the products of respiration are glucose, carbon dioxide, and energy. In anaerobic respiration, the products are alcohol, carbon dioxide, and energy. Fermentation is anaerobic respiration. Use yeast to demonstrate fermentation and brom thymol blue indicator to test for the presence of carbon dioxide. Fill a glass soda bottle half full with warm water. Add 1/4 ounce (7 g) of dry yeast and 3 tablespoons (45 ml) of sugar. Insert the end of a flexible drinking straw into the mouth of the bottle above the liquid level. Use modeling clay to seal the mouth of the bottle around the straw. Insert the free end of the straw into a glass filled with brom thymol blue.
  4. Plants live for long periods of time in terrariums. This ability to live in closed containers without outside supplies is due to the fact that plants carryon two balanced energy—producing processes-photosynthesis and respiration. Fmd out from a plant nursery professional what is needed to construct a terrarium and build one. Use the terrarium as part of your display if a plastic container is used (for safety, glass containers are usually not allowed in most science fairs). Next to the terrarium, display the equations for the two energy reactions to show that the products of one reaction are the raw materials needed for the second reaction.

Get the Facts

  1. Gases enter and leave plants through openings in the leaves called stomata and through openings in the stem called lenticels. You breathe in and exhale out through your nose and mouth, but earthworms absorb and release gases through their moist skin. Find out how other organisms exchange gases in order for respiration to occur.
  2. Respiration is a cellular activity. Where inside the cell does this reaction occur? How does the cell store and release the energy produced by respiration?
  3. Find out more about fermentation. What is the purpose of yeast? How can winemakers assure that alcohol and not acid is the product of the fermentation of their grapes?
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