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Destination: Galapagos Islands Cyber Field Trip
ON THE ISLANDS

Cyber Field Trip Student Experiment
Water World: The Blue Planet


Introduction
Vocabulary
Materials
Safety Precautions
Procedures
     Testing for Salinity
     Testing for Dissolved Oxygen
     Measuring Alkalinity and Acidity Levels
     Effects of Salinity on Aquatic Organisms
Critical Thinking Questions




INTRODUCTION

Since astronauts first traveled in space, they have referred to Earth as the "Blue Planet." Water, which makes our planet appear blue from space, covers approximately 74% of Earth's surface. Interconnecting oceans compose about 71% of Earth's surface, or 97% of the world's water, while fresh water composes only 3% of the planet's water supply. Without water, life as we know it would not exist on Earth -- even the human body is 65% water! As an archipelago in the Pacific Ocean, 600 miles from the nearest mainland, the quality of the Galapagos waters is integral to the survival of the islands' wildlife.



VOCABULARY

Use the glossary to define any unfamiliar terms:

MATERIALS

  • Salinity test kit
  • Dissolved oxygen test kit
  • pH paper, pH meter or a pH test kit
  • Living specimens of Artemia, Daphnia, Elodea and Spirogyra
  • Microscopes, slides and coverslips
  • NaCl solutions: 1% (1g NaCl dissolved in 100 ml of distilled water), 3% (3g in 100 ml water) and 5% (5g in 100 ml water)
  • Dropping pipettes


SAFETY PRECAUTIONS

  • Wear safety goggles
  • Tie long hair back
  • Use extreme care when working with open flames, hot liquids, hot plates, chemicals, living materials, glassware and electrical cords/outlets
  • Follow all laboratory and field safety regulations!


PROCEDURES

Testing for Salinity

  1. Prepare 400 milliliters of NaCl and water in a saturated solution. Your teacher will instruct you in this phase of the experiment. Remember: to saturate, you must add NaCl until no more will dissolve and settling occurs.

  2. Divide the solution into four 100 ml beakers.

  3. Measure the temperature of your room.

  4. Place three beakers on hot plates (a hot plate is best for maintenance of temperature, but Bunsen burners will work as long as you carefully regulate the flame). Set the temperatures at 10°C (50°F), 20°C (68°F) and 30°C (86°F), respectively. (The fourth beaker should remain at room temperature.)

  5. Following the instructions on your salinity test kit, test the level of salinity in each beaker. Note: Salinity tests must be done quickly to maintain temperature balances.

  6. Record all four salinity values in sequential order (from coolest to warmest) in the Water Salinity Data Chart. Click the "Add My Data" button to add your data and see your graphed results.
Testing for Dissolved Oxygen

  1. Obtain water samples from three different sources (such as a water fountain, bathroom sink, hose, pool, pond, lake, etc.).

  2. Using your dissolved oxygen test kit, measure and record dissolved oxygen for each sample.

  3. Use the color comparator (or comparable tool in your test kit) to determine the parts per million of dissolved oxygen in your water samples.

  4. Record the dissolved oxygen value for your three samples in the Dissolved Oxygen Water Analysis Data Chart. Click the "Add My Data" button to sequentially add your data, and to see your graphed results. Data from the Galapagos will be added Monday through Wednesday.
Measuring Alkalinity and Acidity Levels

  1. Obtain water samples from three different sources (such as a water fountain, bathroom sink, hose, pool, pond, lake, etc.).

  2. Using a pH meter, pH paper or a pH test kit, test each sample for pH level.

  3. Following the directions on your test kit, determine the pH values for each of the three samples.

  4. Record the pH values of your three samples in the pH Water Analysis Data Chart. Click the "Add My Data" button to sequentially add your data, and to see your graphed results. Data from the Galapagos will be added Monday through Wednesday.

Effects of Salinity on Aquatic Organisms

  1. Make a wet mount using the Elodea and Spirogyra. With your microscope on low power, locate each and identify at least one cell that can be seen clearly.

  2. Diagram the cell and note the position of cell contents.

  3. Add a drop of 5% NaCl to the slides. Note the condition of the contents of the cells and diagram each. What changes do you observe? What is your hypothesis on the cell condition after NaCl was added?

  4. Now make two slides of Artemia and Daphnia, using distilled water for the wet mount. Observe and diagram each.

  5. Add the 1% NaCl solution. Observe and record any changes in the specimens or their locomotion.

  6. Repeat with 3% NaCl and then 5% NaCl. Observe any changes in behavior, response and locomotion. Record your observations.

  7. Respond to the following questions:
  • Did both species behave the same in different solutions?
  • Which seemed to have the greatest range of tolerance to salinity increases?
  • Which had the smallest range of tolerance?
  • How would you characterize the difference in response to salinity increases that each animal had?


CRITICAL THINKING QUESTIONS

  • Based on your findings, explain the relationship between temperature and salinity.

  • What is the relationship between living organisms and abiotic factors (pH, salinity and dissolved oxygen)?

  • How did your values for abiotic factors compare to those of the Galapagos Islands?

  • How can you account for any differences you noticed between your sample and Sherri's?

  • List two ways that humans affect abiotic factors within ecosystems.




 

Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.