Living in an Alkaline Environment

Handouts

The following master copies may be downloaded as Word documents or viewed online by scrolling down.

Activity Station 1

  1. Wet your fingers with one of the samples.
  2. Describe how the liquid feels when you rub your fingers together.
  3. Record your observations on the sheet.
  4. Repeat Steps 1-3 with the other liquid.
  5. Measure the pH of each liquid using the provided equipment.
  6. Record your measurements on the sheet.
  7. Clean up.
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Activity Station 2

  1. Place a drop of one of the waters on a piece of wax paper.
  2. Record the drop's shape on your sheet.
  3. Repeat Steps 1 and 2 with the other kind of water.
  4. On a piece of wax paper, mix a drop of cooking oil and a drop of one of the waters.
  5. Record your observations on your sheet.
  6. Repeat Steps 4 and 5, using a drop of the other water.
  7. Clean up.
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Activity Station 3

  1. Measure the specific gravity (density) of each liquid with the provided equipment.

    Egg white is a protein-rich material that can serve as a model for a microbe's cytoplasm. This test shows how Mono Lake water might affect a microbe's cytoplasm.
  2. In a clear container, mix equal amounts of one kind of water and egg white (e.g., a teaspoon of each).
  3. Observe for 2-3 minutes and record the egg white's physical characteristics (color, texture, smell, etc.).

    SAFETY NOTE: DO NOT TASTE!
  4. Repeat Steps 2 & 3 with the other water.
  5. Clean up.
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Activity Station 4

  1. Take a spoonful of water, using the appropriately labeled spoon.
  2. Hold the spoon over the flame until all the water boils away.
  3. On your sheet, describe the residue, if any. (You will test any residues in Step 5, so set the spoon aside for now.)
  4. Repeat Steps 1-3 with the other kind of water.
  5. Add several drops of vinegar to the residue on one of the spoons. On your sheet, describe the effect, if any.
  6. Repeat Step 5 with the other spoon.
  7. Rinse both spoons with clean water and remove all residues.
  8. Clean up.
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Part One Student Worksheet

Visit the activity stations as directed by your teacher. Use the following observation table to record your results and then answer the questions based on knowledge acquired from this experience. You may write the answers on your own sheet of paper or download this page in the form of a Word (Microsoft Word 32kB Apr21 05) document.


Observation Table

Observation Table

Questions
  1. Why might organisms adapted to living in a typical pond, lake, or river experience Mono Lake as an extreme environment?

  2. Could a human survive if all he/she had to drink were Mono Lake water? Why or why not?


  3. How could you tell that the Mono Lake water chemically changed the egg white's proteins?


  4. If Mono Lake water changes proteins and causes cells to shrivel, what kinds of adaptations might help a single-celled microbe survive in Mono Lake?


  5. Soil contains many different kinds of microbes. Predict what would happen if soil microbes were grown under neutral conditions (pH=7), slightly alkaline (basic) conditions (pH=8), and very alkaline conditions (pH=10).
    • Neutral:

    • Slightly Alkaline

    • Very Alkaline
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Part Two Student Worksheet


In this activity, you will test bacterial survival over a pH range from 7 to 10. You will inoculate four plates with local environmental samples and then observe bacterial survival patterns over a 24 - 48 hour period. Before you begin, document your predicted results. Upon completion of this exercise, answer the questions at the end. You may write the answers on your own sheet of paper or download this page in the form of a Word (Microsoft Word 24kB Apr25 05) document.

Your Prediction
  • How will pH affect the growth of the soil bacteria in your sample
Materials
  • 4 prepared, sterile agar plates (labeled pH 7, 8, 9, 10)
  • Permanent marker or wax pencil
  • Sterile, cotton-tipped applicator (e.g., cotton swab)
  • Soil sample from local environment
  • Pipette
  • Tape to seal the plates
Procedure
  1. To avoid accidentally contaminating a plate, read the procedure in Step 2 before inoculating your four plates.
  2. Gather the materials and inoculate the four plates, using the following procedure:
    • Set the four plates on the table in front of you.
    • Take the lid off one of the plates. Hold it pointed face down to avoid having airborne particles land on it and contaminate it. Do not set it on a table.
    • Shake the soil slurry and use a pipette to transfer about 1/4 ml (250 microliters)—or about 5 drops - of it to the plate.
    • Streak the plate in a zigzag fashion with a sterile cotton swab.
    • Replace the lid, tape it closed, and turn the plate upside-down.
    • Label the plate with the date, time, pH, and group name.
    • Repeat the procedure with the other three plates.
    • Stack the inoculated plates and place the stack where your teacher directs.
  3. Check for growth over the next 24-48 hours. DO NOT OPEN THE PLATES.
  4. After 24-48 hours, count the colonies on each plate. If there are a lot of colonies, count the number in a segment of the plate (e.g., a quarter of the plate) and use this value to estimate the total number. Record your observations.
  5. Dispose of the plates as your teacher directs.
  6. Make a graph that compares the number of colonies to pH.
Questions
  1. What is the optimum pH for the soil bacteria found in your local environment?

  2. What advantages might bacteria get from living in a high pH environment?

  3. What might be some of the disadvantages of living in a high pH environment?

  4. What can Mono Lake's alkaline-loving bacteria teach us about life on Earth?
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