Laboratory 1: What is Living?

Saccharomyces cerevisiae(Click here for a good yeast site!)

Teacher's notes: Students should have been introduced into how to use the microscope prior to this lab!

Objective: To use the scientific method to investigate unknowns to determine the five characteristics of all living things.

Materials: 4 test tubes with unknowns (Remember NEVER taste, touch or smell chemicals!) (#1= sand, #2= crushed Alka-seltzer tablets, #3 = bread yeast {dry}, #4=baking soda) test tube rack 2 - 50ml beakers scoopula stereomicroscope or 10X magnifying glass 6 eye droppers distilled water watch glass four small balloons to fit over test tubes table sugar standard microscope (4X, 10X, 20X)

Background: Biology is the study of life. What determines if something is living or not? There are five characteristics that ALL living things possess. You will use the scientific method to determine which one of the four unknowns is a living thing. Let's review!

Please list the steps of the scientific method below. (Discuss the steps and logic of using the scientific method with the students)

Procedure: Part I-Dry Examination

1) Use the scoopula to remove a small sub-sample of an unknown and place it on the watch glass.

2) Examine it under the stereomicroscope or magnifying glass. Draw or take a digital image of the sub-sample and give a written description of it. (This should be placed in the results section of the lab.) Can you determine if it is living or not yet?

3) Repeat steps 1 & 2 with each of the unknowns.

Part II- Wet Examination 1) Use the scoopula to remove another small sub-sample of an unknown and place it on the watch glass.

2) Add a couple of drops of tap water to the sample and record your observations in your results section.

3) Repeat steps 1 & 2 with each of the unknowns. What is your hypothesis so far? Record this in your results section.

Discuss with your partner(s) a "plan of attack" to determine which of the unknowns is living. *HINT: Read the section of your biology book that discusses the characteristics of living things! Discuss your procedure with the teacher before proceeding any further. (Student's will have probably eliminated unknown's #1 by now. They will not be sure about # 2, #3 & #4. Remind them that there is some equipment that they have not used yet {i.e. the balloons and table sugar}! Hopefully they will come up with the plan to add water and sugar to the test tubes, put the balloon over the top and collect the gas that escapes! Remind them that one of the page 2 charactistics of living things is "growth"! Growth is only noticed over time! They may have to let their experiment go for a while or begin at the beginning of the next class period ) If the teacher agrees to your plan, write it down in your lab notebook and proceed. Write your observations down in your notebook. Can you tell which one is the living one yet?

(The students will notice that there is gas in the balloons in # 2, #3, #4. Have some more discussion about "scale" of things and encourage them to examine a wet sample under the microscope! They should be able to see clearly that only #3 has distinctive round shapes. If they are good observers they may even see the yeast budding.)

Results Part I: Dry Examinations: (Draw or put image of unknown's below! Don't forget to include a written description!)

Part II: Wet Examinations: (Describe your observations below to the sub-sample of the unknowns when you added the drops of water ) Unknown Observations #1, # 2, #3, & #4

Your Hypothesis: ______________________________________________________________

Part III: Write a description of your "plan of attack"( procedure) below.

Part III Results: Describe what happens to each unknown after you initiated your experiment.

Part III: Microscope observations-Draw or insert a digital image of your microscope observations of the unknowns after completing your approved procedure. Be sure to include a written description of each unknown.

Discussion/Conclusion: 1) Was your hypothesis correct? Why or why not?

2) List your reasons (proof) that the unknown you chose was the living one.

3) Describe any further experiments you could conduct to further prove you were correct.