Name: ________________________________________________________________ Date: ____________
Honors Biology Period: __________
Observing the Characteristics of a Living Thing
Introduction:
Dogs, cats, people, and trees are all living things. Rocks, water, and air are nonliving things. Distinguishing between living and nonliving things seems simple, yet the differences have been a source of argument among scientists for many years. But scientists agree that all living things are made up of one or more cells, reproduce, grow and develop, obtain and use energy, and respond to the environment.
To help you observe some of the characteristics of living things, you will work with bromthymol blue, an indicator used to determine the presence of acids. In this lab, it will determine the presence of carbon dioxide in water. Carbon dioxide is a byproduct of a process called cellular respiration (organisms burn their food and produce energy). In this investigation, you will be working with yeast.
Problem: Identify the problem that you will research in today’s lab: __________________________
Materials:
3 large and 3 small test tubes
3 one-hole rubber stoppers with glass tube inserts
Test tube rack
3 pieces of plastic hose
Glass slides
Microscope
Medicine dropper
Grape Juice
Water
Bromthymol blue
Yeast
Coverslips
Beaker
Funnel Graduated Cylinder
Teacher Demo Procedure A:
1.
Add 30 drops of bromthymol blue to a test tube. Caution: Bromthymol blue is a dye. Use care to prevent spills.
2.
Place a straw in a test tube, making sure that the straw extends into the bromothymol blue.
3.
Gently blow bubbles through the straw into the bromthymol blue. Caution: Do not inhale through the straw. Record observations in data table 1 on the following page.
Teacher Demo Procedure B:
1.
Use a pencil and make three test tubes: A, B, and C.
2.
Place 5 mL of bromthymol blue in each small test tube and place the test tubes in the test tube rack.
3.
Place 30 mL of yeast and clear grape juice in test tube A.
4.
Place a rubber stopper with a glass tube insert firmly into the mouth of test tube A.
5.
Attach a plastic hose to the glass stopper. Place test tube A into the test tube rack next to one of the small test tubes containing bromthymol blue.
6.
As shown in figure below, place the free end of the plastic tube attached to test tube A into the small test tube containing bromthymol blue, making sure it touches the bottom.

7.
Place 30 mL of the yeast and water mixture in test tube B.
8.
Place 30 mL of water and grape juice in test tube C.
9.
Repeat steps 4-6 for test tubes B and C.
10.
Record your initial observations in data table 2.
11.
After 24 hours, again record your observations in data table 2.
Student Procedure C:
1.
Label two glass slides: A and B.
2.
Using a clean medicine dropper and a slide pre-stained with methylene blue, make a wet mount of the yeast and grape juice mixture on slide A.
3.
Using a clean medicine dropper and a slide pre-stained with methylene blue, make a wet mount of the yeast and water mixture on slide B.
4.
Exam each slide under high power objective on the microscope. You may need to adjust the diaphragm to see the yeast clearly. Be sure to note the presence of any buds – small yeast cells still attached to the larger yeast cells. Record your observations in the data section 3.
Data:
Data Table 1 (Teacher Demo A)
Color of Bromthymol Blue Before Color of Bromthymol Blue After
Exhalation
Test Tube
Exhalation

Data Table 2 (Teacher Demo B)
Color
Initial Observation
Presence of
Bubbles
Presence of
CO
2
Test Tube A:
Yeast and
Juice
Bromthymol
Blue
Test Tube B:
Yeast and
Water
Color
After 24 Hours
Presence of
Bubbles
Presence of
CO
2
Bromthymol
Blue
Test Tube C:
Water and
Juice
Bromthymol
Blue
In which test tube(s) did you observe a chemical reaction in which carbon dioxide was produced?
How did you know a chemical reaction was occurring?
Data Section 3:
In the space below, draw what you observed on slides A and B under the microscope.
Total Magnification: __________________
Slide A: Yeast and Juice
Total Magnification: __________________
Slide B: Yeast and Water
Number of cells in field of view: _________
Number of cells budding: ____________
Number of cells in field of view: _________
Number of cells budding: ____________
In which mixture were more buds present? :_________________________________________________

Analysis and Conclusions:
Part A
1.
Why did the bromthymol blue change color when exhaled into the test tube?
Part B:
1.
What does the production of carbon dioxide gas indicate about the yeast?
2.
How do you know that the carbon dioxide gas was produced?
Part C:
1.
What does the presence of buds indicate about the yeast?
2.
Why were more buds present in one of the mixtures?
3.
What have you observed in the laboratory investigation (all three parts) that allows you to classify yeast as a living organism?