Fundamentals of Life Science
Laboratory 1: Applying the Scientific Method to Determine if Yeast is Alive
Group: 405 Team: 5 Names: Manuel Flores, Sofia Lozano, Miguel Villarreal,
and Marcela Medina
Introduction:
Even with the diversity of life, all living things have certain characteristics in
common that allow us to distinguish them from nonliving things. For example,
living things are made up of cells, they acquire materials and energy, reproduce,
respond to stimuli, are homeostatic, grow and develop, and have the capacity to
adapt to their environment. The purpose of this experiment is to discern the
presence of life in yeast using the scientific method. If yeast is a living thing, then it
will be able to acquire materials from the environment and produce energy
(metabolism). During metabolism, sugar is broken down to release energy. When
oxygen is present, carbon dioxide and water are also produced. When oxygen is
absent, then carbon dioxide and alcohol are produced. In either case, carbon dioxide
is a product; therefore, if yeast is a living thing, then it will metabolize sugar to
produce carbon dioxide (gas) that will be trapped inside of a balloon, causing the
balloon to increase in size..
Materials and methods:
The materials to be used in this activity are as follows:
 Copy of the activity
 Yeast
 Table sugar
 Warm water (about 37C)
 4 test tubes
 Test tube holder
 4 balloons
 1 250ml beaker
 Wax pencils
1. Determine the roles for each team member:
2. Number the test tubes from 1- 4 then place them in the test tube holder.
3. Add half a spoon full of sugar and half a spoon full of yeast to test tubes 1 and
2, add half a spoon full of yeast but no sugar to test tubes 3 and 4.
4. Add warm water to all of the test tubes, filling them about ¾ full, then
immediately cover each test tube with a balloon.
5. Test tubes 1 and 2 are your experimental groups and test tubes 3 and 4 are
your control groups.
6. Place your thumb over the balloon on each test tube and shake vigorously.
7. Observe the test tubes for 20 minutes, recording the changes in balloons
volume at 10-minute intervals. Did the volume increase, decrease or stay the
same? Record your results in the results table.
8. Based on the experiment that you carried out, determine the investigation
problem, state your hypothesis and identify the independent and dependent
variables. Record them in the scientific method table.
Results:
Scientific method table
Problem (how does Water, sugar, and yeast create Co2
the independent
variable affect the
dependent
variable?)
Hypothesis (if this
If we add water and sugar to yeast, the balloon will inflate
is done to the
because it consumes it and produces Co2
independent
variable, then this
happens to the
dependent
variable)
Independent
We are testing the yeast to know if it is a living thing
variable (what
variable are you
testing?)
Dependent variable Co2
(What variable are
you measuring?)
Data table
Test tube 1
Test tube 2
Test tube 3
Test tube 4
Balloon volume at
time zero
none
none
none
none
Balloon volume at
after 10 minutes
little
totally
none
none
Balloon volume at
after 20 minutes
increased
none
none
Conclusions:
1. How do your results allow you to determine whether or not yeast is a living
thing?
Our results helped us determine if the yeast was a living thing because when
we mixed sugar, yeast and the water our tubes start to inflate so that’s why
we knew that the yeast was a living thing
2. Did your results support your hypothesis? If not, explain what you think the
problem was and what you could have done differently or better.
Our results did math our hypothesis. We had guesses the tubes with yeast
would inflate because it's a living organism, and it did.
3. Why is it necessary to have both a control group and an experimental group
in the experiment?
It is necessary because you need something to compare the results of the
experiment to. Without a group that didn't have the yeast we couldn't have
compared the results to anything and wouldn't have known that the yeast
was what was causing the balloons to inflate.
4. Why do you need two test tubes for each group instead of just one?
Two test tubes are needed because maybe one of them will not work so you
need to use two. This happened to us, one worked but the other one didn’t
work, so we used the one that did worked for the results.
Evaluation Rubric:
25 points
Procedure
Students
worked
collaboratively,
and correctly
followed the
instructions
for the
experiment,
they cleaned
up afterwards
Scientific
method
Data
20 points
Students
worked
collaboratively,
and correctly
followed the
instructions
for the
experiment,
but they didn´t
clean up
afterwards
Students
Students
determined
determined
the problem,
the problem,
stated the
stated the
hypothesis and hypothesis and
identified the
identified the
independent
independent
and dependent and dependent
variables
variables
correctly.
correctly.
Two of the
three were
answered
correctly.
All data was
Data was
15 points
Students works
collaboratively,
but they didn´t
correctly
follow the
instructions for
the
experiment,
nor did they
clean up
afterwards
Students
determined the
problem,
stated the
hypothesis and
identified the
independent
and dependent
variables
correctly. Only
1 of the
following was
filled in
correctly.
The data
0 points
Students
didn´t follow
instructions.
Nothing was
filled in
correctly
No data was
Conclusions
clearly and
correctly
recorded in the
data table
Students
answered all 4
questions in
conclusions
correctly
recorded in the recorded was
data table, but incomplete.
it wasn´t clear
recorded
Students
answered 2 or
3 of the 4
questions in
conclusions
correctly
Students
didn´t
answer any
of the
questions in
conclusions
correctly
Students
answered 1 of
the 4 questions
in conclusions
correctly