Investigation Design Competition
Name
Cell Respiration in Yeast or Cockroaches
Your Challenge: Design an investigation to determine the effect of one variable on the rate of cell
respiration. To do this, you will need to read and learn about Cell Respiration – mainly the inputs and
outputs and general processes involved – and the two possible test subjects, yeast (Saccharomyces
cerevisiae) or the Madagascar Hissing Cockroach (Gromphadorina portentosa). You will also want to
consider the available materials list below so you know what you can work with outside of your
chosen variable. The class will vote on the one they consider the most interesting, and the
winners will conduct the investigation as a class demo as we all collect data on your
investigation. Winning group will earn a 5% boost on the unit exam!
Yeast
Adapted from http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_p011.shtml#procedure
Yeasts are tiny, microscopic organisms — or microorganisms — that are a type
of fungus. This means that they are more closely related to a mushroom than to plants,
animals, and bacteria (which are also microorganisms). You can see a picture of some
yeasts in Figure 1. These little critters might sound strange and different, but people have
actually been using them for thousands of years to make bread "rise." How does this
work? It has to do with the metabolism of the yeasts, or, in other words, what they eat and
what they turn that food into.
Yeasts must get their food from their surrounding environment to grow and reproduce, or
make more yeast. What do they eat? Yeasts feed on sugars and starches, which are in
bread dough. They turn their food into energy and release carbon dioxide (CO2) gas as a
result. One process they use to accomplish this is cellular respiration – when in the
presence of oxygen gas (O2) and in some cases, through a process called fermentation
when in the absence of oxygen gas. The CO2 gas made during both of these processes is
what makes a slice of bread so soft and spongy. The pockets of gas are produced by
yeasts when the dough is allowed to rise before baking. Yeast fermentation is also used
to make beer, wine, and champagne.
Figure 1. This image shows what individual
yeast cells look like using a powerful
microscope. These are specifically baker's yeast
(Saccharomyces cerevisiae).
Madagascar Hissing Cockroaches
http://animals.nationalgeographic.com/animals/bugs/madagascar-hissing-cockroach/
This insect looks—and sounds—like anything but a run-of-the-mill roach. Madagascar
hissing cockroaches are one of many fascinating animal species to hail from the
island of Madagascar. These cockroaches are shiny brown and oval-shaped, with no
wings and a single pair of antennae. Males sport large horns, which give them an
unusual and impressive appearance. Males use their horns in aggressive encounters
reminiscent of battles between horned or antlered mammals. Rivals ram one another
with their horns (or abdomens) and during the fight often unleash the amazing hisses
that give the animal its name. Winning roaches hiss more than losers, so the sounds
may be used to help determine a roach hierarchy. Hissing is also part of the
cockroach's mating ritual, and can be used as an effective alarm cry. Most insects
that make noise do so by rubbing their body parts together or by employing vibrating
membranes. Madagascar hissing cockroaches, however, exhale air through their breathing holes. This audible use of the respiratory
system is far more common in vertebrates.
Like 99 percent of all cockroach species, Madagascar hissing cockroaches are not pests and do not inhabit human dwellings. These
insects live on forest floors, where they hide amidst leaf litter, logs, and other detritus. At night, they become more active and scavenge
for meals, feeding primarily on fruit or plant materials.
The Madagascar hissing cockroach even begins its life in an unusual manner. Females create a cocoon-like egg case called an
ootheca and carry their eggs (and neonatal nymphs) inside their bodies. They then bear living young—as many as 60 nymph roaches.
Designed Investigations Due Thursday, 5/12. Run it Friday, 5/13
Questions to think about before you design your experiment.
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What do these organisms eat?
What do they turn their food into?
How can the food breakdown activity of the organism be measured using a gas chamber?
What do you think will be the best conditions for the organism to perform cellular respiration or fermentation?
What factors may inhibit the organism from performing cellular respiration?
Available Materials and Equipment
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Variable number of cockroaches
Dry yeast, up to 14g = ½ ounce per trial
An energy source (in the form of food….. or
not!), maximum of 14 g = ½ ounce for yeast,
variable for cockroaches
For yeast, warm water to be provided by water
bath (maintained at 50oC) – recommended no
less than 200mL
Thermometer
Clock or timer
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Gas chamber (closed system)
CO2 probe, O2 probe
Lab notebook, pen, brains
Materials needed to simulate variable:
o
o
o
o
Question:
Reasoned Hypothesis:
Procedure: This can be in list form, or as a flowchart. Include all details necessary to repeat.
Variables:
M:
R:
C:
Class Data: Set up data table and graph in notebook once investigation has been
selected.
Conclusion: Set up conclusion paragraph in notebook once investigation has been
completed using class data collected during demonstration.
3 Stamps