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Biology 101 – Quiz 3 – Exercise 17
Name __________________________________________________________
Day/Time _______________________________________________________
Here is the requisite easy question on today’s lab:
1.
Name the 2 types of microscopes that we will learn how to use today. (2 pts)
Compound and Dissecting
Now here are the slightly less easy questions on what you did last week:
2.
After mixing the supposedly toxic chemical with our bacteria solution, we let
it incubate for 15 minutes. Why? (4 points)
We let them incubate for 15 minutes so that the bacteria and the toxic chemical would
have enough time to interact. To make sure that the toxic chemical would have
enough time to negatively affect the bacteria.
3.
Suppose a chemical compound that you were testing had the tendency to react
with and grab all the surrounding oxygen molecules. Would this
(INCREASE, DECREASE, or NOT AFFECT) bacterial bioluminescence? In
one sentence, explain your answer. (4 points)
This would decrease bioluminescence! If the chemical reacted with all the oxygen
molecules then there would be less oxygen available for the bacteria. And since
bioluminescent bacteria depend on oxygen to generate light, the amount of
bioluminescence would be decreased.
4.
Suppose your automobile oil needs to be diluted in a 1:2000 ratio in order to
be nontoxic. How many LITERS of water would it take to safely dilute 5
MILLILITERS of oil? Show your work! (5 points)
(5 mL of oil) x (2000 mL water/1 mL of oil) x(1 Liter/1000 mL) = 10 L of water
5.
You and your laboratory partner decide to use the techniques in the bacteria
experiment to test the toxicity of laundry bleach. You set up your experiment
using 4 test tubes:
Tube 1 – Full strength bleach
Tube 2 – 1:10 dilution
Tube 3 – 1:200 dilution
Tube 4 – 1:900 dilution
Which tube do you think would be most likely to show the 2ND MOST
bioluminescence? (5 points)
a.
Tube 1
b.
Tube 2
c.
Tube 3
d.
Tube 4
6.
What is the major flaw in your experimental design? (Hint: what is your
experiment lacking?) How would you correct this flaw? (5 points)
This experiment is lacking a control tube – a tube that contained only the diluting
agent and no bleach. This could be corrected by making a control tube!
7.
According to the following data, was Chemical A (circles) more toxic to bacteria
than Chemical B (triangles)? Explain your answer. (5 points)
4
3
Relative Light
Intensity
2
1
0
Full
1:10
1:100
Dilution Level
1:1000
The total amount of light intensity produced by the bacteria mixed with chemical A was
9 units of relative light intensity. The total amount of light intensity produced by
bacteria mixed with chemical B was 11 units of relative light intensity. Since 11>9, the
bacteria mixed with chemical B had a greater light production, and thus it can be
maintained that chemical B is less toxic than chemical A.