Solved by a verified expert:BIO
112: Virtual Lab: Population Biology

1. Please make
sure you have read through all of the information in the “Question” and
“Information” areas. If you come upon
terms that are unfamiliar to you, please refer to your textbook for further
explanation or search the word here:

2. In this
exercise, you will examine the characteristics of population growth and the
effects of competition using two model organisms. To begin, read the text that appears in the “Information”
window that initially opens in order to learn about the aquatic protistParamecium, growth of populations and
the facets of competition. You can close
this window by clicking the “X”; remember you can reopen the file by clicking
the “Information” button at the bottom of the laboratory page.

3. You are now
ready to begin the activity. Start by
clicking on the purple pipette bulb on the far left. Once filled, click and drag the pipette to
the test tube on the far left of the test tube rack in order to fill it with
the first protist culture. Then click on
the bulb on the right and repeat the steps to fill the second test tube with
the next culture. To fill the last test
tube, click and drag a sample of EACH protist culture to the test tube on the
far right of the test tube rack.

4. You will
next need to click on the microscope icon in the laboratory area. This will open up your workspace for
observing the cultures. To make your
wetmount preparations, click the box of clean slides and then the rack of
cultures. You can then click each
individual slide and drag it to the microscope in order to count the organisms
in each culture. Remember to click the
“Grid On” icon on the microscope to aid you in your counting. When you are through counting the cultures,
place your data in the “Data Table” and/or Table I below. Remember to multiply your counts by 2 to
indicate the number of organisms present in 1mL of culture. When you are finished, click “Clear Slides”
and then click the calendar to advance 2 days of growth.

NOTE: there is a “Diagram”
button here to show you detailed structures ofParamecium sp.

5. You are now
ready to repeat the actions in step 4.
Continue to do so until you have counted your cultures for 16 days and
the “Data Table” and/or Table I are complete.
When you are finished with the “Data Table”, click the “Graph” button to
obtain a graph of your data over the 16 days.

Table I:


P. caudatum
alone, cells/mL

P. aurelia
alone, cells/mL

P. caudatummixed,

P. aureliamixed,










GRAPH:using an excel
program. Be sure to title the graph, x
and y axis and key for the lines.

Post-laboratory Questions:
Paramecia possess:
a. A nucleus c.
A contractile vacuole e. All of the above
b.Flagella d. A and C

The organisms used in this
experiment belong to which domain of life?
a. Bacteria b.
Archaea c.

What served as the food for the paramecia in this experiment?
a. Rice b.
Oats c. Bacteria d. Nothing, they are photosynthetic

Which of the following can influence the carrying capacity of a
a. Availability
of food c.
Competition e.
All of the above
of water d. Buildup of toxins

Which type of competition would be observed between organisms within
theP. caudatum culture?
a. Interspecific
c. There would
be no competition, they are of the same species

Which culture reached its carrying capacity
the fastest in this experiment?
a. P. caudatum, alone b.P. aurelia, alone c.P. aurelia, mixed

You have counted 30 organisms in your culture on Day 4. The concentration of organisms in this
culture is:
a. 15 cells/mL b.
30 cells/mL c. 60
cells/mL d. 90

Based upon your data, which
culture experienced the greatest rate of exponential growth?
a. P.
caudatum, alone c.P. caudatum, mixed
b.P. aurelia, alone d.
P. aurelia, alone

Based upon the data, which
organism appeared more efficient at using its resources?
a. P.
caudatum b.
P. aurelia

In a repeat of this experiment, you found that on Days 10-16 the
number of individuals in theP. caudatum,
mixed culture began to gradually rise. A
possible explanation for this is:
a. There was insufficient food in the culture
temperature warmed enough to allow for more growth
c. A genetic
variant of the original population began to experience growth due to its use of
a different food (bacterium) source
d.None of the
above could lead to this scenario

1. Make a hypothesis about how
you think the two species ofParamecium
will grow alone and how they will grow when they are grown together.

2. Explain how you would test
your hypothesis.

3. In this virtual lab, On what
day did theParamecium caudatum
population reach the carrying capacity of the environment when it was grown
alone? How do you know?

4. On what day did theParamecium aurelia population reach the
carrying capacity of the environment? How do you know?

5. Explain the differences in the
population growth patterns of the two Paramecium species. What does this tell
you about howParamecium aurelia uses
available resources?

6. Describe what happened when
theParamecium populations were mixed
in the same test tube. Do the results support the principle of competitive

7. Explain how this experiment
demonstrates that no two species can occupy the same niche at the same time.