Name: ____________________
Teacher: ____________________
Class: ____________________
Virtual Population Biology Lab
Date: ____________________
Background: When a single population of organisms exists in an environment, they are able to use all the available
resources for the growth of their own population. However, when two different species exist in the same environment, there
is competition for those limited resources. Whichever species is best adapted to get those resources will grow faster than
the other population and may eventually exclude that population from the environment.
Purpose: In this lab, you will use a ‘virtual’ lab to grow and count populations of two types of Paramecia. You
will grow individual cultures as well as a mixed culture of both Paramecia. After counting cultures, you will
graph the results and analyze the data. Begin by searching for “population biology virtual lab” on Google, and
click on the link for glencoe.mcgraw-hill.
Procedure: Once at the appropriate site, follow the instructions as noted:
1. Begin by filling test tube 1 with a sample of P. caudatum (blue dot). You fill a tube by clicking on the
bulb of the pipette and dragging it to test tube #1.
2. Fill test tube 2 with a sample of P. aurelia (red dot) by clicking on the bulb of the pipette and dragging it
to test tube #2.
3. In test tube #3, you will pipette a sample of both types of Paramecia. Test tube 3 will have both a red
dot and a blue dot indicating that both types of Paramecia are present in the test tube.
4. After filling the test tubes, click on the microscope on the back counter. To prepare a wet mount for
viewing, click on the “clean slides” button, then click on the test tube rack.
5. Place the first slide on the microscope and count the number of Paramecia that appear. Record this
number in the appropriate row/column of your data table. Then repeat with the other two slides.
6. When you have counted each slide, click on the button to clear the slides. Then click on the clipboard
to advance the number of days.
7. Repeat steps 5-7 for Day 2, placing data into the appropriate row/column in your data table.
8. Beginning on Day 4, when you place the slides on the microscope, click on the button at the base of the
microscope that says “Grid On”. Choose one-quarter of the circle and count the number of Paramecia
in that section. Multiply your answer by 4 to get the number of Paramecia in the sample. Record this
larger number in your data table.
9. Repeat for each of the following days, using the grid to count one-quarter of the organisms and
multiplying by 4 each time.
Data: Use the table on the next page to keep track of the number of Paramecia in each sample. When your
table is complete, transfer the data to a Google Drive Spreadsheet. (Alternatively, create a spreadsheet at the
start of your lab and input your values directly.) To create a graph of the data, drag a box over all the columns
and rows and click the link to “insert chart”. Under “Chart Editor” select the box to use the first column as
labels and the top row as headers. Under “recommended charts”, select a line chart. You will need to edit the
axis labels as well as the title of your graph by clicking on each area and creating labels for each. Print out a
copy of your data and graph to include with your lab report!
Analysis: Answer the following questions in paragraph form. Do not simply write: “1. Your answer…”
Incorporate all your answers into a few sentences in paragraph form.
1. On what day did the Paramecium caudatum population reach the carrying capacity of the environment
when it was grown alone? How do you know? What is the carrying capacity for this species?
2. On what day did the Paramecium aurelia population reach the carrying capacity of the environment?
How do you know? What is the carrying capacity for this species?
3. Explain the differences in the population growth patterns of the two Paramecium species when they are
grown together. What does this tell you about how Paramecium aurelia uses available resources?
4. Briefly state the “competitive exclusion principle”. Then explain how this experiment demonstrates the
competitive exclusion principle.
Conclusion: Summarize the results of this experiment in 2-3 sentences and relate it to what we have been
learning in class.
Data Table
P. caudatum grown P. aurelia grown P. caudatum grown in P aurelia grown in mixed
alone, cells/mL
alone, cells/mL
mixed culture, cells/ mL culture, cells/mL
Day 0
Day 2
Day 4
Day 6
Day 8
Day 10
Day 12
Day 14
Day 16