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5 years ago
Lab 4 Worksheet:  Population Biology

Student instructions:  Follow the step-by-step instructions for this exercise found on the virtual lab and the instructions below and record your answers in the spaces below.  Submit this completed document by the assignment due date found in the Syllabus.

Please make sure that your answers are typed in RED.

Please type your Name and Student ID Number here:


1.   Open the Virtual Lab titled “Population Biology”.

2.   Click “Information” to read about paramecia, population growth, and competition.

3.   If you come upon terms that are unfamiliar to you, please refer to your textbook for further explanation or search the word here:  http://encarta.msn.com/encnet/features/dictionary/dictionaryhome.aspx

4.   Begin the experiment by filling the test tubes with samples from the labeled stock cultures in the flasks. Click the bulb on each pipette to fill the pipette with culture. Then click and drag the pipette to a test tube. Add 10 mL Paramecium aurelia to the first tube, 10 mL Paramecium caudatum to second, and 5 mL of each species of Paramecium to the third tube (5 mL of P. Aurelia AND 5 mL of P. caudatum for a total of 10 mL in test tube #3). There is rice in the test tubes. The rice is food for bacteria, which in turn will be food for the paramecia. The two species of Paramecium do not prey upon each other.

5.   Answer the first lab question below.

6.   Click on the microscope on the back shelf.   This will bring you to the back bench where you will make wet mounts of the samples.

7.   Click the clean microscope slides box to set up clean microscope slides.

8.   Click the test tubes to prepare wet-mount slides of the samples.

9.   Click and drag a wet mount to the stage of the microscope. Count the number of cells of each type of Paramecium. Click the “grid on” button (located at the base of the microscope) for help with counting.

10.   Use the table below to record your data. Note: The well in the microscope slide (area observed under the microscope) holds 0.5mL. You will need to multiply the number of cells you count by 2 in order to obtain the concentration of paramecia per 1.0 mL.

11.   Click the “Clear Slides” button.

12.   Click the calendar to advance days. Then get a new set of clean slides, place samples on them, and count the number of paramecia you see. Record your data in the table below.

13.   Continue the steps above until the Table is complete.

14.   Answer the remaining Lab Questions below.

Table 1:
*Results will vary depending on the samples chosen by the computer.

Day   P. caudatum alone, cells/mL
(from tt#1)   P. aurelia alone, cells/mL
(from tt#2)   P. caudatum mixed, cells/mL
(from tt#3)   P. aurelia mixed, cells/mL
(from tt#3)

Lab Questions:

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

2.   Explain how you tested your hypothesis.

3.   On what day did the Paramecium caudatum population reach the carrying capacity of the environment when it was grown alone? How do you know?

4.   On what day did the Paramecium 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 how Paramecium aurelia uses available resources?

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

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

8.   Paramecia possess:
a.    Flagella
b.   A contractile vacuole
c.   All of the above

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

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

11.   Which of the following can influence the carrying capacity of a population?
a.   Availability of food
b.   Availability of water
c.   Competition
d.   Build up of toxins
e.   All of the above

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

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

14.   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 cells/mL

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

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

17.   In a repeat of this experiment, you found that on Days 10-16 the number of individuals in the P. caudatum, mixed culture began to gradually rise.  A possible explanation for this is:
a.    There was insufficient food in the culture
b.   The 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

Read 7727 times
3 Replies
Valued Member
5 years ago
Sure I can help, have you answered anything yet? What are you stuck on?
5 years ago
 I have completed the graph just need help with the questions
Valued Member
5 years ago
I have completed the graph just need help with the questions

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