Name _____________________________________________________________Period_____________
Population Biology- Bacteria vs.
Protozoa
Directions:
1) Go to the following website to begin your lab:
http://www.mhhe.com/biosci/genbio/virtual_labs/BL_04/BL_04.html
2) Read the purpose, objectives, and procedure of the lab with your partner. After you are done reading,
write a summary of what you will be doing in this lab here…
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3) The first step of the lab tells you to read the information about paramecium, population growth, and
competition. Read the information and answer the following questions.
a) What is exponential growth?
b) What is a limiting factor? Give 2 examples of limiting factors.
c) Define carrying capacity:
4) The next part of the lab instructs you to put specimens in each test tube. You should place ONLY one
specimen in the first two test tubes and then combine them in the last one. Answer the first JOURNAL
question below.
Journal question 1: “Make a hypothesis about how you think the two species of Paramecium will
grow alone and how they will grow when they are grown together.” (2 different hypotheses-don’t
forget “if…then”)
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5) Continue reading the instructions and going through the virtual lab. When you get to the part where it
asks you to count cells, use the paper copy of the data table to record your data, NOT the virtual table.
**Make sure you read the part that talks about cells/ml, and you calculate the number of cells correctly**
6) When you are done collecting all of your data for all 16 days, construct a graph. Your graph MUST
have a title, labels, a proper scale, and a key.
7) When you have finished your graph, complete the remaining Journal questions.
Journal Questions:
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.
Title:
P. aurelia
grown alone
(cells/ml)
P. caudatum
grown alone
(cells/ml)
P. aurelia
grown in mixed
culture
(cells/ml)
P. caudatum
grown in mixed
culture
(cells/ml)
Day 0
Day 2
Day 4
Day 6
Day 8
Day 10
Day 12
Day 14
Day 16
Data Table
Graph
Title:_____________________________
Going Further with Graphing