What were the carrying capacities (maximum population size) for the two species when grown separately and on what day were they reached

What were the carrying capacities (maximum population size) for the two species when grown separately and on what day were they reached

WEEK 8 EXPERIMENT ANSWER SHEET Please submit to the Week 8 Experiment dropbox no later than Sunday midnight.


· Experiment 8 Exercise 1 – Species Interactions: Competition

· Experiment 8 Exercise 2 – Biomes (Part I and II)

Experiment 8 Exercise 1: Species Interactions: Competition

In this exercise you will be evaluating the effect of competition on the population size of two species of microorganisms. Be sure you have read through the readings for Week 8 as well as the introductory information for the Week 8 Experiment. When you are ready to begin, open in the following website:

Glencoe-McGraw Hill. No date. Population Biology http://glencoe.mcgraw-hill.com/sites/dl/free/0078759864/383928/BL_04.html


A. Click on the Information button on the bottom and read through the material before beginning. You will need to scroll down to read all of the information. Close the window when you are done. Note that the two species we will be using will be competing for the same food source; bacteria.

B. First, you need to set up the experiment by distributing the two species to the three test tubes.

a. Click on the pipette (the purple bulb) in the flask containing P. caudatum, fill it and place the contents in Tube #1.

b. Then click on the pipette in the flask containing P. aurelia, fill it and place the contents in Tube #2.

c. Finish by putting a pipette full of both species in the Tube #3.

C. Answer the question below before proceeding.


1. The number of P. caudatum and P. aurelia grown alone would be expected to increase until the population size reaches the carrying capacity of the test tube. What do you think will happen in terms of population growth in Tube #3 that contains both species combined and why (2 pts)?

Procedure (continued)

D. You now need to count the number of organisms in each Tube beginning on Day 0 and continuing every 2 days until you reach Day 16. These values will need to be recorded in Table 1 below (do NOT use the Table provided by the website).

a. Click on the Microscope to get started.

b. Click on Clean microscope slides and then Take Sample.

c. Click on the first slide and drag it on to the microscope. Count the number of P. caudatum (note its shape) and multiply by 2 to get the number of cells per ml (your slide holds 0.5 ml). Record this number in the Table below; this is Day 0.

d. Next, click on the second slide and drag it to the microscope. Count the number of P. aurelia (note its shape), multiply by 2 and record this number in the Table for Day 0.

e. Finally, drag the third slide on to the microscope and count the number of each type of organism, multiply by 2 and enter the data into the Table.

f. Click on Clear Slides (on the bottom) and then on the Calendar that says Day 0 to advance it two days.

g. Repeat steps b – f until you reach 16 days.

h. As the days go on, you will have more and more individuals to count. Click on the Grid On button on the microscope to make them easier to count.

Table 1. Results (4 pts).

  Grown Separately (cells per ml) Grown Together (cells/ml)
Day P. caudatum P. aurelia P. caudatum P. aurelia

E. Now it is time to analyze your data.

a. You will need to generate two graphs, one which depicts the number of both species per day of culture when grown separately and one that depicts the number of both species per day of culture when grown together.

b. You must use the Scatter type graph in Excel and each graph should have two lines (one for each species).

c. Be sure you label your axes and your series; meaning you will need to indicate which line pertains to P. caudatum and which to P. aurelia.

Paste your two graphs below (4 pts):


2. What were the carrying capacities (maximum population size) for the two species when grown separately and on what day were they reached (1 pts)?

3. Describe what happened when the two species were grown together and explain why. Be sure to discuss the magnitude and timing of each species’ carrying capacity compared to when they were grown separately (3 pts).

4. Do these results support the principle of competitive exclusion; why or why not? Be sure to cite your sources. (4 pts).

Experiment 8 Exercise 2: Biomes

In these two relatively short exercises, we will be examining the biotic and abiotic factors that define a biome. You should have completed the readings for this week before beginning.

Procedure – Part I: The Great Graph Match

A. Open the following website:

NASA. No date. The Great Graph Match http://earthobservatory.nasa.gov/Experiments/Biome/graphmatch_advanced.php

B. In the Great Graph Match, you will need to match abiotic information (annual rainfall and temperatures) to the appropriate biome. Follow the instructions on the page and fill-in the Table below. For the Explanation column, you need to briefly explain why you chose the biome you did based on the data presented.

C. Be sure to provide complete citations for the sources used.

Table 2. Locations, biomes and explanations (4 pts).

Location Biome Explanation
Frogmore, England    
Goteborg, Sweden    
Koombooloomba, Australia    
Barrow, Alaska    
Alice Springs, Australia    
San Bernadino, California    
Centralia, Kansas    


Procedure – Part II: To Plant or Not to Plant

A. Open the following website:

NASA. No date. To Plant or Not to Plant http://earthobservatory.nasa.gov/Experiments/Biome/plant_it.php

B. In the To Plant or not to Plant, you will need to determine which in which biomes to plant various plants, based on the information presented. Follow the instructions on the page and fill-in the Table below. For the Explanation column, you need to briefly explain why you chose the biome you did.

C. Be sure to provide complete citations for the sources used.

Table 3. Plants, biomes and explanations (4 pts).

Plant Biome Explanation
Creosote bush    
Flowering dogwood    
Bluestem grasses    
White sage    
Saguaro cactus    


Week 8 Questions

1. Are most invasive (exotic) species K-selected or r-selected species? Explain your choice and why that makes sense in terms of their ecological success.



2. Briefly define a community and an ecosystem and describe how the two are interrelated.



3. Which of the following levels of organization are in order, from simplest to most complex.

a.  population, organism, community, ecosystem b.  community, ecosystem, population, organism c.  organism, community, population, ecosystem d.  population, ecosystem, organism, community e.  organism, population, community, ecosystem

4. Mosses growing on bare rock will eventually help to create soil.  These mosses are involved in ___ succession.

a.  primary b.  secondary c.  tertiary

5. If a farmer sprays a pesticide onto a field and kills half of the insect pests, he has caused a reduction in________.

a.  field capacity b. carrying capacity c. population size d. More than one of the above

6. What type of survivorship curve would you expect for a plant species in which only a few seeds are produced and most of these survive to produce adult plants?

a.  type I b.  type II c.  type III

7.  An ecological niche is an organism’s_______ in an ecosystem.

a. location b.  habitat         c.  resources         d.  function

8. No matter how rapidly populations grow, they eventually reach a limit and begin to stabilize. This is called the ______________.

9. Unicellular algae live in the tissues of coral animals.  The algae provide food for the coral, while the coral provides a stable home for the algae. This is an example of

a.  Parasitism b.  Commensalism c.  Mutualism

10. The vast majority of energy taken into an ecosystem is____________.

a.  converted into biomass by plants. b.  utilized by secondary consumers. c.  lost as heat. d.  used by the primary consumers. e.  concentrated in the decomposers.

11. A farmer is using an insecticide to treat his crops. While most insects do not survive their first exposure to the insecticide some have a gene that enables them to survive. When these survivors reproduce they will likely pass along this resistance to their offspring. This results in an increase in numbers of the insects over time. Which of the following processes applies to this survival?

a. cloning b. mutation c. natural selection d. genetic engineering

12. What is the ecological relationship between insects and crops?

a. mutualism  b. competition c. predation

13. Sea anemones growing on the backs of crabs without damaging the crabs are an example of

a.  Parasitism b.  Commensalism c.  Mutualism

14. Which of these is a population density-independent regulating factor?

a.  Competition b.  Predation c.  Size of population d.  Weather e.  Resource availability

15. Producers are_________.

a.  Autotrophs b.  Herbivores c.  Omnivores d.  Carnivores

16.If biological magnification occurs, the ___ will have the highest levels of toxins in their systems.

a.  producers b.  herbivores c.  primary carnivores d.  top carnivores

17. Given the amount of sunlight that hits the plants on our planet, and the ability of plants for rapid growth and reproduction, how come we aren’t all hip deep in dead plants?




Week 8 Experiment Grading Rubric

Component Expectation Points
Experiment 8 Exercise 1 Correctly conducts experiment, records data (Table 1) and generates two graphs. 8 pts
Experiment 8 Exercise 1 Demonstrates an understanding competition between species and the effect it has on population growth (Questions 1-4). 10 pts
Experiment 8 Exercise 2 Develops an appreciation of the diversity of ecosystems around the globe and understands the environmental conditions that lead to their development (Tables 2 and 3). 8 pts

26 pts

Updated October 2013

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