Name Accelerated Biology

Date Unit 5: Ecology

Period

Ecological Relationship Lab

Hare Today, Gone Tomorrow

In this simulation of a predator-prey relationship, you will discover the link between the two populations of a predator (the lynx) and its prey (the snowshoe hare) over the course of many generations. Pay especially careful attention to the directions at the start of the lab so you can understand what is going on.

Before you begin, make a hypothesis regarding how you expect the populations to grow, decline, fluctuate, change, etc. based on the type of relationship we know the hare and lynx to partake in. You may even have a second hypothesis.

Your hypotheses must be written in correct “if, then…because” form!

Materials (for one group)

  • An area (1.5 feet x 1.5 feet) delineated by tape
  • About 300 squares of paper (1” x 1”) representing the hares
  • One piece of cardboard (3” x 3”) representing one Canadian lynx
  • Graph paper
  • “Hare & Lynx Data Sheet”

Procedure

  1. Tape off an area 1.5 feet by 1.5 feet. This area is the habitat for your hare & lynx populations.
  1. Begin the simulation by populating the habitat with three hares, spatially dispersed within the square.
  1. Assign a data keeper to verify that the number of hares starting generation 1 (3 hares) is entered in data sheet. The data keeper will be responsible for recording the number of hares and lynx at the end of each generation.
  1. Your game will show what happens to the number of hares & lynx that can survive in the “habitat” over 25 generations. Each generation, the number of hares & lynx will change.

RULES FOR THE GAME:

  • Set-up: 3 hares dispersed within the 1.5 feet by 1.5 feet.
  • The lynx card will be tossed into the habitat one time for each lynx that starts a generation.
  • If the lynx lands on any portion of a hare, the hare has been eaten by the lynx and should be removed from the habitat before the lynx card is thrown again.
  • Any lynx that eats three or more hares in a throw survives for the next generation. If a lynx, eats less than three hares, it starves to death.
  • At the end of a generation, you will tally the total number of hares that were eaten.
  • For every 3 hares eaten, one baby lynx is born.
  • After dividing the number of hares by 3 to find the amount of new lynx, round down if you get a decimal.
  • After each generation, the number of hares in the habitat doubles. (They have babies too!!)
  1. There is one lynx that will start the first generation. Have the data keeper verify that this is entered correctly the data table.
  1. Toss the cardboard lynx in an effort to capture as many hares as possible (if it lands on any portion of a hare, it will be eaten). Remove any hares captured and enter the number of hares that were eaten in the data table.
  1. Simulate the reproduction of the hares left in the habitat by multiplying the number of hares left at the end of the generation by #2. Place the appropriate number of new hares in the habitat.
  2. If the lynx has not survived generation 1 (which is likely) another one moves into the area. THIS IS THE END OF GENERATION #1.
  1. Toss the newly recruited lynx, repeating step 6. Remove any hares that were eaten and enter your new data for generation #2.
  2. In filling out this data, review the rules as necessary to find the proper number of lynx that will survive and / or be born.
  1. By generation 5 the lynx should be able to capture 3 hares when tossed. If successful, the lynx survives until the next generation. Remember that any time more than one lynx starts in a generation, the card is tossed once per lynx.
  1. Continue the game for 25 generations by repeating steps # 6, 7, and 8 above for each generation.
  2. After you get to generation 8 or 9 it may be difficult to keep track of how many lynx live or die. Use a separate sheet of paper to tally the population of lynx; keep track after every “drop” of the lynx if it ate enough hares to survive.
  1. *** If at any point, all of the hares are eaten (meaning there are no surviving hares), assume all the lynx but one die of starvation (this one lynx has managed to survive on birds and mice). Also assume that three new hares from a neighboring ecosystem migrate to the area. Begin the simulation from whatever generation you were at and continue to generation 25.

Results:

  1. Tape or glue the Hare & Lynx Data Sheet in your lab notebook.
  1. You will individually make a graph to plot your data. This graph should have one curve for the hares and another for the lynx. Plot the number of organisms at the START of each generation.
  1. Do not forget to include:
  2. Descriptive title for the graph
  3. Label each curve on the graph (use a key to indicate which curve is which)
  4. Title and label your axes (x and y, with data the axis is showing as well the data points)

HINT: this graph will be useful in your formal lab report!

Answer the following analysis questions (which will also be useful in your formal lab report)

  1. About how often does the hare population reach a peak?
  1. About how often does the lynx population reach a peak?
  1. Over the course of 25 generations, which organism demonstrated a larger population size, comparably? WHY? (Think about the type of relationship AND trophic levels)
  1. List two patterns you can find in your graph. For each one, give an explanation for what could cause such a pattern. Be thorough and use complete sentences.
  1. What term describes the population growth trend you observed today? Why does this name make sense?
  1. List four conditions, other than predation, that would result in a decrease in the hare population.
  1. Imagine that at the beginning of generation number 12, the lynx were exterminated and no new lynx could enter your habitat.
  2. Describe what would happen to the population of hares over a small number of generations. If you were to make a graph of this, what kind of curve would you find?
  3. Would the trend you described in 7a continue forever? Why or why not? If not, what trend would you expect to see over MANY generations?

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