PERFORMING A LAB:Population Ecology

In this exercise, you will use dice to model population growth. Each die will represent an individual; new individuals will be born, and individuals will also die. You will track the entire population until the population density (number of individuals) reaches 100.

Procedure

1. Before you begin to model population growth, examine the rules listed below and shown in Figure 4.

Rules:

• Each die represents 1 individual of the population.
• You will start with 4 individuals.
• You will roll the dice to investigate births and deaths of the population.
• The number of dots on each die will represent a birth, a death, or neither birth nor death.
  • Birth = 1, 4
  • Death = 6
  • Neither = 2, 3, 5

1. Select 4 dice and place them in the cup. These dice represent the 4 individuals comprising generation 1, the initial population.

Note: The color of the dice does not matter.

1. In Data Table 1, record the “Initial population size (N)” (for the first generation, the initial population size is 4).
2. Cover the cup with your hand and shake the dice. Gently pour the dice onto a table or work surface.

Important Note! Pouring the dice out too quickly or too high from the work surface may result in lost dice. Take care not to inadvertently lose individuals.

1. Determine the number of individuals that were born (any dice displaying numbers 1 and 4). Determine the number of individuals that died (any dice displaying number 6). See Figure 5.

1. Record the “Number of births (B)” and the “Number of deaths (D)” in Data Table 1.
2. Remove any dead individuals. For example, in Figure 5 above, the dead individual should be removed from the population and returned to the bag.
3. Add a die for each birth. For example, in Figure 5 above, 2 dice should be added to the population.
4. Calculate the final population size and record the value in Data Table 1. Use the following equation:

$\text{DO THE LAB BY FOLLOWING THE INSTRUCTION BELOW AND FILL OUT THE DOCUMENT ATTACHED.}$

$\text{Final population size = N + B – D}$

1. Count the number of dice in your population to ensure that it equals the value recorded for “final population size” and return the dice to the cup.
2. To obtain data for generation 2, repeat steps 3-10.

Note: Because you will be starting with a very small population, extinction is a possibility, but the odds are against it. If your population does go extinct, start again.

1. Continue rolling the dice and recording data until your population size reaches a minimum of 100.
2. Once you have reached a population size of 100, calculate the change in population size for each generation. Record each value in Data Table 1. Use the following equation:

$\text{Change in population size = Final population size – Initial population size}$

1. Graph the initial population size for each generation. To do this, create a scatter plot with the generations on the independent axis (x-axis) and the initial population size on the dependent axis (y-axis). Consider whether the population growth you modeled showed a linear pattern, exponential pattern, or no pattern.
2. Upload an image of the graph into Graph 1.
3. Graph the change in population size for each generation. To do this, create a bar graph with the generations on the independent axis (x-axis) and the change in population size on the dependent axis (y-axis). Consider whether changes in population size were greatest when the population was smaller or larger.
4. Upload an image of the graph into Graph 2.