Exercise 1 Modeling Population Growth

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:

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

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.

Exercise 1 – Questions

1. How many generations did it take to reach a population size of 100?It took 19 generations to reach 100. The 19th generation equals 113

2. Consider the mode of reproduction modeled in your population. Would sexual reproduction or asexual reproduction likely be the cause of a birth? Are individuals of the species likely or unlikely to have separate male and female sexes?

Considering the mode of reproduction sexual reproduction would likely be the cause of a birth. Individuals of the species are likely to have separate male and female sexes.

3. Did the modeled population exhibit linear growth, exponential growth, or no pattern? Use Graph 1 to support your answer.

Yes the modeled population did exhibit linear growth

4. Were changes in population size greatest when the population was smaller or larger? Which generation exhibited the greatest change in size? Use Graph 2 to support your answer.

The changes in population size was greatest when the population was larger. For example, generations 16 and 17 grew from 57 to 71 whereas generations 4 and 5 grew from 9 to 11.

5. What resource constraints were placed on the modeled population?

In this case there were no constraints given that their was linear growth.

6. Could the modeled population exhibit indefinite growth? If so, how? Is indefinite growth observed in nature? Explain why or why not.

Exercise 2 Investigating a Human Population

In this exercise, you will investigate demography of a human population. You will collect birth and death information from a cemetery and analyze trends in the population.

Procedure

1. Research your local area to find a cemetery that you may visit for this exercise.

Note: If you are unable to access a cemetery, you may use the data provided in the “HOL Supplied Cemetery Data” Supplemental Document. If you choose to do this, skip to step 9.

1. Count the number of people who died in each cohort (age interval). Record your data under “Number of deaths (D)” in Data Table 4.
2. Calculate the “Frequency of population in cohort (d).” Record each value as a number with two decimal places. Use the following equation:

$\text{d = D / Total Population Size}$

Note: “Frequency of survivorship of cohort (l)” is based on entry into the cohort. Thus, the first cohort listed will always have a value of 1.00 because 100% of the population was born, entering into the cohort. A value of 1.00 has been entered for cohort # 1 in Data Table 4. With each subsequent cohort, values of “l” will decrease.

1. Calculate the “Frequency of survivorship of cohort (l)” for cohort # 2. Record each value as a number with 2 decimal places. Use the following equation:

${\text{I}}_{\text{cohort2}}{\text{= I}}_{\text{cohort1}}{\text{– d}}_{\text{cohort1}}$

1. Calculate the “Frequency of survivorship of cohort (l)” for each of the remaining cohorts. For example, “Frequency of survivorship of cohort (l)” for cohort 3 will be calculated as:

${\text{I}}_{\text{cohort3}}{\text{= I}}_{\text{cohort2}}{\text{– d}}_{\text{cohort2}}$

Note: The final recorded “l” in Data Table 4 should be equivalent or very close to the final recorded “d.”

1. Calculate the “Probability of death (Q).” Record each value as a number with 2 decimal places.Use the following equation:

$\text{Q = d/I}$

Note: The probability of death is a frequency and may be interpreted as a percentage. For example, if Q = 0.30 for cohort # 1, then there is a 30% probability that a given individual will die between the ages of 1 to 9.

Note: To find Q, use data within a single cohort: Qcohort1 = dcohort1 / lcohort1

1. Create a bar graph of the probability of death within each cohort. Plot the cohort age interval (1-9, 10-19, etc.) on the independent axis (x-axis), and plot the probability of death on the dependent axis (y-axis).
2. Upload an image of the graph into Graph 3.

Exercise 2 – Questions

1. Which cohort had the greatest probability of death? Which had the least probability? Use Graph 3 to support your answer.

2. Overall, does human mortality tend to be greatest at young ages or older ages?

3. How many individuals were male, and how many were female? How many individuals were you unable to assign a gender to?

4. Using the raw data in Data Table 2, calculate the average age at death for males and for females. What inferences can you make about male versus female age at death?

5. If the government made significant cuts in social services, such as prenatal and infant care, how might your data be affected?

Option #2: Population Ecology Presentation

In this laboratory exercise, we will explore the field of population ecology and survey factors involved in the decline, expansion, and maintenance of a population. Simulated growth of a population will be modeled, graphed, and analyzed. You will also use quantitative data from a cemetery population to study demographics.

Complete all sections of the Population Ecology laboratory exercise, in your Environmental Science Lab Kit from Hands-On Labs, Inc. Fill out all parts of the worksheet. It will not be necessary to submit your original worksheet for this assignment.

In a PowerPoint presentation of approximately 12-14 slides, discuss all parts of this lab activity. Your presentation should include the answers to all the worksheet questions. Be sure to include all of your data tables and graphs from this activity in your PowerPoint. References and citations