Population Growth Report

Instructions: In this lab activity, you will investigate how predation, starvation, birthrates, and death rates influence the killer whale and seal populations within a marine ecosystem. Submit your lab report to your instructor when completed.


Your Name:

Teacher Name:


Before you begin, form a hypothesis that predicts the outcome of this study.

If the starting population of the seals is higher than the whales, the carrying capacity of the seals will be _________ (higher or lower) than the carrying capacity of the whales.


  1. Complete the table by performing the following calculations. The first row has been completed for you as a model to follow.
    1. Determine to total of seal deaths for each year of the study.
    1. Calculate the seal population change by comparing the births and deaths for the year. The seal population change can be positive or negative.
    1. Calculate the seal population for the year by adding or subtracting the population change to that of the previous year.
  • Fill in data table 2 with the same seal population from data table 1.
  • Create two line graphs on the plot provided. In one color for the seal population and another for the whale population.
    • Use the drawing tool in word processor to draw the lines.
    • Both lines should be graphed from left to right.
    • Make sure to use the axes value for seals on the left and whales on the right.
    • Draw a horizontal dotted line across the graph that represents the carrying capacity for the whales and seals. (Hint: Where do the populations stabilize and growth slows to zero?)
    • Label the carrying capacity line by inserting a text box or using the draw tool.
  • Complete the conclusion and reflection questions.

Data Analysis:

Data table 1

YearSeal BirthsPredationStarvationSeal DeathsPopulation ChangeSeal Population

Data Table 2

Seal Population100115        
Whale Population5711151917121099


Seal and Whale Populations

# of seals                # of whales
180                    20
170                   18
160                  16
150                 14
140                  12
130                 10
120                 8
110                   6
100                   4
90                    2

           Year 1         Year 2        Year 3        Year 4        Year 5        Year 6        Year 7        Year 8        Year 9        Year 10


Answer the following questions as your conclusion in complete sentences.

  • According to the graph, what happened to the seal population as the whale population increased? 
  • What appears to be the carrying capacity of the whale and seal population in the graph? (Hint: Where do the populations stabilize and growth slows to zero?)
  • Between which years of the study does overshoot occur for each population?
  • Does your data support or fail to support your hypotheses (include examples)?
  • What are the limitations of the population growth study? Is it a realistic representation of an arctic marine ecosystem? Note: Please provide detailed support for your opinion.

Post-Lab Reflection Questions

Answer the reflection questions using what you have learned from the lesson and your experimental data. It will be helpful to refer to your class notes. Answer questions in complete sentences.

  1. If another source of prey were available to the whales, what changes in population size would you expect for the seals and the whales?
  2. Calculate the rate of population change for the whales and the seals for the full length of the study. (Hint: Divide the total change in population size (negative or positive) by the total change in time, which is 10 years.)
  3. In this lesson, you learned about two patterns of population growth and decline, the sigmoid and peak phenomena. Does the seal and killer whale relationship represent a sigmoid or peak phenomenon? Justify your answer with supporting details.
  4. Climate change (an abiotic factor) has slowly decreased habitat for the arctic seals.
    1. how a reduction in habitat could change the behavior of the killer whales.
    1. how this scenario would affect the carrying capacities for both the whales and the seals.