1. Investigating Population Growth Rates
Activity 14
Investigating
Population Growth Rates

2. What ecological conditions might promote growth of a population (rabbits for example)
What ecological conditions might limit population growth?

3. Read the introduction Look at zebra mussel graph…
What does the graph tell you about the population?
What factors do you think contribute to this?
Know these vocabulary terms:
carrying capacity
Population growth rate
Zero population growth rate

4. Carrying capacity is the size of a population an ecosystem can support based on the resources available and the other species present in the ecosystem.
Zero Growth Rate: population NOT growing…remains the same
Population growth rate describes the change in a
population over specified intervals of time

5. Avril Gulf Seal Population
Ask the students: What does the graph show about the seal population?
Then ask: What factors and events might have caused the fluctuations in the population as shown in this graph?
Hand out Student Sheet 14.1, “Avril Gulf Seal Population,” and ask students: What information does the table show?
The image above is from Student Sheet 14.1, “Avril Gulf Seal Population.”

6. Challenge
How do changing variables alter population growth rates and ecosystem carrying capacities?

7. LIMITING FACTORS
Conditions that limit a population from growing larger
Make a list in your notes

8. DENSITY DEPENDENT DENSITY INDEPENDENT LIMITING FACTORS
Factors where the effects on the size or growth of a population vary with the density of the population itself
EXAMPLES?
DENSITY INDEPENDENT
limit the size of a population regardless of the density of the population
POPULATION DENSITY
Number of individuals per area

9. AVRIL SEAL POPULATION View population graphs and answer questions
Complete the activity on the Avril Seal Population
Population equation:
BIRTHS – DEATHS
1000

10. POPULATION GROWTH PATTERNS
View various population growth graphs
Draw each in your notes
Identify and describe the growth for each

11. Linear Growth Curve
Population is growing the same amount at regular intervals
EX: a population that increases by 2 individuals each month
For information on having a class discussion about standard growth curves see your Teacher’s Edition for this Activity.
This image is from Transparency 14.1, “Linear Growth Curve.”

12. Exponential Growth: J-Curve
Rate of increase is continually rising
Resources are plentiful
Few/no predators
Little disease
Low death rate
For information on having a class discussion about standard growth curves see your Teacher’s Edition for this Activity.
This image is from Transparency 14.2, “Exponential Growth: J-curve.”

13. Carrying Capacity: S-Curve
But no population can continue to grow forever…
Carrying Capacity: S-Curve
Populations will eventually run out of resources…fail to find mating partners; or other factors such as disease or predators will cause a population to reach its carrying capacity
Population will remain relatively stable …but there may be flutuations
For information on having a class discussion about standard growth curves see your Teacher’s Edition for this Activity.
This image is from Transparency 14.3, “Carrying Capacity: S-Curve.”

14. Population Crash Rapid decrease in population
What factors could cause this to happen in a population?
Population decline is inevitable when a population exceeds its carrying capacity
For information on having a class discussion about standard growth curves see your Teacher’s Edition for this Activity.
This image is from Transparency 14.4, “Population Crash.”

16. WORLD POPULATION GROWTH
Watch this video to view world population growth over past 2000 years

17. OBSERVING POPULATION GROWTH
Using the data provided…prepare a graph showing the growth of bacteria Using the data provided…prepare a graph showing the growth of the world population Label each graph: LAG PHASE… EXPONENTIAL GROWTH…STABILITY… DEATH PHASE Answer questions

18. Analysis 7
Look at the population graph for the fish population shown below. How would you describe the growth rate? Is this population sustainable?
Analysis Question 7 is a Quick Check which assesses students’ abilities to explain trends and relationships, and make inferences and conclusions from data, components of the Analyzing Data (AD) scoring variable. More information and a sample student response can be found in your Teacher’s Edition for this activity, and in Teacher Resources IV: Assessment.

19. Analysis 8
Examine the data in the Global Human Population graph provided below. Based on your work in this activity, how would you describe the global human population growth rate? Explain your reasoning.
Analysis Question 8 is a Quick Check which focuses on trends and relationships in data and touches on one of the main arguments of human-population sustainability. Many experts believe that the human population long ago exceeded earth’s carrying capacity and that we will experience a population crash if sustainable measures are not put in place. This type of data analysis is a component of the Analyzing Data (AD) scoring variable. More information and a sample student response can be found in your Teacher’s Edition for this activity, and in Teacher Resources IV: Assessment.

20. Revisit the Challenge
How do changing variables alter population growth rates and ecosystem carrying capacities?

21. density-dependent factors density-independent factors population
Key Vocabulary
carrying capacity
density-dependent factors
density-independent factors
population
population growth rate
See Teacher Resources III: Literacy for more information on key vocabulary and the most effective strategies to enhance student vocabulary learning.
Note that bold words are formally defined in this activity. Words in regular font are used in the activity, but not formally defined. The definition of a key vocabulary word should not be discussed as a class prior to the formal definition being introduced.