Investigating Population Growth Rates Activity 14 Investigating Population Growth Rates

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What ecological conditions might promote or limit population growth?

Read the introduction What factors do you think might change the carrying capacity for a population?

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.

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.”

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

Examine Student Sheet 14.1 Set up a blank graph similar to the graph on Student Sheet 14.1 to collect your data from the simulation. During which periods do you think the Avril Gulf seal population have positive growth rates? What is your evidence? The simulation can be found on the student page of the Science and Global Issues page of the SEPUP website, sepuplhs.org/sgi.

Linear Growth Curve 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.”

Exponential Growth: J-Curve 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.”

Carrying Capacity: S-Curve 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.”

Population Crash 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.”

Look at Student Sheet 14.1 What type(s) of growth does the population graph represent? Students should use the words linear, exponential, and carrying capacity to describe their ideas.

Analysis 6 Scientists and policy makers often have to work together to set catch limits on fisheries. Imagine that a policy maker proposes to allow the fishing of a certain species to go on at current rates because, she says, “Fishing at current rates will not impact the ecosystem. We are removing fish at a rate lower than the birth rate of their population.” Is this claim valid? What indicators would you look at to support or disprove this claim? Explain your reasoning. Analysis Question 6 is a Quick Check assessment which provides an opportunity to assess students’ choices of indicators and how to analyze them, 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.

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.

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.

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

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.