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Some Similarities between the Spread of Infectious Disease and Population Growth

Graphs with exponential growth and logistic growthFirst, students analyze a hypothetical example of exponential growth in the number of infected individuals.

Then, a class simulation of the spread of an infectious disease shows a trend that approximates logistic growth.

Next, students analyze examples of exponential and logistic population growth and learn about the biological processes that result in exponential or logistic population growth.

Finally, students analyze how changes in the biotic or abiotic environment can affect population size; these examples illustrate the limitations of the exponential and logistic population growth models. 

Download Student Handout: PDF format or Word format

Download Teacher Preparation Notes: PDF format or Word format

The Teacher Preparation Notes provide instructional suggestions and background information and explain how this activity is aligned with the Next Generation Science Standards.

We invite your comments and questions. If you would prefer to send your comments or questions in a private message, please write Ingrid Waldron at


iwaldron's picture

2018 revision

The questions in the Student Handout have been revised to increase student engagement and clarify the major concepts. Revisions in the Teacher Preparation Notes include expanded learning goals and updated scientific background information.

Carolyn's picture


PE listed in the Teacher notes has a misspelled word. The second PE should read "...affect populations", not effect.

iwaldron's picture

Typo has been corrected

Voice dictation is not as smart as I would like and my proofreading is not as good as I would like.


iwaldron's picture

2017 revision

This is essentially a new activity with a more sophisticated simulation of the spread of infectious disease, improved questions to foster student understanding of the underlying processes that result in exponential or logistic growth, and expanded analysis of patterns of population growth.

Serendip Visitor's picture


I've just been looking at the "Evolution by Natural Selection" worksheets. Can you please correct the grammar when you use "different"? The preposition which goes with "different" is "from" not "than".

I would also appreciate English spellings of words like colour. I realise that Americans spell things differently, but I'm in Australia where we speak and write English, not American.

Phil's picture



Did you know you can download the worksheets and edit them on your own?

iwaldron's picture

Modifying the Student Handouts

Yes, we encourage teachers to adapt the Student Handouts for our activities to best serve their teaching goals and students' needs.


iwaldron's picture

2012 revision

The Student Handout has been revised to improve clarity and make the activity more concise and more focused on exponential and logistic growth curves. Revisions of the Teacher Preparation Notes have clarified the instructions.

Serendip Visitor's picture

Make NaOH solution

I used household baking soda. I added about a teaspoon of baking soda to about 1/4 cup of tap water.

I used a "homebrew" pH paper to test.

iwaldron's picture

Preparing NaOH solution

The safest way to prepare a clear solution with a basic pH of 10 or above is to use Calgon or Borax. 

To use NaOH pellets we think the best approach would be to prepare a 0.25 molar solution, dissolving the appropriate number of pellets in water and using gloves and goggles for safety. 

Either way, you will want to check to make sure that your solution when diluted to 1/8 strength will still change color when the pH indicator is added.


Ingrid Waldron and Jennifer Doherty


Anonymous's picture

NaOH Solution

What is the best and safest way to prepare this NaOH solution? I have access to NaOH pellets- any idea how I can use these?

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