Describe the Perfect Pathogen
Author: Sarah Kenyon and Rachel Hughes

Time: 3 days
Preparation Time:  

In this apply lesson students draw upon their background to design the perfect pathogen.

Students will be able:

1. Apply their background in pathogens and immune systems to develop a model pathogen.
2. As a class articulate aspects of the immune system that would combat various types of pathogens.
3. Identify possible physical or behavioral changes in a pathogen that would be advantageous and possibly selected for (natural selection).

National Science Education Standard:
Content Standard C


  • Cells have particular structures that underlie their functions. Every cell is surrounded by a membrane that separates it from the outside world. Inside the cell is a concentrated mixture of thousands of different molecules which form a variety of specialized structures that carry out such cell functions as energy production, transport of molecules, waste disposal, synthesis of new molecules, and the storage of genetic material.


  • Organisms both cooperate and compete in ecosystems. The interrelationships and interdependencies of these organisms may generate ecosystems that are stable for hundreds or thousands of years.
  • Living organisms have the capacity to produce populations of infinite size, but environments and resources are finite. This fundamental tension has profound effects on the interactions between organisms.



Students will develop a pathogen based upon their knowledge of pathogens (1 day). After presenting it to the class, the class will then suggest ways that the pathogen might be combated (1-2 days). In response to the classes of defenses the immune system has, students will then show how possible changes in structure or modification can be useful adaptations for the pathogen (1 day).

1. Drawing upon the different bugs you have met over the past few days design a pathogen. You can draw upon some of the qualities of pathogens you have encountered. Do not copy an existing pathogen. Address the following issues:

1) Name your pathogen.
2) What is your cell type? Pathogen type?
3) How do you invade your host?
4) How does your host try to defend against you?
5) How do you evade host defense?
6) Describe your life cycle.

2. Present your pathogen to the class. The rest of the class will play the role of the immune system you are testing against. They will try to defend the host you choose with their knowledge of the immune system and how pathogen/host interactions work. Points are given for use of the immune system knowledge used to combat your pathogen. Each group has a secretary to take notes on what they feel are successful defenses that will be addressed in the evolution section. The teacher will assess points for participation and appropriateness of “defense”.

3. Redesign your pathogen based on the defenses (of your classmates!) you encountered. Describe why you make each modification to your pathogen.

As needed

Embedded Assessment

Do students answer the questions in developing their model pathogen? Within a class discussion are they able to identify aspects of the immune system that defend against specific types of pathogens? Can students recognize possible physical or behavioral changes that would have an evolutionary advantage?



PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:

NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award


Supported by NIEHS grant # ES06694

1996-2007, The University of Arizona
Last update: November 10, 2009
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