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Lesson 1.5 – So why aren’t we always sick? Our body’s defenses

This lesson is intended to demonstrate that although we are covered in
bacteria and exposed to viruses all the time, we rarely get sick. You will engage students in discussions that will develop the idea of sterility and the notion that the interior of the body is sterile while the exterior is non-sterile.

This will involve the new concept that exterior is defined as the area in contact with the environment, not merely on the outside. Based on these ideas, you will introduce the concept that our body has natural defenses designed to protect against infection, and that these defenses are either found on the non-sterile exterior or in the sterile interior.

Teacher Prep

1.5 Classroom Materials

1.5 Alternative Approaches

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