Monsters Inside Me: Parasitic Protists (Part 2/2)
Lesson 4 of 11
Objective: Students examine the life cycle of Plasmodium for use as an example of natural selection.
Today students will watch a portion of the television series Monsters Inside Me so they can learn more about how malaria spreads. Then students will debate whether or not people should be allowed to spray to control the mosquito that causes malaria. Here is an overview of what students will learn today.
Students will make wet mount slides of their hay infusions as they continue to collect data for the hay infusion lab that was started three school days ago. Students should make sketches of what they see at 6 different places on the slide. After eight minutes, have the students clean up their lab areas and return to their desks. Microscope slides should be disposed in the glassware bucket.
Preface the showing of the video clip by explaining that malaria is a disease that affect millions world-wide. The video will show how one person was diagnosed with malaria. Using the life cycle graphic for malarial parasite from the NAIAD webpage, give a brief overview of the vector for the parasite and the stages in the protist's life cycle.
Show students a video clip from Season 2: Episode 3: Cold blooded Killers. Start the video at 17:55 and end the video at 31:30.
Before starting the clip, hand students the graphic organizer for the video. Students should fill out the organizer while watching the video.
Here is the answer key to use with this video clip.
The case study, "To Spray or Not to Spray?" can be found at the NSTA Learning Center. It is a free resource, but teachers need to have an account. Provide each student with a copy of the reading from the article. (Note: I modify this case study by giving my students a graphic organizer to help them sift through the arguments given in this reading.)
In this case study, students consider the complex issue surrounding the use of DDT to control malaria. Students should consider the risks and benefits from using DDT as they role play as policy makers. Students should be placed in groups of four and assigned one of the visitors from the case study (Dr. Lund, Ambassador Iogu, or Dr. Canavan.) Students should read through the case. Using the argument organizer, they should summarize the main point of their expert's argument. Then using the talking points given in the case, students should determine what evidence each expert gives to support their argument. Next, student groups should prepare a five minute presentation that argues their visitor's point of view. Student groups can bolster their argument with additional resources, if necessary. Students should pick a spokesperson to present the group's findings. (Note: Here is a video of a portion of my students' group discussions. They are with a partner due to the small class size.)
based on Bierson, Joseph F. and Frank J. Dinan. 2001. "To Spray or Not to Spray." Journal of College Science Teaching (31)1:32-36.
Student groups will explain their expert's argument during a five minute presentation. While groups are giving their presentation, the rest of the class should complete cost-benefit analysis and evaluate each group's claims. Then using the questions in the case as guidelines, the entire class should discuss the risks and benefits of spraying as compared to the risks and benefits of not spraying. Those questions can be answered on the back of the cost-benefit analysis sheet. (Here are some sample presentations.)
At the end of the discussion, all students should assume the role of a delegate to the United Nations. Each student will write a response in his or her lab notebook stating whether they would continue the ban on the use of DDT, allow for some use of DDT, or allow for complete use of DDT. Students should support their recommendation with evidence from the case.
Putting it All Together
Next, refer students back to the flip book that they created in a previous lesson in this unit. Ask students to determine if Plasmodium is a fungus-like, plant-like, or animal-like protists.
(Note: taxonomists classify Plasmodium as an animal-like protist.)
Guide students in listing reasons why Plasmodium would be classified in the animal-like protists.
Possible answers include:
- It is motile for part of its life cycle.
- It is a heterotroph living off of the contents of its host's small intestine.
- It lacks a cell wall in its single cell.
Next, have students consider why Plasmodium should be in the parasitic category. Then ask them how the Plasmodium might have evolved?
Give students a chance to write their ideas down in their notebooks. Explain to them that answers to these questions will be addressed in a later lesson.
Homework: Students will listen to this podcast produced by the CDC about insecticide resistance in malarial mosquitoes. Students should complete a current events summary that outlines the major findings in the study.