Using Protists to Understand Evolution (Part 1/2)

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Using the phylum Apicomplexa, students explore how the common and novel aspects of eukaryotic cell biology arose.

Big Idea

Ever wonder how model organisms are used to explain how eukaryotes evolved? Find out today.

What Students Will Learn in this Lesson

1 minutes

Students will look at the work of David Roos to understand how scientists use model organisms to understand the evolution of the eukaryotic cell. Here is an overview of what students will learn today.  


3 minutes

Using the Frayer method, ask students to define the essential vocabulary mitosis.  Ask student to summarize what happens when a cell divides using mitosis.  

Possible student responses include:

  • Mitosis is part of the cell cycle. 
  • Students may also be familiar with the phases of mitosis including prophase, metaprophase, metaphase, anaphase, telephase. 
  • Students may also refer to the division of the nucleus and the copying of DNA. 


(Note: It is important that students have a basic understanding of the general model of mitosis so they can understand the exceptions to the model discussed by Dr. Roos during his lecture.)

"Guest" Lecturer

35 minutes

Students will view the iBiology lecture by David Roos (Part 1: Biology of Apicomplexan Parasites).  I stream this lecture for my class and provide them a web quest.  

(Note: At certain points in the lecture, I pause the video and check for understanding. During these breaks, we check the web quest to make sure students have not missed any sections because Dr. Roos talks very fast.  I also ask several some questions to help them understand the big picture which I have included in this sections.)

Hand out the web quest to students and play the lecture. Make sure the subtitles are turned on for this lecture as it will aid students as they complete the web quest. Pause the lecture at 6:25 and check the first 5 answers on the web quest. Ask students to summarize this portion of the lecture on the back of their web quest. (See student work sample to see how this is done.)

Give students a minute to write their summary. Ask a student volunteer to read their summary. Continue the lecture until 8:04. Pause the lecture. Check the number 6 and 7.  (Note:  Dr. Roos goes very quickly through the graphic. It is helpful to pause the video and go through the graphic with the students.  While he fails mention it in his lecture, I finds it helpful to include the vector for Crytosporidium which is primarily beavers.) Then give students one minute to write a summary about this portion of the lecture. (See student work sample.)

Continue the lecture until 12:19, then pause the lecture. Check answer 8-10. This is a hard portion of the lecture for students because of the jargon that Dr. Roos uses so help them out with the summary by asking the leading question

  • What is it about apicomplexans that make them a great model organism to study how proteins are made?

(Refer to student work sample)

Continue the lecture until 16:40, then pause the lecture. Check answers 11-13. Help students write their summary for this portion by asking:  

  • What organelles make Apicomplexans special or unique? 
  • What do they do to protect the protist from the host cell.?" 

Ask students to share what they wrote.  

BRAIN BREAK! (See my teacher reflection for more on how I use these with my students)  At this point students are half-way through the lecture. Have them stand up and extend their arms to the ceiling. Then have them bend at the waist and touch their toes.  Have students sit down and begin the lecture again.  

Continue the lecture until 20:13 and then pause the lecture.  Check the answers for questions 14-16 on the web quest. Ask students to summarize this portion of the lecture on the back of their web quest. 

Continue the lecture until 26:56 and then pause the lecture again.  Check the answers for the questions 17-19.  Ask students to summarize this portion of the lecture on the back of their web quest.  To help them focus their thoughts, ask them the following questions:

  • How is the reproduction of Toxoplasma the same as Plasmodium? How is it different than Plasmodium?

Continue the lecture until 29:00 and pause the lecture so students can fill out the data table. Throughout this portion of the video help students notice that the time it takes for the centrioles to copy is shown in pink on the graph, the Golgi apparatus is shown in yellow, the nucleus is shown in light blue, and the apicoplast is shown in green.) Point out that each structure to which Dr. Roos is referring has been labeled with a different color of fluorescent protein. Also help them notice that the mitochondrion is labeled with red and the daughter scaffold is labeled in purple.) Point out that the experiment was repeated and different organelles were labeled with different colors of fluorescent proteins. 

At the end of the lecture, have students write a final summary about the reproduction of this type of protist as compared to yeast (which we commonly use as a model organism for what we know about mitosis in eukaryotes.)

Putting It All Together: What do all eukaryotes have in common?

10 minutes

Students need to make two columns in their lab notebook.  They need to label one column similarities and one column differences.  Students need to list four similarities that all eukaryotes share.   Then students need to list four differences that only apicomplexans have and how these differences help them survive and reproduce in the host cell.  Remind students that these differences are evidence of natural selection, a way that these living things adapted in order to survive in a new environment.  At the end of the hour, students should turn in lab notebooks for evaluation.   (Note: Here is an example of student work for the Putting It All Together summary. This student did not finish the fourth difference between all eukaryotes and amicomplexans.  This students will be asked to add that fourth differences at the beginning of class tomorrow when lab notebooks are returned.  In this way, students are held accountable for their responses on a day to day basis.)

Homework:  Students will watch another iBiology lecture about the organism that causes Chagas' disease.  This lecture is by Norma Andrews, a protist expert from Yale University.  Student will complete the Chagas' Disease web quest and turn it in tomorrow at the beginning of class.