Using Protists as a Model of Succession (Part 1/3)

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Objective

Students will explain how succession occurs in an ecosystem by noting the changes in a hay infusion over a period of time.

Big Idea

By using protists as model organisms, we can shorten period of time succession occurs so we can observe changes in an ecosystem.

What Students Will Learn in this Lesson

1 minutes

Students will set up several hay infusion cultures to model succession.  The purpose of this two week lab is to help students better understand ecosystem dynamics, functioning, and resilience. By studying the changes in a hay infusion over a two week period, students will gain an appreciation of a ditch by the side of the road, an ecosystem they see every day on their way to school. Students will model the ditch ecosystem in an Erlenmeyer flask. Here is an overview of what students will learn today.  

Hook

5 minutes

Have students complete the Launch Lab 19. Students will explore the diversity within the kingdom Protista by using a launch lab powerpoint of several different protists. The protists that they will view include several plant-like protists, fungi-like protists, and animal-like protists (both free-living and parasitic). Students will complete a graphic organizer for Launch Lab 19 in their lab notebooks with their observations. Students will also make a prediction if the protist is animal-like, plant-like, and fungi-like as seen in this example of student work.  (Note: Later in the lesson, students will revisit their predictions and learn more about the classifications of protists.) 

 

Student Activity: Creating a Hay Infusion

25 minutes

Next, explain to students how to create several hay infusions. These cultures will be used to study how succession occurs in an ecosystem.    

Each student group will create three hay infusions using this protocol, Lab Techniques in Microbiology: Creating a Hay Infusion. Once the hay infusions have been made, students will need to remove a small sample from each. They will make a wet mount slide using this protocol and view the slide under the microscope. They will need to make some sketches of what they see in their lab notebook. Using the data table provided, students will need to record how many animal-like, plant-like, and fungi-like protists they see.  

(Note:  Students will be making daily observations for about 2 weeks. I like to start this lab on a Friday so that the cultures will have the weekend to mature. Since the hay infusion culture has had no time to mature, it is unlikely that students will see anything but hay particles on their wet mount slide today.)

 

Teacher Mini-Lecture: What is a Protist?

10 minutes

Ask students to share several their observations from both their wet mount slide cell counts and also from the Launch Lab 19.  

(Here are several examples of student work:  protist succession lab example one,  protist succession lab example twostudent work example Launch lab 19, and day zero student data table.)

 

Next, have students revisit several images of the protists in the powerpoint. After examining the images, have students revise the data table in their lab notebook to record new observations.  Have student look back at the images and then record the similarities and differences between the different types of protists using the bolded questions in the presenter's notes to aid in discussion. Have the students organize the protists with similar characteristics into groups using the student collected data. Have students infer which of the student created groups and animal-like, plant-like, or fungus-like.  

(Note:  It is important to check student lab notebooks daily during this lab to make sure students are collecting careful data. If one has a large class, then a random sampling of student lab notebooks may be the solution. Check out my teacher reflection to see how I hold my students accountable in this type of lab.)

Putting It All Together: What to Do With Euglena

5 minutes

 

Show students a video of Euglena and have them consider the following statement. 

Euglena, with their ability to move and their food-making chloroplast, pose a dilemma for anyone who tries to classify all living things into just two categories: plant and animal

 

Demonstrate to the students how chunk the passage and ask them to determine where Euglena should be placed?  

When students are done, they should turn in their lab notebooks for evaluation. Use this information to help prepare for tomorrow's lesson.