Using Protists as a Model of Succession (Part 2/3)

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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 record more data from their hay infusion cultures.  Today they will perturb the cultures to see what affect salt and fertilizer have on the ecosystem. Here is what students will learn in this lesson.

Hook/Check for Understanding

5 minutes

Show students the following video clips:  Amoeba eating two paramecia

and

Water bear (tardigrade) meets paramecium.  

Using the graphic organizer from yesterday's launch lab, have students add more observations to the graphic organizer.  Ask students if they have seen anything similar in their hay infusion.  Allow time for students to describe the types of living things they have seen in their hay infusion.  

(Note:  It is important to allow students to view short videos with identified protists in them.  By comparing their data with experts, students gain confidence and also are able to realize that there may be variation in their individual hay infusions.)

Collecting Data

20 minutes

Students will need to remove a small sample from each hay infusion. They will make a wet mount slide and view the slide under the microscope. Students will make cell counts from six fields of view using the data table provided. They need to classify the organisms they count as animal-like, plant-like, and fungi-like protists. They will make sketches of anything of interest in their lab notebook. These sketches should be labeled with the magnification, date, and description of what is in the sketch.  

(Note: I have several students that have horrible handwriting.  I started providing a data table template that they could fill in.  They were having a hard time reading their own handwriting so I could not expect others to be able to read it. It is important to remind students to record all data even if the count is zero. Also, since each indiviidual's hay infusion might be different and have different organisms, encourage students to share their findings and independently consult with each other, within reason.)  

 

Teacher mini-lecture: Animal-like protists/Succession: What's Next?

10 minutes

Bring students back together as a class. Ask students where they would find ecosystems like the ones being modeled by the hay infusions. Next ask students how those ecosystems might be disturbed. Lead students in a discussion to determine what substance they will use to perturb their hay infusions.  (Note: We find these ditches near roads that are regularly salted with calcium chloride during the winter.  We also find these ditches near agricultural fields that are fertilized with ammonium phosphate.) The class will briefly discuss the elements of a controlled experiment.  

Aid students in calculating how much calcium chloride (salt) and ammonium phosphate (fertilizer) to add to the hay infusion to make a 1% solution.  Students should weigh that amount using a tare scale and add it directly the hay infusion.  Swirl the hay infusion gently.  (Note:  Add salt to one of the hay infusions.  Add fertilizer to the second hay infusion. Leave the third hay infusion alone to serve as the control.)


Putting It All Together: Creating a Foldable

10 minutes

Next have student create a foldable to help them organize protists into groups by their characteristics.  Students will need to fold a sheet of notebook paper in half vertically.  Then they should fold the sheet into thirds.  Have student cut along the creases of the top layer to form three tabs.  Students should label the edge with holes Protists. They should label the top tab, Animal-like, the middle tab, Plant-like, and the bottom tab, Fungi-like. Students should tape or glue this foldable into their lab notebook.  

Then the teacher should relate the defining characteristics of each group of protists.  

(Note: At the end of the lesson I have student make a foldable to help them synthesize the information they have already learned. I use foldables as an organizational technique for my students.  It is a great way to summarize information and study for the test.

Homework:  Students will finish the foldable outside of class using information they have collected today.