Water on the Move: Osmosis (#3 of 3)

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Students will be able to understand the hierarchical nature of multicellular organisms. Furthermore, students will be able to model the process of osmosis and predict and explain its outcomes given the conditions of the environment.

Big Idea

The structure of the cell membrane in addition to specific internal and external conditions dictate how water diffuses sometimes with drastic results!

Learner Goals

Photo Credit: "Oncorhynchus nerka" by Timothy Knepp of the Fish and Wildlife Service. - US Fish and Wildlife Service. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Oncorhynchus_nerka.jpg#/media/File:Oncorhynchus_nerka.jpg                                          

Note: I recommend that you first check out this resource in order to get the most out of this lesson!

In high school I took several drafting classes and, for a while, I had hoped to become an architect. With respect to planning instruction and teaching, I feel that I can still live out the detailed approach to building something intricate and complex even though the product is a lesson rather than a certain "built environment".

The lesson-planning document that I uploaded to this section is a comprehensive overview of how I approach lesson planning. This template includes the "Big Three" aspects of the NGSS standards: Disciplinary Core Ideas, Crosscutting Concepts, and Science Practices. Of course, there are many other worthy learning goals, skills, instructional strategies, and assessments that can be integrated into a class session. I don't feel compelled to check every box but, rather, use it as a guide to consider various options and tailor the lesson in light of these.

With regard to this particular lesson...

1) Understand that multicellular organisms have a hierarchical structural organization, in which any one system is made up of numerous parts and is itself a component of the next level. (LS1.A)

2) Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. (HS-LS1-2)

3) Generate a logical conclusion that is supported by evidence from the investigation and/or provide a scientific reason to explain the trend in data given a description of and the results from a scientific investigation. (WA-INQC-1)

I hope you get some value from my work!

Anticipatory Set ("Hook")

5 minutes

Please click here to link to the previous lesson in the series.

Hierarchical Structure*: Using the Think-Pair-Share technique, students are prompted to sequence the following items from smallest to largest: organ, nucleus, organism, cell membrane, nucleolus, tissue.

For context and relevance, I explain a bit of the life history of the noble salmon and how the regulation of water (itself a function of the kidney) is greatly affected by the dual threats** of its juvenile (fresh water) and adult (saltwater) habitats. Furthermore, I explain a bit about the adaptations salmon employ to maintain homeostasis throughout their lives.

*Photo Credit: http://www.sciencecontrol.com/wp-content/uploads/2011/04/Levels-of-Organization.jpg

**Copyright Notice: The experimental data contained in the previous link are copyrighted by the University of New Mexico. Proper legal notification is provided here.

Instructional Input/Student Activities

40 minutes

1) EOC Short Answer Prompt Conclusions: Students will peer review each others' homework.  As a class, review the four attributes by which student work will be graded. Solicit (open-ended) student responses for possible correct entries. For correct answers move to another student to share what she wrote. For incorrect answers, solicit responses from students to diagnose what is missing or incorrect and suggestions to correct it.

If necessary (scoring fewer than 2/2 points), students will be required to revise their work and resubmit it at the next class session. For more details on my approach to teaching students how to write proper conclusions, please click here.

Teaching Challenge: How do I support students to develop and use scientific models?

2) Membrane Model (Student): How must a membrane be built in order to permit the following forms of cell transport (Active Transport, Diffusion, Osmosis)?

Students are to draw a simple (visual) model of a lipid bilayer and include the appropriate parts that permit small, uncharged solutes to diffuse (e.g. glucose), charged or larger solutes (e.g. proteins or starch), and those that are hydrophilic (e.g. water) in order to osmosis to occur.

The model ought to be labeled with these terms: phospholipid bilayer, channel proteins, and integral proteins, solute, water in addition to where diffusion (simple and facilitated), osmosis, and active transport occur.
Click here here for a look at a student sample!

Closure: What did we learn? Where do we go from here?

10 minutes

Membrane Model (Teacher): Students will be shown an exemplar of the cell membrane model created by the teacher. Salient features will be pointed out with an emphasis on connecting the structures of the cell membrane with its resulting functions (i.e. diffusion, osmosis, active transport). Students will then be directed to peer evaluate each other's models based on the stated criteria; 1 point per criteria for a total of 8 points.

Time permitting: The role of aquaporins (certain membrane bound protein channels permitting hydrophilic water to pass through hydrophobic barriers) will be explained. These, in turn, are controlled via negative feedback processes but can be temporarily disrupted by consumption of coffee and/or alcohol. The hormone ADH increases the absorption of water back to the body from the kidney and decreases urine output. This is reversed by alcohol and/or coffee.

It's never a bad thing to reinforce the role of negative feedback on the healthy functioning of the body.

Lesson Extension & Follow-Up Activities

Complete any and all revisions to the Saltwater Fish Conclusion if she scored below 2/2.