A Day of Discovery (C how Elegant Model Organism Nervous Systems Are!)

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Objective

Students will develop and use models to qualify C elegans as a model organism for human nervous system studies.

Big Idea

C elegans are ideal model organisms which provide researchers with insight to the repercussions of environmental agents that could potentially cause harm to the human nervous system.

Introduction

Lesson Background & Justification:

    A model organism is a species that has been widely studied, usually because it is easy to maintain and breed in a laboratory setting and has particular experimental advantages. Over the years, a great deal of data has accumulated about such organisms and this in itself makes them more attractive to study. Model organisms are used to obtain information about other species – including humans – that are more difficult to study directly.

    Caenorhabditis elegans  is a free-living (not parasitic), transparent nematode (roundworm), about 1 mm in length, that lives in temperate soil environments. As one of the first organisms to have their genome and nervous system mapped, C elegans have gained notoriety in the research community as ideal model organisms. In this lesson, students explore physical characteristics that make these organisms ideal for study and to serve as an introduction to their cumulative research projects for the class. Their projects will focus on the introduction of pollutants and toxins to a biological or model system to assess its impact on humans. 

Prerequisite Knowledge: It is recommended that students be familiar with the structure and function of a neuron, the concept of neurotransmission, the action potential mechanism, metabolic process of cellular respiration, structure and function of DNA,  enzyme structure and function and organelle function. 

Lesson Preparations:

 In the effort to prepare for this lesson, I make certain that I have the following items in place: 

a) A class set of Getting to Know Your Worms curriculum: Pages 7-8 (background information), and 24 & 28 (student resource and worksheet). Provide 1 copy of these sheets to each student pair. 

b) Student lab books.

c) Lab Protection Wear

d) Carolina Biological's C elegans culturing kit

Common Core and NGSS Standards:

SP1- Asking questions (for science) and defining problems (for engineering).

SP2- Developing and Using Models.

SP4- Analyzing and interpreting data.

SP7- Engaging in argument from evidence.

XC-SSM-HS-4- Models can be used to predict the behavior of a system but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models. 

Standards Rationale:

      Modeling is the process by which scientists represent ideas about the natural world to each other, and then collaboratively make changes to these representations over time in response to new evidence and understandings. It is intimately connected to other scientific processes (asking questions, communicating information, etc.) and improves students ability to recall scientific jargon through association. In the classroom, it is important that teachers engage students in modeling practices, to set the foundation of success in a lesson or instructional unit. In this lesson modeling is used in concert with other science practices in the classroom to promote students’ reasoning and understanding of core science idea presented (animal models in research.) 

Engage

10 minutes

Section Sequence:

a) Slide 1: Say: "This year everything that we have learned about the human body hinged on our understanding of the diagram that you are looking at. What does this diagram show? What are some human body functions that depend on this process?" Students should identify this as neurotransmission or the steps within the process (reception, synthesis, uptake, etc) and share body functions related to the senses, motion, and involuntary functions for example.

b) Ask: Are there internal or external factors that could cause dismay in this process and consequently disrupt the fidelity of this system? Take any examples presented throughout the course (genetics, drugs, etc. )

c) Slide 2: Present and read the question aloud to the class. Encourage or prompt students to consider items that they hadn't discussed in class thus far (specifically pollutants and toxins). Once pollutants are mentioned, share that this is what they will seek to find answers for while completing their end of year project. Ask: How can we potentially find out how specific pollutants impact the nervous system? Take suggestions from students and probe them until they arrive at using some sort of model organism to test this variable. 

Standards Covered:

SP1- Asking questions (for science) and defining problems (for engineering).

Explore

40 minutes

Section Sequence:

a) Share with students that in the scientific research community, worms called C elegans are commonly used to assess the potential impact of factors like the ones they mentioned as a class or in assessing new over the counter medications that they commonly buy in the store. Say: Today, we are going to make observations of these organisms and decide if they are good candidates to model the responses of human nervous system (even if in part) to external factors such as pollutants. 

b) Slide 3: Read the instructions as they appear on the board to the class. Student sheet (page 24) and Worm Life Cycle Sheet (page 28). During the class discussion piece, encourage students to connect behaviors observed to necessary nervous system activity such as movement and feeding. Also encourage students to consider the variations between the two types of worms and think about how this too could be an asset to the research process. The idea is for them to see that the worms, while simple offer benefits to assess certain nervous system activity in research studies. 

Standards Covered:

SP1- Asking questions (for science) and defining problems (for engineering).

SP2- Developing and Using Models.

SP4- Analyzing and interpreting data.

SP7- Engaging in argument from evidence.

XC-SSM-HS-4- Models can be used to predict the behavior of a system but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models. 

Explain/Extend

30 minutes

Section Sequence:

a) Slide 4: Ask the question presented at the top of the screen. Take several responses from the class and ask students to support their responses based on their initial set of data/information. 

b) Supply students with the teacher background section (pages 7-8) and provide instructions for the activity by way of the items on the board. Share the following image with students as well and draw their attention to similar molecular events that occur in the nerve cells of the worm and tell them to consider these events when completing the activity.  

c) Share: Let's now generate a class list of items that we feel would be viable when assessing the effects of pollutants and/or toxins on this model organism based on your highlighted sections. Instruct for student groups to read off their blue highlighted items to you as you record them on the board. Direct the class to vote on a list of characteristics that they could potentially study in their individual research project. Stress here that this list should qualify the nervous system's activity specifically and that they should use the information highlighted in pink to support their selections. Once the list has been decided upon, instruct students to record it in their lab books for future reference. 

d) Revisit the initial question presented at the top of the slide and prompt students to provide evidence for their responses this time . 

Standards Covered:

SP1- Asking questions (for science) and defining problems (for engineering).

SP7- Engaging in argument from evidence.

XC-SSM-HS-4- Models can be used to predict the behavior of a system but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models.  

Evaluate

10 minutes

Section Sequence:

a) Slide 5: Share with students that they will introduce 1 of 3 pollutants and/or toxins (heavy metals, nicotine and/or Bisphenol A) to their model organism in their studies. Inform them that they will spend a class block becoming acclimated with each item, so that they can make informed choices on studies that suit their interests. Present and discuss the schedule and timeline for their final project as it appears on the screen. Clarify questions as you move along. 

b) Slide 6: Say: Now that we have an idea of where we are going with our projects, share with me why C elegans would make good or quality models for human nervous system studies. Stress for students to specify terminology and justifications acquired throughout the class. Draw their attention to the specific prompt on the board. 

Standards:

SP7- Engaging in argument from evidence.

XC-SSM-HS-4- Models can be used to predict the behavior of a system but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models.