Are You Smarter than a Worm? (Operant Conditioning in C. elegans ) Day 2

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Objective

Students will precisely follow a multi-step procedure that will lead to the collection, analysis and interpretation of data on operant conditioning in C. elegans to better understand human behavioral systems.

Big Idea

C elegans can be used as animal models to predict human learning behaviors as there are many parallels in the neural circuitry that can be interpreted in an interchangeable fashion.

Introduction

Lesson Background & Justification:

          Operant conditioning, sometimes referred to as instrumental learning, is a method of learning that occurs through reinforcements and punishments for behavior. It encourages the subject to associate desirable or undesirable outcomes with certain behaviors. Caenorhabditis elegans is a microscopic (~1 mm) nematode that normally lives in soil. It has become one of the "model" organisms in biology as it displays similar internal metabolic activity as humans, including neurological functions such as learning and memory. As such, these organisms have been used to study operant conditioning in animals and teaches us a great deal about the neurophysiology of our brains. In this lesson, (Part 2 of 3) students set set up investigations which allow for them to collect and interpret data about these worms and their capacity to learn by association.

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 and the neurobiology of learning (covered in a previous lesson). 

Lesson Preparations:

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

a) 1 Biorad elegans Behavior Kit. (Provide investigation materials for student pairs). Use theinstructor's manual for preparation planning. 

b) Student lab books.

c) Class set of safety wear (glasses, lab aprons and gloves)

Common Core and NGSS Standards:

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

SP7- Engaging in arguments using evidence. 

HS-LS1-3-Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

RST.11-12.3- Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks; analyze the specific results based on explanations in the text.

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 (mechanisms that direct specific biology of memory and learning in organisms.) 

Explore (Day 2)

80 minutes

Section Primer:

        Chemotaxis (from chemo- + taxis) is the movement of an organism in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. In day two of the lab, students will continue to their conditioning investigation using chemotaxis as a natural training mechanism to achieve operant learning. 

Section Sequence:

      In this section of the lesson, students are ready to execute the conditioning experiment with the worms that they primed in the previous exploration lab segment. During this time, students will follow a protocol to exact the science for more fruitful results (guided inquiry). The section proceeds as follows:

a) Review the investigation question as a class via basic Q and A. (eg. What is the question that we are investigating? Why are we using C. elegans as subjects?, etc.)

Activity at a glance: In day 1 of this investigation, students sub-cultured their worms. That is, by this point, they have transferred an actively growing culture of worms in E. coli  to a fresh lawn of bacteria that was growing on salt infused agar. The worms, at this point and if capable of operant conditioning, have been taught to associate salt with their food source for 24 hours. In this part of the lesson, students pick up the baton and  utilize the quick guide to navigate through a structured investigation procedure to assess if the worms had been conditioned. Specifically, students will be provided with agar plates whose halves have been deferentially treated at its poles (1/2 salt and 1/2 buffer) to test their conditioned worms preferences. This is executed with both wild type worms (no genetic voids) and mutant worms (genetically voided of Daf-18, an associative learning gene) and concludes with students taking a count of the number of worms on each side for both plates.

b) For Day 2, dispense the  Biorad's C elegans Learning Behavior Quick Guide and instruct students to gather their materials set out by the instructor (see page 34) and to work in the same groups that they had worked in when they completed part 1/lesson 1 of the lab. 

c) Share with students that for clarity, they are executing a chemotaxis study to assess learning in worms. Play the following video to clarify the concept of chemotaxis for student prior to pursuing the lab. 

                   

d) Allow students to complete part 2/lesson 2 of the lab with requested guidance (accommodate upon request). Students will work through step 19 on page 38.

Standards Covered:

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

SP7- Engaging in arguments using evidence. 

RST.11-12.3- Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks; analyze the specific results based on explanations in the text.

Wrapping Up!

10 minutes

        As an exit ticket of the day, instruct students to summarize their observations and results from the lab in three sentences on a post it note. They should submit their summaries prior to leaving on classroom's parking garage (a place to leave sticky notes requested in assignments).