Lesson 3: How Can We Refine Our Experimental Designs?
At the conclusion of this lesson, students will have refined their experimental designs based on peer feedback and set up their experiments. (They will conclude their experiments, collecting and interpreting data, in Lesson 6, three to five days from today.)
The homework assignment draws the distinction
between acute and chronic doses, and then directs students to play the
role of a senior executive at a pharmaceutical company and consider the
quantitative criteria for determining the safety and effectiveness of a
By the end of the lesson, students will be able to:
refine experimental designs to address peer review concerns to instructor satisfaction.
explain the importance of deliberate and creative planning prior to conducting an experiment to instructor satisfaction.
differentiate between acute and chronic doses (and responses) with 100% accuracy.
assess the criteria of safety and effectiveness for the approval of a new drug to instructor satisfaction.
9th through 12th
Prepping the Lesson
It is our recommendation that you walk through the teacher and student materials for this lesson to ensure that students will be able to receive the information through the modes of delivery that we intended prior to using the material in the classroom. If you or your school does not have the resources needed, you may need to make some modifications depending on the resources you have available.
The following materials/technical resources will be needed to complete the lesson. We recommend using Option #1 to provide the materials to your students in the manner in which they were intended to be delivered.Option #1:
(Preferred Technology Requirement) You will need to have access to a computer, the Internet, and a projection device during the entire lesson. Your students will need to have access to computers and the Internet. You and your students will simultaneously step through the module while using their given computers. You may have to make special arrangements for all of your students to have a computer. Be sure you and your students will not be blocked from Google Documents, YouTube, and your selected online collaborative tool. You may be currently using an online collaborative tool but if not, we recommend Facebook groups, Edmodo, or eChalk.Option #2:
Requirement) If you do not have a way for your students to access the
Internet individually, then you will need to facilitate their access to
the information. You will need access to a computer, the Internet, and a
projection device during the entire lesson. You will step through the
module as your students watch and complete the presented activities.
There may be modifications to the delivery of the materials that you
will need to make, depending upon the resources you have available. Be
sure you have access to Google Documents, You Tube, and your selected
online collaborative tool. You may be currently using an online
collaborative tool but if not, we recommend Facebook groups, Edmodo, or
Lesson Time and Supply List:
will provide you with information on prep time needed, a list of
supplies, and total lesson time for this particular lesson.
Prior to starting this
module, it is important to determine which online collaborative tool
you and your students will be using. Once you have had an opportunity to
review all of the lessons, decide how you will facilitate the homework
discussions and submissions using your selected online collaborative
tool. Be sure to give your students clear directions and objectives on
your expectations of the use of this tool and their participation in
their homework activities. We highly encourage you to participate with
your students in their homework discussions to enhance the quality of
crystals, cardiovascular, cholesterol, chronic effects, continuous
exposure, coronary disease, environmental concentration, experimental
systems, germinate, long-term responses, median germination failure
concentration or GFC50, neurological
disorders, pharmaceutical, plasma membrane, regulator, short-term
responses, tubules, vitamin D (See Lesson 1 and 2 for additional
Laboratory notebooks are arguably the most useful tool at an experimenter’s bench. Remind students of the critical importance of recording all experimental observations, and especially recording all experimental conditions (e.g., the type of chemical treatment, the range of concentrations, number and species of seeds, etc.) when starting an experiment so that they can maintain comprehensive, unambiguous control over those variables when they follow up with subsequent experiments.
Implementing the Lesson
1. Guided Discussion: Comparing Experimental Designs (10 Minutes)
one or two students’ experimental designs to review with the entire
class. Be sure to provide guidance to designs that are not still
sufficiently complete to be carried out. Students should also be given
the opportunity to revise their experimental designs based on feedback
from their peers in the homework assignment, appropriately updating
their observation tables and otherwise documenting the changes in their
2. Group Activity: Setting Up the Experiment (35 Minutes)
Starting with a comprehensive and clear experimental design, and an observation table to collect their data, students should proceed to set up the experiment: mixing dilutions, preparing and labeling petri dishes, planting seeds, and the like. Students can review the “Serial Dilution” video if needed.
When students are done
setting up the experiment, collect the petri dishes and incubate them
in the dark (an easy way to do so is to put the stacked petri dishes
back in the box they were shipped in).
3. Guided Discussion: Conclusion (1 Minute)
As students are finishing their experimental setup, address any student questions or concerns, and introduce the homework assignment.
4. Video: Acute Versus Chronic Toxicity (5 Minutes)
The homework assignment includes two parts:
The "Acute Versus Chronic Toxicity" video explains concepts students will apply in the activity;
In the “Pharmaceutical Company Scenario,” students will consolidate their understanding of the dose/response relationship and extend it to cover chronic as well as acute effects.
post both the video and the activity to your class’s online
collaborative tool for your students to review and complete.
5. Activity: Pharmaceutical Company Scenario (30 Minutes)
Imagine that you are a senior executive for a large pharmaceutical company. You are responsible for the safety and effectiveness of the new drugs that your company introduces to the market.
The company is preparing to launch a new pain reliever. What sorts of effects would you examine in order to convince yourself (and regulators) that the drug is safe and effective? Remember to consider both acute and chronic effects!
Select at least three biological responses that you would evaluate for your new drug. Choose any biological responses, harmful and beneficial, acute and chronic, that you think would be relevant to evaluating a pain reliever. Sketch your best guess of the dose/response curves for each response. The precise values of the median doses are not so important as your educated guesses about which will be lower and which will be higher.
Which responses are acute? Which are chronic?
What criteria would you use in order to call a new drug “safe”? (You might recall the concept of the Therapeutic Index.) What criteria would you use in order to call a new drug “effective”? (Are these criteria different for chronic, as opposed to acute, effects?) On the basis of your results, would you call your new drug "safe?" Would you call it "effective?"
Using your online collaborative tool, share your answers (including the dose/response curves) with your classmates. You might find these sharing suggestions to be helpful examples.
Using your online collaborative tool, comment on at least one other student’s response to these questions.
Are they measuring appropriate responses?
Are they drawing the correct conclusions about safety and effectiveness?
What did they think of that you did not?
During your next class you will review some of your answers and discuss them together.
Answers: Students might suggest both acute and chronic therapeutic uses, and may suggest any number of possible side effects—death, coma, stomachache, insomnia, diarrhea, ringing in the ears, dizziness, stroke, stomach ulcer, allergic reaction, etc.
This video is an example of a good response to this activity. It may help to frame the discussion of the activity at the beginning of the next meeting, but don't share it with the students before they try thinking it through themselves.
Two main ideas to review during the next class meeting: (1) There is more to toxicity than lethality—dose/response curves depend on measured response. (2) There is more to toxic effects—and beneficial effects—than those that can be measured immediately (acutely); many effects can only be measured over the long term (chronically).