ISOPOD LAB INSTRUCTIONS

Working quietly, read the first page of the lab up to “experiments designed to scientifically answer questions”. Working with your neighbor, discuss and be ready to define the terms listed below Manipulated variable Responding variable(s) Controlled variable(s) Control group

Designing an experiment - Day 1 Manipulated variable The variable that you change in an experiment (what you’re testing) Reasonable conditions of the MV Three different levels that make sense in experiment Students struggled last year with “reasonable” Example: if temperature is the MV, three conditions could be 40ºF, 50ºF, 60ºF Responding variable(s) The variable(s) you are measuring (your data) Controlled variables (these increase validity) Variables kept the same in all trials Reasonable control group The group used for comparison (it has NO manipulated variable) Should be similar to “normal” state of what you’re testing. Students struggled last year with “reasonable” control group Replicates/trials (these increase reliability) Do everything at least 3 times

Example experiment – Day 1 Example question: What is the effect of caffeine on student heart rate? Example MV: Caffeine Example conditions One cup, two cups, three cups of coffee Example responding variable Student heart rate Example controlled variables Many… Example control group Students with NO caffeine

Example hypothesis If isopods are exposed to increasing amounts of salt water, then they will be repelled from the location of the salt because salty solutions have a negative effect on terrestrial organisms. Note: “increasing” could be “decreasing”, but not “changing”. Must be clear how MV is being changed

Back to lab benches… Who will read directions? Hands up. Decide upon chemical Anything in back, or bring in your own Do Pre-lab assignment (write hypothesis) Review guidelines, recommendations, materials Start brainstorming/discussing experimental design (procedure) Review materials and guidelines in handout!

Instructions – Day 2 As a group: Choose chemical and develop hypothesis Record experimental design on SCRATCH PAPER – one/group Mr. Welman must approve materials, variables, procedure Call me over at any time; spokesperson prepared to explain See me to borrow one isopod for practice (no chemicals) Tonight: complete “Experimental Design part 1” in YOUR packet. Develop experimental design Complete materials list, identify clear variables Write step-by-step procedure Must have way to quantify (count/measure/etc) data. Don’t just plan on making observations – time/count/etc their behavior! Start thinking about data table, including averages

Isopod Lab Day 3 As a group: Practice your lab one time (no need to sign in) One isopod One amount/concentration of your chemical “Play around” until you think you have a good plan Discuss/revise your experimental design out loud Extra time? Sketch out a rough draft of possible data table ideas on scratch paper as a group. Used isopods: if injured, put in small “hospital” container; if they are fine, back in big container

Instructions – Day 4 Swap data tables. Listen and be ready to give feedback CHECK IN and assign jobs Everyone needs a job! See me to get all isopods you’ll need – right away Return “healthy” ones to same container Return “sick” ones to “hospital” (smaller container) CHECK OUT with about 3-5 minutes remaining. Rinse everything well; return to original locations Pipettes are not reusable (throw away) Your lab participation score reflects how well you use your time. Done early? Calculate average, complete data table, HW alone Quietly work on conclusion questions by yourself