CBL Interfacing

Breathing: Germinating Peas vs. Earthworms

Procedure

SAFETY GOGGLES MUST BE WORN DURING THE LAB

(Previous Page)

Set up the experiment as described and shown in the figure below.

Respirometer Set Up.

Setting Up the CBL/TI82 and Barometer.

Entering the Program.

Setting Up Probes.

Running the Experiment.

Attach the tubes.

Initiate the Experiment.

Process the data.

Continue the Experiment Using Peas.

Respirometer Set Up

1. Place absorbent cotton balls in each of two vials. Soak each one with KOH so that they are wet, but not dripping. Place a dry non-absorbent cotton ball on top of each of the KOH soaked cotton balls.
2. Pick out 3 earthworms and measure their mass. Record the mass on your data sheet.
3. Measure their volume by water displacement using a graduated cylinder. Record the volume on your data sheet. (Earthworms can survive for days submerged in water.) Place the earthworms on a paper towel and blot dry.
4. Using water displacement to measure volume, add glass beads to a graduated cylinder until the volume of the glass beads equals the volume of the earthworms. Place the glass beads on a paper towel and blot dry.
5. Place the earthworms on top of the dry cotton ball of one vial and call this vial the experimental. Place the glass beads on the dry cotton ball of the other vial and call this vial the control. Stopper each vial with a rubber stopper, glass tube and rubber tube as shown in the diagram above. Place each vial in a beaker containing enough room temperature water to cover the vial up to the level of the earthworms. Weigh the vials down with sandbags. Allow the vials to equilibrate with the temperature of the water while you set up your calculator and CBL. Do not attach the respirometers to the barometer until you are ready to start the experiment.

Back (Previous Page)

B. Setting Up the CBL/TI82 and Barometer

• Connect the CBL unit to the TI-82 graphing calculator using the unit-to-unit link cable and the I/O ports located at the bottom edge of each unit.
• Connect 2 Vernier Barometers to the channels 1 and 2 ports located at the top edge of the CBL unit. Place the barometers on the ring stand assemblies.

Back (Previous Page)

C. Entering the Program

Press ON to turn on your CBL.

Press ON to turn on your TI-82 calculator.

Press PRGM.

Choose LONGTERM.

prgm LONGTERM will appear on your screen. Press ENTER

VERNIER SOFTWARE, LONG TERM CONNECTION WITH CBL will appear on your screen. Press ENTER.

Back (Previous Page)

D. Setting Up Probes

A menu will appear. Choose SET UP PROBES.

ENTER NUMBER OF PROBES WILL APPEAR. Press 2 and then ENTER.

A menu will appear. Choose BAROMETER.

USE LOWEST AVAILABLE CHANNELS. ENTER CHANNEL NUMBER will appear. Press 1 and then ENTER.

A menu will appear. Choose BAROMETER.

A menu will appear. Choose USE STORED.

USE LOWEST AVAILABLE CHANNELS. ENTER CHANNEL NUMBER will appear. Press 2 and then ENTER.

A menu will appear. Choose USE STORED.

Back (Previous Page)

E. Running the Experiment

A menu will appear. Choose RUN EXPERIMENT.

A menu will appear. Choose TIME GRAPH.

ENTER TIME BETWEEN SAMPLES IN SECONDS: will appear. Press 10 and then ENTER.

ENTER NUMBER OF SAMPLES: will appear. Press 50 and then ENTER.

SAMPLE, TIME 10.00 S, SAMPLES 50, EXPERIMENT LENGTH 500.00 S will appear. Press ENTER.

A menu will appear. Choose USE TIME SETUP.

USE [CH VIEW] ON CBL TO MONITOR DATA will appear. Press CH. VIEW on CBL. Press ENTER on TI-82.

READY EQUIPMENT. NO REAL TIME GRAPH AVAILABLE. PRESS [ENTER] TO BEGIN EXPERIMENT will appear.

It is time to set up the rest of your apparatus. (Don't press ENTER.....yet)

Back (Previous Page)

J. Attach the tubes

Attach the tube from the respirometer with the earthworms to the barometer plugged into channel 1. Attach the tube from the respirometer with the beads to the barometer plugged into channel 2. Wait about 10 seconds.

Back (Previous Page)

K. Initiate the Experiment

With the CBL unit and TI-82 graphing calculator on, press Enter to initiate the experiment. The CBL is now collected data for 500 seconds. Relax for a while. Every 10 seconds the probe is measuring the pressure and storing the data for you. You will know when the experiment is over when the word DONE appears on the CBL. Be careful not to touch the apparatus. The probe detects very slight pressure changes! The calculator has a battery saving device and may go off by itself. That is OK, the CBL has already been instructed to collect data.

Back (Previous Page)

L. Process the data

Back (Previous Page)

M. Continue the Experiment Using Peas

Clean the glassware and then repeat the entire procedure, steps A-L, using germinating peas. Be sure that the volume of peas is the same as the volume of earthworms. Be sure to measure the mass of the peas. Record all results on your data sheet. Then go on to repeat processing the data steps a-e for the germinating peas.

Back (Previous Page)

Technology in Education Index

Let's Collaborate Index