Materials Included In Kit

Additional Materials Required

Prelab Preparation

Water Baths

1. Label the four 600-mL borosilicate beakers as follows: 5 °C, 10 °C, 15 °C and 20 °C.
2. Add 400 mL of non-chlorinated water, such as aged tap water, spring water or pond water, to each of the four 600-mL borosilicate beakers.
3. Place a thermometer into each beaker.
4. Add enough ice to cool the first beaker to 5 °C, the second beaker to 10 °C, and the third beaker to 15 °C.
5. Adjust the remaining beaker as necessary in a microwave oven or on a hot plate to achieve 20 °C.

Daphnia

1. Age two or more gallons of tap water for several days before the Daphnia cultures arrive. (Purchased spring water may also be used.)
2. Maintain Daphnia in indirect light at 18 to 24 °C.
3. Feed by adding several milliliters of unicellular algae or active yeast three times a week.
4. Subculture Daphnia once a month or more often if the water begins to foul.
5. Do not aerate Daphnia cultures, the air bubbles will collect under the animals and float them to the surface where they will die.
6. The average heart rate of a resting Daphnia at room temperature is 180 bpm.

Safety Precautions

Isopropyl alcohol is a moderate fire risk; flammable liquid; slightly toxic by ingestion and inhalation. Wear eye protection and avoid sources of ignition when handling isopropyl alcohol. Remind students to wash hands thoroughly with soap and water before leaving the laboratory. Follow all normal laboratory guidelines. Please consult current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The cotton balls may be disposed of in the regular garbage. Isopropyl alcohol may be disposed of according to Flinn Suggested Disposal Method #18a. The cotton balls may be disposed of according to Flinn Biological Waste Disposal Method VI. Daphnia may be disposed of according to Flinn Biological Waste Disposal Method IA or IB. 

Lab Hints

• Enough materials are provided in this kit for 8 groups of students. Both parts of this laboratory activity can reasonably be completed in two or three 50-minute class periods. The laboratory should be read before coming to lab, and the data compilation and calculations can be completed after the lab.
• Daphnia Culture Kit (LM1111) includes D. Magna, a culture of unicellular algae as a food source, timothy hay, vial of vital minerals and complete instructions.
• Use the Daphnia to conduct inquiry based laboratories testing involving bioassays (toxicology indicator), environmental impacts (pollution, acid rain) or as a step in a food web.
• Daphnia are not insects; they are Crustaceans and breathe using gills.
• Obtain exercise mats from the PE department for the reclining portion of the experiment.

Sample Data

Fitness

Observations and Analysis
Results for the activity tables are specific for each group. Remind students that these figures are not for diagnostic purposes.

Ectotherm Heart Rate

Observations and Analysis

Answers to Questions

Fitness

1. Explain why blood pressure differs when measured in a reclining position and in a standing position.

   When a person is lying down, the blood in the head and extremities is at the same elevation as the heart. When a person stands up, gravity causes the blood in the head and upper extremities to “fall” toward the trunk and lower body causing the blood pressure in the upper body to decrease.

2. Explain why heart rate differs when measured in a reclining position and in a standing position.

   In order to counteract the lower blood pressure in the upper body, the baroreceptors increase the heart rate to push the blood back into the head and extremities.

3. Explain why high blood pressure is a health concern.

   High blood pressure causes greater force to be placed on the arteries and arterioles. The greater force can cause the blood vessels to rupture or otherwise damage the heart, liver, kidneys or brain.

4. Explain why smoking causes a rise in blood pressure.

   Smoking causes arteries to constrict, increasing blood pressure and causing hypertension, stroke and heart attacks. Smoking leads to atherosclerosis, the plaque buildup on the blood vessel walls also leads to higher blood pressure. Smoking causes the lungs to become coated with foreign material, leaving less surface area for oxygen and carbon dioxide to diffuse across the alveoli.

Ectotherm Heart Rate

1. On graph paper draw a graph showing the temperature versus heart rate data. Determine and label the independent variable and dependent variable.
   1. Independent Variable—Temperature
   2. Dependent Variable—Heart Rate (bpm)
      {10799_Answers_Figure_8}
2. Why does temperature affect the heart rate in ectothermic organisms?

   The body temperature of ectothermic organism increases as environmental temperature increases causing the rate of chemical reactions within the body to increase.

3. Describe four behaviors that an ectotherm uses to help regulate its temperature.

   Ectotherms move to a warmer or cooler location and bask, burrow, seek shade or sun to change their internal temperature. They may also shiver, extend their wings, raise or lower their body to change their temperature in their present location.

4. Explain the results you would expect from a similar experiment using an endothermic organism.

   The endothermic organism’s heart rate would remain relatively constant because it is able to control its internal body temperature.

References

Biology: Lab Manual; College Entrance Examination Board: 2001.

Introduction

Multicellular organisms have evolved a variety of methods for delivering oxygen and nutrients to cells, and also for removing metabolic wastes from cells. Acoelomate multicellular organisms, such as Cnidarian and Platyhelminthes, have evolved gastrovascular cavities rather than organ systems. An acoelomate has a solid body without a cavity between the gut and the outer body wall. Oxygen, nutrients and waste products are able to diffuse through the few cell layers without the need for a circulatory system. Pseudocoelomates and coelomate organisms have an internal body cavity that contains many organ systems, including a circulatory system. A circulatory system is composed of blood vessels, a pump and a fluid for delivery of oxygen and other nutrients and removal of waste products.

Objectives
After doing this laboratory, you should be able to:

• Measure heart rate and blood pressure in a human.
• Describe the effect of changing body position on heart rate and blood pressure.
• Explain how exercise changes heart rate.
• Determine a human’s fitness index.
• Analyze cardiovascular data collected by the entire class.
• Explain the relationship between heart rate and temperature in ectotherms.

Concepts

• Baroreceptor reflex
• Cardiac output
• Heart rate
• Blood pressure
• Closed/open circulatory system
• Pulmonary/systemic circuit
• Cardiac cycle
• Systole/diastole
• Stroke volume

Background

Some invertebrates such as mollusks and arthropods have an open circulatory system (see Figure 1). In an open circulatory system, the central body cavity (called the hemocoel) is open so that the organs are bathed in the circulatory fluid (called hemolymph), which is diverted around the hemocoel as the muscles contract during the animal’s movements. As the hemolymph moves throughout the body, diffusion causes nutrients, oxygen, and metabolic waste products to diffuse into or out of the hemolymph. When the rudimentary “heart” or pump relaxes, the hemolymph is drawn back toward the heart to be redistributed throughout the body. Organisms with an open circulatory system are all ectothermic organisms. An ectotherm gains most of its heat from the environment and so its heart rate is influenced by the temperature of the environment. As the environment surrounding the animal cools, the animal itself cools, causing the heart rate to slow. The heart rate increases when the animal is in a warm environment.

All vertebrates, annelids and cephalopods have a closed circulatory system (see Figure 2). Of these, some are ectotherms and some are endotherms. Endotherms use their metabolic heat to regulate body temperature and other body functions. A closed circulatory system means that the blood never leaves the system of blood vessels and the heart. Mammals, including humans, have a four-chambered heart that serves as the pump in the closed circulatory system. In animals with a four-chambered heart, the blood follows two distinct circuits as it passes through the body. The systemic circuit carries oxygenated blood from the left side of the heart, through the arteries and arterioles, and finally to the capillaries, where the oxygen is delivered to the cells via diffusion. The deoxygenated blood then travels back through venules and the larger veins to the vena cava where it finally reaches the right atrium of the heart. In the pulmonary circuit, deoxygenated blood travels from the heart through the pulmonary arteries to the lungs where oxygen diffuses into the blood and into the pulmonary veins before returning to the heart. Note: Arteries carry blood away from the heart and veins carry blood to the heart, regardless of whether the blood is oxygenated or deoxygenated (see Figure 2). The human heart has a very specific pattern of relaxing and contracting the cardiac muscle tissues—this pattern is called the cardiac cycle. One cardiac cycle equals one full sequence of contraction (emptying) and relaxation (filling) of the heart. The contraction phase of the cardiac cycle is called systole. The relaxation phase is called diastole.

Cardiac output is the measure of the volume of blood per minute pumped into the systemic circuit by the left ventricle. Cardiac output depends upon the heart rate (rate of contraction) and the stroke volume. The stroke volume is the amount of blood the left ventricle pumps with each contraction. At rest, the average stroke volume is approximately 70 mL for a man and 60 mL for a woman. At rest, the average heart rate for a man is 72 beats per minute (bpm) and 76 bpm for a woman. The cardiac output for an average man (at rest) is 70 mL x 72 bpm = 5040 mL of blood per minute. When this “average man” is not at rest, the body must deliver more oxygen to the tissues in order to maintain homeostasis. The cardiac output increases by increasing the heart rate because the stroke volume is nearly constant.

The body has a biofeedback system that increases or decreases the cardiac output based on the needs of the body tissues. Exercise, for example, causes the biofeedback system to increase the heart rate, increase the respiration rate and depth, increase the arterial pressure, decrease the blood flow to nonmuscular tissues, and increase the blood flow to the muscles (by dilating the arterioles and capillaries in the muscle tissue). One way to determine the general or overall physical fitness of an individual is to measure how well the body responds to exercise. If an individual is physically fit, the body will be more efficient at delivering oxygen to the tissues, and the individual’s heart rate, respiration rate and arterial pressure will be lower than that of a similar, but unfit, person.

Blood Pressure
The entire circulatory system is under pressure, but the amount of pressures varies by location. Arteries have a higher pressure than veins, but within the same artery the blood pressure is greatest when the ventricles contract (systole). The point at which the arteries are under the highest pressure is called the systolic pressure. It is the systolic pressure that may be felt as a heartbeat or “pulse” in the carotid arteries of the neck or in the radial artery in the wrist. Blood pressure in the arteries depends on both the cardiac output and the resistance to blood flow through the slightly smaller arterioles called peripheral resistance. It is the additional pressure caused by the peripheral resistance that causes the artery to “bulge.” This bulge may be observed by resting an arm on a table thumb side up and carefully observing the area adjacent to the median vein in the wrist for a pulse. The artery snaps back into shape during diastole and the pressure inside the artery is now at its lowest pressure called the diastolic pressure.

Blood pressure may be measured using a device called a sphygmomanometer (pronounced sfĭg'mō-mə-nǒm''ĭ-tər). A sphygmomanometer consists of an inflatable cuff connected by one rubber hose to a hand pump and by a second rubber hose to a pressure gauge. By convention, the pressure gauge is graduated in millimeters of mercury (mm Hg). The deflated cuff is wrapped around the upper arm (brachial artery) and inflated to a pressure above the systolic pressure. This restricts the blood flow through the artery. The artery is silent when there is no blood flowing past the inflated cuff (see Figure 3). The examiner places a stethoscope in the inside of the elbow, near the brachial artery, to listen for the sounds of blood flow. If the artery is silent, the examiner slowly opens the air valve to release the pressure on the cuff until some of the blood is pushed through the compressed walls of the artery in spurts. The blood flows in spurts because the pressure in the artery first rises above the pressure in the cuff and then drops back down, resulting in turbulence. The turbulence causes the artery to vibrate and creates heart sounds called Korotkoff sounds. The sounds are named after Dr. Nikolai Korotkoff (1874–1920), a Russian physician who, in 1905, first described five different heart sounds made within an artery just after blood flow is allowed to resume after having been cut off using the a pressure cuff. Dr. Korotkoff noted a snapping sound that occurs when the pressure in the cuff is just below the systolic pressure. At the first snapping sound, the pressure on the gauge is noted by the examiner. This is the systolic pressure and it is the first number in the blood pressure. As the pressure in the cuff falls further, murmurs are audible. These sounds persist as long as the pressure in the cuff is between the systolic and diastolic pressures, as the arterial pressure keeps on rising above and then dropping back below the pressure in the cuff. The third sound is another loud thumping sound, although it is less clear than the initial thumping. The fourth sound appears within 10 mm Hg of the diastolic pressure. The sounds are muted thumps. The fifth “sound” is actually silence as the cuff pressure drops below the diastolic pressure. Prior to 2000, the last of the fourth sounds was used as the diastolic pressure. After 2000, health professionals have been using the beginning of the fifth “sound,” silence, as the diastolic pressure. Blood pressure is commonly reported as a fraction with the systolic pressure as the numerator and the diastolic pressure as the demoninator.

Blood pressure measurements depend on a person’s age, gender, heredity and health. Blood pressure measurements that are chronically elevated may indicate a health problem. This condition is called hypertension and is a major contributing factor in heart disease and stroke. Hypertension may be controlled using both lifestyle changes and prescription drugs. The National Institute of Health has determined that blood pressure readings for an adult that are consistently greater than 140/90 represent hypertension. Blood pressure readings of 120–139 systolic and 80–89 diastolic indicate prehypertension. Lifestyle changes are often sufficient to lower the blood pressure in someone suffering from prehypertension.

Children and young adults have different “normal” ranges for both heart rate and blood pressure than adults. In general, heart rate drops as a person ages from an infant to an adult, whereas blood pressure increases. This is due to the size of the heart and arteries—a larger heart is able to pump more blood per contraction, and fluid pressure decreases as the diameter of the blood vessels increases. Table 1 provides the typical blood pressure range and heart rate for both genders according to age. Note: This table is for experimental use only, and should not be used for diagnostic purposes. Heart Rate
In order for muscle tissue to receive more oxygen during physical exertion, the heart increases its contraction rate. A heart rate, also called the cardiac rate or pulse, is measured in beats per minute (bpm). The more times the heart contracts (beats) within one minute, the faster the heart rate. Many factors influence heart rate including heart disease, stress, thyroid problems, anemia, stimulants, depressants and other medications.

The maximum rate that a heart can beat is the same for people within the same age group. The maximum cardiac rate for an individual is calculated by subtracting the person’s age from 220. Individuals who are in good physical condition can deliver more oxygen to their muscles before reaching the maximum cardiac rate than can individuals in poor condition. People who are physically fit pump a greater volume of blood with each contraction during physical exertion. Therefore their hearts do not need to beat as fast to deliver the same amount of oxygenated blood to the muscle tissues. An adult athlete in peak fitness may have a resting heart rate of 50–57 bpm, compared to a resting heart rate of 70–76 bpm for an average adult male. During physical exertion, a person who is in poor physical condition reaches the maximum cardiac rate at a lower work level than a person of comparable age who is in better shape. During physical exertion, the goal is not to reach the maximum cardiac rate but rather the target heart rate. The target heart rate is a range of heart rates that is calculated by multiplying the maximum cardiac rate by 60% and 80%—is considered the optimum value for each age group. This is the optimum level for achieving physical conditioning and strengthening of the circulatory system.

Physicians use several methods, including the resting heart rate and blood pressure, to determine how well the heart handles work. If a physician suspects a problem, other tests, such as the patient’s baroreceptor reflex, may be recommended. The baroreceptor reflex is determined by measuring the patient’s heart rate and blood pressure while reclining and then immediately after standing upright. The reclining heart rate is subtracted from the standing heart rate. The increase in the heart rate is initiated by baroreceptors (pressure receptors) in the carotid (neck) artery and in the aortic arch which detect a drop in blood pressure to the upper body upon standing. When these baroreceptors detect a drop in blood pressure in the upper half of the body they signal the medulla of the brain to increase the heart rate to increase the amount of blood flowing to the heart, lungs and brain. The baroreceptor reflex is a simple, noninvasive test that can be performed during an office visit. The stress test (also called a treadmill test or exercise test) is a more complicated test that can show if the blood supply is reduced in the arteries that supply the heart. An individual’s heart rate, breathing, blood pressure, electrocardiogram (EKG) and level of exhaustion are monitored as the individual walks on a treadmill with a slight incline. A patient who fails the stress test may undergo more invasive and more expensive testing to determine the cause of the problem.

Experiment Overview

In Activity 1, a sphygmomanometer and stethoscope will be used to measure the blood pressure of each lab partner. In Activity 2, the reclining and standing blood pressure for each lab partner will be determined. In Activity 3, each lab partner’s resting heart rate will be measured. In Activity 4, the baroreceptor reflex of each lab partner will be calculated. In Activity 5, the endurance and relative cardiac fitness will be determined by measuring the response of the cardiovascular system to sudden changes in demand. In Activity 6, the heart rate of an ectothermic animal will be observed as the temperature is increased from 10 °C to 30 °C.

Materials

Safety Precautions

Do not attempt this exercise if strenuous activity will aggravate a health problem. Isopropyl alcohol is a flammable liquid and a moderate fire risk. It is slightly toxic by ingestion and inhalation. Wear eye protection and avoid sources of ignition when using isopropyl alcohol. Wash hands thoroughly with soap and water before leaving the laboratory. Activity 6 Although the materials used in this activity are considered nonhazardous, please follow all regular laboratory safety guidelines. Wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

Activity 1. Resting Blood Pressure

1. Work in pairs. One partner will act as the patient (partner 1) and the other as the examiner. The partners will then switch rolls and the examiner (partner 2) will become the patient. Note: Do not switch partner numbers during the laboratory—procedure while the blood pressure and heart rate are being measured.
2. Saturate two cotton balls with isopropyl alcohol. Use one to clean the bell and diaphragm of the stethoscope (see Figure 4) and the second one to clean the earpieces of the stethoscope. Dispose of the cotton balls in the regular garbage.
   {10799_Procedure_Figure_4}
3. Partner 1 should be seated with his or her left shirtsleeve rolled up 5 inches above the elbow. However, make sure that the sleeve is not tight or binding. Place the left arm at heart level onto a desk or table, palm up.
4. The examiner should attach the cuff of the sphygmomanometer snugly around the upper arm of the patient, centering the bladder over the brachial artery (see Figure 5). The tubing should be aligned with the small finger and the lower edge of the cuff should be about one inch above the inner elbow. The examiner should be able to fit two fingers between the cuff and the arm.
   {10799_Procedure_Figure_5}
5. Place the bell of the stethoscope directly below the cuff in the bend of the elbow joint.
6. Close the valve of the bulb by turning it clockwise. Pump air into the cuff until the pressure gauge goes past 180 mm Hg. Note: Do not inflate the cuff above 260 mm Hg.
7. Turn the valve of the bulb counterclockwise and slowly release the air from the cuff (about 2–3 mm Hg per second). Listen for the thumping sounds while watching the gauge.
8. When the first sounds are heard note the pressure on the gauge. This is the systolic pressure. Remember the number indicated on the gauge when the first sound is heard.
9. Continue to slowly release air and listen until the clear thumping sound of the pulse becomes strong and then fades. Note the pressure on the gauge when the silence begins. This is the diastolic pressure.
10. Record the systolic and diastolic pressures in the Activity 1 table on the Fitness Worksheet.
11. Repeat the measurement two more times and record the systolic and diastolic pressures each time in the Activity 1 table on the Fitness Worksheet.
12. Calculate the average systolic and diastolic pressure for partner 1.
13. Switch roles and repeat steps 2–12, recording the systolic and diastolic pressures for partner 2.

Activity 2. Reclining and Standing Blood Pressure

1. Saturate two cotton balls with isopropyl alcohol. Use one to clean the bell and diaphragm of the stethoscope and the second one to clean the earpieces of the stethoscope. Dispose of the cotton balls in the regular garbage.
2. Determine partner 1’s reclining blood pressure using the Activity 1 Procedure.
   1. Partner 1 should recline on the floor for at least 5 minutes.
   2. After 5 minutes determine the systolic and diastolic pressure following steps 3 to 12.
   3. Record these values in the Activity 2 table of the Fitness Worksheet.
3. Determine partner 1’s standing blood pressure.
   1. Partner 1 should remain reclining for two minutes.
   2. After 2 minutes partner 1 should stand up with his/her arms at his/her sides.
   3. immediately determine the systolic and diastolic pressure.
   4. Record these values in the Activity 2 table of the Fitness Worksheet.
4. Determine the change in systolic pressure from reclining to standing by subtracting the standing measurement from the reclining measurement. Record the value in the Activity 2 table of the Fitness Worksheet.
5. Assign fitness points based on the table and record the value in the Activity 2 table of the Fitness Worksheet.
   {10799_Procedure_Table_2}
6. Switch roles and repeat steps 1–5, recording the systolic and diastolic pressure and fitness points for partner 2.

Activity 3. Resting Heart Rate

1. Saturate two cotton balls with isopropyl alcohol. Use one to clean the bell and diaphragm of the stethoscope and the second one to clean the earpieces of the stethoscope. Dispose of the cotton balls in the regular garbage.
2. Determine the resting heart rate for partner 1.
   1. Partner 1 should remain seated and quiet for 2 minutes before the resting heart rate is measured.
   2. Place the stethoscope over partner 1’s heart and count the number of beats for 20 seconds. Record the number of beats in the Activity 3 table on the Fitness Worksheet.
   3. Determine partner 1’s resting heart rate (bpm) by multiplying the number of beats in 20 seconds by 3. Record the value in the Activity 3 table on the Fitness Worksheet.
   4. Assign fitness points based on the table and record the value in the Activity 3 table on the Fitness Worksheet.
      {10799_Procedure_Table_3}
3. Switch roles and repeat steps 1 and 2, recording the resting heart rate and fitness points for partner 2.

Activity 4. Baroreceptor Reflex

1. Determine partner 1’s reclining heart rate.
   1. Partner 1 should recline on the floor for 5 minutes. Note: Partner 1 should remain reclining throughout step 1 of this procedure.
   2. After 5 minutes, place the stethoscope over partner 1’s heart and count the number of beats for 20 seconds. Record the number of beats in the Activity 4 table on the Fitness Worksheet.
   3. Determine partner 1’s reclining heart rate (bpm) by multiplying the number of beats in 20 seconds by 3. Record the value in the Activity 4 table on the Fitness Worksheet.
   4. Assign fitness points based on the table and record the value in the Activity 4 table on the Fitness Worksheet.
      {10799_Procedure_Table_4}
2. Determine partner 1’s baroreceptor reflex.
   1. Partner 1 should stand up with their arms at their sides.
   2. Immediately determine partner 1’s standing heart rate by placing the stethoscope over his/her heart and counting the number of beats for 20 seconds. Record the number of beats in the Activity 4 table on the Fitness Worksheet.
   3. Determine partner 1’s standing heart rate (bpm) by multiplying the number of beats in 20 seconds by 3. Record the value in the Activity 4 table on the Fitness Worksheet.
   4. Determine partner 1’s baroreceptor reflex by subtracting the reclining heart rate from the standing heart rate. Record the value in the Activity 4 table on the Fitness Worksheet.
3. Assign fitness points based on the table and record the value in the Activity 4 table on the Fitness Worksheet.
   {10799_Procedure_Table_5}
4. Switch roles and repeat steps 1–3, recording the heart rates and fitness points for partner 2.

Activity 5. Endurance

1. Saturate two cotton balls with isopropyl alcohol. Use one to clean the bell and diaphragm of the stethoscope and the second one to clean the earpieces of the stethoscope. Dispose of the cotton balls in the regular garbage.
2. Determine partner 1’s endurance.
   1. Partner 1 will simulate climbing a short flight of stairs.
      1. Partner 1 should place his/her right foot on an 18-inch high stool.
      2. Raise his/her body so that his/her left foot comes to rest by the right foot.
      3. Return the left foot to the original position.
      4. Repeat the exercise five times, allowing three seconds for each step up.
   2. The examiner must immediately count the number of beats for 15 seconds. Record the number of beats in the Activity 5 table on the Fitness Worksheet.
   3. Continue counting partner 1’s heart rate, recording the rate after an additional 15 seconds. Record the number of beats in the Activity 5 table on the Fitness Worksheet.
   4. Continue counting partner 1’s heart rate for the next 30 seconds. Record the number of beats in the Activity 5 table on the Fitness Worksheet.
   5. Continue counting partner 1’s heart rate for the next 30 seconds. Record the number of beats in the Activity 5 table on the Fitness Worksheet.
   6. Continue counting partner 1’s heart rate for the next 30 seconds. Record the number of beats counted in the Activity 5 table on the Fitness Worksheet.
   7. Multiply each 15-second measurement by four and each 30-second measurement by two to determine the number of beats per minute. Record the values in the Activity 5 table on the Fitness Worksheet.
   8. Determine the amount of time that it took for the heart rate to return to the resting heart rate.
   9. Assign fitness points based on the table below and the time to return to the resting heart rate. Record the value in the Activity 5 table of the Fitness Worksheet.
      {10799_Procedure_Table_6}
3. Determine the heart rate response.
   1. Subtract partner 1’s resting heart rate from the heart rate immediately after completing the simulated stair climbing exercise (the 0 to 15 second interval). Record the value in the Activity 5 table of the Fitness Worksheet.
   2. Assign fitness points based on the table and record the value in the Activity 5 table of the Fitness Worksheet.
      {10799_Procedure_Table_7}
4. Determine partner 1’s relative cardiac fitness level.
   1. Determine the sum (total) of all the fitness points and record the total in the Activity 5 table of the Fitness Worksheet.
   2. Compare the total number of fitness points to the values in the table and record the relative cardiac fitness of partner 1 in the Activity 5 table of the Fitness Worksheet. Note: The value is for experimental purposes only.
      {10799_Procedure_Table_8}
5. Switch roles and repeat steps 1–4, recording the heart rate and fitness points for the second partner.
6. Answer the questions on the Fitness Worksheet.
7. The cotton balls may be disposed of in the regular garbage.

Activity 6. Ectotherm Heart Rate

1. Pull off several cotton fibers from a cotton ball and place these into the depression of one glass depression slide. Note: The cotton fibers trap the Daphnia and prevent it from moving during the observations.
2. Place a rubber band around the short ends of the slide (see Figure 6).
   {10799_Procedure_Figure_6}
3. Use a disposable pipet to capture one Daphnia from the Daphnia culture.
4. Add the Daphnia to the depression slide with the cotton fibers.
5. Create an observation chamber by placing the second depression slide on top of the first one, concave side facing down and over the Daphnia.
6. Twist the rubber band and loop it over the second depression slide to secure the slides together. Note: The rubber band between the two slides allows for sufficient circulation of water and oxygen to keep the Daphnia alive.
7. Create an individual water bath by transferring about 45 mL of non-chlorinated water at 5 °C into a Petri dish. Record the actual temperature of the water bath on the Ectotherm Heart Rate Worksheet.
8. Place the 5 °C water bath under a stereomicroscope. Keep the stereomicroscope off until observations are being made. (Daphnia do not like light.) Work quickly to avoid changing the temperature of the water bath.
9. Place the Daphnia observation chamber into the 5 °C bath. Allow the Daphnia to equilibrate for 1 minute.
10. Turn on the stereomicroscope and locate the Daphnia’s heart (see Figure 7).
    {10799_Procedure_Figure_7}
11. Count the number of heartbeats in 10 seconds. Record the number of heartbeats in Table 1, Trial 1 on the Ectotherm Heart Rate Worksheet. Repeat for two more trials.
12. Calculate the average number of heartbeats in 10 seconds for the Daphnia’s heart while it was submerged in the 5 °C water bath.
13. Multiply the average number of heartbeats in 10 seconds by 6 to calculate the beats per minute (bpm). Record the number on the Ectotherm Heart Rate Worksheet.
14. Remove the Daphnia’s observation chamber from the 5 °C water bath. Pour the water into a beaker.
15. Repeat steps 7–14 using the 10 °C water bath first followed by the next warmest bath until the heart rate has been determined for each water bath temperature. Note: Water baths greater than 35 °C may harm the Daphnia.
16. Return the Daphnia to the Daphnia culture dish.
17. Answer the questions on the Ectotherm Heart Rate Worksheet.
18. Consult your instructor for appropriate disposal procedures.

Student Worksheet PDF

10799_Student1.pdf