Lesson 1.3: Investigation: Heart Rate

You learned that the heart beats faster when you are exercising or under stress.  The heart rate is also dependent on temperature.  A simple experiment was designed to compare the heart rate of daphnia when the temperature is changed.  Daphnia, commonly called "water fleas", are tiny crustaceans that are transparent so you can see all of the organs in their body with a simple light microscope.  Wim van Egmond has an excellent site on daphnia at

h ttp://www.microscopy-uk.org.uk/mag/artmar02/fleanatomy.html

Here is one of his diagrams of a daphnia.

Read the entire investigation "How Does the Heart Respond to Temperature Changes?" on pages 218, 219, and 220 in your textbook.

Question 1. Answer the "Prediction" question #1 on page 218.

Question 2. Answer the "Prediction" question #2 on page 218.

Then, return here to continue this lesson.

 

A student performed the experiment and recorded the following information.

Test

Number of Heartbeats

Average Number of Heartbeats
Trial 1 Trial 2 Trial 3 Trial 4

Room Temperature Water

 41 40 39 40  

Cold Water

 26 25 24 26  

  Hot Water

 54 56 54 55  

 

Question 3. Complete the table by calculating the average number of heartbeats for the four trials.

Question 4. Answer questions 1 to 5 in "Analyze" and "Conclude and Apply" on page 220.

 

Then, return here to continue this lesson.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. Answer the "Prediction" question #1 on page 218.

The heart rate of the Daphnia should slow down when they are exposed to temperatures lower than room temperature. 

Question 2. Answer the "Prediction" question #2 on page 218.

The heart rate of the Daphnia should speed up when they are exposed to temperatures higher than room temperature.

 

Click to return to where you left off in this lesson.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 3. Complete the table by calculating the average number of heartbeats for the four trials.  

Test

Number of Heartbeats

Average Number of Heartbeats
Trial 1 Trial 2 Trial 3 Trial 4

Room Temperature Water

 41 40 39 40 40

Cold Water

 26 25 24 26 25

  Hot Water

 54 56 54 55 55

Question 4. Answer questions 1 to 5 in "Analyze" and "Conclude and Apply" on page 220.

1.  Taking a heartbeat count at room temperature gives you a number to compare to when the temperature is lower or higher.
2.  Cold water slows the heartbeat.
3.  Hot water speeds up the heartbeat.
4a.  If you are wearing a winter coat on a hot day, you will obviously get too hot.  According to the experiment results, your heartbeat should speed up.
4b.  Wearing indoor clothing and going put in a blizzard will mean that you get cold.  According to the experiment results, your heartbeat should slow down.
5.  When there is a change in the external environment, an organism will make changes to maintain an internal balance.
 


Now it is time to do Assignment 11A.  Page forward to access it.