Lab Activity 2.1
Responding to Changes in Temperature

  Directions

Study the instructional material below. Be sure to click on each of the photographs for an enlarged view in a separate window. The larger version is necessary to complete the assignment. It opens in a separate window which can be resized by grabbing the bottom right corner and dragging it. It can also be moved by grabbing the top heading bar and dragging it. Be sure to close the extra window by using the X in IBM, or the close box in MAC when you are finished using them.

  Introduction


Some marine organisms such as seabirds and marine mammals are endothermic. They are able to generate heat and maintain a constant internal temperature despite changes in the environment that surrounds them. Most marine organisms such as invertebrates and fishes are ectothermic. They are unable to regulate body temperature and are more severly effected by changes in the environment. In this experiment we will observe the effects of differing temperatures on living Daphnia, waterfleas. Waterfleas are tiny ectothermic crustaceans and their internal temperature closely matches that of the environment that surrounds them. To determine their responses to changing temperatures we will use each animal's heart rate as a measure of its overall condition. By comparing its heart rate at various temperatures we will be able to determine the overall effect of cooling or warming on a waterflea's condition.

Top  Instruction

Study the information, photographs, and graphs in the experiment that follows. Be sure to complete the observations and formulate answers to the questions you're asked.

Be sure to write about what you are learning in the lab section of your notebook. You will be expected to answer questions about the lab activity during the lab self test and lab quiz. It helps to have your text and coloring books open beside you for support.

 
Supporting Information
Refer to the Assigned Readings Below:
Marine Biology Textbook Chapter 4, pages 80 to 82
Marine Biology Coloring Book None
 

Observing Living Daphnia

Living Daphnia were observed with microscopes by placing the tiny crustacea in water filled depression slides. Each depression slide acted like a tiny aquarium that could be placed on the stage of a light microscope.

Experimental Set Up:

  1. We obtained a culture of the microcrustacea Daphnia and observed it under a dissecting microscope.

  2. We obtained a depression slide and coverslip. With a spoon we transferred a waterflea (Daphnia) to the depression in the slide and filled the depression with water from the culture. We placed the coverslip over the depression capturing the waterflea so that it couldn't swim around.

  3. We observed the waterflea at 35X magnification with a dissecting microscope to become familiar with its anatomy.
 

Observations:

  1. Observe the photograph of the waterflea. Notice its antennae and legs. Their movement establishes feeding currents and helps it respire.

  2. Observe the photograph of the waterflea. Note its heart which is located dorsally, just behind its head and eye.

 

Observing Daphnia Heart Beats

A live Daphnia in a depression slide was examined at high magnification to watch and count its heart beats.

Experimental Set Up:

  1. We set up a compound microscope and focused on the waterflea's heart at 160X magnification.

  2. We removed the slide from the microscope being careful not to disturb the waterflea. We set it on the countertop and allowed it to remain at room temperature for 30 seconds.
 
Observations:

  1. Observe the photograph of the waterflea's heart.

  2. Note the outline of the heart which has been enhanced so you can get a good idea of how it looks.

 

Observing Daphnia at Room Temperature

A live Daphnia in a depression slide was examined at room temperature to determine its heart rate.

Experimental Set Up:

  1. We carefully replaced the slide on the microscope, focused on the heart, and videotaped the heart beating. We did not let the waterflea remain on the microscope stage to long before starting the recording to prevent the lamp from heating it up above room temperature.

  2. We determined the heart rate of the waterflea at room temperature by counting the heart beats of the waterflea for 60 seconds and graphed the heart volume versus time.

Observations:

  1. Observe the graph of the room temperature waterflea's heart beat.

  2. Determine the number of beats per minute.

 

Observing Daphnia Cooled on Ice

A live Daphnia in a depression slide was chilled and examined to determine its heart rate when it was cold.

Experimental Set Up:

  1. We removed the slide from the microscope, being careful not to disturb the waterflea, and set it on ice for 30 seconds.
  2. We carefully replaced the slide on the microscope, focused on the heart, and videotaped the heart beating. We did not let the waterflea remain on the microscope stage to long before starting the recording to prevent the lamp from heating it up.
  3. We determined the heart rate of the iced waterflea. Count the heart beats of the waterflea for 60 seconds and graphed the heart volume versus time.

Observations:

  1. Observe the photograph of the waterflea slide on ice.

  2. Observe the graph of the iced waterflea's heart beat.

  3. Determine the number of beats per minute.

  4. How does the cooled waterflea's heart rate compare to its heart rate at room temperature?

 

Observing Daphnia Warmed on a Heating Block

A live Daphnia in a depression slide was warmed and examined to determine its heart rate when it was hot.

Experimental Set Up:

  1. We removed the slide from the microscope being careful not to disturb the waterflea. We set it on a 30 degree centigrade heating block for 30 seconds.
  2. We carefully replaced the slide on the microscope, focused on the heart, and videotaped the heart beating. We did not let the waterflea remain on the microscope stage to long before starting the recording to prevent it from cooling down.
  3. Determine the heart rate of the heated waterflea. Count the heart beats of the waterflea for 60 seconds and graphed the heart volume versus time.

Observations:

  1. Observe the photograph of the slide containing the waterflea on the heating block.

  2. Observe the graph of the heated waterflea's heart beat.

  3. Determine the number of beats per minute.

  4. How does the heated waterflea's heart rate compare to its heart rate at room temperature?

 


Lab Activity 2.2 Responding to Changes in Salinity