Biology 1107- 102 (Tuesday 1:00 – 3:50)
04/ 07/ 2009
For any animal that is too large and/or too complex a circulatory system is needed to obtain essential chemicals by the process of diffusion alone. A circulatory system transports nutrients, oxygen and other important chemicals to all body cells. This system have three components: circulating fluid, a heart or pulsating vessel in charge of pumping the fluid, and vessels through these fluids travels. There are two types of circulatory system. In an Open circulatory system, the vessels are open at one end allowing hemolymph fluid to flow among the cells. Most mollusks and arthropods have this type or system. In a closed circulatory system, the fluid is called blood and this fluid remains in the vessels as it circulates the body. Most vertebrates and annelids have this type of system. The purpose of this laboratory exercise was to demonstrate and explain the effects caffeine on the circulatory system of blackworms and to test the hypothesis that high concentrated caffeine will double the heart rate pulsation of blackworms. Blackworms have several complex systems including a closed circulatory system: a complete digestive tract: and a nervous system, including a brain and a cord. Because of the transparent skin of the blackworm, its large dorsal blood vessel is very easy to see through the microscope. Since the rate of pulsation is easily seen and calculated it’s easy to test the effects of different chemicals on their cardiovascular system. Since it’s known that caffeine increases the blood pressure one might expect that the blackworms under the influence of caffeine will show a grater average of pulsation rate. II. Material and Methods
• High concentrated caffeine
• Plastic pipette
• 4 blackworms
• Microscope slide
• 2 little bowl dishes
• Spring water
1) Fill both of the bowls with spring water to a depth of 2 cm approximately.
2) Select four worms that are equal in size. Do not pick any worms that are recently regenerated.
3) Using the plastic pipette, remove the worms from the water and place two worms per bowl.
4) Label each bowl.
5) Remove a whole worm from the first bowl with the plastic pipette.
6) Place the worm on the microscope slide.
7) Remove any excess water with the plastic pipette.
8) Place the slide on the microscope and observe the worm at scanning power (4x).
*Note: Use a low amount of light and avoid exposing your worms for long period of time to the light since intense light exposure can fry your worms and/or make the hyperactive.
9) Looking through the microscope, count the number of pulsations over 15 seconds. Multiply this by four to get rate per minute and record the data on the result table.
10) Return the worm to the bowl.
11) Run through steps #4-10 again using the last worm from the first bowl and record the data on the result table.
12) Using the plastic pipette, put 10 drops of the high concentrated caffeine to the second bowl and wait two minutes.
13) Remove a whole worm from the second bowl with the plastic pipette.
14) Place the worm on the microscope slide.
15) Remove any excess water with the plastic pipette.
16) Place the slide on the microscope and observe the worm at scanning power (4x) (remember to use a low amount of light).
17) Looking through the microscope, count the number of pulsations over 15 seconds. Multiply this by four to get rate per minute and record the data on the result table.
18) Return the worm to the bowl.
19) Run through steps #13-18 again using the last worm from the second bowl and record the data on the result table.
20) Get the average pulsation rate per minute from both...