A Fishy Tale. Observing the Circulatory System of a Goldfish with a Compound Light Microscope

Transcription

1 A Fishy Tale Observing the Circulatory System of a Goldfish with a Compound Light Microscope A Fishy Tale About this Lesson In this lesson, students will explore a computer animation of the human body s circulatory system and directly observe vessels in the circulatory system of a goldfish using a microscope. This lesson is included in the LTF Middle Grades Module 10. Objectives Students will: Compare and contrast the structure and function of an artery, vein, and capillary Observe blood flowing through arteries, veins, and capillaries in the tail of a live goldfish Level Middle Grades: Life Science Common Core State Standards for Science Content LTF Science lessons will be aligned with the next generation of multi-state science standards that are currently in development. These standards are said to be developed around the anchor document, A Framework for K 12 Science Education, which was produced by the National Research Council. Where applicable, the LTF Science lessons are also aligned to the Common Core Standards for Mathematical Content as well as the Common Core Literacy Standards for Science and Technical Subjects. T E A C H E R Code Standard Level of Thinking (LITERACY) RST Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks, attending to special cases or exceptions defined in the text. Apply Depth of Knowledge II Connections to AP* AP Biology: This lesson addresses concepts contained in Big Idea 2 in the revised AP Biology curriculum under the following section: 2.D.2.c *Advanced Placement and AP are registered trademarks of the College Entrance Examination Board. The College Board was not involved in the production of this product.

2 A Fishy Tale Materials Each lab group will need the following: computer with online access cotton balls goldfish, feeder size microscope cover slip microscope, compound paper towels pencil, colored Petri dish pipette, thin stem water, spring Assessments The following types of formative assessments are embedded in this lesson: Visual assessment of student sketches The following assessments are located on the LTF website Middle Grades Life: Human Body II Assessment th grade Posttest, Free Response Question 2 T E A C H E R

3 A Fishy Tale Teaching Suggestions A Fishy Tale provides students with the opportunity to explore the circulatory system using an Internet exercise and then the opportunity to directly observe and explore the circulatory system in a goldfish tail using a microscope. This lab could serve as an introduction to the circulatory system and typically would be completed within a body system unit. The students are expected to make a biological diagram. The lesson Picturing Life: Making a Biological Diagram should be completed prior to performing this exercise. It is absolutely imperative for you to practice the goldfish observation component of the lab before trying with students. It is highly recommended that you demonstrate the proper wrapping procedure and placement in the Petri dish for students. The goldfish, commonly called feeder goldfish, can be obtained from any pet store for a minimal cost, probably $ a fish. The fish need to be kept in a tank of spring (or dechlorinated) water with an aeration device (available at most pet stores for less than $10). If kept in non-aerated water, the fish will live only a few hours. If kept in aerated water, the fish will survive well over a week. It is recommended that you purchase more fish than you think you will need. Students, even acting very carefully and ethically, can kill the goldfish during the observation due to the intense heat of the microscope. (Of course, prior to any lab that uses live organisms, a discussion of your expectations regarding ethical and humane treatment of the animals is mandatory at the junior high/middle school level.) Please refer to Figure 2 in the student procedure for the correct set up of the goldfish in the Petri dish. Also refer to Figure 1, a photograph taken through the microscope lens at 100X magnification showing the correctly labeled parts of the fish tail. However, your best guide for learning the logistics of this lab is to place the goldfish in the Petri dish and directly observe the blood coursing through the vessels of the tail using your own microscope. T E A C H E R If necessary Parts I and II may be completed on separate days. Your students will really enjoy this lab. You will find that seeing the individual blood cells moving through the capillaries will not be easily forgotten by anyone, including you!

4 BIOLOGICAL DIAGRAM-PART II Red blood cell This is an artery. In the microscope it will appear to be full of moving blood cells, all moving at a rapid pace, caused by the pressure of the artery being closer to the heart. This is a pigment cell. In the goldfish, these will appear orange in color. Vein: will be full of blood cells, moving at a much slower rate. T E A C H E R Another pigment cell. In the goldfish, these will appear orange in color. This is the edge of one of the goldfish tail cells. Capillaries are identified as a small vessel with blood cells moving along single file. Figure 1: Photo taken through the microscope eyepiece lens, viewing the goldfish tail at 100 magnification.

5 POSSIBLE ANSWERS TO THE CONCLUSION QUESTIONS Part I: Exploring the Circulatory System via the Internet 1. What is the responsibility of the cardiovascular and respiratory systems? The cardiovascular and respiratory systems together are responsible for carrying oxygen from the air to the blood stream and expelling the waste product of carbon dioxide. 2. Why is blood such an essential fluid to the cardiovascular and respiratory systems? Blood carries oxygen (to the cells) and carbon dioxide (from the cells) throughout the body, through the vessels from the heart. 3. How do arteries differ from veins? Arteries carry blood filled with nutrients away from the heart to all parts of the body. Arteries are thick-walled tubes. Arteries contain a lining of muscle that absorbs the high pressure wave of a heartbeat. Veins deliver deoxygenated blood back to the heart. Veins, unlike arteries, have thin, slack walls. 4. How does the function of capillaries fit into the cardiovascular system? Capillaries join arteries to veins. Also, the capillaries deliver what the cells need (primarily O 2 ) and take away the waste products (primarily CO 2 ) that they do not need. 5. How does the pressure of the blood in the veins compare to the pressure of the blood in the arteries? Blood from the heart is under much greater pressure and moves much more quickly away from the heart. As deoxygenated blood moves back to the heart, it is under much less pressure and oozes much more slowly. 6. How many square miles do capillaries cover in our bodies? Capillaries provide a total surface area of 1,000 square miles. 7. Why do you think there are so many square miles of capillaries? Capillaries are the site of gas exchange in the cells. To provide the oxygen and carbon dioxide exchange in so many cells requires a huge amount (and length) of capillary vessels. T E A C H E R 8. How much more pressure does an artery have than a vein? The pressure of an artery is roughly fifty times more than a vein. 9. Why do you think that the pressure in an artery is so much greater than in a vein? The artery is taking blood directly from the heart, and as this system of tubes is closer to the heart, receives more pressure than the veins, which are taking blood back to the heart and lungs and have less pressure. 10. As the blood in the arteries approaches the capillaries, what gas is the blood rich in? The blood, as it approaches the capillaries, is rich in oxygen. 11. In your own words, describe the flow of blood as it leaves the heart and moves through the various vessels until it returns to the heart. Include the following terms in your description: blood cells, heart, artery, vein, capillary, O 2, CO 2. Blood cells flow from the heart in arteries through the body to capillaries, after dropping off O 2 and picking up CO 2 and returning to the heart through the veins.

6 Part II: Exploring the Circulatory System in the Fish s Tail 1. Explain how you can quickly tell the difference between the three kinds of vessels (capillary, vein, and artery) in the tail of a fish. Capillaries are much smaller and you can see the blood, individual cell by individual cell, moving through the capillary. Veins have much slower rate of blood movement. Arteries have much faster rate of blood movement. 2. Which type of vessel seemed to be most numerous in the tail of the fish? Explain why it is essential that there be more vessels of this kind? Capillaries are found all over the tail. They are so numerous because the capillary is the primary site of cellular respiration. 3. In your observation of the fish s tail, in which blood vessels does the blood move the slowest? Why? Veins have less pressure, being further removed from the heart, and cause the blood to move at a slower rate. 4. In your observation of the fish s tail, in which blood vessels does the blood move the fastest? Why? Arteries have much more pressure, being closer to the heart, and cause the blood to move at a much higher rate. 5. Describe another way that you could tell the difference between the arteries and veins in the tail of the fish. (Hint: All the images that you see in the microscope are reversed!) The direction of blood flow would be another way to observe the difference between arteries and veins. The blood in the arteries is coming from the anterior end of the fish, where the heart is in relation to the tail. The blood in the veins is traveling back to the heart and gills, from the posterior end toward the anterior. But all this is reversed in the compound light microscope due to optics. So the blood that, in the microscopic view, looks like it is coming at high pressure and velocity from the posterior end, from the tail, but it is really coming from the anterior end of the fish. T E A C H E R

7 A Fishy Tale Observing the Circulatory System of a Goldfish with a Compound Light Microscope A Fishy Tale PURPOSE In this activity you will compare and contrast the structure and function of an artery, vein, and capillary. You will then observe blood flowing through arteries, veins, and capillaries in the tail of a living fish. MATERIALS Each lab group will need the following: computer with online access cotton balls goldfish, feeder size microscope cover slip microscope, compound paper towels pencil, colored Petri dish pipette, thin stem water, spring Safety Alert 1. Always dry the bottom of the Petri dish completely before placing it onto the microscope. 2. Whenever you are not viewing the fish remember to turn off the microscope too much exposure to the heat of the microscope light will kill the fish. PROCEDURE The lab is divided into in two parts. The first part of the experiment will be spent exploring a computer animation of the human body s circulatory system. The second part of the experiment is for you to directly observe vessels in the circulatory system of a goldfish using a microscope. Part I: Exploring the Circulatory System on the Internet 1. Go to 2. Click on Enter Here to enter the Human Anatomy Online website. 3. Click on the image for the Cardiovascular System link.

8 4. Click on the link, Cardiovascular System Overview (located next to See Also ), and read the information that appears on the left side of the screen. 5. Click on the second Cardiovascular System (simplified) link (located next to See Also ), and read the information that appears on the left side of the screen. 6. Click on Animations on the left side of the screen. 7. Click the Capillary link from the menu. 8. In the middle of the screen an animation will show the blood cells moving through the capillaries. 9. Draw, color, and label a sketch of the capillary animation in the space provided on your student answer page. Show all the details of the animation, including the flow of oxygen, carbon dioxide and water. Use the chemical symbols O 2, to represent oxygen, CO 2 to represent carbon dioxide and H 2 O to represent water and show how each of these are diffused in and out the capillary and the cell. Use all rules for biological diagrams when making your diagram. Title your drawing: Model of Capillaries in the Circulatory System. 10. Answer the Part I questions on the student answer page using the animations and the text from the Human Anatomy Online web site. Part II: Exploring the Circulatory System in the Fish s Tail READ ALL DIRECTIONS CAREFULLY BEFORE PERFORMING THIS PROCEDURE! Whenever you are not viewing the fish remember to turn off the microscope too much exposure to the heat of the microscope light will kill the fish. 1. Dip the cotton ball into the aquarium water. 2. Gently pull the wet cotton ball and stretch it slightly into a flattened disk. 3. Lay the stretched and wet cotton ball into the Petri dish. 4. Use the transfer pipet to put 2 or 3 ml of aquarium water into the Petri dish. 5. Your teacher will come to your table to bring your group a fish. Try to handle the goldfish as little as possible because touching it removes its protective mucus coating. 6. Gently lay the fish onto your cotton in the Petri dish. 7. Wrap the wet cotton around the body, head, and gill area of fish so that just the tail is visible. Make sure that the head of the fish is covered completely with the cotton. The fish will move very little when secured in the cotton. 8. Place a microscope cover slip over just the tail fin, in the Petri dish. See Figure 2, showing a properly positioned fish in the Petri dish. A Fishy Tale

9 9. Carefully wipe any water off the bottom of the Petri dish before placing it on the microscope stage. 10. Place the Petri dish on the stage of the microscope. Adjust the diaphragm settings to allow a LOW amount of light to pass through the specimen. Too much heat generated by the light will kill your fish. 11. Turn the nosepiece until the low power objective (4 ) is positioned over the tail. Focus on a thin section of the tail using the low power objective. 12. Use the coarse adjustment knob to bring your specimen into focus. 13. Carefully turn the nosepiece to the medium power objective (10 ). Focus using the fine adjustment knob. Again refer to Figure 2 to make sure you have the Petri dish, fish, cotton ball and cover slip set up correctly. A Fishy Tale Figure 2: This photo shows a fish properly positioned in the Petri dish, securely wrapped in the cotton, and ready to be observed with the compound light microscope. Be sure there is plenty of aquarium water saturating the cotton and the cover slip over the tail.

10 14. Closely observe the blood flowing through the blood vessels. Determine which vessels are arteries, which are veins, and which are capillaries. Make sure that when you and your partner are not directly observing the fish tail that you turn OFF the light to avoid overheating the fish. Work carefully but quickly to make sure that your fish survives this procedure. 15. Use colored pencils to draw a section of the tail as it appears under 100 magnification (or medium power) in the space provided on the student answer page. Follow all rules for creating a biological diagram and indicate labels for: an artery, a vein, and a capillary. Be sure to add as much realism and detail as you can. The orange dots that you see in the tail are pigment cells and not blood cells. 16. As soon as you and your partner have observed and made diagrams of the capillaries, arteries, and veins, return the fish to the aquarium water. 17. Using your knowledge about the circulatory system from the website and your observations in the microscope, answer the Part II conclusion questions on your student answer page. A Fishy Tale

11 A Fishy Tale Observing the Circulatory System of a Goldfish with a Compound Light Microscope A Fishy Tale BIOLOGICAL DIAGRAM-PART I

12 A Fishy Tale BIOLOGICAL DIAGRAM-PART II

13 A Fishy Tale CONCLUSION QUESTIONS Part I: Exploring the Circulatory System on the Internet 1. What is the responsibility of the cardiovascular and respiratory systems? 2. Why is blood such an essential fluid to the cardiovascular and respiratory systems? 3. How do arteries differ from veins? 4. How does the function of capillaries fit into the cardiovascular system? 5. How does the pressure of the blood in the veins compare to the pressure of the blood in the arteries? 6. How many square miles do capillaries cover in our bodies? 7. Why do you think there are so many square miles of capillaries? 8. How much more pressure does an artery have than a vein (a %)? 9. Why do you think that the pressure in an artery is so much greater than in a vein? 10. As the blood in the arteries approaches the capillaries, what gas is the blood rich in? 11. In your own words, describe the flow of blood as it leaves the heart and moves through the various vessels until it returns to the heart. Include the following terms in your description: blood cells, heart, artery, vein, capillary, O 2, CO 2.

14 Part II: Exploring the Circulatory System in the Fish s Tail! 1. Explain how you can quickly tell the difference between the three kinds of vessels (capillary, vein, and artery) in the tail of a fish. A Fishy Tale 2. Which type of vessel seemed to be most numerous in the tail of the fish? Explain why it is essential that there be more vessels of this kind? 3. In your observation of the fish s tail, in which blood vessels does the blood move the slowest? Why? 4. In your observation of the fish s tail, in which blood vessels does the blood move the fastest? Why? 5. Describe another way that you could tell the difference between the arteries and veins in the tail of the fish. (Hint: All the images that you see in the microscope are reversed!)