Paramecium Homeostasis Gizmo Answer Key

Name: Luke Watson Date: 08-14-2022 Student Exploration: Paramecium Homeostasis Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Vocabulary: adaptation, cell mouth, cilia, concentration, contractile vacuole, food vacuole, homeostasis, hypertonic, hypotonic, macronucleus, micronucleus, oral groove, osmosis, paramecium, solute, solution, solvent Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. The images show red blood cells (RBCs) in three different solutions. A. Which image shows RBCs in normal blood plasma? B B. Which image shows RBCs in pure water? C C. Which image shows RBCs in a very salty solution? A 2. What do you think is happening in images A and C? Red blood cells either expel or take in water. Red blood cells become hypertonic as seen in image A as a result. Alternately, hypotonic, as in figure C. Gizmo Warm-up A paramecium is a one-celled organism that lives in ponds and other bodies of water. One of the challenges for a paramecium is to maintain a stable size and shape. On the Paramecium Homeostasis Gizmo, turn on the Show labels checkbox. Try to determine the function of each of the labeled structures. 1. Through which two structures do you think food enters the paramecium? The cell mouth and oval grove. 2. Which two structures contain DNA? Macronucleus and micronucleus. 3. Which tiny structures help the paramecium to move around? Cilia 4. Which structure pumps out excess water and wastes? The Vacuole Contractile. Get the Gizmo ready: Activity A: ● Select the User controlled setting. ● Check that the Water solute concentration is 1.00%. Maintaining a water balance Introduction: Every organism needs to maintain stable internal conditions—a process known as homeostasis—in order to survive. A paramecium maintains homeostasis by responding to variations in the concentration of salt in the water in which it lives. (The concentration of a solution is equal to the amount of solute that is dissolved in a given amount of solvent.) Question: How do changing solute concentrations affect a paramecium? 1. Predict: In the Paramecium Homeostasis Gizmo, the solute is salt and the solvent is water. A. Look at the top left of the Gizmo. What is the water solute concentration? 1.00% A solute concentration of 1.00% means that for every 1 gram of water there is 0.01 grams of solute (salt). B. What is the concentration of solutes inside the paramecium? 1.80% The water solution outside the paramecium is said to be hypotonic because it has a lower solute concentration than the solution inside the paramecium. C. Based on the internal and external solute concentrations, do you think the paramecium will swell up or shrink in this solution? Explain your reasoning. Because there are so many grams in the fluid, i think the paramecium will swell up in it. 2. Observe: Click Play ( ), and observe the size of the paramecium. A. What do you notice? The Paramecium grows in size. B. What happens after about 16 seconds? Explosion of the Paramecium. 3. Observe: Click Reset ( ). Set the Water solute concentration to 2.00%. (This is a hypertonic solution because it has a higher solute concentration than the solution inside the paramecium.) Click Play. What happens to the volume of the paramecium now? The Paramecium shrinks in size. 4. Infer: Water moves into and out of the paramecium by a process called osmosis. Osmosis is the movement of water across a membrane from a region of lower solute concentration to a region of higher solute concentration. A. If the solute concentration in the water is low (hypotonic solution), does water move into or out of the paramecium? The water will move into The Paramecium. B. If the solute concentration in the water is high (hypertonic solution), does water move into or out of the paramecium? The water will move out of the Paramecium C. In which situation is the paramecium in danger of swelling up and bursting? It's possible for the Paramecium to enlarge and explode. 5. Experiment: The contractile vacuole is a star-shaped structure that helps the paramecium to pump out excess water. This adaptation allows the paramecium to survive in hypotonic (low solute concentration) solutions. Click Reset, and set the Water solute concentration to 1.00%. Click Play. When the contractile vacuole fills up, click Contract. Do this for a while, and then click Pause ( ). A. How does contracting the vacuole affect the volume of the paramecium? The Paramecium's volume reduces when the vacuole contracts. B. Click Play, and then click Contract many times rapidly. What happens? Dehydration kills the Paramecium. 6. Experiment: Click Reset. This time, try to maintain a steady volume for the paramecium. Pause the simulation after about one minute and select the TABLE tab. How many contractions per minute were required for the paramecium to maintain a relatively stable internal solute concentration and stay the same size? It takes about 24 contractions per minute. 7. Summarize: How does the contractile vacuole help the paramecium survive in a freshwater environment? A paramecium can keep its volume from shrinking in a hypertonic solution by retaining as much water as it can. Get the Gizmo ready: Activity B: Contractions and concentrations ● Click Reset. ● Select the Paramecium controlled setting on the DESCRIPTION tab. Question: How does a paramecium respond to changing solute concentrations? 1. Form a hypothesis: How do you think the number of contractile vacuole contractions will change when the water solute concentration is reduced? Explain why you think so. The quantity of vacuole contractions will rise as the concentration of the water solution is decreased. However, as the solute concentrations increase, fewer contractions will occur. 2. Gather data: Set the Water solute concentration to 2.00%. Click Play. Pause after 30 seconds. On the TABLE tab, add the total number of contractions. Record the results in the table below. Click Reset, and repeat this procedure for all of the listed concentrations. Water solute concentration Contractions in 30 seconds 2.00% 0 1.50% 3 1.00% 8 0.50% 13 0.00% 18 3. Analyze: What pattern do you see in your data? How does this compare to your hypothesis? The number of contractions rises as the water solute falls. This supports my hypothesis. 4. Predict: How many contractions would you expect in 30 seconds if the water solute concentration was 0.75%? Test your prediction with the Gizmo. Predicted contractions: 10 Actual contractions: 11 5. Think and discuss: Paramecia that live in freshwater have contractile vacuoles, while those that live in salt water do not. Why do you think this is the case? I believe this to be the case because paramecia that thrive in salt water have an environment that is hypertonic, which means that the cell needs water in order for the contractile vacuole to function properly and release additional water into the cell. Freshwater Paramecia survive in a hypotonic environment, requiring a contractile vacuole to remove the extra water.