Paramecium Homeostasis

Name: ______________________________________ Date: ________________________ Student Exploration: Paramecium Homeostasis 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. B A. Which image shows RBCs in normal blood plasma? __________ C B. Which image shows RBCs in pure water? __________ A C. Which image shows RBCs in a very salty solution? __________ 2. What do you think is happening in images A and C? _ In_i_m_a_g_e_A__an_d__C_H _2_O _ le_av ter_i_ng _is_ei _t_h_er__ _i_n_g_or __en __ __th_e_r_e_d_bl _o_o_d_c_el_l_s._T _h_is __m_a_k_es__th_e_r_ed __bl_o_o_d_c_el_ls_____ yp_e_rt_o_ni_c_li_k_e_i_n_i_m_a_ge _h_ __A. __O_r_h_y_p_ot_o_ni_c, __li_ke __in__im _a_g_e_C _._ _________________ 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 T_ he__ ov_al the paramecium? __ __gr_o_v_e_a_n_d_c_el_l_m_o_u_th ________ 2. Which two structures contain DNA? ____________________________________________ The micronucleus and the macronucleus Cilia 3. Which tiny structures help the paramecium to move around? _________________________ The contractile vacuole 4. Which structure pumps out excess water and wastes? ______________________________ 2019 Activity A: Maintaining a water balance  Select the User controlled setting.  Check that the Water solute concentration is 1.00%. 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. 1.00% A. Look at the top left of the Gizmo. What is the water solute concentration? _________ A solute concentration of 1.00% means that for every 1 gram of water there is 0.01 grams of solute (salt). 1.80% B. What is the concentration of solutes inside the paramecium? _________ 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. ___________________________________________________________________ I believe that the paramecium will swell up in this solution due to the number of grams in the solute. ___________________________________________________________________ ___________________________________________________________________ 2. Observe: Click Play ( ), and observe the size of the paramecium. The size of the paramecium increases. A. What do you notice? __________________________________________________ The paramecium explodes B. What happens after about 16 seconds? ___________________________________ 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 volume of the paramecium decreases. _________________________________________________________________________ (Activity A continued on next page) 2019 Activity A (continued from previous page) 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 The water will move into the paramecium into or out of the paramecium? __________________________________________ B. If the solute concentration in the water is high (hypertonic solution), does water move The water will move out of the paramecium. into or out of the paramecium? __________________________________________ C. In which situation is the paramecium in danger of swelling up and bursting? The paramecium is in danger of swelling up and bursting ___________________________________________________________________ 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 ( ). When the A. How does contracting the vacuole affect the volume of the paramecium? _________ vacuole is contracted, the paramecium's volume decreases. ___________________________________________________________________ B. Click Play, and then click Contract many times rapidly. What happens? __________ The paramecium dies of dehydration. ___________________________________________________________________ 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? About 24 contractions are needed per minute. _________________________________________________________________________ 7. Summarize: How does the contractile vacuole help the paramecium survive in a freshwater environment? In a hypertonic solution, a paramecium can maintain its volume by preventing itself from shrinking by _________________________________________________________________________ holding in as much water as it can. _________________________________________________________________________ 2019 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. _________________________________________________________________________ When the water solution concentration is reduced, the number of vacuole contractions will increase. But when the solute concentrations rise, the number of contractions will decrease. _________________________________________________________________________ 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 2.00% Contractions in 30 seconds 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? _________________________________________________________________________ As the water solute decreases, the number of contractions increases. This goes along with 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. 10 Predicted contractions: __________ 11 Actual contractions: __________ 5. Think and discuss: Paramecia that live in fresh water have contractile vacuoles, while those that live in salt water do not. Why do you think this is the case? I think this is the case because paramecia that live in salt water have a hypertonic environment, meaning _________________________________________________________________________ that the cell has a need for water so the contractile vacuole can do its job and release more water into the _________________________________________________________________________ the cell. While paramecia that live in freshwater live in a hypotonic environment, which calls for a contractile vacuole to pump out the excess water. 2019