VIEWS: 20 PAGES: 9 POSTED ON: 11/20/2011
Teacher Background Information for Population Dynamics—Hands-on Simulation Day 1 simulation: Background: This activity is one component of a unit on Ecology. Prior to the activity students have learned about Mendelian genetics, populations, food webs, natural selection, and computational modeling. The activity shows how all of the above processes converge to affect population dynamics in an ecosystem. Engagement: The hands-on simulation (based in part on lab from Lach, Michael, and Loverude, Michael. The American Biology Teacher. February, 1998. p132) .is explained to the students, and students are asked to write a hypothesis/prediction based on their background knowledge. Materials: For a class of 30 students 30 rabbit cards 30 grass cards 30 wolf cards chart for recording data for each generation Lab set-up: The teacher needs to establish the following groups for the simulation: 8 students given grass cards 8 students given wolf cards 8 students given rabbit cards two students to act as actuaries and record data for each generation three students to act as morticians and reincarnation specialists to recycle the “dead” Exploration: Students conduct the following hands-on simulation: 1. Ten students are given cards labeled grass, ten labeled rabbits and ten labeled wolves. They move randomly around the classroom, and when signaled, they compare cards with closest student. Rules of Engagement: Rabbits and wolves must eat at least every other generation or they die wolf -- rabbit = rabbit dies wolf -- wolf = 1 baby wolf added wolf -- grass = nothing happens Rabbit -- rabbit = 1 baby rabbit added Rabbit -- grass = grass dies Grass -- grass = 1 baby grass added 2. After each generation students show by hand count how many surviving members there are in each population and this is recorded by the actuaries. Students who have “died” report to the mortuary/reincarnation center where they are assigned new identities and re-enter the simulation. 3. The simulation ends when two of the three populations are extinct. Explanation: 1. Students graph data from charts, analyze the data, and evaluate their original hypothesis. . Day 2 simulation: introduction of fast rabbit gene This activity is the same as the Day 1 simulation but a “fast rabbit” gene is introduced and the above items are modified with the following changes: 1. Materials: add 1 group of 30 cards for “fast rabbits” 2. Exploration: add 2 students with “fast rabbit” cards 3. Add to rules of engagement: Fast rabbit -- rabbit = coin toss to determine type of offspring produced fast rabbit--fast rabbit = add 1 fast rabbit Fast rabbit -- wolf = coin toss to determine if rabbit lives or dies 4. Students repeat the above simulation but begin with even population numbers. Example: 5 wolves, 5 grasses, 5 rabbits, 5 fast rabbits Extension: 1. Students explore the effect extrinsic variables (climate and natural disasters) and intrinsic variables (reproductive rates, mutations and diseases) on population dynamics by use of computer models. 2. Students reevaluate original hypotheses in light of new data. Teaching tips: Actuary Data: It is very efficient for data collection and relay to the rest of the class if a transparency is made of the actuary data charts, and the actuaries record the numbers for each trial of the simulation where appropriate. This can be shared with the class later, and the data transferred easily Lab write-up: Each teacher may tailor the lab write-up to their individual preferences depending on level of class and time available. Graphs are highly encouraged for visual comparisons between these two simulations as well as for a later comparison to the computer model simulation results. Analysis/Conclusion Questions: Additional questions can be added to this section from the Instructional Framework relating to modeling. This can be tailored to class level and time. Lab Grading Rubric: Available to assist in grading labs Actuary Data Tables Simulation # 1: Normal populations generation wolves rabbits grass start=P F-1 F-2 F-3 F-4 F-5 F-6 F-7 F-8 F-9 Simulation #1: Uneven Populations generation wolves rabbits grass start=P F-1 F-2 F-3 F-4 F-5 F-6 F-7 F-8 F-9 Simulation #2: Fast Rabbit Introduction—uneven populations (2 fast rabbits) generation wolves rabbits fast rabbits grass start=P F-1 F-2 F-3 F-4 F-5 F-6 F-7 F-8 F-9 Simulation #2: Fast Rabbit Introduction—even populations generation wolves rabbits fast rabbits grass start=P F-1 F-2 F-3 F-4 F-5 F-6 F-7 F-8 F-9 Population Dynamics: Hands-on Simulation Normal Rabbits Purpose: Hypothesis/prediction Procedure: Data: Simulation # 1: Normal populations generation wolves rabbits grass start=P F-1 F-2 F-3 F-4 F-5 F-6 F-7 F-8 F-9 Simulation #1: Uneven Populations generation wolves rabbits grass start=P F-1 F-2 F-3 F-4 F-5 F-6 F-7 F-8 Graphs: Graph the population size dynamics over time for the above two simulations on different graphs. Use three colors to represent the three groups of organisms. Analysis and conclusions: 1. Which population decreased most quickly? Why did this happen? 2. How did the decrease in one population affect the other two populations? Be specific giving data to support your answer. 3. Reproductive potential is the ability of a species to populate an environment without any restrictions such as predators, nutrient limits, natural disasters, or disease. Did our simulation take into account reproductive potential? Explain your answer. 4. Did any of the above graphs show characteristics of logistic or exponential growth curves? Support your answer with examples. Population Dynamics: Hands-on Simulation Fast Rabbit Purpose: Hypothesis/prediction Procedure: Data: Simulation #2: Fast Rabbit Introduction generation wolves rabbits fast rabbits grass start=P F-1 F-2 F-3 F-4 F-5 F-6 F-7 F-8 F-9 Simulation #2: Fast Rabbit Introduction generation wolves rabbits fast rabbits grass start=P F-1 F-2 F-3 F-4 F-5 F-6 F-7 F-8 F-9 Graphs: Graph the population size dynamics over time for the above two simulations on different graphs. Use three colors to represent the three groups of organisms. Analysis and conclusions: 1. How did the introduction of the fast rabbit to the food chain affect the dynamics of the three populations? Why do you think this happened? 2. Compare this simulation to the first lab simulation without fast rabbits. How does the life expectancy change among rabbits, wolves, and grass? Why do you think this happened? 3. List five factors which will impact these 3 populations but which could not be included in our simulation because of our limited ability in a hands-on activity (ex: grass reproduction rate). Name(s) LAB REPORT RUBRIC 0 1 2 3 PREPARATION Not attempted. Missing a Problem Defines problem, component. defined is formulates hypothesis unclear, stated with appropriate hypothesis or variables, designs variables not experimental method. complete, poor experimental method. DATA Not attempted Missing a Data collected Data collected and COLLECTI component. and recorded, recorded, raw data is ON raw data poorly organized and organized and present. presented DATA Not attempted. Missing a Processes raw Processes raw data ANALYSIS component. data correctly, correctly, presents but data not processed data presented appropriately. appropriately. CONCLUSION Not based on Somewhat Based on data, Well formed, based data, not based on data. somewhat on data, realistic. realistic. realistic.
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