Updated: May 3
The cell energy simulation can be used for photosynthesis, respiration, and primary productivity virtual labs. This post will outline the variables that can be tested using the simulation. The resources page includes both guided and inquiry based labs that can be used with the simulation.
Dissolved oxygen (DO) is the measurement for this simulation. Before starting the simulation, students should understand what is produced/consumed in photosynthesis and cellular respiration. Students do not necessarily need to know complete balanced equations or the specific steps of these processes. Basically, they just need to know that oxygen is produced in photosynthesis and consumed in cellular respiration. Students should also understand that all organisms perform cellular respiration (although there are prokaryotes that do not utilize oxygen) and that photoautotrophs carry out photosynthesis. In this simulation, the plants perform both photosynthesis and cellular respiration and the fish are performing cellular respiration.
Students can test the cellular respiration rate for either the fish or plant species. To test the fish respiration, set the number of plants to 0. Students can then test the effect of any of the variables (light intensity, temperature, and light color). While light doesn't directly affect the processes involved in respiration, light factors could potentially affect the "behavior" (the simulation doesn't visually show any variations) of the fish, which could in turn affect respiration rates.
In order to measure the cellular respiration of the plant, set the light intensity to 0. With no light, there is no photosynthesis and any changes to DO are the result of plant respiration. The effect of temperature on plant respiration can be studied by leaving the light at 0 and manipulating the temperature. The plant respiration measurement will also be needed to study photosynthesis.
To find a value for photosynthesis, the oxygen consumed in respiration needs to be added to the amount of oxygen production measured. When a plant is undergoing both photosynthesis and respiration, the DO measurements represent the net amount of oxygen produced. Some of the oxygen produced in photosynthesis is consumed by respiration, so to find the total amount of oxygen produced in photosynthesis the amount consumed must be added. Once students understand how to measure photosynthesis using the simulation they can test how each of the variables affect it.
Students will need to be aware that temperature affects the rate of respiration as well, so they will have to take that into account if they are testing the effects of temperature on photosynthesis (Photosynthesis B is a guided lab available in the Resources has space to record this data).
In addition to testing photosynthesis and respiration independently, students can also use the simulation to study primary productivity in the tank. This simulation is a good opportunity to practice with the concept of primary productivity and the calculations involved before applying that to a lab or ecosystem setting.
Currently, several resources are available for this simulation. There are three versions of photosynthesis virtual labs. 'A' walks through testing light intensity, light color, and temperature. 'B' does the same, but takes respiration into account for the calculations. 'Inquiry' requires students to select a variable to test and write a procedure. All three can be found as Word documents on the Resources page or in a digital format in the Google Drive.