NetLogo User Community Models
by Edmund Hazzard (Submitted: 09/08/2008)
WHAT IS IT?
This is a model of photosynthesis in a chloroplast which is inside a leaf. It was written for grades 5-6.
This model is used by the Concord Consortium in the UDL (Universal Design for Learning) project. To see the model in the context of an activity, go to http://udl.concord.org. Find the Intermediate Plants Unit (Grades 56) and go to the activity called "Photosynthesis: a closer look".
HOW IT WORKS
The following inputs can be adjusted with sliders:
In the center of the leaf is a black circle representing a chloroplast. The rules for the model are as follows:
HOW TO USE IT
Run the model and watch for the reactions that are described above. Slow the model down if that is helpful.
Water, carbon dioxide in the air, and sunlight can be controlled with the sliders.
THINGS TO NOTICE
Notice that there are two reactions needed to make sugar. The first one is energy-dependent (#2 above); the second is energy-independent (#3 above). So a leave can continue to make sugar for a while after the sunlight goes away, but soon it runs out of excited-state chloroplasts and stops making sugar.
THINGS TO TRY
Change each of the sliders in turn and see what effect they have on the production of sugar.
EXTENDING THE MODEL
This model includes only the main inputs and final products of the photosynthesis reaction, which is very complex. One could try to expand the reactions that are included in the model.
Think of a better way to graph rates of production. Figure out how to make the graph smoother.
Have the leaf do something (grow?) in response to the production of sugar. Have it turn brown if water is turned off for too long.
The photosynthesis reaction is not linear; it also has an initial threshold. Figure out how to add this to the model.
Note that the image "aspenleaftrans.png" must be in the same folder as the model in order to be displayed. This image underlies but does not interact with the model.
An effort was made to highlight the reactions so that one could notice what was being used up and what was being created. When a reaction happens, the model pauses for two seconds; then each of the reactants gets larger in turn for a short time.
A related model, "leaf-macro.nlogo", looks at the same process but with a slightly different presentation. It is also posted on Community Models.
CREDITS AND REFERENCES
This model was written by Edmund Hazzard as part of the Universal Design for Learning Project (UDL) at the Concord Consortium (http://www.concord.org) in March of 2008.
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