Tag Archives: biomass

Ecology and Systems Biology: Structured Talk

Last Thursday, my 4th period students participated in Studio Day.  The lesson involved using structured talk to discuss student predictions around population modeling of organisms in the Great Salt Lake.  Today, I taught the first day of that lesson to my 1st, 2nd, 3rd, and 5th period students.  My 4th period students continued the lesson from last Thursday, using mathematical modeling and knowledge of biomass and energy transfer to determine the number of organisms in each trophic level present in an area of the Great Salt Lake.

Updated: On Tuesday, my 1st, 2nd, 3rd, and 5th period students continued the lesson be started yesterday.  We returned to the halobacteria growth curves and calculated the amount of biomass available to the primary consumers (the brine shrimp).  Students learned that there were only enough halobacteria to support 2 brine shrimp, which is not enough energy to support an Avocet (secondary consumer) or a Northern Harrier (tertiary consumer).  Students completed the modeling activity and explained their population curves using the science concepts we have learned this unit, focusing on biomass, limiting factors, and carrying capacity.  My 4th period students read about the ecosystem of Yellowstone National Park following the reintroduction of wolves back in 1995.

Ecology and Systems Biology: Food Web Game Results

We began the day by revisiting the grass/cow/hamburger slide from yesterday,  Students were challenged to apply their understanding of the food web by figuring out how much grass a cow has to eat to produce a hamburger.  Understanding that grass is at the bottom of the food chain (like halobacteria in the Great Salt Lake), and recognizing that cows eat grass (like brine shrimp eat halobacteria), students reasoned that it would take 10 times as much mass in grass to produce one hamburger.  If a hamburger has a mass of 100 grams, then a cow would have to eat 1000 grams of grass to produce the hamburger.  Several students wondered how much land is required to produce 1000 grams of grass, and I encourage all of my students to research that question for extra credit!

We continued our discussion of the food web game by analyzing group results, assembling a table of class results, and calculating the average number of organisms at each level of the food chain.  Students observed the 10-fold decrease in organism mass as we move up the food chain, and we connected the concept of biomass with energy.  The results for each class period are reported at the end of the slide deck.  We also discussed the variables involved in the food web game activity, with students identifying distance from the seed-trading space, number of students per group, and the efficiency with which groups worked as key variables contributing to how many higher-level organisms a group obtained.

After the slide deck and discussion, students worked in groups to complete the back side of the worksheet from yesterday.  Students learned that while the amount of matter in a system stays constant, the amount of energy in a given level decreases as we move up the food chain.  This is not always obvious, especially because organisms at the bottom of the food chain tend to be very small (yet great in number).