Column Ecosystems and Yeast

Students are settling back into the routine and the class is humming along. I’m enjoying the shift from teaching a math / science rotation to solely science. At the same time, I realize how my reflection time and work on this blog has languished over the last year. I’m going to start with an attempt to review weekly activity and hopefully build upon this routine.

We’re about three weeks in and trying to juggle a couple of units at a time. As the school transitions to the NGSS, shifting of units between grade levels has taken place. Holes in the curriculum were also identified and new units placed on the docket for the year. It is going to be a busy one! The immediate impact is that ecosystem concepts traditionally in 7th grade will move to 6th grade to take the place of cell form and function, which is heading to 7th. Wanting to at least expose students to both topics in this transition year, we’re double dipping our time. I would love to know how other schools are setting up the flow of units. We have chosen to move from large systems in 6th through a process year in 7th to the “tiny” interactions in 8th.

This week completed the creation and loading of bottle ecosystems.


Each ecosystem has three chambers: decomposition, terrestrial and aquatic. Once the bottles were constructed, my teaching partner and I set-up an “assembly” line in a main corridor to load each chamber. I was surprised at how quickly (and relatively cleanly!) students passed through the line. The following class, baseline measurements of water quality, organism counts and layers descriptions were made.

With the ecosystems looking out of the window, we continued with an earlier conversation regarding the characteristics of live. Beginning with the claim that yeast is a living organism, students are being asked to collect evidence to either support or refute the claim. I have the feeling that the concept of collecting evidence is a new one for most of these budding scientists. As a first lab, it is highly structured to provide a model for students though we will soon begin dropping much of the scaffolding as students begin designing their own investigations.

IMG_0155Students measured amounts of yeast and sugar, added warm water and topped the flask off with a balloon. After ten minutes of observation, we regrouped for a quick discussion to link our evidence with the characteristics of living things. The “grand finale” was to send the captured gas through a straw into a test tube of Btb solution with the hope of a color change. As a whole, classes had about a 50% success rate on the final step.

Where do we go from here? More evidence is needed in order to say that the yeast is living or not. Moving into a discussion of variables, students will modify the experiment to search for a response to stimuli. We’ll pull out the microscopes to look at cells and try to link an increased rate of gas production to yeast reproduction. During each step, I hope to slowly pull back as students become familiar with investigations.



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