Look for: Students are able to identify that as the amo…

Students are able to identify that as the amount of food available on the agar plates increased (as indicated by an increase in percentage of nutrients on the agar plate, or concentration), the bacteria increased. They should be able to interpret these data as an indication that the bacteria do need food (and other nutrients) to make more of themselves.

If students are struggling to identify patterns in the data, it may help to have them trace the streaks they can see on each plate with a highlighter. Ask, Which plate has the most highlighting? What was different about that plate? It may help to refer back to the independent, dependent, and control variables in these investigations. Say, How does changing ____ affect _____?

If students are struggling to use cause-and-effect language when discussing patterns in the data, point out that it helps to identify the effect by thinking about what happened or what was one finding from the investigation (i.e., lack of bacterial growth). Then, you can identify the cause by looking at what was done in order to produce that effect, or obtain that outcome (i.e., provide no nutrients). As additional support, consider offering sentence starters to help students discuss cause and effect, such as the following:

• When there was/were _______ (cause), the result was _______ (effect).
• If ______ nutrients were used (cause), then we see _______ (effect).
• As a result of ______ (cause), we see _______ (effect).