Points of a Compass

One of the books I'm currently reading is The Story of Edgar Sawtelle by David Wroblewski. During the first part of the book the protagonist, Edgar, witnesses a disturbing scene between two family members. Afterwards, he goes into the kitchen and describes the silence there. During his description of this, the author, through Edgar, refers to the chairs arranged around the kitchen table as the points of a compass.

This passage is really sticking with me. I think it speaks to the way that this young man orients his view of the world. His direction...that part of his life that provides orientation for everything else...comes from the family that shared meals around that table. The family unit is what Edgar depends on to guide him through the rough spots in his young life.

When I pass a stranger on the street, or a student in my classroom, or a co-worker in the hallway...what serves as their orientation point? What is their compass? What guides them?

What guides me?

Biology Lab (continued)

Results from our photosynthesis lab were mixed. In a lot of cases, both test tubes turned blue. This is easy to explain, since in both treatments a living plant was placed in the bromothyl blue solution. Plants use carbon dioxide for photosynthesis. As carbon dioxide is used by the elodea plants in the test tubes, the BTB solution gradually turned from yellow back to blue. We hypothesized that if we surrounded one of the tubes with foil then photosynthesis would stop and the BTB solution would stay yellow (since the carbon dioxide wasn't being absorbed). For many of the groups, this wasn't the case...photosynthesis still occurred in spite of the darkening treatment. The question now becomes what other changes could we make that might keep photosynthesis from happening, or might give us the results that we expect?

There were several groups, however, that did observe results that supported their hypotheses. The darkened tube still had a yellowish tint to it, while the tube in the light was completely blue.

This illustrates two important points: First of all, failure of results to support a hypothesis is NOT failure of the experiment or of the scientific process. As long as we are able to look at our results critically, learn from them, and use them as a springboard for new testing, then this can actually be one of science's greatest moments. We're going to learn in the next couple of weeks about a man named Oswald Avery who, although he never achieved the results that he dedicated his life to, managed to make one of the most profound conclusions in the history of biology.

The second point here is the importance of repeated trials. By having many groups doing the same experiment, we were able to get data and record observations as a class that gave us a much better idea of what was happening in those tubes than we would have been able to by looking only at any one group.

Biology Lab

Today in biology we set up a classic photosynthesis experiment. Bromothyl blue (BTB) is an indicator chemical that turns yellow in the presence of carbon dioxide. So we started with a beaker of (blue) BTB. Using a straw, each group blew into their beakers of BTB until it turned yellow. We figured out that the color change was due to the carbon dioxide in exhaled air reacting with the BTB. Each group then poured the (now yellow) solution into two separate test tubes, and added an aquatic plant to each.

Question: What will happen to the BTB? After some discussion we decided that the plants, through photosynthesis, will use up the carbon dioxide in the water and produce oxygen. This should result in the BTB color changing back to blue.

Question: How do we know that any color change results from the plant and not from something else? Through discussion, we figured out that oxygen in the air might affect our results, so we decided to seal up the test tubes with parafilm so that they'd be airtight. Now if the color changes, we know that it's from the plants sealed inside and not from the gases in the atmosphere.

Question: How can we make sure that photosynthesis is what produces oxygen, and not some other process in the plant? We thought about this for awhile, and decided that, by keeping one of the test tubes in the dark, we would prevent the plant inside from doing photosynthesis. So each group enclosed one of their two test tubes with aluminum foil to block out all light.

Our working hypothesis, then, is that if a plant is exposed to light, then it will absorb carbon dioxide and produce oxygen which will turn its BTB solution from yellow to blue.