2. Life Traps - Assessments
- Collect students’ lab notebooks with their observations and conclusions.
- Revisit the characteristics of life list from the Is It Alive? activity. Revise the criteria as necessary.
- Test the effects of various antiseptics. After growth has taken place, add a piece of filter paper soaked in an antiseptic cleaning agent (Lysol®, bleach, 409, rubbing alcohol, Neosporin®) to the plate. Be very careful when opening the agar plates. Wear a dust mask and stay in a well ventilated area since the high concentrations of spores can cause lung distress.
- Make new life traps and test the effect of different environmental factors. For example, with similarly seeded plates, place one at room temperature, one in a warm place like near the water heater, and one in the refrigerator. Or investigate the effect of sunlight versus darkness.
- Make new life traps and compare the effectiveness of various manipulations thought to disinfect surfaces. Compare plates seeded with unwashed versus washed hands. Compare a table top before and after cleaning.
- Trap wild yeast from the air and use it to make sourdough bread! A mixture of water and flour provides the nutrient base for the yeast to establish itself. There are hundreds of recipes and different ways to create a sourdough culture. Before store bought yeast, sourdough cultures were the primary means of leavening bread. Since each culture has a slightly different population of yeast, every culture will produce its own distinctive flavor. Starting a sourdough culture is very simple to do and extremely fun. The Exploratorium website provides one way to start a culture using a lump of dough. Other sourdough starters use a more liquid culture with a consistency more similar to pancake batter than bread dough. For instance, the How Things Work website describes the procedure for creating a wild yeast starter with this more liquid consistency. I started my own sourdough starter using a procedure found in the cookbook, The Cheeseboard Collective Works, published by my all time favorite Berkeley bakery and cheese shop, The Cheeseboard.
Submitted by irene on Mon, 2006-07-24 13:34