2. Life Traps - Assessments


  1. Collect students’ lab notebooks with their observations and conclusions.
  2. Revisit the characteristics of life list from the Is It Alive? activity. Revise the criteria as necessary.

Going Further

  1. 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.
  2. 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.
  3. 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.
  4. 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.