Ozone and Bacteria

Examine the effect different types of light have on bacteria growth.

1. Prepare and label the petri dishes according to the location where they will be stored.

2. Inoculate the petri dishes with the bacteria culture.

3. Place one petri dish in each of the following locations : a window with daily exposure to sunlight, a cabinet with a UV light source, a cabinet with an infrared light source, a cabinet with a fluorescent light source, and a dark area with no light source.

4. On a daily basis, record the changes in the bacteria colonies.

5. Measure the size and extent of the colonies by tracing the outline onto an acetate sheet. Place the sheet over a piece of graph paper and count the number of squares covered by colonies. Record this information onto a data sheet.

6. At the end of the experiment, discuss which conditions enabled the bacteria to thrive. Under what wavelengths of light? Why is that important considering that the thinning of the ozone layer allows more UV light to pass through the atmosphere?

7. What implications could future thinning of the ozone layer have on bacteria populations?

Circadian rhythms

People and animals are usually adapted for a daily cycle of light and dark. They adjust their daily schedules based on the sun. What happens during the Antarctic winter when it is dark 24 hours a day? Examine how bacteria, lichens, and people adjust to the lack of sunlight in the winter. Conversely, what are some of the problems associated with 24 hours of sunlight in the summer?