Joe Dua Per. 6 5/9/14 Discovery Project Biology How does temperature affect bacterial growth?

 Biology  The study of all life or living matter  The living organisms of a particular region.  I choose this field because I was always interested in how living organisms worked

 Career: Marine biologist  Specialized in the scientific study of organisms in the ocean or other bodies of water  Bacteria in the experiment and plankton in the ocean share similar properties

 1928: Alexander Fleming accidentally discovered penicillin  Bacteria growth is the dependent variable in the experiment. × 1595: Scientists Hans and Zacharias Janssen constructed the first compound microscope  Microscopes are used to observe bacteria.

Title: How does temperature affect the growth rate of bacteria? Hypothesis: If the temperature is decreased, then the growth rate of the bacteria will decrease because in the low temperature, molecules in the bacterial cells will not be able to move and multiply, restraining the bacteria’s ability to grow. Independent Variable: Temperature (Celsius) Levels of IV (Temperature)-15 C 5 C 15 C 25 C 40 C Number of Trials: Dependent Variable: Bacterial growth (cm squared) Controlled Variable: Type of bacteria, heating device, location (same house), amount of starting bacteria, time bacteria allowed to grow, cooling device, size of dish, material of dish, cleanliness of dish, initial state of bacteria

 Preferred temperature of household bacteria is 37 degrees Celsius  Bacteria in experiment are found at home  Bacteria in 40 degrees Celsius climate should reproduce the most  The cooler a substance, the slower it moves  Bacteria placed in the freezer and refrigerator will move slower, and be unable to reproduce/grow

2cm x 3cm grids Petri Dishes Ultra fine point sharpie

Scrapes from the cups Bacteria and stroke lines Q-Tip

Remember to use caution and have adult supervision when cutting out the make shift Petri dishes.

How does temperature affect bacterial growth? Temperature (Celsius)Bacterial Growth (cm squared) Trial 123Averages

 Set Up  Cup bottom is smooth  Bacteria looked green and mossy,  No distinct smell  Experiment:  Bacteria in freezer developed frost along stroke lines  Trial two day four, 25 degrees Celsius bacteria: slight texture (soft and moist)  Measurement:  Exact growth of the cells was difficult to measure; rounding was required  Dust landed on some of the Petri dishes; deciphering actual growth was difficult

 Investigative Question:  How does temperature affect bacterial growth?  Hypothesis  If the temperature is decreased, then the growth rate of the bacteria will decrease, because in the low temperature, molecules in the bacteria cells will not be able to move and multiply, restraining the bacteria’s ability to grow

 Claim:  The lower the temperature a bacteria’s climate is, the slower the bacteria will grow.  Evidence:  -15 degrees Celsius bacteria: no growth  40 degrees Celsius bacteria: Average growth of 2.7 cm squared  -15 and 5 degrees Celsius bacteria dishes: smooth and colorless  Reasoning:  Cold temperature, bacteria slow down  -15 degrees Celsius bacteria moved too slowly to duplicate and grow: no significant growth shown

 Experimental Design Improvement: Temperatures above 40 degrees Celsius  Real-World Application/Connection: Scientists need lab rooms with few bacteria  Can use a room with a cold temperature to work in  Future Experimental Design: How does amount of light affect bacterial growth?

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