Biology 8th Edition by Kenneth Mason ,Jonathan Losos,Susan Singer,Peter Raven,George Johnson

تمرين 11

The classic experiment by Pasteur (see figure 1.4) tested the hypothesis that cells arise from other cells. In this experiment cell growth was measured following sterilization of broth in a swan-neck fl ask or in a fl ask with a broken neck.
a. Which variables were kept the same in these two experiments
b. How does the shape of the fl ask affect the experiment
c. Predict the outcome of each experiment based on the two hypotheses.
d. Some bacteria (germs) are capable of producing heat-resistant spores that protect the cell and allow it to continue to grow after the environment cools. How would the outcome of this experiment have been affected if spore-forming bacteria were present in the broth
Figure 1.4 Experiment to test spontaneous generation versus germ hypothesis.