Refer to the figure below, showing two flasks of broth that were prepared and heated to boiling.Immediately after heating, one flask was left open and the other was sealed with a cork.Both flasks were allowed to cool and then left undisturbed for several days.Only one of the flasks developed a cloudy appearance, as shown. When these results were presented as proof against spontaneous generation, a criticism was raised about the design of the experiment.Which is a valid criticism in this case?
A) The experiment lacked a control.
B) The heating step was not sufficient to destroy all microorganisms in the broth.
C) The experiment did not allow enough time for microorganism growth.
D) The experimental flask was sealed off from two variables: air and microorganisms.
E) The broth in the two flasks must have differed in microbe content before heating.

Question

Refer to the figure below, showing two flasks of broth that were prepared and heated to boiling.Immediately after heating, one flask was left open and the other was sealed with a cork.Both flasks were allowed to cool and then left undisturbed for several days.Only one of the flasks developed a cloudy appearance, as shown.  When these results were presented as proof against spontaneous generation, a criticism was raised about the design of the experiment.Which is a valid criticism in this case?
A) The experiment lacked a control. 
B) The heating step was not sufficient to destroy all microorganisms in the broth. 
C) The experiment did not allow enough time for microorganism growth. 
D) The experimental flask was sealed off from two variables: air and microorganisms. 
E) The broth in the two flasks must have differed in microbe content before heating.

Quizplus · Accepted Answer

The experimental flask was sealed off from air and microorganisms, making it impossible to determine if the cloudy appearance was due to spontaneous generation or simply microorganisms present before heating.

Refer to the Figure Below, Showing Two Flasks of Broth