Biology Help: Pasteur's Experiment?

Question

I'm a freshman in college - need help answering another one of these "challenge questions"

The classic experiment by Pasteur tested the hypothesis that cells arise from other cells. In this experiment cell growth was measured following sterilization of broth in a swan-neck flask or in a flash with a broken neck:

a. Which variables were kept the same in these two experiments?

b. How does the shape of the flask 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?

Appreciate the help - thanks!

Answer 1

a. The variables that were kept the same are the size of the flask, the broth, boiling, temp, ...

b. The swan-neck flask prevents bacteria from entering the flask from the environment. The broken neck allows bacteria to enter from the environment.

c. After boiling the broth, the broth in the swan-necked flask should remain clear because no additional bacteria can enter and the bacteria in the broth were killed by boiling.

The broth in the broken-necked flask should become cloudy. Even though the boiling killed the bacteria in the broth, more bacteria can enter the flask from the environment and begin growing in the broth.

d. If the bacteria in question produce heat-resistant spores, then the bacteria in the broth will not be killed by the boiling. As the broth cools the spores can resume activity. In that case, the broth in both types of flasks should become cloudy because both will harbor live bacteria and it doesn't matter if any bacteria can enter from the environment or not.

Answer 2

the broth and all its components and preparation were identical. One flask was open to the air, while the other prohibited contact with the air indefinately. It was thought that cells arose spontaneously, and this experiment showed that this is not the case. The closed neck contained sterile broth which to this day has never been exposed to the atmosphere and is clear and pure. You can see it in the pasteur institute. The other one was putrid within a few days.

Spores are produced when the cell detects a rapid drop in viable resources. However once the spore is within a suitable environment that will sustain life it has no choice (unless dead) but to open and begin replicating itself. The broth mix is a rich medium which the spores would relish. It is sterile.

Answer 3

20. Gragor mendel crossed 2 pea plant to see why offspring look like thier parents. He chose pea plants because they reproduce sexually. 28. A vestigual structure is something such as a snakes pelvis or a humans appendix, which ancestors may have used but have evolved and no longer need it. But we still have it. Sorry I can't answer all of them, but I hope these two help.

Answer 4

Oh, come now - you should be able to work out most of this without too much difficulty. Better to get used to doing as much of your own work as possible!