You take a large sample of soil and put it all into individual pots. You then divide the pots into two groups. In the first group, every pot of soil has been sterilized, and thus contains no bacteria. In the second group, none of the pots of soil have been sterilized. You plant soybean seeds in all the pots. What would you expect to see as the seeds sprout and grow?
A) The plants growing in the sterile soil are bigger because they have not been exposed to any bacteria.
B) The plants growing in the non-sterile soil are bigger because they have mutualistic associations with nitrogen-fixing bacteria.
C) The plants growing in the sterile soil are bigger because they do not have to compete with nitrogen-fixing bacteria in order to obtain usable nitrogen.
D) The plants growing in the non-sterile soil are bigger because saprotrophic bacteria produce nutrients for them.
E) There is no difference in size between the plants growing in the sterile soil and those in the non-sterile soil.

Question

Quizplus · Accepted Answer

Mutualistic, nitrogen-fixing bacteria live in the root nodules of certain plants, such as soybeans. They reduce atmospheric nitrogen to ammonia, which can be used by plants. Plants are unable to fix nitrogen for themselves.

You Take a Large Sample of Soil and Put It