Figure 36.15 on page 780 describes a study of the interaction between legumes and the root nodules that house nitrogen-fixing bacteria. In the study, the scientists let the plants germinate and start forming root nodules. Then they grew the plants in hydroponic cultures. The treatment groups were: a) hydroponic culture with all the essential nutrients (including nitrogen) and b) hydroponic culture with all the essential nutrients except nitrogen. Why did the scientists use these treatment groups? To prevent the plants from growing nodules. To make sure they had roughly equal numbers of plants in each group. To prevent the plants from learning which treatment group they were in. To control for the difference in nodule growth that might be expected if the plant has enough nitrogen vs. not enough nitrogen. Question 7 0.25 pts Why did it turn out to be important that the researchers ran the legume nodule study for more than 10 days? Because the root nodules are initiated in the first 10 days after germination. Because plants don't reproduce until they are at least ten days old. Because ten days worth of data was not enough to produce statistically significant results. Because it takes plants and bacteria at least two weeks to learn to work together. Question 8 0.25 pts Why is it accurate to claim that the nature legume-bacteria mutualism described in the text varies with the environment the partners find themselves in? O Whether the the plants benefit from the interaction depends on whether there is nitrogen in the soil. O Mutualisms are best thought of as "reciprocal parasitism," with each species under selection to maximize its fitness benefits. The bacteria benefit only when there is nitrogen present in the soil.

In the study, the scientists let the plants germinate and start forming root nodules then they used the plants in hydroponic cultures beacuse to control for the difference in nodule growth that might be expected if the plant has enough nitrogen vs. not enough nitrogen.

The greater oxygen withinside the hydroponic developing mediums allows to stimulate root growth. Plants with adequate oxygen withinside the root additionally take in vitamins faster. The vitamins in a hydroponic are combined with the water and despatched without delay to the basis .

Hydroponics gets rid of soil and soil-borne pests and disease, so there's no want to apply big quantities of pesticides. This, in turn, reduces soil erosion in addition to air and water pollution. Pesticides from conventional soil-primarily based totally agriculture run off into rivers and streams, harming fish populations.