I need help on this question

Which of the organisms listed below performs nitrogen fixation? a. legumes b. plants c. bacteria d. fungi

The small molecule cyclic amp (camp) takes about 0.2 second to diffuse 10 μm, on average, in a cell. suppose that camp is produced near the plasma membrane on one end of the cell; how long will it take for this camp to diffuse through the cytosol and reach the opposite end of a very large cell, on average? assume that the cell is 200 μm in diameter.

What are 3 reasons that natural selection occurs