Question

Nitrogen in the atmosphere must be "fixed" before it can be used by plants. Atmospheric nitrogen is "fixed" by

Answer 1

D) bacteria and lightning.

Step-by-step explanation:

According to USA Testprep (Where the question came from), "Nitrogen is fixed or chemically combined with other elements to form a usable chemical compound. Plants are then able to use nitrogen in this form; they are not able to use it in its atmospheric form." I hope this helps those that try to find the answer.

Answer 2

Atmospheric nitrogen is "fixed" by bacteria.

Step-by-step explanation:

Nitrogen gas (N2) is the most abundant in the earth's atmosphere, representing 79% of air volume. In organisms, nitrogen atoms are part of several organic substances, such as proteins and nucleic acids. However, most living things cannot use nitrogen in the N2 molecular form. Only a few species of bacteria are able to use it by incorporating nitrogen atoms into their organic molecules and making it available in other molecular forms for use by various species through a process called Biological Nitrogen Fixation. Similarly, the bacteria that perform the fixation are called nitrogen fixers.