8. Which organisms act as a bridge between the nitrogen in the atmosphere and the nitrogen on land?

Bacteria act as a bridge between the nitrogen in the atmosphere and the nitrogen on land.  

•Nitrogen moves into the living world with the help of microbes, that is, bacteria. The bacteria transform atmospheric nitrogen, that is, N2 into usable biological forms by the process of nitrogen fixation.  

•Some nitrogen-fixing bacteria are free-living in water or soil, while some are beneficial symbionts, which reside within the plants.  

•The nitrogen-fixing bacteria capture the atmospheric nitrogen by transforming it to NH3 that can be taken by the plants and are utilized to produce organic molecules.  

•The nitrogenous molecules are passed onto animals when they consume plants. These gets incorporated within the body of the animal and are excreted in the form of urea in urine.  

Thus, bacteria act as a bridge between the nitrogen in the atmosphere and the nitrogen on land.  

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Well, Bacteria plays a key role in the nitrogen cycle, but also some species of nitrogen-fixing bacteria are free-living in soil or water, while others are beneficial symbionts that live inside of plants.

Explanation:

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2. d.

3. a.

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6. c.

these are the only ones that i know, i hope this , and good luck.