Which of the following statements is true about the atmosphere? a.) the different layers overlap
b.) it extends about 1,000 miles into space
c.) the layers are not affected by the sun’s radiation
d.) all of the above

a. by using fur or clothes to trap heat energy near the body

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.