Why is rna necessary to act as a messenger? why cant the code be taken directly from the dna

Because there's one copy of the gene in DNA (2 for diploid species including humans). It would take a LONG time to make an appreciable amount of protein from two copies of the gene. But the cell can make many copies of mRNA to quickly make larger amounts of the desired protein.

the dna of humans and mice is almost 92% similar. this similarity indicates that . mice have a tail, while humans have a tailbone. the tailbone is a structure in humans.yes it's true.

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.