Answer:
break down dead mat and produce oxygen
I believe that the answer is biosphere<span />
Hydrogen bonds.
The nucleotides in a base pair are complementary which means their shape allows them to bond together with hydrogen bonds. The A-T pair forms two hydrogen bonds. The C-G pair forms three. The hydrogen bonding between complementary bases holds the two strands of DNA together
<span>Variation among individuals in a species is real and important.</span>