A molted external skeleton.
They are both made up of subunits called nucleotides, which include a sugar, a phosphate group, and a nitrogen base.
Coral reefs<span> are also being degraded by many other factors. The list of problems can seem endless: overfishing, fishing using cyanide and dynamite, pollution from sewage and agriculture, massive outbreaks of predatory starfish, invasive species, and sedimentation from poor land use practices</span>
