A certain seaweed plant is found in estuaries. At high tide, the plant is exposed to sea water; at low tide, the plant is exposed to brackish water (less salty water). The concentrations of some dissolved materials remain virtually constant in the cells of the seaweed.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus. this is so because calcium carbonate is the main component in the shells.

explanation:

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

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