Which element provides strength to the exoskeletons of clams and oysters?

What is a limitation of using a chemical formula, such as c6h1206, to represent a compound? the chemical formula does not show the types of elements that make up the compound. the chemical formula does not show how the atoms are connected to one another the chemical formula does not show the number of atoms of each element in a molecule. the chemical formula does not show the chemical symbols of the elements in the compound

This is the interaction of two organisms where one is and the other is neither nor harmed.

Does all the energy stored by the phytoplankton reach the top level of the pyramid