Answer:
phosphorus
Explanation:
Since Phosphorus is an essential component of phospholipids, nucleic acids, phosphoproteins (casein), high energy phosphate esters (ATP), hexose phosphates, creatine phosphate, it also provides strength to the exoskeletons of clams and oysters.
Heterozygous- a certain gene that can carry two different alleles
Homozygous- a certain gene that carries two copies of the same alleles
Cells,tissue,organ organism,organ system