Zinc in the organism . As a biogenic element, zinc is always present in the tissues of plants and animals. The average content of zinc in most terrestrial and marine organisms is on the order of thousandths of a percent. Fungi, especially poisonous ones, are rich in zinc, as are lichens, coniferous plants, and certain marine invertebrates, such as oysters ( percent dry weight). Calamine plants, which accumulate zinc, are encountered in zones of rocks with high zinc content. Plants obtain zinc from the soil and water, while animals obtain it through food. In man, the daily requirement of adults for zinc is 5–20 mg and is met by ingestion of bread products, meat, milk, and vegetables; in infants, the zinc requirement of 4–6 mg is met by breast milk.