Secretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland.In contrast to excretion, the substance may have a certain function, rather than being a waste product.ecretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland.
The oldest shark fossils. The oldest fossilized evidence of prehistoric sharks comes from shark-like scales that date to 455 million years ago during the Ordovician Period, in Colorado. Some paleontologists do not agree that these scales are sufficiently shark-like to pronounce them sharks.
People have been finding giant fossilized teeth for hundreds of years. Long ago, people thought the teeth came from dragons! In 1611, a scientist figured out that they belonged to ancient sharks. By comparing the teeth with those of modern sharks, scientists have learned megalodonâs size, what it ate, and more.