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.
Fossilized shark teeth are not white because they are usually covered with sediment (which prevents oxygen and bacteria from getting to them). 9. It takes about 10,000 years for a shark tooth to fossilize. The most commonly found shark teeth fossils are from 65,000 year ago (the Cenozoic era).