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.
Fossil Shark Teeth are one of the few remains we have of ancient sharks. Because their skeletons are made of cartilage instead of bone, the teeth are the only parts that were left behind.Shark like fish have been present in the oceans of the world since the late Paleozoic Era.ossil Shark Teeth are one of the few remains we have of ancient sharks. Because their skeletons are made of cartilage instead of bone, the teeth are the only parts that were left behind. Shark like fish have been present in the oceans of the world since the late Paleozoic Era.