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.
The name bull shark comes from the shark's stocky shape, broad, flat snout, and aggressive, unpredictable behavior. In India, the bull shark may be confused with the Sundarbans or Ganges shark. In Africa, it is also commonly called the Zambezi River shark or just Zambi.he bull shark is a special case in evolutionary history. Some of its closest living relatives do not have the capabilities of osmoregulation. The bull shark's genus, Carcharhinus, is shared by the sand bar shark that is not capable of osmoregulation.