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.
SHARKS SKELETON. The skeleton of the shark has evolved and adapted to suit and aid the habitat, migration, hunting habits and diet of these acclaimed carnivores. Unlike terrestrial animals, humans, and even other marine animals, sharksâ skeletons are made purely of cartilage and connective tissue, or muscle. There is no bone. This type of skeleton means that the shark is lighter, as cartilage is about half the density of bone. This is important because, unlike other fish, the shark has no swim bladder to prevent it from sinking to the bottom of the ocean.