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.
Megalodon (/ËmÉÉ¡ÉloÊËdÉn/ MEG-É-lÉ-don, /ËmeÉªÉ¡É-/ MAY-gÉ-; meaning big tooth, from Ancient Greek: Î¼Î­Î³Î±Ï (megas) big, mighty and á½Î´oÏÏ (odoÃºs), toothâwhose stem is odont-, as seen in the genitive case form á½Î´ÏÎ½ÏÎ¿Ï, odÃ³ntos) is an extinct species of shark that lived approximately 23 to 2.6 million years ago, during the Cenozoic Era (early ...