Our analysis of production and cost begins with a period economists call the short. run. Theshort run in this microeconomic context is a planning period over which the. managers of a firm must consider one or more of their factors of production as fixed.
Sharks have two sets of paired fins on the sides of their body, in the same general position as the main wings and horizontal tail wings of a plane. The shark can position these fins at different angles, changing the path of the water moving around them.
1 Both sharks and bony fish have caudal fins, or tail fins with two lobes. 2  The caudal fin of a shark is considered heterocercal, meaning the two lobes are unequal in size and the vertebral column extends up into the top lobe. The skull of a shark is made of only 10 cartilaginous elements while a bony fish skull has about 63 bones. 2  Bony fish have pleural ribs formed from dermal bone and sharks lack these ribs. 3  Unlike bony fish that have a protective bony plate covering their vulnerable gills, the gill slits of a shark are exposed and visible.