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.
The outer design of sharks and bony fish is also contrasting. 1  Shark skin is covered by dermal denticles, toothlike placoid scales that are covered with enamel. 2  Shark fins are stiff and lack the fine bony spines and muscle control found in teleost. 3  Both sharks and bony fish have caudal fins, or tail fins with two lobes. Bony fish are covered in flat scales, either cycloid, ctenoid or ganoid, that grow as the fish grows. 2  The rings on these scales can be used to estimate age in bony fish, just as you would count the rings on a tree. 3  However, dermal denticles do not grow with the shark so they can not be used in age estimation.