Sharks have adapted to their habitat by having streamlined, hydrodynamic bodies. Their skeletons aren't made of bone like other fish but cartilage. This makes their skeletons lighter and more flexible.
Like most other fish, sharks are cold-blooded. This gives them a low metabolism and allows them to fast for weeks. However, when it's time to eat, sharks benefit from having short but wide esophagi and jaws that aren't firmly attached to their skulls. This allows sharks to gulp down their prey whole or in large chunks. Sharks' teeth are also replaced constantly.
Sharks' livers, fins and constant movement keep them from sinking. The liver is enormous and filled with a substance called squalene, which helps to keep the shark buoyant.
Sharks also have an astonishing sense of smell and can smell blood in the water as far as one-quarter of a mile away. They also have a tapetum lucidum, a membrane at the back of the eye that lets them see in low light. They can change the size of their pupils to adjust to light conditions, which is an adaptation not found in other fish.
Sharks can also sense electrical fields through organs in their heads called ampullae of Lorenzini.Learn More
Reaching a maximum length of about 6 feet, the frilled shark is an eel-like species that is poorly known to science. The sharks derive their name from gills that feature “frilly” extensions. A primitive species, frilled sharks have six pairs of gill slits, rather than five, as seen in most other shark species. Frilled sharks live in deep water, and they are only rarely seen near the surface.Full Answer >
As of June 2014, bull sharks are not endangered, but it is likely that their numbers are decreasing. They are widely fished for their meat, hides, oil and fins.Full Answer >
In a shark's circulatory system, the heart pumps blood first to the gills where it is oxygenated, then to the organs and muscles, and finally back to the heart. To remain oxygenated, the blood must flow continually, and this is accomplished through the opening and closing of a shark's mouth as well as the muscle movements of its body.Full Answer >
The bull shark life cycle starts when a mother gives birth to anywhere between one and 13 babies per litter. Its gestation period lasts 10 to 11 months, according to Wildscreen Arkive, and they generally give birth between late spring and early summer. They live in estuaries, river mouths and sometimes freshwater lakes. While scientists believe that mating takes place at a certain time, they haven't directly observed the practice.Full Answer >