Sharks, belonging to the subclass Selachii, are a group of cartilaginous fish known for their streamlined bodies and formidable presence in the oceans. Evolving over 400 million years ago, they've adapted to a wide range of aquatic habitats, from shallow coastal waters to the deep sea. Sharks possess a unique skeletal structure made entirely of cartilage, lighter than bone, enabling their efficient movement through water. Their evolution has equipped them with keen senses like electroreception and an impressive set of teeth that continuously replace themselves. Despite their often fearsome reputation, sharks play a vital role in maintaining marine ecosystems as apex predators.
Sharks are fascinating creatures with a streamlined body, perfect for gliding through water. Unlike bony fish, their skeletons are made of flexible cartilage. They have multiple rows of replaceable, sharp teeth that keep them ready for their next meal. Sharks lack a swim bladder; instead, they rely on a large, oil-filled liver for buoyancy. Their powerful tails propel them forward, while their fins help in steering. Sharks have an extraordinary sense of smell and can detect electrical fields using special organs called the Ampullae of Lorenzini. Though they can't make sounds as we do, sharks communicate through body language and movements.
Sharks have long fascinated and terrified humans, a dichotomy reflected in our culture and media. They star as misunderstood monsters in films like "Jaws," yet are also revered for their role in ocean ecosystems. Historically, humans have hunted sharks for their fins, teeth, and as trophies, leading to declines in many shark populations.
Recognizing their ecological importance and the threat of extinction, conservation efforts have intensified. Organizations advocate for sustainable fishing practices and the creation of marine sanctuaries. From fear to admiration, the human-shark relationship is evolving towards respect and a desire to protect these magnificent creatures.
Sharks do not have any bones in their bodies, as their skeleton system is made up of cartilage and connective tissue. This classifies them as Chondrichthyes fish. Cartilage is flexible and has about half of the normal density found in bones.
The diet of a shark varies from shark to shark depending on the species, habitat, and available prey. There are over 400 species of sharks. Most sharks are carnivorous and predators, while some are planktivorous. Sharks aren’t picky and are able to adjust their diet to what is available in order to survive.
It is not known if sharks are able to sleep, but they do seem to have periods of rest. Sharks need to keep water moving over their gills to receive oxygen. Some sharks need to keep moving all the times to keep water over their gills, while others have spiracles, an opening behind each eye, that allows them to breath while they are still.
