It is thought that sharks almost certainly evolved from placoderms, a group of primitive jawed fishes. It took a long series of successful and unsuccessful mutations with fin, jaw positions etc to give us all the different designs of sharks around today. When asked to draw a shark, most people would draw a shape along the lines of the whaler shark family, tigers or a mackeral shark such as a porbeagle. However many people do not realise the sheer diversity in the shape of sharks, or that rays are really sharks.
Sharks are a cosmopolitan species, with many makes and models. The endothermy, electro-sensory apparatus, and the optics of several species are all better than top of the line, they are superlative. Indeed a 1200lbs mako shark slow cruising the open seas at 6 knots certainly represents an apex predatorat the top of the food chain, a trophic juggernaut, but sharks can also be found at all levels of that vast chain. Whether the setting is benthic, pelagic, sub-tidal, or estuarine, there is a specialized shark for that environment. From the tiny cigar shark to the massive whale shark, sharks are a formidable biotic mode.
Sharks are nearly impervious to infections, cancers and circulatory diseases and have shown the ability to heal and recover from severe injuries while healing rapidly.
Compared to other fishes like salmonids or tuna that may lay millions of eggs, sharks typically have litters of a dozen or so, but some species can have as many as 136 pups or as few as 2. Most species of sharks give birth to live young whose eggs were hatched internally whereas some drop egg cases of various design.
Gestation can take as long as 14 months, but many species of sharks simply aren't well understood by science. Movements, migrations and breeding habits of most sharks are blank spots and many of the best known species are not well studied. In many respects, humanity still exhibits vast deserts of ignorance when it comes to the natural world and sharks are still on the frontiers of that desert.
Basic Shark Physiology & External Anatomy Shark Myths & Reality Shark Conservation Shark Links Webrings Back to Mike's World
Shark Myths & Reality
Shark Conservation
Shark Links
Webrings
Back to Mike's World