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Evolution of Sharks
Transcript of Evolution of Sharks
Location of the oldest known articulated fossil shark remains, some 380 million years old. (Antarctilamna)
Evolution of Sharks
Early Fossil Shark Teeth
The earliest known fossil shark teeth are those of Leonodus dating back some 400 million years.
Reconstruction of Xenacanthus, an eel-shaped shark that haunted freshwater habitats in what is now Europe during the early Permian (about 280 million years ago).
Cladoselache was something of an oddball among ancient sharks. A four-foot (1.2-meters) long inhabitant of late Devonian seas (about 370 million years ago), it exhibited a strange combination of ancestral and derived characteristics.
Compare and Contrast
Modern Day Sharks
Sharks have several adaptations that help them swim without expending too much energy, and enable them to maneuver quickly and with agility.
Sharks have several means of sensing prey.
When sharks lose a tooth, a new one grows to replace it.
Most sharks are dark with pale bellies
Sharks have a variety of habitats that they live in. They adapted over the years to live in different temperatures. Some live in salt and some live in fresh water and then there's some that can live in both
Temperature is an important factor affecting the distribution of sharks (as is the case with most, if not all, animals). Availability of suitable prey will also impact population growth rates. Salinity of the water body may differentially affect different shark species. Finally, harvesting by humans is having a major impact on many sharks and allies.
Sharks do live in a co-existing environment but will establish territories and could compete for food.
Abiotic factors such as dissolved oxygen, tide, photoperiod, barometric pressure and pH are some reasons that sharks will migrate to another location if they cannot adapt. Biotic factors such as Marine life and Plant life determne the sharks sources of food.
The shark’s closest relatives are skates and rays, of which there are over 600 different species. Sharks, rays and skates have placoid scales, otherwise known as dermal denticles. This gives their skin a rough feel when felt in a certain direction, much like sandpaper. In fact, shark skin has been used as sandpaper for this very reason. These denticles reduce turbulence, allowing the shark, ray or skate to move through the water using less effort.
Sharks has been swimming in the ocean for about 450 million years. They have become one of the oceans most feared predators. They' ve adapted to many of Earth' s water sources. There are over 1000 different types of sharks.