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Tree of Life
Plant Flower, Tree
Invertebrate Octopus, Ant, Bee, Butterfly, Spider, Lobster
Vertebrate Fish, Seahorse, Ray, Shark, Frog, Turtle, Tortoise, Dinosaur
Bird, Ostrich, Owl, Crow, Parrot
Mammal Bat, Rabbit, Giraffe, Camel, Horse, Elephant, Mammoth
Whale, Dolphin, Walrus, Seal, Polar Bear, Bear, Cat, Tiger, Lion, Dog, Wolf
Monkey, Chimpanzee, Human
These are organized by a classification scheme developed exclusively for Cosma. More…
shark : any of numerous mostly marine cartilaginous fishes of medium to large size that have a fusiform body, lateral branchial clefts, and a tough usually dull gray skin roughened by minute tubercles and are typically active predators sometimes dangerous to humans — Webster
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the rays. However, the term “shark” has also been used for extinct members of the subclass Elasmobranchii outside the Selachimorpha, such as Cladoselache and Xenacanthus, as well as other Chondrichthyes such as the holocephalid eugenedontidans. Under this broader definition, the earliest known sharks date back to more than 420 million years ago. Acanthodians are often referred to as “spiny sharks”; though they are not part of Chondrichthyes proper, they are a paraphyletic assemblage leading to cartilaginous fish as a whole.
Since then, sharks have diversified into over 500 species. They range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species of only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (40 ft) in length. Sharks are found in all seas and are common to depths of 2,000 metres (6,600 ft). They generally do not live in freshwater although there are a few known exceptions, such as the bull shark and the river shark, which can survive and be found in both seawater and freshwater. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.
Well-known species such as the great white shark, tiger shark, blue shark, mako shark, thresher shark, and the hammerhead shark are apex predators—organisms at the top of their underwater food chain. Many shark populations are threatened by human activities. — Wikipedia
10 Best Places to Swim With Sharks (Professional Association of Diving Instructors, Condé Nast Traveler)
25 Best Destinations for Sharks and Adventure (Travis Marshall, Scuba Diving)
Shark Diving Tips and Advice (Shart Trust)
10 Shark Diving Tips (Dive Magazine)
Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.
- Sharks, lies, and videotape: Scientists document...on July 23, 2021 at 9:01 pm
Shark Week is many things. First and foremost, it's a week of shark-themed documentary programming on the Discovery Channel. Now in its 33rd year, it's the longest-running cable event in history. It's the biggest audience that marine biologists and ocean conservationists get, attracting millions of viewers who might otherwise not ever think about sharks at all. It's a stage that has launched careers of shark scientists and inspired many others to pursue jobs as ocean scientists.
- New 3D images of shark intestines show they...on July 20, 2021 at 11:00 pm
Contrary to what popular media portrays, we actually don't know much about what sharks eat. Even less is known about how they digest their food, and the role they play in the larger ocean ecosystem.
- World's coral scientists warn action is needed...on July 20, 2021 at 2:10 pm
The Chagos Archipelago is one of the most remote, seemingly idyllic places on Earth. Coconut-covered sandy beaches with incredible bird life rim tropical islands in the Indian Ocean, hundreds of miles from any continent. Just below the waves, coral reefs stretch for miles along an underwater mountain chain.
- 3D printed replicas reveal swimming capabilities...on July 16, 2021 at 12:08 pm
University of Utah paleontologists David Peterman and Kathleen Ritterbush know that it's one thing to use math and physics to understand how ancient marine creatures moved through the water. It's another thing to actually put replicas of those creatures into the water and see for themselves. They're among the scientists who are, through a range of methods including digital models and 3D printed replicas, "de-fossilizing" animals of the past to learn how they lived.
- Fossil rodent teeth add North American twist to...on July 15, 2021 at 4:52 pm
Two fossil teeth from a distant relative of North American gophers have scientists rethinking how some mammals reached the Caribbean Islands.
- Sharks in Costa Brava: evidence of an ongoing...on July 15, 2021 at 1:10 pm
Some shark species, such as the basing shark and the spiny dogfish, are in populational decline in the Costa Brava, and even blackspotted smooth-hounds can have disappeared due to the fishing pressure of this marine region in the Catalan coasts. The coincidence of fishing areas with the distributional natural habitat of the sharks worsens the risk of bycatches of sharks by the fisheries.
- Monster shark movies harm shark conservation...on July 14, 2021 at 7:05 pm
Undeniably the shark movie to end all shark movies, the 1975 blockbuster "Jaws" not only smashed box office expectations, but forever changed the way we felt about going into the water—and how we think about sharks.
- Ancient shark teeth lost in Antarctica millions...on July 13, 2021 at 11:59 am
Tens of million years ago, sand tiger sharks hunted in the waters off the Antarctic Peninsula, gliding over a thriving marine ecosystem on the seafloor below.
- Scientists explore seamounts in Phoenix Islands...on July 9, 2021 at 2:41 pm
Marine scientists aboard Schmidt Ocean Institute's research vessel Falkor have identified likely new marine species and deep sea organisms on nine seamounts that were explored for the first time in the remote Phoenix Islands Archipelago. In a 34-day expedition that ended today, scientists also conducted high-resolution seafloor mapping of more than 30,000 square kilometers and video exploration of five additional seamounts.
- Sharks of different species hunt for prey at...on July 7, 2021 at 1:20 pm
A team of researchers from Murdoch University, the New England Aquarium and Mote Marine Laboratory, has found at least one instance of sharks of different species hunting at different times so as to avoid each other. In their paper published in Proceedings of the Royal Society B, the group describes tagging and monitoring several species of sharks in the Gulf of Mexico.