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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.
Here we go again: Earth's major 'mass extinctions'
on April 25, 2019 at 5:06 pm
Most scientists agree that a "mass extinction" event is underway on Earth, with species disappearing hundreds of time quicker under the influence of human activity. […]
Long live Nemo! New animal model in aging...
on April 25, 2019 at 1:48 pm
The colorful Clownfish lives longer than 20 years in the aquarium. Researchers of the Scuola Normale Superiore in Pisa, Italy, in collaboration with the Leibniz Institute on Aging (FLI) in Jena, Germany, have investigated the genetics behind the longevity of clownfish. By sequencing the genome and comparing the sequences with other species, they were able to show, that the secret of this longevity lies in the mitochondria and lysosomes of the clownfish. Because it is uncomplicated to keep and […]
Sand tiger sharks return to shipwrecks off N.C....
on April 22, 2019 at 2:55 pm
Photos taken months, and in some cases years, apart by scuba divers show female sand tiger sharks returning to the same shipwrecks off the North Carolina coast, a new study co-led by scientists at Duke University reveals. […]
Groundbreaking Indian Ocean science mission...
on April 18, 2019 at 2:54 pm
The British-led Nekton scientific mission on Thursday completed a seven-week expedition in the Indian Ocean aimed at documenting changes beneath the waves that could affect billions of people in the surrounding region over the coming decades. […]
Drones, supercomputers and sonar deployed against...
on April 18, 2019 at 7:24 am
An arsenal of new technology is being put to the test fighting floods this year as rivers inundate towns and farm fields across the central United States. Drones, supercomputers and sonar that scans deep under water are helping to maintain flood control projects and predict just where rivers will roar out of their banks. […]
Catfish use complex coordination to suck in prey
on April 16, 2019 at 11:10 pm
Catfish do not have arms or tongues to help them catch and swallow their prey—instead, a catfish ready to strike moves its head. […]
Study finds white sharks flee feeding areas when...
on April 16, 2019 at 2:41 pm
New research from Monterey Bay Aquarium and partner institutions published today in Nature Scientific Reports challenges the notion that great white sharks are the most formidable predators in the ocean. The study "Killer Whales Redistribute White Shark Foraging Pressure On Seals" shows how the great white hunter becomes the hunted, and the elephant seal, the common prey of sharks and orcas, emerges as the winner. […]
Sharks more vulnerable than originally thought
on April 15, 2019 at 1:40 pm
A study of small-scale fisheries operating from Kenya, Zanzibar and Madagascar, has revealed the massive underreporting of sharks and rays caught annually in the region. […]
Shark bite research reveals politicians' fishy...
on April 15, 2019 at 7:40 am
More than a decade's worth of research has revealed how politicians manipulate highly emotional incidents like shark bites to influence public sentiment and protect their own interests. […]
Off the Seychelles, a dive into a never-seen...
on April 12, 2019 at 10:08 am
The submersible dropped from the ocean's surface faster than I had expected. With a loud "psssssss" the air escaped from the ballast tanks and the small craft suddenly tilted forward. […]