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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.
- Marine Protected Area status can boost fish...on September 9, 2021 at 7:24 am
Protecting areas of the ocean and coastlines with "whole-site" Marine Protected Area (MPA) status can result in four-fold increases in the abundance and diversity of fish populations, a new study has shown.
- The world in a drop of water: DNA tool transforms...on September 7, 2021 at 3:54 pm
In their search for pink river dolphins, researchers in the Peruvian Amazon scooped up river water sloshing with genetic material that they hoped could trace the elusive creatures.
- As mysterious disease kills Florida's reefs, a...on September 6, 2021 at 3:58 pm
In 2014, a mysterious coral disease known as Stony Coral Tissue Loss Disease was first identified off Miami. In the years since, it has raged like an underwater wildfire, becoming what some scientists call the worst marine epidemic they have ever witnessed.
- Komodo dragon, 2-in-5 shark species lurch towards...on September 4, 2021 at 7:27 pm
Trapped on island habitats made smaller by rising seas, Indonesia's Komodo dragons were listed as "endangered" on Saturday, in an update of the wildlife Red List that also warned overfishing threatens nearly two-in-five sharks with extinction.
- 290-million-year-old shark with large...on September 3, 2021 at 2:03 pm
The fossil of a 290-million-year-old shark with petal-shaped teeth was found in China for the first time, according to Gai Zhikun, an associate researcher at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences. The Petalodus teeth were found in the Qianshi limestone in Yangquan City, north China's Shanxi Province.
- Social tiger sharks may hold the secret to...on September 3, 2021 at 2:03 pm
A team of conservation scientists looking at the impact of tourism on tiger sharks have, for the first time observed them in social groups near an area called Tiger Beach off the north-west side of Little Bahama bank in the Bahamas, a popular spot for tourists.
- Study reveals decline in predatory fish catch on...on August 30, 2021 at 2:41 pm
In an article published in the journal PLOS ONE, Brazilian scientists show that one of the effects of overfishing in Arraial do Cabo, Rio de Janeiro state, Brazil, is the replacement of large, valuable species by smaller species for which there used to be little demand.
- Estimating man's danger to sharkson August 24, 2021 at 1:56 pm
Southern Australia has many species of sharks and their relatives. Very few of these species pose any danger to humans, but we humans pose a serious danger to most of them.
- Understanding cookiecutter sharkson August 23, 2021 at 5:04 pm
For years, researchers studying marine life in the wild would occasionally come across animals—such as dolphins, swordfish, leatherback sea turtles, whales, white sharks and even humans—with oddly shaped plugs of tissue taken out of their bodies. Those fresh bites and scars were almost like someone took a cookie cutter and surgically removed a hunk of tissue. These bites were not only restricted to animals, as submarines in the 1970s and 1980s were having their rubber-coated sonar sensors […]
- Penis worm: Widespread yet understudied sea...on August 18, 2021 at 10:56 am
Australia's oceans are home to a startling array of biodiversity—whales, dolphins, dugongs and more. But not all components of Aussie marine life are the charismatic sort of animal that can feature in a tourism promotion, documentary, or conservation campaign.