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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's why shark researchers are concerned about...on October 29, 2020 at 8:03 pm
Science's steady march to find a vaccine capable of ending the coronavirus pandemic may come at the expense of another species: sharks.
- International study uncovers secret surfing life...on October 28, 2020 at 10:00 pm
Sticking to the bodies of sharks and other larger marine life is a well-known specialty of remora fishes (Echeneidae) and their super-powered suction disks on their heads. But a new study has now fully documented the "suckerfish" in hitchhiking action below the ocean's surface, uncovering a much more refined skillset that the fish uses for navigating intense hydrodynamics that come with trying to ride aboard a 100-ft. blue whale (Balaenoptera musculus).
- Leaving more big fish in the sea reduces CO2...on October 28, 2020 at 6:00 pm
An international team of scientists has found leaving more big fish in the sea reduces the amount of carbon dioxide (CO2) released into the Earth's atmosphere.
- Researchers find most shark fins in fish markets...on October 28, 2020 at 1:55 pm
A team of researchers affiliated with several institutions in the U.S. has found that most shark fins sold around the world in fish markets come from sharks caught in coastal zones rather than in the open ocean. In their paper published in the journal Biology Letters, the group describes their genetic study of fish market fin samples and the habitat modeling that they conducted for sharks.
- Crisis in the Galapagos: Chinese fishing fleets...on October 23, 2020 at 4:45 pm
Just south of the Galapagos' Marchena Island, there's a dive spot known by locals as the "fish arena."
- NOAA report reveals condition of natural and...on October 21, 2020 at 8:14 pm
NOAA has published a peer-reviewed State of the Monument report that was jointly produced by the co-trustees of Papahānaumokuākea Marine National Monument. The report includes information on the status and trends of living resources, habitats, ocean conditions, maritime and cultural archaeological resources, and the human activities and natural events that affect them.
- Restoring seagrasses can bring coastal bays back...on October 20, 2020 at 5:30 pm
A century ago Virginia's coastal lagoons were a natural paradise. Fishing boats bobbed on the waves as geese flocked overhead. Beneath the surface, miles of seagrass gently swayed in the surf, making the seabed look like a vast underwater prairie.
- Eastern Pacific is a major supply chain for...on October 13, 2020 at 4:45 pm
New research reveals the Eastern Pacific is a particular hotspot for the shark fin trade—and a danger zone for an endangered species fighting for survival.
- Shark-free COVID-19 vaccine petition makes waves,...on October 6, 2020 at 6:50 pm
An online movement to save sharks from becoming the next victims of the COVID-19 pandemic is growing in support.
- Tracking sea turtle egg traffickers with...on October 5, 2020 at 3:00 pm
By placing 3-D-printed and GPS-enabled decoy sea turtle eggs into nests on the beach, it's possible to gather key evidence needed to expose rampant illegal trade of the eggs, suggests a study publishing in the journal Current Biology on October 5. The researchers specifically tested how well the decoy eggs work and their safety for the endangered turtles.