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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.
After two months of red tide scare, cold...
on December 13, 2019 at 3:47 pm
After a quick spread over 100 miles of Florida's west coast, red tide has receded and it would seem the colder temperatures may be the reason why.
Study: The human lifespan is written into our DNA
on December 13, 2019 at 1:31 pm
Humans have a "natural" lifespan of around 38 years, according to a new method we have developed for estimating the lifespans of different species by analyzing their DNA.
Scientists devise 'lifespan clock'
on December 12, 2019 at 4:00 pm
An Australian research team say they have come up with a "lifespan clock" which provides accurate maximum age estimates for vertebrates, a key variable in the study of both living and extinct animals.
Researchers on the hunt for the 'pupping ground'
on December 12, 2019 at 11:25 am
The waters off the southern tip of Cat Island, Bahamas are one of the last remaining strongholds for oceanic whitetip sharks.
Study to help manage shark populations in Pacific...
on December 11, 2019 at 4:16 pm
Sharks play a critical role in keeping oceans healthy, balancing the food chain and ensuring species diversity. However, the demand for shark derivatives has led to their exploitation, often without appropriate management strategies in place. In an assessment of Pacific Panama fisheries published in Aquatic Conservation: Marine and Freshwater Ecosystems, scientists from the Smithsonian Tropical
Key to helping southern sea otter is in...
on December 10, 2019 at 5:00 pm
The picture of sea otters frolicking among kelp beds and rocky shoals has become an iconic image of the California coastline. But it may be drawing attention away from the value of other habitat that could truly help the endangered species in its recovery—estuaries.
Experts puzzled as 10-foot great white shark...
on December 10, 2019 at 3:42 pm
Great white sharks are known for racing past the Mid-Atlantic states to get someplace else, so experts pay attention in rare cases when one not only stops, but stays put.
Coral gardeners bring back Jamaica's reefs, piece...
on December 3, 2019 at 9:31 pm
Everton Simpson squints at the Caribbean from his motorboat, scanning the dazzling bands of color for hints of what lies beneath. Emerald green indicates sandy bottoms. Sapphire blue lies above seagrass meadows. And deep indigo marks coral reefs. That's where he's headed.
Rezone marine parks to better conserve sharks
on December 3, 2019 at 2:20 pm
A lack of habitat protection is hindering our ability to manage the conservation of endangered open-ocean sharks in Australian waters, according to new research by The University of Western Australia.
To save Everglades, guardians fight time—and...
on December 3, 2019 at 7:50 am
Grabbing a clump of vegetation to steady herself, Tiffany Troxler gingerly slides her feet along the makeshift boardwalk as she ventures out into the marsh. The boards sag, dipping her up to her knees in the tea-colored water.