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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.
New study to examine feeding habits of Cape Cod...
on June 19, 2019 at 1:44 pm
Researchers on Cape Cod are launching a new study focused on the hunting and feeding habits of the region's great white sharks following last year's two attacks on humans, including the state's first fatal one in more than 80 years. […]
Dinosaur bones are home to microscopic life
on June 18, 2019 at 2:35 pm
Bad news, Jurassic Park fans—the odds of scientists cloning a dinosaur from ancient DNA are pretty much zero. That's because DNA breaks down over time and isn't stable enough to stay intact for millions of years. And while proteins, the molecules in all living things that give our bodies structure and help them operate, are more stable, even they might not be able to survive over tens or hundreds of millions of years. In a new paper published in eLife, scientists went looking for […]
Palau changes ocean sanctuary plan to allow Japan...
on June 17, 2019 at 6:30 am
The Pacific nation of Palau has amended plans to create a huge marine reserve so Japanese fishing boats still have partial access to its waters. […]
Small steps, big leaps – how marram grass...
on June 14, 2019 at 2:00 pm
The size and shape of dunes varies greatly around the world: in Europe they're tall and narrow, while in the US they're low and wide. A new study has found that this is partly because dunes are constructed by plants with different 'movement strategies' determining the shape of the dune. The study was carried out by ecologists from Radboud University, the Royal Netherlands Institute for Sea Research (NIOZ) and the University of Groningen. The findings, which will be published in Nature […]
Softening the blow for hammerhead sharks and...
on June 13, 2019 at 1:43 pm
What do spectacular sharks and a priceless tropical timber have in common? The answer is that they are in equally urgent need of conservation attention, and both stand to benefit from the intervention of the latest Conservation Leadership Programme (CLP) award winners. […]
Dolphins form friendships through shared...
on June 11, 2019 at 11:00 pm
When it comes to making friends, it appears dolphins are just like us and form close friendships with other dolphins that have a common interest. The findings, published in the Proceedings of the Royal Society B by an international team of researchers from the Universities of Bristol, Zurich and Western Australia, provides further insight into the social habits of these remarkable animals. […]
First study of world's largest marine stingray...
on June 11, 2019 at 3:39 pm
Smalleye stingrays are the largest marine stingrays on record, reaching disc widths of up to 222 cm, and yet almost nothing is known about them. Scientists from the Marine Megafauna Foundation have for the first time used photo IDs to study this elusive animal in southern Mozambique, one of the only locations where it is regularly seen in the wild. Their findings are published today in the journal PeerJ. […]
New Irish research reveals the secret lives of...
on June 7, 2019 at 1:10 pm
A team of scientists led by experts from Trinity and a US-based NGO have just returned from the Bahamas where they learned all about the secret lives of the region's tiger sharks. […]
Sharks popping up all around Florida for summer...
on May 30, 2019 at 4:18 pm
There are sharks off Florida's coast. That's not news, but with Memorial Day weekend's traditional summer season kickoff, there are now thousands more people venturing to Florida's beaches, so that means more shark sightings. […]
Sound barrier to chase seals, prevent shark...
on May 29, 2019 at 7:30 pm
A plan to develop an acoustic system to chase away seals in order to prevent shark attacks is the latest front in the debate about how Cape Cod should respond in the wake of last year's shark attacks. […]