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 See also OneLook
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
Biology is the scientific study of life. Biologists study life at multiple levels of organization, from the molecular biology of a cell to the anatomy and physiology of plants and animals, and evolution of populations. Biologists also study and classify the various forms of life, from prokaryotic organisms such as archaea and bacteria to eukaryotic organisms such as protists, fungi, plants, and animals. — Wikipedia
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- Shark fin hunters in the soup as wildlife summit...on November 18, 2022 at 9:40 am
A global wildlife summit in Panama took an important step Thursday towards upgrading protection for sharks, the ancient ocean vertebrates targeted for their fins used in a status-symbol soup.
- Toxins from harmful algae found in bull sharks of...on November 17, 2022 at 6:37 pm
Stretching 251 kilometers along Florida's East Coast, the Indian River Lagoon has experienced large-scale, frequent blooms of toxic harmful algae in recent decades. Harmful algal blooms (HABs) occur when an overgrowth of aquatic microalgae over-accumulate in a body of water, negatively affecting wildlife and humans and degrading aquatic habitats.
- Reducing bycatch with sensory deterrentson November 17, 2022 at 3:11 pm
A new study has revealed the potential for sensory deterrents to reduce marine megafauna bycatch in fisheries.
- Ray of hope? One place where reef manta rays are...on November 15, 2022 at 9:32 pm
In a rare piece of good news in the marine world, scientists have found one place where reef manta rays are thriving.
- Sharks, turtles, disease on agenda of wildlife...on November 12, 2022 at 8:45 pm
The trade in shark fins, turtles, and other threatened species will come under scrutiny at a global wildlife summit in Panama, starting Monday, that will also focus on the spread of diseases such as COVID-19.
- Tuna and billfish are recovering from extinction...on November 11, 2022 at 2:11 pm
A team of researchers with members from the AZTI, Marine Research, Basque Research and Technology Alliance, the International Seafood Sustainability Foundation and Simon Fraser University's, Earth to Ocean Research Group has found that while tuna and billfish are responding positively to conservation efforts, sharks are not and their numbers continue to drop.
- Tiger sharks that interact with tourists are...on November 8, 2022 at 7:32 pm
Tiger Beach in the Bahamas is famous for its paradisiacal beauty and for being frequented by an animal that might scare most people away but is actually an outstanding diving tourism attraction: the Tiger shark (Galeocerdo cuvier). The sea is crystal clear and only 5 m deep on average, so the sharks, which can surpass 3 m in length, can easily be seen. They are drawn to the site by local tour operators, who throw fish and other food into the water.
- Using tiger sharks to help estimate the size of a...on November 2, 2022 at 3:40 pm
An international team of researchers has used movements of tiger shark populations to make estimations regarding the size of a seagrass ecosystem. In their paper published in the journal Nature Communications, the researchers describe the methods they used to measure the amount of seafloor covered by seagrass in the Bahama Banks in the Bahamas.
- Prehistoric reptile casts turn out to be copies...on November 2, 2022 at 1:43 pm
Scientists found copies of a lost fossil destroyed in WWII hiding in a U.S. museum.
- Climate change negatively affecting school sharkson October 31, 2022 at 1:59 pm
Preliminary research data suggest warmer temperatures and increased salt levels might have negative effects on the behavior and physiology of school sharks. A clear indicator of physiological changes is higher levels of stress markers such as glucose and lactate concentrations in the blood.
Here are links to pages about closely related subjects.
Tree of Life
Prokaryote Archaea, Bacteria
Eukaryote Protist, Fungi, Algae, Protozoa (Tardigrade)
Plant Flower, Tree
Cnidaria Coral, Jellyfish
Cephalopod Cuttlefish, Octopus
Crustacean Lobster, Shrimp
Arachnid Spider, Scorpion
Insect Ant, Bee, Beetle, Butterfly
Fish Seahorse, Ray, Shark
Amphibian Frog, Salamander
Reptile Turtle, Tortoise, Dinosaur
Bird Penguin, Ostrich, Owl, Crow, Parrot
Mammal Platypus, Bat, Mouse, Rabbit, Goat, Giraffe, Camel, Horse, Elephant, Mammoth
Walrus, Seal, Polar Bear, Bear, Panda, Cat, Tiger, Lion, Dog, Wolf
Cetacean Whale, Dolphin
Primate Monkey, Chimpanzee, Human