Why is it rationale behind taxonomists placing sharks and dolphins in different taxonomic groups, even though they are both aquatic, have ve?
Sharks and dolphins are placed in different taxonomic groups, because their ancestral heritage is completely different. The way the vast majority of taxonomists categorise organisms is now based on DNA similarly -- not based on morphology and lifestyle. In the case of the shark and dolphin, both can swim -- but their fins are analogous rather than homologous structures. The specific term for this is convergent evolution. A land based example of convergent evolution is the wings of bats, birds, and insects evolved independently from each other but all are used to perform the function of flying. Accordingly bats, birds and insects belong to different taxonomic groups.
Why do taxonomists place sharks and dolphins in different taxonomic groups?
Because 1. they don't share a more recent common ancestor with each other than with other animals. For example, dolphins share a more recent ancestor with hippos, cows, goats, and camels than they do with sharks. Sharks share a more recent common ancestor with the coelacanth and lungfishes than they do with dolphins. To place sharks and dolphins into the same taxonomic group while excluding such animals as hippos and coelacanths would result in a polyphyletic group. No known biologist knowingly recognizes polyphyletic groups. There is, nevertheless, one taxonomic group that includes both sharks and dolphins, but this group also includes the salmon, lungfish, coelacanth, reptiles, amphibians, birds, dolphins, and human beings. Scientists call this group Vertebrata. 2. Sharks and dolphins are morphologically distinct from one another. Even though they look similar, sharks have gills but dolphins have lungs but no gills. Sharks have a cartilaginous skeleton, but dolphins have a bony skeleton. Dolphins have inner ears, but sharks don't. Dolphins have a vertebral column that flexes vertically, but sharks have a vertebral column that flexes horizontally. Sharks have vertical tail fins, but dolphins have horizontal tail flukes. Even if you group them on the basis of morphological similarity, they still cannot be put in the same group.
How do we know that Sharks and dolphins are different species?
One has bones, the other doesn't. (A shark skeleton is all cartilage.) One has gills, the other doesn't. One feeds its young with milk, the other doesn't. One has a lower jaw composed of only a single bone, and replaces its teeth on a maximum of just once. The other has a multi-boned lower jaw and replaces teeth again and again and again. And then there are the huge host of other differences as well. "... and why do they look so similar even though they are different species?" Convergent evolution. Fast ocean swimmers are best shaped like torpedoes whether they be dolphins, sharks or even torpedoes. That's the shape that happens to work best.
Adaptive radiation, by definition, isn't going to produce convergent evolution within the same group. What makes it "radiation" is differing from the original form, not being similar to it.Separate populations may have adaptive radiation, in which one subgroup of each population tends to converge with a subgroup of another group. When you see convergent evolution, that's likely what has taken place, even if we don't see the various other parts of the various radiations. For example, sharks are part of one adaptive radiation (that also includes rays), while dolphins are part of a separate adaptive radiation (that also includes whales), and they've both converged on a similar lifestyle (aquatic, carnivorous, somewhat similar body shapes, although sharks swim by swiveling side to side because they're fishes while dolphins swivel up and down because they're mammals).
What is the difference between sharks and dolphins?
Sharks have a skeleton made of cartilage and dolphins have a skeleton made of bone. Sharks have gills and extract oxygen from water (as fish have a tendancy to do) and dolphins have to go to the surface and breath air (as mammals do). Also, Sharks play hockey (and make it to the playoffs) and Dolphins play football.
Basically everything. There’s nothing that all whales have in common that all dolphins don’t have in common, or vice versa. Whales and dolphins aren’t even taxonomically distinct groups, they’re all kind of mixed together in the cetacean family tree.Image sourceNotice how there are whales and dolphins (and porpoises) kind of all over the place. For example, right at the top are the Pilot whales Globicephala . Very close relatives are the common dolphin Delphinus. Both are more closely related to one another than either are to Killer whales, and so it goes on as you go down the diagram, with whales and dolphins appearing more or less at random. Even the various river dolphins (marked with red lines) aren’t particularly closely related.Basically, whales are the big ones, dolphins are the small ones. It doesn’t get much more technical than that.
Are dolphins and sharks related?
no they are not related whatso ever. Dolphins are whales and whales belong to the mammel group. just like you and I dolphins hold their breath underwater and come up to the surface for air. Sharks are fish and like all fish they breath with gills which are openings just behind their eyes. and unlike dolphins, never sleep and must continue to swim in order to keep the flow of oxygen. but very few are able to breath without moving. But overall, no. Dolphins and sharks have 2 completely different DNA structures and genuses.
Surprisingly all the dolphins within British Waters are supposed to be property of Queen Elizabeth.A law was framed in 1324, during the reign of King Edward II, which gave powers to the Royal Crown to own all the sturgeons, Whales and Dolphins of UK within 3 miles from the shore.According to an article in Time, although this statute dates back to 1324 it “is still valid today, and sturgeons, porpoises, whales, and dolphins are recognised as ‘fishes royal’: when they are captured within 3 miles (about 5 km) of UK shores or wash ashore, they may be claimed on behalf of the Crown. Generally, when brought into port, a sturgeon is sold in the usual way, and the purchaser, as a gesture of loyalty, requests the honour of its being accepted by Elizabeth.”(Courtesy Business Insider)Incidents have been reported where sale of dolphins have been investigated by the Police and clearances from the royal family or authority were required for legal sale of dolphins on the shore.Now, that is one strange power to have and also exercise[1] .Footnotes[1] The Queen owns every dolphin in Britain, and other incredible powers you didn't know she had