this is called "porpoise"
a result of wing and breast muscles movement
please refrain from cursing. ty
Fish vs Aquatic Mammals
- Thread starter curioucity
- Start date
this is called "porpoise"
a result of wing and breast muscles movement
please refrain from cursing. ty
loved it fool
The physicists tell us that the more advanced an aquatic animal is, the more efficient a swimmer it is.
The earliest vertebrate swimmers, like lampreys, wriggle rather inefficiently. Sharks move a good portion of their bodies. Bony fish, though, just move their tail, keeping the rest of their body rigid. Supposedly, this reduces the energy cost of moving through a liquid.
Why don't the other fish swim like th ebony ones do? Presumably because you need bones to do it. I don't know what any of this has to do with dolphin tails, though.
The earliest vertebrate swimmers, like lampreys, wriggle rather inefficiently. Sharks move a good portion of their bodies. Bony fish, though, just move their tail, keeping the rest of their body rigid. Supposedly, this reduces the energy cost of moving through a liquid.
Why don't the other fish swim like th ebony ones do? Presumably because you need bones to do it. I don't know what any of this has to do with dolphin tails, though.
have you ever seen a water snake swim? I am not sure, but think the most efficient swimmer would be the ones that give the least energy to the water. Surely there are large eddies made by a "wagging tail" but the traveling wave a water snake makes appears to resemble and be as efficient as a rack and pinon gear. I.e. hardly inparts any motion to the water.
Last edited by a moderator:
But it loses TONS of energy to moving as much back and forth as it does forward.
Bony fish are wonderfully successful creatures; the assumption is that they are better at swimming than their ancestors, who lacked bones.
Dolphins may be able to get away with swimming less efficiently, but more powerfully, because as air breathers, they're not confined by the extremely low levels of O2 in water.
Fraggle Rocker
Staff member
Mammals originated on the land so the marine mammals have to have evolved from them. We always wondered which land mammal wandered out into the sea and decided to stay there. DNA analysis gives the answers. The pinnipeds (seals, walruses, etc.) are members of the order Carnivora, with the felines, canines, bears, hyenas, weasels, etc. It turns out that the cetaceans (dolphins and whales) are members of the order of artiodactyls (even-toed hooved mammals) with cattle, deer, goats, antelope, camels, pigs, etc. Their ancestors were primitive hippopotamuses who swam all the way down the river to the sea and liked what they found there.
Cetaceans have a vestigial pelvis. Specifically, they have some fragments of a pelvis that float out in their flesh, not connected to any other bones. The pelvis has two main functions. Support, which is unnecessary when water distributes the weight over the entire lower surface of the body; and anchoring of the legs, which is unnecessary if you ain't got no legs.
You may have to go to Japan for that.
Penguins are the avian equivalent of... well not dolphins but seals. They can still barely live on land and in fact have to go there to breed. But they're much better adapted to water.
Interesting to ponder whether a fully aquatic bird could evolve. The cetaceans give birth in the water and then push the baby to the surface for his first breath. Whatcha gonna do if your baby is growing inside an egg instead of inside you? Where do you lay the eggs so you can protect them but still breathe?
It may be vice versa. They're called cartilaginous fishes because their skeletons are composed of cartilage, which is softer than bone. Perhaps the more rigid skeleton of the true fishes does not allow them to bend that way.
My presumption was that since swimming more efficiently is advantageous, everyone would want to swim efficiently. However, since the cartilaginous ones don't, there must be some reason, yes? We'd likely see some sort of convergent evolution where sharks evolved the same swimming pattern of bony fish, since it's better. But we haven't- sharks move almost half their body in propelling themselves.
There are many instances where very different organisms evolved analogous structures, though without sharing a common ancestor for hundreds of millions of years. Yet often, we also see certain things failed to be evolved, simply because the exaptations aren't conducive to further modification, or lacking completely.
I was also assuming sharks would want to swim like bony fish, given that bony fish are what, an order of magnitude more successful than the cartilaginous ones?
An ovoviviparous avian?
I do not think nearly as much as the eddies that roll off the sid's of the fishes tail as this motion of the water is OCSILLATORY AND STREAMLINED FLOW. - sort of like a pendulum swinging. Consider any water molecule. First it swings to the right and then half a cycle later it is swinging to the left. In oscillatory motion the disipation can be quite small - that is never true of motions that induce eddies.
You can even see this in humans swiming to a slight extent. Although I do swim routinely I never did competively. Thus, not sure of the name of the stoke, but a couple of years ago, someone set new records by a new technique in that stroke. Previously one dove in and quickly surfaced to start doing the "breast stroke," I think it is. He took advantage of the fact there was no time limit on how long you can swim under water following the initial dive in. He did undulate his body, sort of snake like but vertically, nearly to the far end of the pool before surfacing to do one or two "breast strokes." - I do not know if the rules have changed to disallow this now. Perhaps there is a note by his record setting invention. - Clearly more efficient use of "oscillation of water" than the disipation of the breast stroke's splashes and eddies. (Swimming almost any stroke at record setting levels is mainly limited by the sustained power the swimmer can produce and the efficiency of his tecnique. I doubt if he was the most powerful swimmer EVER in the pool - just the most efficient one - when he set the world record)
Last edited by a moderator:
Any major city's best restraurants in Norway also, I think. My first wife was Norwegian. I ate some in Bergan once, but other than noting that it is red meat, I did not find anything that I can now remember notable about it. Bergan is on the West Coast and it was not expensive there I am sure (I would not have ordered it if it were.)
Some Inuits along the Artic Ocean eat a lot whale. I don't think they can sell it, though: you'd have to be invited to dinner.
My guess is that it's good food, and the destruction of the whales for oil was the equivalent of stripmining Iowa topsoil to get at some coal underneath.
My guess is that it's good food, and the destruction of the whales for oil was the equivalent of stripmining Iowa topsoil to get at some coal underneath.
Loons are pretty close. They build floating nests, basically cannot walk.fraggle said:
Depends on the shark - there are some very fast sharks.roman said: