Why do dolphins have lungs?

[KhlulHloo]

Since when does any statement in God's Autobiography need to be supported by evidence?

No such thing
Even the Scriptures extolling Me aren't an Autobiography (although they are inspired)

 

[JustMeSee]

Why do dolphins have lungs, and not gills?

They probably have wondered why we (other mammals) live on land.

I guess that their ancestors were better candidates for ocean than land. Better swimmers and at holding their breath. More food maybe. Without scientific evidence and knowledge, I can make all kinds of blind guesses.

It would have been interesting to have had land dolphin-like creatures, or human-like ocean dwellers. I guess we have to settle for things like seals and swimming apes/monkeys.

 

[Naraoia]

I have often wondered if this is an ecological niche specific for creatures with lungs. Cetaceans evolved for this role, as did ichthyosaurs, mosasaurs and plesiosaurs. They all evolved in competition with large sharks. Perhaps the increase in oygen capacity leads to an increase in activity which is advantagous compared to gill-using animals like sharks.

Are sharks really that inactive compared to whales? I mean, many of them are non-stop swimmers, as are tuna and other bony fish.

 

[Sphinx777]

Family Guy Black Dolphins



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[Sphinx777]

Family Guy - Shark Attack!!!



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[HarryCovert]

Mmmm, yummy, mmm.

I have a feeling dolphins have lungs because it's really hard to do a Woody Woodpecker impression underwater without them. I've never heard a good tuna Woody Woodpecker. It's all, "Gah,gah, gah, sploosh. Gah, gah, gah, sploosh."

 

[Doveaman]

Right, but why do all mammals have lungs, as opposed to some of them having gills and others having lungs as it would most benefit them in their habitat?

Aren't animals supposed to have evolved to fit their habitat as it would most benefit them in their habitat?

The point is that their lungs illustrates something about their past, as do the bones of their flippers, whale's legs, etc., etc.

Could it be that they did not evolve to fit their habitat?

 

[Lion Hearted Man]

Aren't animals supposed to have evolved to fit their habitat as it would most benefit them in their habitat?

Well, they have to co-opt or adapt structures that they already have. Dolphins and whales evolved from mammals, which means they already had a very complicated and sophisticated way of obtaining oxygen from the environment. The niche that was filled, however, was one that involved spending more time in the water, so over many generations the populations of mammals that eventually gave rise to these mammals adapted to a life of water-dwelling. The path of least resistance for entering the water niche was modifying existing traits at the expense of having to come up and breathe air every once in a while, instead of re-inventing the wheel when it comes to oxygen utilization.

When land creatures evolved, embryologically they co-opted the gill structure to give rise to other structures. In my embryology coursework, we learned how the pharyngeal arches are analogous to gills. In humans, the pharyngeal arches give rise to skull bones, connective tissue of the head, cranial blood vessels, and some endocrine organs, among other things. Point being - you really can't go back once you've made that drastic a change to the body plan. Thus, dolphins and whales don't have gills.

 

[Nathan Poe]

Could it be that they did not evolve to fit their habitat?

Except they do fit -- the dolphins are doing just fine, last I checked.

Evolution doesn't make a perfect fit -- just a good enough one.


Of course, since there are plenty of people out there who think that the only alternative to evolution is creationism/ID, then their only alternative is that the Big Designer in the Sky screwed up.

See how far you get suggesting that to them.

 

[Doveaman]

Well, they have to co-opt or adapt structures that they already have. Dolphins and whales evolved from mammals, which means they already had a very complicated and sophisticated way of obtaining oxygen from the environment. The niche that was filled, however, was one that involved spending more time in the water, so over many generations the populations of mammals that eventually gave rise to these mammals adapted to a life of water-dwelling. The path of least resistance for entering the water niche was modifying existing traits at the expense of having to come up and breathe air every once in a while, instead of re-inventing the wheel when it comes to oxygen utilization.

When land creatures evolved, embryologically they co-opted the gill structure to give rise to other structures. In my embryology coursework, we learned how the pharyngeal arches are analogous to gills. In humans, the pharyngeal arches give rise to skull bones, connective tissue of the head, cranial blood vessels, and some endocrine organs, among other things. Point being - you really can't go back once you've made that drastic a change to the body plan. Thus, dolphins and whales don't have gills.

That's a very impressive explanation. To bad it can't be proven to be true. So we can only wonder what the truth really was.

A much simpler explanation would be that God did it and how He did it is totally irrelevant to the purpose of our existence.

 

[Lion Hearted Man]

That's a very impressive explanation. To bad it can't be proven to be true. So we can only wonder what the truth really was.

A much simpler explanation would be that God did it and how He did it is totally irrelevant to the purpose of our existence.

Sorry that reality isn't simple enough for you.

 

[Jro]

That's a very impressive explanation. To bad it can't be proven to be true. So we can only wonder what the truth really was.

Same way we can't prove that our senses accurately depcit the world, but we're given a pattern, and numerous clues that that pattern accurately depicts the world. We have a pattern in the fossil development of whales and dolphins, a pattern in their genetics that demonstrates a pattern of relatedness (whales and dolphins are more similar to hippos than they are to ruminants than they are to dogs and cats etc.) and then morphological similarities in modern whales and dolphins to other mammals. None of these patterns makes any sense if not for evolution.

A much simpler explanation would be that God did it and how He did it is totally irrelevant to the purpose of our existence.

A much simpler explanation of the Kreb's cycle is that god did it, but that doesn't make it right. Maybe evolution is irrelevant to your existence, but I'm interested in why organisms are the way they are.

 

[KCfromNC]

A much simpler explanation would be that God did it and how He did it is totally irrelevant to the purpose of our existence.

An even simpler explanation is that it just happened. If you're going for ideas which are simple but wrong and ignore the consequences, go all out.

 

[Naraoia]

Aren't animals supposed to have evolved to fit their habitat as it would most benefit them in their habitat?
Could it be that they did not evolve to fit their habitat?

Aham, but here's the catch: evolution can only build on random variation in what's already there. Any gill capable of supplying a large endotherm with enough oxygen is bound to be a pretty complicated structure, i.e. a lot of lucky variation. Compared to that, staying with your already working system, stuffing your muscles with myoglobin and tweaking some physiology sounds like an evolutionary piece of cake.

That said, it would be... interesting if aquatic mammals with gills existed - and those gills would be totally non-homologous to those of fish

When land creatures evolved, embryologically they co-opted the gill structure to give rise to other structures. In my embryology coursework, we learned how the pharyngeal arches are analogous to gills.

They aren't really "analogous", though. Some of them give rise to gills in fishes, and the same arches make the co-opted stuff in tetrapods. That makes gills and tetrapod pharyngeal arches closer to homologous than to analogous, at least by the definition of analogous I know. (But gods, is homology a complicated issue...)

In humans, the pharyngeal arches give rise to skull bones, connective tissue of the head, cranial blood vessels, and some endocrine organs, among other things. Point being - you really can't go back once you've made that drastic a change to the body plan. Thus, dolphins and whales don't have gills.

Excellent point.

Speaking of which, the internet seems to be full of neat tables of what comes out of which arch in humans. Do you know anywhere that has the same kind of information for fish? (I guess it gets a bit more boring after the first two... "yep, another gill arch. Yep, another gill blood vessel." But still, inquiring minds are not entirely satisfied with "pharyngeal arches turn into gills")

A much simpler explanation would be that God did it and how He did it is totally irrelevant to the purpose of our existence.

Too bad it can't be proven to be true. Impossible standards cut both ways.

 

[Lion Hearted Man]

They aren't really "analogous", though. Some of them give rise to gills in fishes, and the same arches make the co-opted stuff in tetrapods. That makes gills and tetrapod pharyngeal arches closer to homologous than to analogous, at least by the definition of analogous I know. (But gods, is homology a complicated issue...)

Good correction. I always screw up homology/analogy. Doh!

Excellent point.

Speaking of which, the internet seems to be full of neat tables of what comes out of which arch in humans. Do you know anywhere that has the same kind of information for fish? (I guess it gets a bit more boring after the first two... "yep, another gill arch. Yep, another gill blood vessel." But still, inquiring minds are not entirely satisfied with "pharyngeal arches turn into gills")

Unsure, but most of those tables for humans probably come from anxious medical students studying for boards. For some reason they love asking about pharyngeal arches on the first licensure exam...

There's a lot of good work that's been done with zebrafish though. Worth checking out for sure.

 

[Nathan Poe]

A much simpler explanation would be that God did it and how He did it is totally irrelevant to the purpose of our existence.

That's a very impressive explanation.* To bad it can't be proven to be true. So we can only wonder what the truth really was.

*Actually, it's complete dreck, but I have to call it "impressive" for the sake of irony.


And if willful ignorance is relevant to the purpose of your existence, that's your business -- don't drag the rest of us down to that level.

 

[Naraoia]

Unsure, but most of those tables for humans probably come from anxious medical students studying for boards. For some reason they love asking about pharyngeal arches on the first licensure exam...

There's a lot of good work that's been done with zebrafish though. Worth checking out for sure.

Hmm. Searching zebrafish was a good idea. Still no über-detailed medical student tables, but at least I get bits of description.

Well, it still pretty much seems to say "pharyngeal arches turn into gills". At least now I have that from an authoritative source

 

[Lion Hearted Man]

Hmm. Searching zebrafish was a good idea. Still no über-detailed medical student tables, but at least I get bits of description.

Well, it still pretty much seems to say "pharyngeal arches turn into gills". At least now I have that from an authoritative source

Haha. You should write a grant and figure it all out for good!

 

[sfs]

Dolphins have lungs so they can do this: YouTube - Dolphin Bubbles: An Amazing Behavior

 

[AV1611VET]

Without lungs, they could not have gone 17-0 in the 1972 season.