Legless LAND Dwelling Fish
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The Dude

Macclesfield, UK

#61 Dec 5, 2013
muffy wrote:
For it to be obviously transitional with regards to being terrestrial, it has to lead to a future species that spends all its time out of the water.
No it doesn't.

In fact that's not required at all.
muffy wrote:
How much would it have to change for scientists to say its not a fish or whatever but it's now something else?
As much as it likes.

Our arbitrary labels do not matter.
The Dude

Macclesfield, UK

#62 Dec 5, 2013
muffy wrote:
<quoted text>
I thought I knew the answer to this but I'm not so sure I do any more, but would it have DNA closer to a shark or to a human?
The answer is in the very post you quoted.
muffy

Glasgow, UK

#63 Dec 5, 2013
The Dude wrote:
<quoted text>
Our arbitrary labels do not matter.
Wiki lists the definition of terms (characterizations) as one of the four essential elements of the scientific method. This implies that the careful definition of the "arbitrary labels" used is very important, but you have my permission to disagree.
muffy

Glasgow, UK

#64 Dec 5, 2013
The Dude wrote:
<quoted text>
The answer is in the very post you quoted.
For reference, here's your quote:
The Dude wrote:
And we'll go further - if they get around to sequencing the genome of this thing it's DNA will be closer to fish and amphibians, somewhat less so to reptiles, somewhat less than that to birds, and less again to mammals such as humans - in that order.
And my question was: "would it [the Blenny in the article] have DNA closer to a shark or to a human"?

Using the concept of "clade" and referring to the links that polymath257 provided, I can see that Blennies are in the Phylum Chordata and the clade Teleostomi. This clade also includes humans. Sharks are not included in this clade. They are thought to have separated earlier and are now classified in the Class Chondrichthyes.

So I think the DNA test would show it being close to other bony fish, then amphibians, then reptiles (another strange group!), birds, mammals (us!), then sharks.

If I'm wrong here can someone explain in simply because I've looked at a lot of pages to try to get this right!

“Help religion science wander”

Level 9

Since: Jan 11

into the night.

#65 Dec 5, 2013
muffy wrote:
<quoted text>
For reference, here's your quote:
<quoted text>
And my question was: "would it [the Blenny in the article] have DNA closer to a shark or to a human"?
Using the concept of "clade" and referring to the links that polymath257 provided, I can see that Blennies are in the Phylum Chordata and the clade Teleostomi. This clade also includes humans. Sharks are not included in this clade. They are thought to have separated earlier and are now classified in the Class Chondrichthyes.
So I think the DNA test would show it being close to other bony fish, then amphibians, then reptiles (another strange group!), birds, mammals (us!), then sharks.
If I'm wrong here can someone explain in simply because I've looked at a lot of pages to try to get this right!
Muffy, as near as I can determine from the article the genome of the blenny hasn't been sequenced, so as to which taxa the greatest portion of its DNA may overlap with is technically up in the air. I would venture to say that it likely shares more DNA with sharks based on the proximity of the divergence between Chondrichthyes and Osteichthyes.
muffy

Glasgow, UK

#66 Dec 5, 2013
DanFromSmithville wrote:
<quoted text>Muffy, as near as I can determine from the article the genome of the blenny hasn't been sequenced, so as to which taxa the greatest portion of its DNA may overlap with is technically up in the air. I would venture to say that it likely shares more DNA with sharks based on the proximity of the divergence between Chondrichthyes and Osteichthyes.
I hope they do end up testing this. I'd be really interested to know the results! I've just read this page:
http://www.redorbit.com/news/science/11130083...

I think this implies that the answer may be very complicated and only possible to answer by testing.

“Maccullochella macquariensis”

Since: May 08

Melbourne, Australia

#67 Dec 6, 2013
Fish are one of my primary areas of interest. However, the word "fish" is not at all useful scientifically. There is far more diversity in a biological sense between different groups of what we call fish than, for example, there exists between any two species of mammal. In other words, biologically, a mouse is more closely related to a blue whale than a snapper is to a shark.
The Dude

Birkenhead, UK

#68 Dec 6, 2013
muffy wrote:
<quoted text>
Wiki lists the definition of terms (characterizations) as one of the four essential elements of the scientific method. This implies that the careful definition of the "arbitrary labels" used is very important, but you have my permission to disagree.
Your dictates aren't relevant. What you're not getting is that reality doesn't care what arbitrary labels we assign to it. The problem with labels is that they tend to encompass particular groups of definitions or facts or characteristics. We then use those definitions to communicate ideas or concepts. Then every now and then reality throws us a curveball by giving us something which straddles our definitions or includes more than one group of characteristics. This is a limitation of language, not of biology itself.
muffy wrote:
<quoted text>
For reference, here's your quote:
<quoted text>
And my question was: "would it [the Blenny in the article] have DNA closer to a shark or to a human"?
Using the concept of "clade" and referring to the links that polymath257 provided, I can see that Blennies are in the Phylum Chordata and the clade Teleostomi. This clade also includes humans. Sharks are not included in this clade. They are thought to have separated earlier and are now classified in the Class Chondrichthyes.
So I think the DNA test would show it being close to other bony fish, then amphibians, then reptiles (another strange group!), birds, mammals (us!), then sharks.
If I'm wrong here can someone explain in simply because I've looked at a lot of pages to try to get this right!
Sharks are fish.

“Leave That Thing Alone!”

Since: Nov 07

Location hidden

#69 Dec 6, 2013
muffy wrote:
<quoted text>
Wiki lists the definition of terms (characterizations) as one of the four essential elements of the scientific method. This implies that the careful definition of the "arbitrary labels" used is very important, but you have my permission to disagree.
Of course it's important. When attempting to discuss the science involved it's always a good idea for those doing the talking to all agree on the terminilogy and classification methods being used. How would anything ever get accomplished if a group of scientists discussing a topic related to a particular group of animals were all working with different ideas concerning the classification of the animals being discussed??

“Help religion science wander”

Level 9

Since: Jan 11

into the night.

#70 Dec 6, 2013
Bluenose wrote:
Fish are one of my primary areas of interest. However, the word "fish" is not at all useful scientifically. There is far more diversity in a biological sense between different groups of what we call fish than, for example, there exists between any two species of mammal. In other words, biologically, a mouse is more closely related to a blue whale than a snapper is to a shark.
So my guess supporting a greater degree of overlap of DNA between the land-dwelling blenny and sharks may not be that strong after all.
muffy

Macclesfield, UK

#71 Dec 6, 2013
Bluenose wrote:
Fish are one of my primary areas of interest. However, the word "fish" is not at all useful scientifically. There is far more diversity in a biological sense between different groups of what we call fish than, for example, there exists between any two species of mammal. In other words, biologically, a mouse is more closely related to a blue whale than a snapper is to a shark.
You and a couple of others have pointed out some things that would have been useful to know earlier so thank you. Over this discussion I've come to learn much more about fish and clades, which has been interesting.

I'm genuinely interested in how much more this fish would have to change until it would be in its own separate group like tetrapods are now and how long that might take. Any ideas? Genuine question, I promise it's not a lame setup for something else, I only want an opinion from someone with relevant knowledge.
Gillette

Fairfield, IA

#72 Dec 6, 2013
I think that it';s a new species or group would only be evident in retrospect. perhaps LONG after.
The Dude

Macclesfield, UK

#73 Dec 6, 2013
muffy wrote:
I'm genuinely interested in how much more this fish would have to change until it would be in its own separate group like tetrapods are now and how long that might take. Any ideas?
As long as we say so. Groups are labelled, remember.

In evolutionary terms it's simply not that simple.

Let's say you have a line of thousands of animals, each slightly different than the previous, representative of a chronology. You have a scope that can only see a hundred at a time. Those at the beginning of the line represent animals who lived earlier, those towards the end of the line represent animals who lived later. All the animals you can see in the scope are capable of interbreeding. This remains this way no matter what, even as you move the scope from left to right. As you move along the line one more person crops up just as one disappears. As you move more animals arrive and more disappear, but you still only ever see a hundred animals. And always, only those who can be seen in the scope are capable of breeding with each other.

If we draw a line encompassing 100 animals and name it a "species", no matter what it would be arbitrary. But this does not prevent the fact that those on either side of that group are unable to breed with them. And while those 100 are not very different from each other, quite clearly the animals at the beginning of the line are quite different from those towards the end. The reason? Changes accumulate over time.

So how much would they have to change? Whatever the norm for genetic drift is for that animal (in humans may average a couple of hundred mutations per generation). How long will it take? Merely one generation.
muffy

Stoke-on-trent, UK

#74 Dec 7, 2013
The Dude wrote:
<quoted text>
As long as we say so. Groups are labelled, remember.
In evolutionary terms it's simply not that simple.
Let's say you have a line of thousands of animals, each slightly different than the previous, representative of a chronology. You have a scope that can only see a hundred at a time. Those at the beginning of the line represent animals who lived earlier, those towards the end of the line represent animals who lived later. All the animals you can see in the scope are capable of interbreeding. This remains this way no matter what, even as you move the scope from left to right. As you move along the line one more person crops up just as one disappears. As you move more animals arrive and more disappear, but you still only ever see a hundred animals. And always, only those who can be seen in the scope are capable of breeding with each other.
If we draw a line encompassing 100 animals and name it a "species", no matter what it would be arbitrary. But this does not prevent the fact that those on either side of that group are unable to breed with them. And while those 100 are not very different from each other, quite clearly the animals at the beginning of the line are quite different from those towards the end. The reason? Changes accumulate over time.
So how much would they have to change? Whatever the norm for genetic drift is for that animal (in humans may average a couple of hundred mutations per generation). How long will it take? Merely one generation.
That's really interesting. I've got a good mental image of that. So would you say the line is more fuzzy than exact?

Whatever is really happening, evolution or something else, it's fascinating. Thanks for this response.

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