Always wondered this...Biology question

jerthunter

Active Member
Originally Posted by 1journeyman
Of course the existence today of the "primitive" fish calls into question our current theory of evolution.
Not really but since this isn't a decision about mode of change I don't think it would be useful to get into this.
 
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jrthomas40

Guest
Originally Posted by Jerthunter
Not really but since this isn't a decision about mode of change I don't think it would be useful to get into this.

what is your thought on the "de-evolution" of cave or deep water fish that have deleted the gene for "functional" eyes....in situation like these i see it as a "use or lose" you dont use it apparently you dont need it why expend time and energy to produce it?...those are primative species and i may not have made any sense with this post...lol...but i hope it makes some sense
 

jerthunter

Active Member
Originally Posted by jrthomas40
what is your thought on the "de-evolution" of cave or deep water fish that have deleted the gene for "functional" eyes....in situation like these i see it as a "use or lose" you dont use it apparently you dont need it why expend time and energy to produce it?...those are primative species and i may not have made any sense with this post...lol...but i hope it makes some sense
I think saying 'de-evolution' can be misleading. It is still evolution since it is heritable change. My thought is always that change happens and many changes aren't helpful and some are. Which ever changes survive can get passed on so if eyes are not needed having or not having eyes won't have much impact on survival. There could be a slight selective pressure due to the saved energy in those individuals that do not spend energy on developing eyes but that would be an almost impossible idea to test.
 
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jrthomas40

Guest
that is true and de-evolution can be misleading only used because some people believe that the lose of such a vital organ is kind of a backward regression but i am like you it is still evolution because in my opinion it is "fine tuning" an individual (species) for its environment based on the selective pressures at the time and in this case the absence of light...i have a thing i am going to try and find and post it is pretty commical
 
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jrthomas40

Guest
i cant find it but the bulletin (of course it was on myspace) was called the problem science has with god...it was a pretty funny bulletin i wish i could share it with everyone
 

jon321

Member
I dont think anyone has mentioned this yet, but there is actually 1 species of amphibian that lives in salt water (or brackish). The crab-eating frog (Rana cancrivora, although Ive heard the name was changed?). I dont have any specifics about this frog, but we learnt about them in animal physiology. Apparently they live in mangrove swamps or coastal areas and if memory serves they have huge quantities of chloride cells (or similar) that constantly pump salt out of their bodies at huge energetic expense.
Jon
 

jon321

Member
And about evolution, what my profs use to "prove" it is looking at the eye. Its hard to imagine how an organ so complex could just appear, but if you look at the molluscs, the simplest species have 'eyes' that are a light sensitive spot thats little more than a clump of nerves near the skin surface, while advanced molluscs like the cephs have advanced eyes quite similar in complexity as ours. And there is every step in-between if you look at the molluscs from least advanced to most advanced. I wish I had the diagram from a famous book/paper as it is very thought invoking, not that there arnt arguments or flaws in this view however.
Jon
 
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jrthomas40

Guest
Originally Posted by Jon321
I dont think anyone has mentioned this yet, but there is actually 1 species of amphibian that lives in salt water (or brackish). The crab-eating frog (Rana cancrivora, although Ive heard the name was changed?). I dont have any specifics about this frog, but we learnt about them in animal physiology. Apparently they live in mangrove swamps or coastal areas and if memory serves they have huge quantities of chloride cells (or similar) that constantly pump salt out of their bodies at huge energetic expense.
Jon
learnt sounds like an ebonics word....lol..learned sounds a bit better
...just poking fun....some times people get confused that an animal is marine because it lives around the ocean or in brackish water....most time these animals are not marine in a true sense but the are tolerant of the conditions that occur around mangroves and coast lines....98% of the time the term marine includes those animals that live in strictly marine environments such out deep ocean critters or critters that spend most of their life in the wild blue yonder
 

1journeyman

Active Member
Originally Posted by Jerthunter
Not really but since this isn't a decision about mode of change I don't think it would be useful to get into this.
Hehe, I'm just pointing out the primitive fish were mentioned by a couple of posters on this thread and they are not actually the evolutionary habringers some folks claim they are.
 

jon321

Member
Originally Posted by jrthomas40
learnt sounds like an ebonics word....lol..learned sounds a bit better
...just poking fun....some times people get confused that an animal is marine because it lives around the ocean or in brackish water....most time these animals are not marine in a true sense but the are tolerant of the conditions that occur around mangroves and coast lines....98% of the time the term marine includes those animals that live in strictly marine environments such out deep ocean critters or critters that spend most of their life in the wild blue yonder
The original post says, "found in salt water" not "marine". I agree I would not consider these frogs even close to the same catagory as a sea turtle or sea snake, but I think you can safely say they are found in salt water.
Jon
 

jerthunter

Active Member
Originally Posted by 1journeyman
Hehe, I'm just pointing out the primitive fish were mentioned by a couple of posters on this thread and they are not actually the evolutionary habringers some folks claim they are.
I am not sure what you mean by this. However you can see a lot of diversity around us and observe trends from one character state to another. What I consider primitive is something that is less derived, so if there is no reason to change or if changes would be harmful to a trait there is a good chance it will stay 'primitive'. So in my opinion primitive does not imply that nothing has changed just that certain characters are not as derived as you see in other groups.
 

jerthunter

Active Member
Originally Posted by Jon321
I dont think anyone has mentioned this yet, but there is actually 1 species of amphibian that lives in salt water (or brackish). The crab-eating frog (Rana cancrivora, although Ive heard the name was changed?). I dont have any specifics about this frog, but we learnt about them in animal physiology. Apparently they live in mangrove swamps or coastal areas and if memory serves they have huge quantities of chloride cells (or similar) that constantly pump salt out of their bodies at huge energetic expense.
Jon
So that is very interesting. Out of curiousity does its juvenile state live in the salt water or does it lay its eggs in freshwater and migrate to saltwater as an adult?
 

jon321

Member
This is what Wikipedia says, so I guess maybe I was wrong about the chloride cells, but I coulda sworn..
"The Crab-eating Frog (Fejervarya cancrivora formerly Rana cancrivora), is a frog native to south-eastern Asia including the Philippines and more rarely as far west as Orissa in India. It inhabits mangrove swamps and marshes and is the only known modern amphibian which can tolerate salt water. It is locally favored for its eating quality and is often farmed for its edible legs. Call described as …dododododok …dododok.
This frog can tolerate marine environments (immersion in sea water for brief periods or brackish water for extended periods) by increasing urea production and retention, and also by remaining slightly hyperosmotic within urea and sodium."
If you google "crab eating frog tadpole" there is a scientific paper that did a study on the tadpoles and how they survive in salt water so I assume the tadpoles do not live in fresh water, although probably more brackish than anything.
Jon
 

ophiura

Active Member
Originally Posted by Jerthunter
So in my opinion primitive does not imply that nothing has changed just that certain characters are not as derived as you see in other groups.


My goodness, stop it or I'll call you out as a cladist!!!!!!!
I think It is important to draw a distinction, IMO, between what evolutionary biologists may think and what "lay" people may think. It is similar to everyone running around shouting "its just a THEORY." Well, lay folks and scientists have a very different idea of what that word means.
Many in the general public look for "missing links" and such and point to so called "primitive" animals as examples. Scientists do not view these in this way. "Primitive" is relative. The example frequently used are stalked crinoids, which currently now only reside in the relatively low predation intensity environment of the deep sea. Prior to the mesozoic, in particular, the were all over the place. It has been hypothesized that the evolution of agile efficient teleost fish ( the so called "mesozoic marine revolution") resulted in the extinction of many groups, or in other terms introduced significant selective pressure. Comatulid crinoids, which are motile, came to dominate, and stalked crinoids were (it is hypothesized) limited to deeper water, lower predation environments.
The fact that they are "primitive" in how WE interpret their characteristics has little significance in the debate.
And my apologies because I have participated in taking this thread off topic. DANG!!
 
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jrthomas40

Guest
Originally Posted by ophiura

My goodness, stop it or I'll call you out as a cladist!!!!!!!
I think It is important to draw a distinction, IMO, between what evolutionary biologists may think and what "lay" people may think. It is similar to everyone running around shouting "its just a THEORY." Well, lay folks and scientists have a very different idea of what that word means.
Many in the general public look for "missing links" and such and point to so called "primitive" animals as examples. Scientists do not view these in this way. "Primitive" is relative. The example frequently used are stalked crinoids, which currently now only reside in the relatively low predation intensity environment of the deep sea. Prior to the mesozoic, in particular, the were all over the place. It has been hypothesized that the evolution of agile efficient teleost fish ( the so called "mesozoic marine revolution") resulted in the extinction of many groups, or in other terms introduced significant selective pressure. Comatulid crinoids, which are motile, came to dominate, and stalked crinoids were (it is hypothesized) limited to deeper water, lower predation environments.
The fact that they are "primitive" in how WE interpret their characteristics has little significance in the debate.
And my apologies because I have participated in taking this thread off topic. DANG!!

but it should be ok to be off topic by now because the question was answered and answered correctly on the first page
 

mie

Active Member
Originally Posted by jonthefishguy
I would just lke to point out that although this is off topic and is not ENGLISH 101, Mie...I have noticed that many of the same words you spell over and over are completely misspelled. If it were one word you happend to misspell I could understand that your finger slipped and that it is a typo. However, you tend to spell the same exact word(s) not just in this thread but other threads and it makes me wonder how old you are and what was the extent of your education. I not only ask this because of your continous misspelling but of your way of not thinking outside the box. Just curious!!!


First off thanks, Second what does me mispelling a few words have to do with anything? Not everyone is as properly educated as you are i guess.
And what makes you think i dont think outside the box? Just because i express my opinions and feel very strongly about them, and enjoy a healthy debate, does not mean i do not think outside the box. It makes you sound close minded. And fyi 31 years old, no college, yet i make a very nice living.
(imagine that)
 
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