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Member (Idle past 1432 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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Author | Topic: "Macro" vs "Micro" genetic "kind" mechanism? | |||||||||||||||||||
RAZD Member (Idle past 1432 days) Posts: 20714 From: the other end of the sidewalk Joined: |
I was reading one article on archea at cold seeps
Cold vent | encyclopedia article by TheFreeDictionary Unlike hydrothermal vents, which are volatile and ephemeral environments, cold seeps emit at a slow and dependable rate. Likely owing to the differing temperatures and stability, cold seep organisms are much longer-lived than those inhabiting hydrothermal vents. Indeed, recent research has revealed seep tubeworms to be the longest living noncolonial invertebrates known, with a minimum lifespan of between 170 and 250 years. these bacteria live in slow motion compared to others. we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
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Loudmouth Inactive Member |
We are getting a little off topic, but just a quick reply and we can maybe try to veer back on topic.
quote: First, the tubeworms that you referenced are not bacteria but metazoans. Secondly, lifespan is not the variable under question but rather generation time. Lizards reproduce once a year asexually while many bacteria (in the right conditions) can reproduce once every 20 minutes. This is quite a difference. Usually (and I stress usually) a healthy population of organisms that only reproduces once a year relies on gametes produced by meiosis to ensure a mixture of alleles to the next generation.
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RAZD Member (Idle past 1432 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Sorry. In a hurry looking for the right reference. Had one on deep underground archea type bacteria that were long slow-motion livers. Can't find it now.
Bacteria also don't have multiple children -- they split one "adult" into two "children" -- and it is hard to compare length of life to length of time between offspring. There are as many opportunities for "division error" as there are for mutation that can contribute to genetic diversity. we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
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Mammuthus Member (Idle past 6502 days) Posts: 3085 From: Munich, Germany Joined: |
I certainly was not trying to imply that you sound like an idiot..hope it did not come across that way. The lizards are strange. Sexual reproduction confers such a benefit on a species that it has evolved multiple times in many varieties. Even bacteria are not true cloners...they exchange genetic information by horizontal gene transfer all the time which is sort of pseudo sexual reproduction. There are also really strange animals like the Daphnia species complex which can reproduce sexually, parthenogenetically, etc...they can really screw themselves if they want to Strange that a reptile would forgoe the benefit.
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arachnophilia Member (Idle past 1371 days) Posts: 9069 From: god's waiting room Joined: |
I certainly was not trying to imply that you sound like an idiot..hope it did not come across that way. nah, i've just gotten about three hours of sleep in the last three days. i'm not even tired anymore. so i occasionally miss stuff here and there. i'm kind of curious though how a species evolves into a situation like the whiptail's. any ideas?
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Rrhain Member Posts: 6351 From: San Diego, CA, USA Joined: |
Arachnophilia writes:
quote: No, I'm not so sure about that. One of the things that helps to keep bacteria going is their profligacy. They reproduce so quickly that even horrendous selection pressures can be stood up to because so many progeny are created. I don't think these lizards reproduce every 20 minutes. It would be interesting to see if there were any sexual reproduction in their history and if, given the appropriate pressures, they could flip to sexual reproduction as some other lizards do when variation is needed and then return to parthenogenesis when times are flush. It may be that we just haven't found the trigger. Rrhain WWJD? JWRTFM!
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Mammuthus Member (Idle past 6502 days) Posts: 3085 From: Munich, Germany Joined: |
It is likely that sex was in their history as within the same genus, there are sexually reproducing whiptail lizards...strange why they gave it up...must have been a lousy dating scene
J Neuroendocrinol. 1995 Jul;7(7):567-76. Related Articles, Links Species differences in estrogen receptor and progesterone receptor-mRNA expression in the brain of sexual and unisexual whiptail lizards. Young LJ, Nag PK, Crews D. Department of Zoology, University of Texas at Austin 78712, USA. Circulating concentrations of gonadal steroid hormones and reproductive behavior in female vertebrates vary as a function of ovarian state. Steroids secreted by the ovary, specifically estrogen and progesterone, influence the expression of behaviors associated with reproduction by intracellular sex steroid receptors located in specific regions of the brain. Using in situ hybridization, we analyzed estrogen receptor and progesterone receptor messenger RNA expression in several brain regions of ovariectomized, vitellogenic, and postovulatory individuals from two species of whiptail lizards (Cnemidophorus uniparens and C. inornatus). Although these species are genetically very similar, they differ in two aspects of their reproductive biology: (i) the unisexual C. uniparens alternate between expressing female-typical and male-like pseudosexual behaviors while female C. inornatus normally express only female receptive behavior, and (ii) circulating estradiol concentrations in reproductively active female C. uniparens are approximately five-fold lower than in reproductively active female C. inornatus. We found that the regulation of sex steroid receptor gene expression was region specific, with receptor-mRNA expression being increased, unchanged, or decreased during vitellogenesis depending on the area. Furthermore, several species differences in the amount of sex steroid receptor-mRNA were found that may be relevant to the species differences in circulating estrogen concentrations and sexual behavior.
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Lithodid-Man Member (Idle past 2958 days) Posts: 504 From: Juneau, Alaska, USA Joined: |
In partially parthenogenic invertebrates, fish, and amphibians (but not reptiles) there are two mechanisms, hybridogenesis and gynogenesis. In both cases the parthenogenic 'species' is a hybrid between two closely related species. In hybridogenesis sperm from one of the parent species fertilizes the egg of the parthenogenic species without recombination but the male genomic contribution is subesequently deleted during gametogenesis in the offspring. As I understand it the female gametes are clonal generation after generation but the genotype of the individual varies by the paternal contribution (hemiclonal). In gynogenesis the presence sperm from a parent species (of the hybrid) is required for cleavage to occur but no actual fertilization takes place. All genotypes are therefore clonal.
Here is a picture from a class lecture by Dr. Nicole Hillgruber: I believe that the lizards in question are two species that are the descendants of hybrids of the same two parent species (which is which is determined by which ancestral parent species was male or female). I am drawing the lizard info from a seminar I saw years ago, so please don't quote me on this. Using the fish information it seems possible to me that the lizards represent a situation akin to gynogenesis in fish except that there is no longer a need for sperm from the parent species but still the need for the pseudocopulatory stimulus. I wonder if the ancestral population was gynogenetic but selection favored mutations that could do without a male from the parent species. I can see how this would be advantageous. For any geneticists out there: is it possible that a gynogenetic species would "drift" away from its original hybrid genotype therefore making the parental sperm all the more extraneous? I think this discussion is fascinating and quite on-topic because it shows one mechanism by which a "species" (kind?) can come into existence virtually overnight, like polyploidy in plants. I recognize, of course, that the response "but they are still lizards" can be used, but it does address the point "no new species have ever been witnessed coming into existence". (edited to add a useful ref)
http://spot.colorado.edu/~noyesr/...pdf {Shortened display form of URL, to restore page width to normal - AM This message has been edited by Lithodid-Man, 07-14-2004 05:57 PM This message has been edited by Adminnemooseus, 07-14-2004 10:32 PM
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Brad McFall Member (Idle past 5060 days) Posts: 3428 From: Ithaca,NY, USA Joined: |
There may be a named but undiscovered "adaptive oversight" that Fisher id'd BEFORE discounting any difference between Mayr and Wright IN THE US such that this WAS NOT "the response" corrected!
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Lithodid-Man Member (Idle past 2958 days) Posts: 504 From: Juneau, Alaska, USA Joined: |
This is the shortest Brad McFall response I have seen, one sentence. But try as I might, I have absolutely no idea what it means. I deeply admire Sewall Wright, I think he is one of the most brilliant men who have ever lived. I belive that his ideas have yet to be mined for their full potential. However, he was a verbose writer and extremely confusing (remind you of anyone?).
(edited to replace atrocious with verbose, I meant atrocious in the sense of "verbose is gross, concise is nice" writing philosophy, not that he or anyone else implied lacks command of written English) This message has been edited by Lithodid-Man, 07-17-2004 11:30 PM
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KCdgw Inactive Member |
I couldn't make head nor tail of it either.
KC
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Brad McFall Member (Idle past 5060 days) Posts: 3428 From: Ithaca,NY, USA Joined: |
The adaptation"" that was missed MIGHT indeed have been noticed in point of fact by Aggaiz when he related softshell turtles to tortises. I have indeed been able to sythesize my own thought on Galelio not to NUMBERS OF INDIVIDUALS (which is what I was thinking of when I first wrote that this) (which would be caluculated from any switch in the levels via Wright (no matter the potential)) but to water content ON THE SUPRAMOLEUCLAR STANDARD. There are other population genetic possibilites however. I am uncertain if I should introduce a non standard mathematical way of assesing the equilibrium of gene flow or if I should just try to use current numerical techinques. Some of the difficulty involves trying to get a correlation without biasing the causality of gravity in all of it. But I guess that would come first no matter what the seperation of the spontaneous from the nonsponteous IS (were). Regardless this results in an oversight of form-making by not isolating the secondary characters subject NOT TO MENDELIAN ERROR but only biochemical variance( a difficlut point I will likely need some more time to rethink how to reexpress it more clearly). A tunicate and a seed are not the same creature but the equilbrium has the same possible intersection of temporal and structural hierarhices just so.
Fisher was granting this point to Wright and I am fairly sure that I have been able to recover the same as my Grandfather studied with Zelensky as did Wright. Wright is not all that hard to follow we are just not educated to think as he did. Agassiz thought of domestic creatures simply to show that they may have been the same species as in the wild but Mendel showed the SPACE of this not the TIME. Wright was able to realize the mutation part but the migration which space and time give (biogeographicalllly) has yet to be worked up in limit of the physical agent process that the Earth itself systematizes no matter mans moral or intellecutal progress. Perceiveing such a standard for agriculture is one thing but making the thought which involves a switch between algebra and geometry clear is exceeding difficult within the clarity of a phenomenology. It was inexcusible that Barbra McClintock's work took so long to get recognized. This rethiniknig of the difference of topobiology and neophenogensis in terms of instructed chemical mixtures and not simply compounds is a hard task. The Lambda symbol in calculations being zero for hydrocarbons seems to contain the morphological extent of the the Radiata of Aggaisz and I venture rahter shakly to porpose that verts are parmagnetic compared with diamagnetic echinoderms etc where I trend on my thin physics KNOWLEDGE. I said something like this on Wolfram's site but they are not programmed to consider that it would be a mistake to think of a magnetic shell from an electon orbit. These could be two things biologically but only one physicochemically. It requires a determined relation of levels of organization and levels of selection which we dont have as (of) yet.
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Lithodid-Man Member (Idle past 2958 days) Posts: 504 From: Juneau, Alaska, USA Joined: |
To paraphrase Robin Williams in 'The Fisher King', that was a glorious BM .
"Statistics are like a bikini. What they reveal is suggestive, but what they conceal is vital." Aaron Levenstein
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KCdgw Inactive Member |
I still can't make head nor tail of it.
KC
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Brad McFall Member (Idle past 5060 days) Posts: 3428 From: Ithaca,NY, USA Joined: |
You may have to wait till half way through next semester as I DO statistics homework. I have some Ideas on DImension and 1-2-D mappings that would be cool to try to think in terms of correlation coeffients but this is not something I have worked up/out/on yet. Lets hope by then this is "mind reading" and not the digestive "system" in process.
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