posted
Oh, when it's working, the system is astonishingly precise. It all comes down to the physics of electrochemical gradients in the end, so as long as your proteins are being expressed properly, and you aren't exposed to teratogens, you have very little to worry about in terms of developmental defects.
But as MightyCow noted, the vast majority of mutants defective in a master regulator are lethal, and are picked off pretty early (often never even making it past the embryonic stage). Not surprisingly, master regulatory genes like the homeotic genes show extremely high homology, and often the only way for evolution to really alter the function such a gene is for a gene duplication to occur, so that one copy can continue to work normally while the other is free to diverge independently.
Mutations in the lower-level regulators tend to have subtler effects, and I wouldn't be surprised to learn that such mutations are the primary source of physiological and morphological variation in higher multicellular organisms. But ultimately, a mutation at any of these stages could turn out to be harmful or beneficial, depending on its aggregate effect.
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posted
I love electrochemical gradients, though I'm more familiar with them in physiology. Of course, that may be how they are functioning in embryology, how the genes know how far they are from the middle of things.
You know what occurs to me, though? That a lot more natural selection goes on before birth than after.
Anyway, I guess I just get irritated easily by children's programs that screw up evolution quite a bit, like Kratt's Creatures. They were forever using Lamarckian explanations of things.
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Why bash Lamarkian evolution? I'm spending as much time as possible here so when I have kids they'll be obstreperous and sarcastic Posts: 3950 | Registered: Mar 2006
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posted
They aren't mules. The mules occur when crossed with other types of fruit flies. That this happens indicates the fruit flies which breed true are actually a separate species. The mules in question are strong evidence speciation has occurred, not a reason to dismiss it.
quote:In 1958 this strain produced fertile hybrids when crossed with conspecifics of different strains from Orinocan. From 1963 onward crosses with Orinocan strains produced only sterile males.
And if you keep reading, you'll see that after that second initial experiment there are instances of selective breeding that are reproduced (the inability to reproduce was using the same method for attempting to create selective breeding. Other methods work:
quote:In a series of papers (Rice 1985, Rice and Salt 1988 and Rice and Salt 1990) Rice and Salt presented experimental evidence for the possibility of sympatric speciation. They started from the premise that whenever organisms sort themselves into the environment first and then mate locally, individuals with the same habitat preferences will necessarily mate assortatively. They established a stock population of D. melanogaster with flies collected in an orchard near Davis, California. Pupae from the culture were placed into a habitat maze. Newly emerged flies had to negotiate the maze to find food. The maze simulated several environmental gradients simultaneously. The flies had to make three choices of which way to go. The first was between light and dark (phototaxis). The second was between up and down (geotaxis). The last was between the scent of acetaldehyde and the scent of ethanol (chemotaxis). This divided the flies among eight habitats. The flies were further divided by the time of day of emergence. In total the flies were divided among 24 spatio-temporal habitats.
They next cultured two strains of flies that had chosen opposite habitats. One strain emerged early, flew upward and was attracted to dark and acetaldehyde. The other emerged late, flew downward and was attracted to light and ethanol. Pupae from these two strains were placed together in the maze. They were allowed to mate at the food site and were collected. Eye color differences between the strains allowed Rice and Salt to distinguish between the two strains. A selective penalty was imposed on flies that switched habitats. Females that switched habitats were destroyed. None of their gametes passed into the next generation. Males that switched habitats received no penalty. After 25 generations of this mating tests showed reproductive isolation between the two strains. Habitat specialization was also produced.
They next repeated the experiment without the penalty against habitat switching. The result was the same -- reproductive isolation was produced. They argued that a switching penalty is not necessary to produce reproductive isolation. Their results, they stated, show the possibility of sympatric speciation.
posted
Our definition of species gets a bit strained sometimes. Take the wolphin- a dolphin and a whale mated, baby produced. Baby matured and mated with one of its parental species. Yet no one is suggesting that we consider dolphins and whales the same species. There are some other examples where captivity or environmental shifts lead to weird matings with viable offspring. Of course, once you start working with phage (viruses) and bacteria, species becomes a pretty meaningless word.
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posted
Actually, the "whale" in question is a false killer whale, which (like the "true" killer whale, aka the orca) is actually a species of dolphin. See the Wikipedia page for more information. But your point still stands- false killer whales and bottlenose dolphins are indeed classified as different species, even though they can apparently produce fertile hybrids in captivity.
"Species" was only ever a term of convenience, anyway. We've had this debate on Hatrack before- there's nothing inherently "real" about the species concept (that is, a group of organisms capable of producing fertile offspring with one another). We just use it because it's a simple, convenient way to categorize many of the organisms we study, and it's shorter to say "bottlenose dolphin" than to say "the population of air-breathing aquatic animals with a grey body coloration and a pointed muzzle that grows to about 12 feet long and hunts for fish in oceans all over the world" every time we want to refer to them.
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posted
Even 'capable of producing fertile offspring' doesn't encompass how species are defined. For instance, populations which never interbreed but could are frequently considered separate species.
As noted, species is blurry in macro-organisms, too, its just less blurry. It is a term of convenience, not a reflection of some clear natural distinction.
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posted
To paraphrase your link above, bluefish in different lakes are not considered different species just because they would never have the opportunity to mate.
The third fruit fly scenario, in which all the females who would switch were killed, is not impossible, but it is the kind of improbable event I don't think would happen very often. And because of what we said earlier about meiotic crossover, killing the females in particular would have the effect of the population breeding excessively true.
A wolfin? Really? Phew, I thought I was losing it. It was a killer whale, not an actual cetacean.
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posted
As noted, species is a vague term. We generally consider populations in the same general area that subsist on different nutrients and do not interbreed different species, even if they could. Such as the flies in question. And the ones that produce mules can't produce fertile offspring, so they don't even have that problem.
If you reread the scenario, you'll see that even when they didn't kill the females the same effect was observed. And it doesn't have to happen very often; a speciation event every few million years will produce billions of species over time (see my previous post). We've been studying fruit flies for 50 years.
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posted
As for "new species" of fruit flies, that's rather specious (haha). The so-called new species have less genetic information than the parent population. A case for devolution perhaps, but certainly not proof that natural selection is any kind of mechanism for macro-evolution. Of course, being someone who doesn't accept macro-evolution a priori, I don't know what I'm talking about so feel free to ignore me.
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quote:The so-called new species have less genetic information than the parent population. A case for devolution perhaps, but certainly not proof that natural selection is any kind of mechanism for macro-evolution.
Evolution says nothing about the amount of genetic information. It doesn't have to increase to allow adaptation, it just needs to result in a more fit phenotype. There are some remarkably primitive critters with much more "information" in their genome than humans have.
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... a speciation event every few million years will produce billions of species over time (see my previous post). We've been studying fruit flies for 50 years.
Unless I never took math in the third grade, wouldnt it take millions of billions of years for a billion species to develop if a "speciation event" only occurs every few million years? Can't you guys see how patently ridiculous the whole concept is?. I commend your faith, though. You're all just in the wrong field.
edit: hmm. The underline function doesnt work (at least not the way I tried it: [u][/u])
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quote:The so-called new species have less genetic information than the parent population. A case for devolution perhaps, but certainly not proof that natural selection is any kind of mechanism for macro-evolution.
Evolution says nothing about the amount of genetic information. It doesn't have to increase to allow adaptation, it just needs to result in a more fit phenotype.
Well, Macro-evolution says a little something about it. It says that massive amounts of information (i.e, human DNA) has developed from essentially no information, just a bunch of randomness. This in spite of all evidence to the contrary (i.e; every observable natural event which without exception results in the destruction of information.)
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posted
I was imprecise. I was talking about a speciation event for each species every few million years. See my previous post where I post the numbers of species that would lead to.
As for information, that's not worth addressing until you propose a way of quantifying the amount of information in a population. Once you've done so I'll address why it either doesn't matter or why there can be an increase in information.
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quote:Originally posted by Reshpeckobiggle: (i.e; every observable natural event which without exception results in the destruction of information.)
Do two animals having a thousand offspring result in a destruction of information? Seems to me that it results in a great deal of new information, if you count each new sequence of mixed genetic information as an individual and unique set of information describing that particular new animal.
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quote:Unless I never took math in the third grade, wouldnt it take [u]millions[/u] of [u]billions[/u] of years for a [u]billion[/u] species to develop if a "speciation event" only occurs every few [u]million[/u] years?
But every time you add a species, you increase the number of opportunities for new speciation events. If we say that in 3 million years species A will beget species B, then in 3 million more years A may beget species C and B may beget species D. In a billion years, 333 3-million-year cycles will have passed, allowing for 2^333 speciation events. That's many billions of billions of billions of...
Obviously we don't have that many species so the production of new species is more rare and irregular, but there's nothing wrong with the math.
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posted
Ahh. So there would be an exponential sort of thing going on then. Or functional, rather. I got you.
Quantifying information: You take the DNA and you quantify it. How? I don't know how they do it, but I kniw that they do. Buncha people a whole heck of a lot smarter than me. I don't see how the total amount of information in a population is relevant to what I'm saying, though. I'm talking about results. The only thing that ever happens in a laboratory setting is loss of information. The only thing that breeding in general does is erode the total information of the population.
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posted
Every naturally observable event resulting in the destruction of information? You are misinformed, or please explain how all of the following are not new information.
We've already discussed polyploidy in this thread (doubling in the number of genes in the organism, which can then change in different ways, meaning the organism can have all the genes of its parent organism plus new genes).
Then there are beneficial mutations, which have been observed to change a gene doing nothing or something unessential into a gene that does something very useful.
Then there are genetic exchanges (sex) that create new combinations of existing genes, which is new information (you do know information theory, right?).
Then there're viruses inserting significant new sequences into cell genomes, that happens all the time.
Or, to put it another way, I added genetic information (antibiotic resistance) to bacteria in AP Biology in high school using naturally occurring enzymes in their normal method of functioning (just a lot more of them in a much quicker sequence).
And then there's that randomness is the least part of evolution, though a certain amount of it (which we observe constantly happening -- we see mutations all the time, we see chromosomal abnormalities all the time, et cetera) is necessary to drive things. Evolution involves detrimental random changes causing the individuals involved to be killed off and beneficial changes helping the individuals survive to pass on the changes. Where the changes come from (we have good evidence for randomness) is irrelevant to the changes driving evolution.
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posted
Every way I can come up with quantifying the information in DNA I can name several ways in which it increases. Perhaps you can link me to someone who proposes a method, and then I can come up with an example of information increasing by that measure?
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posted
Sorry, can't stick around. I'm in Mexico for a few more weeks and my opportunities to spend time on the internet are restricted more often than not. I knew I shouldn't have gotten into this because now I want to blow off my 'sponsibilities.
MightyCow, you aren't getting anything new there. It's just a bunch of the same old same old. You have those original two parents, and then you get 100 generations away from them and they all have the same coded information, minus some bits that have been lost along the way.
See, this whole evolution thing works great in theory, but since it can't be observed, and it is logically impossible, and because there are better explantions out there, why keep trying to fix it? It never happened, and that's a scary concept to a sinner, isn't it? Talk to ya's when I get back. Sorry for being a troll.
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Blayne Bradley
unregistered
posted
so I geuss gravity can't be real then because it cant be observed.
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We've observed several speciation events. We've done simulations using observed rates of random changes that result in growth in "diversity". How is it impossible to observe or logically impossible, and what better explanations are there?
As for the two parents and losing information, you start with two combinations of genes. At the end you have thousands of combinations of the same genes, which can result in significantly different physical traits, which can significantly change the survivability of the species and change its ability to interbreed. Plus each of those individuals can have mutations which change the genes they carry into things that were not previously present.
You're right, you are a troll, and you've been told this stuff before, but you continue to say things you've been given counterexamples to.
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quote:Originally posted by Reshpeckobiggle: MightyCow, you aren't getting anything new there. It's just a bunch of the same old same old. You have those original two parents, and then you get 100 generations away from them and they all have the same coded information, minus some bits that have been lost along the way.
By that argument, your post is adding nothing new to the thread, because it's just a bunch of the words that have already been used, arranged in a different order.
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posted
Yes, clearly despite all the publishing going on, all those books that use the same words are adding no new information.
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quote:You have those original two parents, and then you get 100 generations away from them and they all have the same coded information, minus some bits that have been lost along the way.
This was specifically refuted by fugu13 only two posts prior. (polyploidy) You need to actually address the argument if you want to convince anyone, not just pretend it wasn't made.
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posted
"See, this whole evolution thing works great in theory, but since it can't be observed, and it is logically impossible, and because there are better explantions out there, why keep trying to fix it? It never happened, and that's a scary concept to a sinner, isn't it? Talk to ya's when I get back. Sorry for being a troll. "
But... evolution... HAS been observed... and you even mentioned an example, in trying to disprove it... isn't THAT an illogical... I... gah!
quote:And it doesn't have to happen very often; a speciation event every few million years will produce billions of species over time (see my previous post). We've been studying fruit flies for 50 years.
Flies have been studied since 1910 (a wiki "fact" ) which I think I argued (it's just an argument, there is no right or wrong in academia, just soundness of argument) that 100 years of fruit fly generations is equal to 100 million years of human generations.
What I have not yet done is look at the intermediary phases between homo sapiens and other mammals to see what kinds of life spans might be looked for, and an estimate of total generations.
Okay, here we go. From the wikipedia entry on monotremes:
quote: Fossil and genetic evidence shows that the monotreme line diverged from other mammalian lines about 150 million years ago
I mistakenly called the tribosphenic molar a trilobdontic tooth earlier. There is ongoing controversy about whether such a tooth could have evolved more than once. That is, my evolution textbook from college (Cowen, Richard, History of Life 1990[/quote] says : "Because the tribosphenic molar is complex, it probably evolved only once." It then mentions the recent discovery of steropodon, which was also mentioned in the wiki monotreme listing, and how much hinged on whether it had such teeth. If the monotremes did not have such teeth, that moves the start point of this evolutionary innovation around somewhat.
I hadn't realized monotremes were so weird before. I mean, I knew they laid eggs and platypuses had venom, but they really are quite reptilian. And the electrolocation stuff.. this thread has lead to some awesome reading. But for the relevant part, platypuses have a lifespan similar to cats and dogs, up to 20 years with wild specimens known to last 11 years.
quote:See, this whole evolution thing works great in theory, but since it can't be observed, and it is logically impossible, and because there are better explantions out there, why keep trying to fix it? It never happened, and that's a scary concept to a sinner, isn't it? Talk to ya's when I get back. Sorry for being a troll.
So if evolution can be observed and is actually logically possible, your position is kind of s.o.l., huh.
God gave you this big ol' beautiful brain to figure out stuff, so let's see if you ever apply it to this matter. Ever.
Sometimes, it's time to crawl out of the hole.
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posted
Tarsiers are pro-simians. Of course, like anything we have nowadays, they are only descended from a common ancestor. But they have 6 month gestation and bear 1 young at a time. I don't know how this translates into lifespan. Oh, I forgot to check the species pages. I just love that picture on the link, though. Okay, I'm not finding any lifespans or even age of sexual maturity. Ah, sexual maturity as early as 1 year, bearing an offspring 1/4 the body mass of the mother. So glad I'm not a tarsier. The fossil record of tarsiers goes back 45 million years and is considered very extensive. I can't really claim anything conclusive about that. I mean, if I go back to the primate page I'll probably find a bolder number.
quote:Primates, insectivores, and condylarths are recognized by the beginning of the Cenozoic, and by the start of the Eocene, most modern groups had become established.
So it has been about 65 million years since the forbears of mice and the forebears of men diverged. Referring back to something I quoted from wiki earlier, the split between homonids and chimpanzees is about 5 mya. Well, I should get to bed.
posted
I would say that Resh has apparently never heard of polyploidy, or gene duplication, or chromosome duplication, or transposable elements or meiotic recombination, all of which are common ways to "add information" to the genome, but I know for a fact that we've described them all to him repeatedly, in detail. So either the knowledge is bouncing off an adamantium skull (wrapped in tinfoil, naturally), or he's trolling. Again.
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posted
Studied in the sense of being able to notice a speciation event, which has only been happening about 50 years.
And yes, we think speciation is much more common than would be necessary for it to readily explain all the life on earth, that's just a minimal necessary rate for evolution to be a reasonable explanation. Also, some of the 'bigger' leaps probably took much, much longer -- its far easier to see how something tarsier like could evolve into something human like than many of the other transitions in evolutionary history, though each has left behind at least a few species filling the same niches such transitions would involve.
And of course,
1) species is a vague concept, especially viewed at a distance, so exactly when speciation occurs is somewhat up in the air. I mean, we have a hard enough time with ring species -- how many species are in the ring?
2) species do all sorts of funky things, so even if there've been a ton more species, at any given time there are a relatively limited number. There also seem to be some sorts of major events that result in many, many species emerging (for instance, there have been several periods with multiple members of the homo genus around -- what could easily be called 'other species' of humans, particularly in later cases), that later settle down to a smaller selection of well-adapted species filling out the new niches. Its not exactly punctuated equilibrium, but its a similar concept.
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posted
I'd be willing to grant there are probably domestic dogs that I'd say are not the same species anymore, or possibly constitute a ring species in that there are breed which can breed with slightly larger or smaller breeds to maintain a pool. But when speciation is brought about through human interference, that is not an argument against Intelligent Design, you know? Again, I'm not sure what is involved in saying I support or don't support ID, since it apparently goes beyond believing in God and rejoicing in nature.
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posted
Dogs are generally special cased. Ring species usually refers to natural ring species found around a geospatial ring.
Speciation brought about through human intervention is perfectly a part of evolution. We're part of nature, and if interacting with us is creating selective pressure, that's as natural as if interacting with a new type of fish.
That there's a notion built up around humans as outside of nature doesn't exclude us from nature.
And of course, if we can bring about speciation through no unique action (we make certain dogs breed with certain other dogs, how unnatural! Populations breeding selectively happens in nature all the time) in a short amount of time. That is strong evidence that the same could happen "by chance" over a much, much longer period of time.
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posted
Okay . If you've read my posts in this and the other evolution threads, I think the belief that God is somehow involved is perfectly reasonable. It is the belief that the current scientific standing is unreasonable that I find suspect.
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