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Author Topic:   Simple to Complex - Reproduction
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 61 of 69 (170967)
12-22-2004 8:18 PM
Reply to: Message 59 by TheLiteralist
12-22-2004 6:36 PM


I'd be interested in reading it (or at least trying to).
Observed Instances of Speciation
quote:
5.9.1 Coloniality in Chlorella vulgaris
Boraas (1983) reported the induction of multicellularity in a strain of Chlorella pyrenoidosa (since reclassified as C. vulgaris) by predation. He was growing the unicellular green alga in the first stage of a two stage continuous culture system as for food for a flagellate predator, Ochromonas sp., that was growing in the second stage. Due to the failure of a pump, flagellates washed back into the first stage. Within five days a colonial form of the Chlorella appeared. It rapidly came to dominate the culture. The colony size ranged from 4 cells to 32 cells. Eventually it stabilized at 8 cells. This colonial form has persisted in culture for about a decade. The new form has been keyed out using a number of algal taxonomic keys. They key out now as being in the genus Coelosphaerium, which is in a different family from Chlorella.
Boraas, M. E. 1983. Predator induced evolution in chemostat culture. EOS. Transactions of the American Geophysical Union. 64:1102.

This message is a reply to:
 Message 59 by TheLiteralist, posted 12-22-2004 6:36 PM TheLiteralist has replied

Replies to this message:
 Message 63 by TheLiteralist, posted 12-22-2004 8:55 PM crashfrog has replied

  
TheLiteralist
Inactive Member


Message 62 of 69 (170973)
12-22-2004 8:43 PM
Reply to: Message 60 by Ooook!
12-22-2004 6:49 PM


Re: Apples & Oranges
Ooook!,
When we look at the fossil record what is the order we find things cropping up? Single cellssimple multi-cellularorganisms with two germ layers (like jelly fish)organisms with three germ layers
When we look at embryogenesis what do we see? A single cella ball of cellstwo cell layersthree cell layers. It echoes the pattern suggested by the fossil record, and emphasises the step by step nature of evolution.
I might be misunderstanding you, but it sure sounds like you are implying something like Ernst Haeckel's "recapitulation theory."
Here is a TalkOrigins article quote regarding that theory:
quote:
Ernst Haeckel's post-Origin views in particular (the famous and now discredited "biogenetic law" that "ontogeny recapitulates phylogeny" or that embryological development was a recapitulation of the adult stages of ancestors)...
{by edit: you have to scroll down quite a bit to get to the section on Ernst Haeckel}
But I might not be understanding you correctly. I certainly don't see what adult forms of whatever creatures (fossilized or not) has to do with embryonic stages of whatever creatures (fossilized or not).
This message has been edited by TheLiteralist, 12-22-2004 09:35 PM

This message is a reply to:
 Message 60 by Ooook!, posted 12-22-2004 6:49 PM Ooook! has replied

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TheLiteralist
Inactive Member


Message 63 of 69 (170978)
12-22-2004 8:55 PM
Reply to: Message 61 by crashfrog
12-22-2004 8:18 PM


Observed Evolution
Crashfrog,
Thanks for the quote and link. That is interesting, to some extent. I have to wonder whether C. vulgaris possesses this trait (i.e., as a standard response to some certain conditions) independently of this experiment or not (i.e., was it a pre-existing trait?).
It matters not, though, for it is a long ways from single-cell to human. I will, however, for the present, withdraw my contention that evolution from single-celled to multi-celled organisms has never been observed.

This message is a reply to:
 Message 61 by crashfrog, posted 12-22-2004 8:18 PM crashfrog has replied

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crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 64 of 69 (170981)
12-22-2004 9:01 PM
Reply to: Message 63 by TheLiteralist
12-22-2004 8:55 PM


I have to wonder whether C. vulgaris possesses this trait
No. This was new; the result of selection pressures and mutation. Chlorella in the wild don't do this.
It matters not, though, for it is a long ways from single-cell to human.
It sure is. But thanks to this experiment the distance is just a little shorter.

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Ooook!
Member (Idle past 5816 days)
Posts: 340
From: London, UK
Joined: 09-29-2003


Message 65 of 69 (171119)
12-23-2004 11:15 AM
Reply to: Message 62 by TheLiteralist
12-22-2004 8:43 PM


Re: Apples & Oranges
Hello again,
I might be misunderstanding you, but it sure sounds like you are implying something like Ernst Haeckel's "recapitulation theory."
Nice try, but no I wasn’t referring to Haekal’s biogenetic law. As you rightly point out, the idea that an embryo passes through all of the adult stages of it’s descendents as it develops was thrown out quite sometime ago as a bucket-load of fraudulent codswallop. I was talking about the relatively new (and very much alive) concept of evolutionary developmental biology (understandably known as Evo-Devo).
Here’s another link to Talkorigins talking about Haeckel and misrepresentation of Evo-Devo by a particular creationist. These sections are particulary pertinent:
quote:
What modern developmental biology has been discovering is that these earliest stages in different vertebrate embryos are substantially similar. The differences are superficial, and in many cases a consequence of different amounts of maternal investment
and
quote:
The processes of cell signaling important in inducing new tissues during gastrulation are similar in all vertebrates, and the same answers are turning up in fish and mice, despite the morphological differences in their layouts.
So when you say:
But I might not be understanding you correctly. I certainly don't see what adult forms of whatever creatures (fossilized or not) has to do with embryonic stages of whatever creatures (fossilized or not).
It’s all about looking at the type of animals that appear in the fossil record and looking at embryogenesis of modern equivalents. Evo-Devo uses the techniques and knowledge from the field of developmental biology and then applies them to evolution. If we share common ancestry with something, then it stands to reason that we share developmental processes. That’s what we see: common genes controlling common processes, and a step-by-step introduction of these processes through time in the fossil record.

This message is a reply to:
 Message 62 by TheLiteralist, posted 12-22-2004 8:43 PM TheLiteralist has not replied

  
Dan Carroll
Inactive Member


Message 66 of 69 (172096)
12-29-2004 12:14 PM
Reply to: Message 58 by TheLiteralist
12-22-2004 6:34 PM


Re: Apples & Oranges
Whoops... busy time of year, missed your post. Lemme get it now...
No, that is not what I have said at all. You may not know what "zygote" means (I had to look it up myself before using it in my post that you are quoting). This definition might be helpful in clarifying what I have said.
My bad. Now it's just a strawman. Because I was asking about the sperm and egg.
What changes of complexity occur in the evolutionary process when going from that hypothetical first cell to humans?
Take a gander at a single-celled organism, take a look at a human, and see for yourself. Do you really not see any differences?
How do these changes in complexity occur?
The mechanisms of evolution. But why are you bringing this up? The issue was whether it was possible to go from so very simple to so very complex, not what means are used for it to happen. If you'd like to say that the mechanisms of evolution themselves are unlikely, go start a topic.

This message is a reply to:
 Message 58 by TheLiteralist, posted 12-22-2004 6:34 PM TheLiteralist has replied

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TheLiteralist
Inactive Member


Message 67 of 69 (172460)
12-31-2004 2:50 AM
Reply to: Message 66 by Dan Carroll
12-29-2004 12:14 PM


Re: Apples & Oranges
Dan,
My bad. Now it's just a strawman. Because I was asking about the sperm and egg.
No strawman here. A zygote is the single cell that results from the union of the sperm and egg (and a human zygote has the full human genome--or complete human DNA code--if I understood my high school biology correctly). Sperm and egg cells each contain only HALF of the parents' chromosomes (DNA codes). When the two combine, the resulting cell, the zygote, has a full set of chromosomes (a full DNA code). A human zygote has a full human DNA code.
Even the BSBC approved, chock-full-o-evolution high school biology text book, Heath's 1990 edition of Biological Science: A Molecular Approach says on page 248:
quote:
New individuals begin at fertilization, when the nuclei of two cells--one from each parent--unite. If these cells contained the same number of chromosomes as the rest of the cells of each parent...the [chromosome] number would double...

--emphasis theirs to indicate the word can be found in the book's glossary


Human body cells contain 46 chromosomes (the full human DNA code). Sperm and egg cells only get 23 chromosomes (half the human DNA code--sort of). When the sperm and egg unite, the resulting zygote has 46 chromosomes (the full human DNA code). The text book, which is NOT pro-life, by any stretch of the imagination, actually states that the "new individuals begin at fertilization."
The Literalist asks:
1) What changes of complexity occur in the evolutionary process when going from that hypothetical first cell to humans? How do these changes in complexity occur?
2) What changes of complexity occur in embryogenesis when going from a human zygote to a human baby? How do these changes in complexity occur?
Dan Carroll responds:
Take a gander at a single-celled organism, take a look at a human, and see for yourself. Do you really not see any differences?
If I were to compare a typical, non-human single-celled organism to a human, I would see giant differences in body form AND giant differences in DNA structure. However, if I were to compare a human zygote to a human, I would see giant differences in body form, but I would NOT see giant differences in DNA structure. A human zygote has human DNA. The hypothetical first cell would NOT have human DNA.
The mechanisms of evolution that cause the hypothetical first cell to develop into humans involves changes not only in body form but also in DNA structure. The body becomes more complex but so does the DNA.
Differentiation, the process that a human zygote undergoes in developing into a human baby, results in a change in body form, but the DNA does not change.
Changing the complexity of body form has not, as I recall, been an issue in the evolution versus creation debate. Rather, complexity debates normally revolve around the DNA code and how changes to it could have occurred since a creature's body form is an expression of the creature's DNA sequences. Even the various differentiation processes of various creatures are expressions of the various DNA codes.
In other words, while I find the development from human zygote to human baby marvelous, I understand that the instructions for such development exist in the zygote's human DNA. This is simply different from the evolution process, which must first change the first cell's DNA into human DNA.
Your opening post appears to be using the following reasoning:
COMMONLY KNOWN BIOLOGICAL FACT:
All humans develop from single cells
CONCLUSION BASED ON ABOVE FACT:
Therefore, development from a single cell to a human is possible
CONCLUSION BASED ON ABOVE CONCLUSION:
Therefore, evolution from the hypothetical first cell to humans over billions of years is possible.
Here is my reasoning:
PREMISE BASED ON MY UNDERSTANDING OF EVOLUTION THEORY:
Evolution from hypothetical first cell to humans involves tremendous changes to DNA sequences through random mutations and natural selection.
PREMISES BASED ON MY UNDERSTANDING OF HUMAN BIOLOGY:
1)The single cell that a human develops from is a human zygote (the resulting cell of the union of a human sperm and a human egg). A human zygote has a human genome (complete human DNA sequence).
2)When a human zygote differentiates into a human baby, tremendous changes to the zygote's DNA do not occur.
CONCLUSION BASED ON ABOVE 3 PREMISES:
Zygote differentiation, since it doesn't involve tremendous changes to DNA sequences, cannot indicate that evolution is possible.
Your reasoning overlooks the DNA issue. I still see it as apples and oranges.
The issue was whether it was possible to go from so very simple to so very complex, not what means are used for it to happen. If you'd like to say that the mechanisms of evolution themselves are unlikely, go start a topic.
Human zygote development goes from simpler body form to more complex body form while DNA complexity remains unchanged. Evolution of the hypothetical first cell into humans involves changes in both body form and DNA structure.
Your opening post mentions evolution and describes, in a general way, the differentiation process a zygote undergoes. You attempt to compare the two processes. I see nothing off-topic by examining not only the actual changes that occur in both processes but also the mechanisms involved in both processes.
I also don't recall indicating, in this thread, whether the mechanisms of evolution are unlikely or not. I have tried to focus on simply comparing evolution's proposed mechanisms with embryogenesis's actual mechanisms.

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 Message 66 by Dan Carroll, posted 12-29-2004 12:14 PM Dan Carroll has not replied

Replies to this message:
 Message 68 by RAZD, posted 01-01-2005 8:30 PM TheLiteralist has not replied

  
RAZD
Member (Idle past 1406 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 68 of 69 (172856)
01-01-2005 8:30 PM
Reply to: Message 67 by TheLiteralist
12-31-2004 2:50 AM


Apples & Oranges have a common ancestor too.
TheLiteralist writes:
I would see giant differences in body form AND giant differences in DNA structure
Actually you wouldn't. The structure of DNA is composed of 4 amino acids in two sets of pairs, arranged in a certain order. The same amino acids in the same pairs are arranged in single cell bacteria as in humans. The only differences are the numbers of pairs and the specific order of the arrangements.
To change one pair at a time into the DNA of human from the DNA of bacteria would leave plenty of time for the evolution of all intermediate steps and stages.
The big misconception here is that it would have to be all changed at once. That is not how evolution operates.
Humans also do not have a 3.5 billion year gestation, so the comparison is faulty between evolution from a single cell and growth from a zygote on that score as well.
But.
If you compare the growth of a human zygote with that of a chimpanzee you will see very little difference - even at the fetal stage they are quite similar. And there is very little difference in the DNA structures as well. We are 98% similar.
We can map that difference onto a tree like structure and say {this branch human} and {this branch chimp}.
We can do the same with the {human\chimp} common ancestor and the ancestoral gorilla\orangutan\etc and find the genetic difference between them: a difference that is present in both the human and the chimp, because the genetic markers are retained in later species (they are inherited in the same manner as hair and eye color). We have something like 95% similarity to gorillas, if memory serves.
We can continue to go back into the genetic past by comparing genes and we can do this for all species and a remarkable thing happens ... there is a distinctive tree-like structure with no cross-connections and no radically unconnected limbs. But also with continual little differences between branches, an accumulation of small changes that adds up over time to the difference from bacteria to human.
But there is something else, and ‘ook’ has referred to this: the development of each species from zygote to adult goes through certain stages, and the earlier the stage of development the more universally it is observed in all species. I can see a day coming when a scientist says at this stage of development we diverged from (for instance) fish into land creatures: they go left and we go right ... and then at this point we diverged from (for example) reptiles.
This is because the development of the zygote is controlled by the DNA, and a change in the DNA makes one go left while the other goes right ... a little change caused by mutation that made a variational change within a species that later diverged into different species.
So we can also map the developmental stages of the zygotes of species into a tree of life to see where each species diverges from the others in the development of their zygotes into adults.
Any guesses on how similar the {zygote development tree} is to the {genetic tree}?
And it should take no great leap of faith to get from that back to a single cell ancient ancestor (that is probably much simpler than even one of today’s simplest single cell denizens of life, for they too have evolved added complexity).

we are limited in our ability to understand
by our ability to understand
RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}

This message is a reply to:
 Message 67 by TheLiteralist, posted 12-31-2004 2:50 AM TheLiteralist has not replied

  
AdminNosy
Administrator
Posts: 4754
From: Vancouver, BC, Canada
Joined: 11-11-2003


Message 69 of 69 (175583)
01-10-2005 5:18 PM


Thread moved here from the Biological Evolution II forum.

  
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