Single cell to multi-cell

Discussion in 'Creation vs. Evolution' started by Administrator2, Jan 22, 2002.

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    NALDACON
    [In another thread] John Paul wrote:
    I would like to see a line of evidence from biology that shows a single-celled organism can 'evolve' into something other than a single-celled organism. Do you have any such evidence? I kind of like the 'just-so' stories about how eucaryotic cells first came into being. Pat discusses them in another thread. Too bad those stories can't be observed, tested for, repeated or verified.


    John Paul,
    A single-celled to multicelled transition has been observed. I suspect you will object that the colonies are not truly "multicelled," but I offer the evidence to show that the single-celled to multicelled transition indeed has some experimental support. If subsequent generations were to show any diversification in any of cells of the colony, you would have a truly multicellular organism.

    In 1983, Boraas reported that a single-celled species of green algae began to form multi-celled colonies shortly after the accidental introduction of a flagellate predator. The multi-celled colonies could not be consumed as readily by the predator - the presence of the predator represented natural selection pressure. The multi-celled form was a mutant strain that had enhanced chances of survival in that enviroment. Initially, colony size ranged from 4 to 32 but stabilized at 8. The multi-celled colonies were maintained for several years after their initial formation. The multi-celled colonies technically belong to a completely different family of green algae.

    Boraas, M. E. 1983. Predator induced evolution in chemostat culture. EOS. Transactions of the American Geophysical Union. 64:1102 as summarized at http://www.talkorigins.org/faqs/faq-speciation.html


    JOHN PAUL
    I understand that colonies form. I understand the volovox and slime molds. I also understand that this is not indicative of the theory of evolution. That is what I am talking about.


    If subsequent generations were to show any diversification in any of cells of the colony, you would have a truly multicellular organism.

    IF is right. The first part is easy to show- colonies do form. The second part is not so fortunate. As it stands these are just aggregates of the same single-celled organism. The organisms these colonies give 'birth' to basicallty the same as the single-celled organisms before they formed the colony. What you would need is for one of those organisms to become a multi-cellular organism on its own. Also I was told that cell differentiation does take place in some colonies. However this is temporary as the colonies offspring are right back to what they were before the colony formed.
    What would have to be shown that this process, colony forming, was not a built-in or designed feature so that the organism could survive and did indeed evolve via purely natural processes.


    In 1983, Boraas reported that a single-celled species of green algae began to form multi-celled colonies shortly after the accidental introduction of a flagellate predator. The multi-celled colonies could not be consumed as readily by the predator - the presence of the predator represented natural selection pressure. The multi-celled form was a mutant strain that had enhanced chances of survival in that enviroment. Initially, colony size ranged from 4 to 32 but stabilized at 8. The multi-celled colonies were maintained for several years after their initial formation. The multi-celled colonies technically belong to a completely different family of green algae.

    Great stuff. It looks like the 'colony' was a direct result of environmental conditions. Basically that is the same premise that Dr. Lee Spetner uses for his Non-Random Evolutionary Hypothesis.


    Yesterday I received the book "VOLVOX: Molecular- Genetic Origins of Multicellularity and Cellular Differentiation" by David L. Kirk, via UPS. He and I exchanged several emails on this subject last summer but since school has re-opened (he is a prof. at Washington University in St. Louis) we haven't been in contact. The book is available through Cambridge University Press, if anyone is interested.


    NALDACON
    I would be interested in your opinion of the Volvox book. Sounds interesting.
    Well, I was right about your objection. Still, the step from individual cells to a multi-celled colony is indeed the first step necessary to get a truly multicellular organism, even if the cells are no different from the individual cells other than the fact than they stick together. Communication between cells and diversification of function would be the next steps. And while I don't know of experimental observations for these steps, I don't see why they would be impossible.

    Would a transition from individual cells to multicelled colonies be expected in a creation model? Why? It seems to me those individual cells would be going against the will of their Creator by clumping together. What would be the cause for the transition? What would be the benefit? Does this have something to do with the Non-Random Evolutionary hypothesis you mentioned? How so?


    JOHN PAUL
    I have heard your reasoning before but that doesn’t mean it is substantiated. That is what I am looking for. As you know claims come and they go. The only ones to stand the test of time are the ones that are substantiated by the experimental data. As a person who was once into design but am now into debug I know the difference between what works on paper and what works in real life.

    I am one who is under the impression that to be ‘truly’ multi-cellular an organism has to be born that way and that aggregates are just that- aggregates. Kind of like a mob mentality type effect. Once the mob disperses all that is left are the wandering individuals. Even if there was such a thing as mob sex , individuals would be born and not mobs.

    Communication between cells and diversification of function would be the next steps. And while I don't know of experimental observations for these steps, I don't see why they would be impossible.

    A mob communicates also. The thing is what does the colony reproduce?


    Would a transition from individual cells to multicelled colonies be expected in a creation model? Why?

    I don’t see it as a problem because of what is reproduced by the colony. It would still be under ‘everything after Its Kind’.


    It seems to me those individual cells would be going against the will of their Creator by clumping together.

    That would be saying we know the will of the Creator.


    What would be the cause for the transition?

    Environmental pressures.


    What would be the benefit?

    Survival of the organism.


    Does this have something to do with the Non-Random Evolutionary hypothesis you mentioned? How so?

    It could because the individual organisms would most likely contain the information required to form the colony and if the colony formed via direct result of environmental pressures that would be a sign of the NREH. All that is saying is the formation of the colony was a non-random event.

    I am still a way from finishing the book but if this is what evolutionists pin their hopes on (single-cell to multi-cellularity), there are still many unanswered questions. The fact that scientists are looking into it is a good thing, but it also shows a type of desperation which can lead to grasping at convenient answers.


    DANEEL
    In regards to the evolution of single celled organisms into multicellular I don't think anybody is going to see it in their life time. It took billions of years to go from prokaryotic to eukaryotic and many millions to go from single eukaryotic to truly multicellular. The volvocine line of evolution gives us a hint as to how it may have happened.
    Volvox can be considered as multicellular since it shows specialization and division of labor in its cells. There are a number of less specialized similar genera which are thought to be ancestral to Volvox. Gonium sp. and Pandorina sp. are isogamous while Eudorina sp and Volvox sp. are Oogamous.

    Remember, the evidence for evolution does not come from one area or example. There are numerous areas that by themselves may not be too strong but taken together the odds that each could be correct are multiplied. This is how all theories are compiled. Experiments and observations piled on top of one another until the weight becomes too heavy to deny. You can refute each area with an if statement but this is not enough to tear down the theory. Contrarians have been trying for over 100 years. If you keep up with the latest you know that new discoveries and observations continue to support evolution.


    FROGGIE
    Hey--I just read an article in Nature (or was it Science?) the other day about possible ways that evolution of multicellular organisms could have occured. Unfortunately it is at home, and I am not. I'll try to find it on medline...

    Bah. I can't find it. But I did find some interesting stuff.

    Here's an article: Evolution from unicellular to multicellular organisms. Tanpakushitsu Kakusan Koso. 2001 Aug;46(10):1324-31. Review. Japanese. No abstract available.
    Anyone know Japanese?

    Here's an abstract I can actually read (not necessarily comprehend):
    Mol Biol Evol 2001 Sep;18(9):1611-30
    "The evolution of controlled multitasked gene networks: the role of introns and other noncoding RNAs in the development of complex organisms."
    Mattick JS, Gagen MJ. Centre for Functional and Applied Genomics, Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia.

    Eukaryotic phenotypic diversity arises from multitasking of a core proteome of limited size. Multitasking is routine in computers, as well as in other sophisticated information systems, and requires multiple inputs and outputs to control and integrate network activity. Higher eukaryotes have a mosaic gene structure with a dual output, mRNA (protein-coding) sequences and introns, which are released from the pre-mRNA by posttranscriptional processing. Introns have been enormously successful as a class of sequences and comprise up to 95% of the primary transcripts of protein-coding genes in mammals. In addition, many other transcripts (perhaps more than half) do not encode proteins at all, but appear both to be developmentally regulated and to have genetic function. We suggest that these RNAs (eRNAs) have evolved to function as endogenous network control molecules which enable direct gene-gene communication and multitasking of eukaryotic genomes. Analysis of a range of complex genetic phenomena in which RNA is involved or implicated, including co-suppression, transgene silencing, RNA interference, imprinting, methylation, and transvection, suggests that a higher-order regulatory system based on RNA signals operates in the higher eukaryotes and involves chromatin remodeling as well as other RNA-DNA, RNA-RNA, and RNA-protein interactions. The evolution of densely connected gene networks would be expected to result in a relatively stable core proteome due to the multiple reuse of components, implying that cellular differentiation and phenotypic variation in the higher eukaryotes results primarily from variation in the control architecture. Thus, network integration and multitasking using trans-acting RNA molecules produced in parallel with protein-coding sequences may underpin both the evolution of developmentally sophisticated multicellular organisms and the rapid expansion of phenotypic complexity into uncontested environments such as those initiated in the Cambrian radiation and those seen after major extinction events.

    Here's another one, for the computer-geek types (I'm computerily-challenged, so don't expect me to understand any AI or AL stuff!!)
    Artif Life 2000 Fall;6(4):265-81 "Complex organization in multicellularity as a necessity in evolution."
    Furusawa C, Kaneko K.
    Department of Pure and Applied Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153, Japan.

    By introducing a dynamical system model of a multicellular system, it is shown that an organism with a variety of differentiated cell types and a complex pattern emerges through cell-cell interactions even without postulating any elaborate control mechanism. Such an organism is found to maintain a larger growth speed as an ensemble, by achieving a cooperative use of resources, than do simple homogeneous cells, which behave "selfishly." This suggests that the emergence of multicellular organisms with complex organization is a necessity in evolution. According to our theoretical model, there initially appear multipotent stem cells, which undergo stochastic differentiation to other cell types. With development and differentiation, both the chemical diversity and the complexity of intra-cellular dynamics are decreased, as a general consequence of our system. Robustness of the developmental process is also confirmed.

    And one more, that's more up my alley:
    Heredity 2001 Jan;86(Pt 1):1-7 "Cooperation and conflict in the evolution of multicellularity."
    Michod RE, Roze D.
    Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA. [email protected]

    Multicellular organisms probably originated as groups of cells formed in several ways, including cell proliferation from a group of founder cells and aggregation. Cooperation among cells benefits the group, but may be costly (altruistic) or beneficial (synergistic) to individual cooperating cells. In this paper, we study conflict mediation, the process by which genetic modifiers evolve that enhance cooperation by altering the parameters of development or rules of formation of cell groups. We are particularly interested in the conditions under which these modifiers lead to a new higher-level unit of selection with increased cooperation among group members and heritable variation in fitness at the group level. By sculpting the fitness variation and opportunity for selection at the two levels, conflict modifiers create new functions at the organism level. An organism is more than a group of cooperating cells related by common descent; organisms require adaptations that regulate conflict within. Otherwise their continued evolution is frustrated by the creation of within-organism variation and conflict between levels of selection. The evolution of conflict modifiers is a necessary prerequisite to the emergence of individuality and the continued well being of the organism. Conflict leads--through the evolution of adaptations that reduce i--to greater individuality and harmony for the organism.

    I found these by searching for "evolution multicellular organisms" on pubmed and received 182 hits.


    JOHN PAUL
    Daneel: In regards to the evolution of single celled organisms into multicellular I don't think anybody is going to see it in their life time.

    Perhaps with the increasing knowledge from genetic engineering we can cut out some of the "time" you say is required.


    It took billions of years to go from prokaryotic to eukaryotic and many millions to go from single eukaryotic to truly multicellular.

    That would be alleged as there isn't any evidence, other than the fact we are here, that would substantiate that claim.


    The volvocine line of evolution gives us a hint as to how it may have happened. Volvox can be considered as multicellular since it shows specialization and division of labor in its cells.

    That is what I had heard and why I forked out the bucks and bought the book "VOLVOX: Molecular- Genetic Origins of Multicellularity and Cellular Differentiation" by David L. Kirk
     

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