Does life evolve towards intelligence?

Discussion in 'Biology & Genetics' started by Xylene, Nov 11, 2005.

  1. invert_nexus Ze do caixao Valued Senior Member

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    Valich,

    Not 'colonizing'.
    Colony organisms are organisms where single cells come together and cooperate but are still considered single-cells rather than multicellular.
    Simple stuff.

    That is the leading theory on how eukaryotes formed. Yes.
    First the nucleus. Then the mitochondria and/or chloroplast. I don't seem to remember any other organelles that are conjectured to have been prokaryotic in origin... Might be forgetting something though.

    My. That's a lot of question marks. You must be really confused. No surprise there.

    Yes. First colonial then multicellular. You'd think you'd have learned this somewhere in your 30 years of school or what the fuck ever. (Bah. Couldn't help myself with this last jibe at you. Forgive me, dear?)
     
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  3. TheAlphaWolf Registered Senior Member

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    Yes. Muscle cells have extra nuclei and mitochondria, liver cells have extra smooth ER, capillary cells have extra vesicles (because of the pinocytosis they do), etc. They don't have different organelles (I guess some do but on average they don't), they just have more or less of each organelle.
    hmm. I don't think the nucleus was of prokaryotic origin. Makes sense though. You didn't mention other plastids, but I guess they count as chloroplasts

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    yes. Let me try to get that one page that talked about how multicellular organisms first came about...

    edit: well, I can't find it. I know it cited volvox and said something about gastrulation and stuff, but can't find it.
     
    Last edited: Nov 26, 2005
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  5. spuriousmonkey Banned Banned

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    Apparently there is no single solution to multicellularity. (I have a feeling this is one of these areas that hardly recieve any attention of researchers. Because all the money is in medical related biology. Don't blame us for that though. Society dictates what they want to spend money on.)

    http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=dbio.section.203
     
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  7. CharonZ Registered Senior Member

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    Actually there is quite some work going on here. For instance there is some extensive work on social prokaryotes like Myxobacteria that form multicellular complexes, mostly to construct fruiting bodies or for hunting in packs:
    http://cmgm.stanford.edu/devbio/kaiserlab/about_myxo/about_myxococcus.html
    On the other hand, it is not clear whether these mechanisms are related to the rise of multicellular life-forms or if it is a complete different path.
     
  8. spuriousmonkey Banned Banned

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    side note:

    (i was talking about relatively little research. I can't remember the last time I even met someone doing this kind of research. In fact I never met anyone. I know of buildings filled with people working on cancer etc.)
     
  9. CharonZ Registered Senior Member

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    Well, you are right, compared to cancer/medical research everything else is background noise (well, almost

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  10. valich Registered Senior Member

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    They differentiate between adventurous (A) and social (S) motility systems but from the frames it appears no difference in cellular specializations? Lot of colonization: "100,000 individual cells aggregate to form a structure called the fruiting body."
     
  11. valich Registered Senior Member

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    Anyways, my original post that led up to the discussion about prokaryotes that colonize to form these huge colonies, was not about colonies leading toward intelligence. As stated, the event that triggered the advent of evolving toward intelligence - the necessary precondition - was multicellular "specialization," not multicellularity.
     
  12. CharonZ Registered Senior Member

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    During social mobility they swarm together but remain single entitites (more or less). However, if they form a fruiting body they lose their individuality and form a single structure.
     
  13. valich Registered Senior Member

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    But that single structure is a colony. The individual cells have no difference in specialization functions, right?
     
  14. CharonZ Registered Senior Member

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    Of course they have. Fruiting bodies are very different from normal bacterial colonies. The complex morphology of some forms of fruiting bodies alone shows that it is not merely an accumulation of cells but the result of a number of directed morphological changes. Some of the cells for instance undergo the rather drastic change into spores, whereas other form the main body.
     
  15. valich Registered Senior Member

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    The article you cited makes no reference to this. "Fruitful" means to proliferate, just like a colony. Can you supply another source so that I can understand this? Thanks.
     
  16. valich Registered Senior Member

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    Fruiting bodies:

    "Long-range signals are often related to different aspects of the social life of microorganisms. The most studied example of long-range signalling is quorum sensing, which has been described in various bacteria. Quorum sensing allows microorganisms to monitor their density and consequently leads to a specific response by the whole bacterial population. It is based on the principle of autoinduction by diffusible signal molecules (known as 'autoinducers' or 'pheromones'), which are produced by bacterial populations. The system of autoinduction allows the amount of a signalling compound to increase more efficiently than could be achieved by a simple increase in the number of non-induced cells. Therefore, the population can change its behaviour before reaching a critical density. Quorum-sensing signals are usually specific for particular microorganisms; for example, N-acyl-homoserine lactones in Gram-negative bacteria and post-translationally modified peptides in Gram-positive bacteria....the existence of a universal signalling molecule, furanosyl-borate diester, which is used for interspecies bacterial communication. Quorum sensing regulates diverse physiological processes, including bioluminescence, swarming, antibiotic synthesis, the production of virulence determinants in pathogenic bacteria and biofilm formation....

    Autoinduction also has an important role in the formation of multicellular fruiting bodies by Dictyostelium discoideum. During this process, starving vegetative amoebae start to produce the signalling molecule cAMP, which diffuses into the surroundings and induces its own production by other cells. In this way, the signal spreads throughout the neighbouring population and an orientated concentration gradient is established, which determines the direction of cell movement towards an aggregation centre where an unorganized aggregate is formed.

    As indicated, long-range signalling is usually based on the production of a chemical compound that is spread through liquid or air. However, an intriguing case of non-chemical signalling between bacterial colonies has been described. Using the example of the bacteria Bacillus carbophilus growing dependently on activated charcoal, this study showed that bacteria growing around the carbon material transmitted colony-forming potential to cells and spores in distant locations. Moreover, transmission was not interrupted by plastic or glass barriers, which points to the existence of a physical signal. The authors showed that signal transmission still occurred even in the absence of graphite and when B. carbophilus was substituted with Bacillus subtilis or E. coli.

    Source: "Multicellular microorganisms: laboratory versus nature," by Zdena Palková, EMBO reports, vol. 5, no. 5, pp470-476, 2004. http://emboreports.npgjournals.com/cgi/content/full/5/5/470
     
  17. valich Registered Senior Member

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    "An early step in the evolution of multicellular organisms was the association of unicellular organisms to form colonies. Myxobacteria stay together in loose colonies in which the digestive enzymes secreted by individual cells are pooled, thus increasing the efficiency of feeding (the "wolf-pack" effect). These cells represent a peak of social sophistication among procaryotes, for when food supplies are exhausted, the cells aggregate tightly together and form a multicellular fruiting body, within which the bacteria differentiate into spores that can survive even in extremely hostile conditions. When conditions are more favorable, the spores in a fruiting body germinate to produce a new swarm of bacteria.

    Green algae eucaryotes exist as unicellular, colonial, or multicellular forms. Different species can be arranged in order of complexity, illustrating the kind of progression that probably occurred in the evolution of higher plants and animals. Unicellular green algae, such as Chlamydomonas, resemble flagellated protozoa except that they possess chloroplasts, which enable them to carry out photosynthesis. In closely related genera, groups of flagellated cells live in colonies held together by a matrix of extracellular molecules secreted by the cells themselves. The simplest species (those of the genus Gonium) have the form of a concave disc made of 4, 8, 16, or 32 cells. Their flagella beat independently, but since they are all oriented in the same direction, they are able to propel the colony through the water. Each cell is equivalent to every other, and each can divide to give rise to an entirely new colony. Larger colonies are found in other genera, the most spectacular being Volvox, some of whose species have as many as 50,000 or more cells linked together to form a hollow sphere. In Volvox the individual cells forming a colony are connected by fine cytoplasmic bridges so that the beating of their flagella is coordinated to propel the entire colony along like a rolling ball. Within the Volvox colony there is some division of labor among cells, with a small number of cells being specialized for reproduction and serving as precursors of new colonies. The other cells are so dependent on one another that they cannot live in isolation, and the organism dies if the colony is disrupted.

    In some ways Volvox is more like a multicellular organism than a simple colony. All of its flagella beat in synchrony as it spins through the water, and the colony is structurally and functionally polarized and can swim toward a distant source of light. The reproductive cells are usually confined to one end of the colony, where they divide to form new miniature colonies, which are initially sheltered inside the parent sphere. Thus, in a primitive way, Volvox displays the two essential features of all multicellular organisms: its cells become specialized, and they cooperate. By specialization and cooperation the cells combine to form a coordinated single organism with more capabilities than any of its component parts.

    Organized patterns of cell differentiation occur even in some procaryotes. For example, many kinds of cyanobacteria remain together after cell division, forming filamentous chains that can be as much as a meter in length. At regular intervals along the filament, individual cells take on a distinctive character and become able to incorporate atmospheric nitrogen into organic molecules. These few specialized cells perform nitrogen fixation for their neighbors and share the products with them. But eucaryotic cells appear to be very much better at this sort of organized division of labor; they, and not procaryotes, are the living units from which all the more complex multicellular organisms are constructed.

    Multicellular organization depends on cohesion between cells. To form a multicellular organism, the cells must be somehow bound together, and eucaryotes have evolved a number of different ways to satisfy this need. In Volvox, as noted above, the cells do not separate entirely at cell division but remain connected by cytoplasmic bridges. In higher plants the cells not only remain connected by cytoplasmic bridges (called plasmodesmata), they also are imprisoned in a rigid honeycomb of chambers walled with cellulose that the cells themselves have secreted (cell walls).

    Source: "From Single Cells to Multicellular Organisms," from Molecular Biology of the Cell, 3rd edn, 1994.
    http://www.ncbi.nlm.nih.gov/books/bv.fcgi?db=Books&rid=cell.section.61
     

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