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Was The Transition From Unicellular To Multicellular

  1. May 22, 2005 #1
    Bound to happen?, was it inevitable since multicellular organisms has alot more advantages than unicellular organisms.
     
  2. jcsd
  3. May 22, 2005 #2
    Also...Alien Cells To Alien Civilizations

    Do you think we are alone or they are out there? (not alien organisms but going farther than that intelligent alien species)

    Personally, I think there are millions of alien civilizations out there at any one time, the building blocks of life are found in abundance in deep space, plus the c0mplexity of organisms has only two directions it will either stay the same or it will increase in c0mplexity but it can never decrease in c0mplexity, so over time there eventually will be a growth in maximum c0mplexity in atleast one ogranism. The fittest will survive while the weak gets "weeded out" over time, the more "fitter" an organism is the more complex it has to be (they go hand in hand) and when there are alot of "fit" organisms there will be an arms race and that will lead to an explosion of c0mplexity, when the more simpler niches are filled that will make way for more complex niches to be filled. Lets say organism one can survive in environments A and B but organism two can survive in environments A,B and C...over time who do you think will get "weeded out" and who do you think will thrive.

    Survival of the fittest, the more adaptive specie will survive and thrive.

    And once there are creatures like the animals have emerged, then there is a great chance that atleast one of those animals will evolve into an intelligent bunch.
     
  4. May 22, 2005 #3

    JamesU

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    do you put the "0" in complex or only complexity?
     
  5. May 22, 2005 #4
    Complexity..it was because on the original message board I posted this in the word complexity was ***'d out for some reason.
     
  6. May 22, 2005 #5

    arildno

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    Oh ,do they?
    That's new to me.
    Please note that the overwhelming part of the Earth's biomass is in the form of unicellular organisms.

    Multicellular organisms are just exotic aberrations to the norm.
     
  7. May 22, 2005 #6
    Or you could get alot more done if you work together, thats a big advantage, its not just "exotic abberations".
     
  8. May 22, 2005 #7
    To this I query: If multicellular organisms had such an advantage over unicellular organisms then why have they not gone extinct (unicellular life)? Life has many solutions. There are many ways to deal with the physical world organims are placed against. Different organims find different solutions to this problem. And how do they know if the solution is correct? Well natural selection will guide this evolving process to a path that works. All the organisms that are around today have found a way to survive and procreate. So multicellular organisms as well as intelligence is not an essential ingredient of life and therefore not inevitable.
     
  9. May 22, 2005 #8

    arildno

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    A lot more done???
    What ARE you talking about?

    Instead of indulging in silly and misplaced value judgments, you might do better to actually learn to OBSERVE and UNDERSTAND things around you.
     
  10. May 22, 2005 #9

    Moonbear

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    There are a number of misconceptions about evolution apparent in your post, so I'm going break it down part by part to explain where the misunderstandings are.

    That's not true. Certain parasites, like tapeworms, are an excellent example of organisms that have become less complex than ancestral species. Because they can extract nutrients directly from their hosts, they don't need complex digestive systems.

    Natural selection is very specific to the environment it is occurring in. It also doesn't necessarily require that one variant of a species be "weak." It just means that another variant is better suited to the environment, so the proportion of the species exhibiting that trait, over time, increases (Hardy-Weinberg Principle). The other variant does not necessarily disappear entirely, which is good if the environment changes and that variant is more suited for the changed environment. If a variant is sufficiently detrimental in a particular environment, such that no individuals exhibiting it can survive to reproduce, and the trait is lost, this is a loss of variation. It could even be a loss of complexity. Niches are not more or less complex either. Niches are just environments.

    That's overly simplistic. Both species may coexist in the same environment. Or, the organism that can only survive in environment A&B (Organism 1) may be thriving there, while the other organism (Organism 2) is competed out of that environment and forced into only environment C. Now, another species may come along and start destroying environment C, say a simple fungus that kills the plants Organism 2 needs to eat.

    Keep in mind, adaptability is dependent on pre-existing genetic variability, and a lot of chance that among the variants of that species, at least one exists that can survive in a new environment. And sometimes living in a highly selective environment for a long period of time (thriving) leads to loss of some of that variation due to strong selection for a few traits. In the end, this thriving species may be the least able to adapt to an environmental change because it has become too specialized. So, thriving and adaptability do not necessarily need to go together as long as the environment is present where the specialized species can survive.

    Maybe, maybe not. There's no predetermined direction for evolution to occur, so this is not a guaranteed outcome, and not necessarily even highly probable. You may end up with nothing more than a bunch of animals that never even develop a true brain, such as worms.
     
  11. May 22, 2005 #10

    Moonbear

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    That would be an advantage to colonial organisms (colonies of single-celled organisms), but not relevant to multicellular organisms. Multicellular organisms, and in general, more complex organisms, require increased energy to maintain their function. This is a disadvantage of multicellular organisms relative to single-celled organisms.
     
  12. May 22, 2005 #11

    arildno

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    Great posts, Moonbear!

    As I see it, it is the abundance of bacteria and other small-scale life which opens up new niches for new forms of life which have the bacteria themselves as their primary food source.

    Thus, we ought to regard "higher" organisms as ourselves as secondary life forms, and not as having reached the pinnacle of evolution or something.
    Our existence is largely irrelevant for the microbial world (other than being an alternative food source for them); in contrast, multicellular life would practically collapse overnight if we removed the bacteria from the earth..
     
  13. May 22, 2005 #12
    Well, wow I was very misinformed about evolution then. Would you guys say then intelligence is a rare occurance? and if Earth was restarted ten times it would happen only once?

    "Multicellular organisms, and in general, more complex organisms, require increased energy to maintain their function. This is a disadvantage of multicellular organisms relative to single-celled organisms." - Then, why did the transition to unicellular to multicellular happen? I am just asking because it seems like multicellular does not have alot of advantages over unicellular now.

    "Maybe, maybe not. There's no predetermined direction for evolution to occur, so this is not a guaranteed outcome, and not necessarily even highly probable. You may end up with nothing more than a bunch of animals that never even develop a true brain, such as worms." - Even with environmental pressures?
     
    Last edited: May 22, 2005
  14. May 23, 2005 #13

    Moonbear

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    No problem. It's a common mistake. It's probably a topic textbooks should spend a little more time emphasizing in the chapters on evolution and natural selection since it's such a common misunderstanding. But, there's only so much you can include in a single textbook.

    It's hard to predict an answer to that question. Certainly among all the species that currently exist on our planet (since we can't assess intelligence directly in extinct species), it is a rare occurrence (even if you use a liberal definition of intelligence, it's pretty much limited to vertebrates and cephalopods, and possibly only in humans and maybe dolphins and the other primate species if you use a more conservative definition).

    I'm not exactly sure what you're asking here. Do you mean if the environmental pressures/changes were exactly the same? If so, here's the rub. There's still a good deal of chance involved. Most mutations that contribute to variability and speciation are "errors" in chromosome replication during cell division in the gametes (or damage caused by environmental factors). While there are areas of chromosomes that are more susceptible to mutations (probably something Monique can talk more about than I can), any part could have a mutation during cell division.
    So even under identical environmental conditions, completely different mutations or none at all could occur.

    In anticipation of the next question or where the above might start getting confusing, keep in mind that natural selection and evolution are not synonymous. Natural selection is how environmental factors influence the survival of individuals within a species that have certain traits and affects the proportion of individual in a population that have that trait. These variations in traits must already exist for natural selection to be a factor. Evolution is the change of the species over time, the overall accumulation or loss of traits (not just selection from among previous variations of those traits), until they have become sufficiently different to be unable to interbreed with the ancestral species, thus, at a population level, a new species is formed. Natural selection helps this process along by eliminating unfavorable traits, but it's not the "cause" of evolution, which is sometimes another misconception people hold.
     
    Last edited: May 23, 2005
  15. May 23, 2005 #14

    arildno

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    GoldBarz:
    Why do you keep talking about a "transition" from unicellular life to multicellular life?
    There hasn't been any such "transition", since the vast majority of life is still in a unicellular form.
     
  16. May 23, 2005 #15

    matthyaouw

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    In some circumstances perhaps they do have advantages, hence why they are able to survive, but in others, simple organisms can dominate. Take for example your skin and intestines- they themselves are ecological niches, filled primarily with bacteria living in symbiosis with humans. You would be hard pressed to find a complex organism more suited to either environment, and that is just one example out of many. Simple organisms can generally withstand a much wider range of ph, temperature etc than complex ones, giving them many niches where they have the advantage. I don't honestly think its posible to effectively compare the advantages and disadvantages of such broad groups with no reference to specific conditions.


    You still seem to be under the misconception that when faced with any kind of problem, complexity is the way to go. This is not the case. I think its fairly safe to say that all species are under constant environmental pressures of some degree, and yet, as has already been said, the most numerous organisms on the planet are simple and unicellular still.
     
  17. May 23, 2005 #16
    You knew what I meant, sorry.

    Wow, I got roasted on this thread lol. I am willing to learn though.

    But I think I made a mistake stating something, I did not mean that the average organism will increase in complexity over time I meant that the maximum complexity an organism could have could in fact increase.

    I think the best definition of evolutionary progress by means of natural selection that I can think of is a growth in the overall complexity of organisms that allows them to exercise increasing control over their environment.

    Anyways, you guys should read the link below, its a good read.

    http://pespmc1.vub.ac.be/Papers/ComplexityGrowth.html
     
  18. May 23, 2005 #17

    matthyaouw

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    No. Evolution is non-directional process. It is still evolution if the species simplify over time. Control over environment could be a result of evolution, but it is in to way integral to its definition.
     
  19. May 23, 2005 #18
    Did you read the link above
     
  20. May 23, 2005 #19

    arildno

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    In the end, that's all that matters. :smile:
     
  21. May 23, 2005 #20
    So do you guys think intelligence is a one in a million type thing in the universe and that we are likely alone in the galaxy?
     
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