Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Action v Structure

  1. Jan 19, 2008 #1
    Do you think that it maybe possible to categorise life by actions rather than by structure?
     
  2. jcsd
  3. Jan 20, 2008 #2

    Danger

    User Avatar
    Gold Member

    Welcome to PF, Nughret.
    You can categorize life (or anything else, for that matter) according to whatever criteria you decide upon. Do you have something specific in mind?
     
  4. Jan 24, 2008 #3
    Thanks Danger
    I guess what i would really like to know is if we replaced the traits of structure by action in Darwins theory of evolution, would it still be true?
     
  5. Jan 24, 2008 #4

    jim mcnamara

    User Avatar
    Science Advisor
    Gold Member

    Have you heard of parallel evolution - two unrelated species end up looking very similar and doing often very similar things to stay alive in their respective ecosystems.
    Ostriches and emus are an example. We call them ratites as a group, but that does not mean they have recent common ancestry.

    FWIW -
    The emerging primary means of putting species into taxonmic cubbyholes is to use DNA comparisons as the defining characteristic. For hundreds of years the lotus lilly and the sycamore tree (plane tree) were parked in very different parts of the plant cubbyhole system. It turns out they are very closely related, in terms of common DNA segments.
    B
     
  6. Jan 24, 2008 #5

    Heck yeah! I have always said to people that IMHO Darwin and Lamarck were BOTH correct. While Natural Selection is the judge, jury, and executioner as to what adaptations pass or fail, the driving "force" of evolutionary adaptations is a change in behavior due to changes in environmental conditions.

    ...although some would disagree with the statement I just made.
     
  7. Jan 24, 2008 #6

    Danger

    User Avatar
    Gold Member

    I'm ashamed to admit that I never really studied biology, and don't even know what Darwin set forth in regard to this topic. (And I've never even heard of Lamarck.)
    'Traits of structure' would imply to me that he considered physically similar critters to be related. That's a common-sense approach, but not necessarily correct. For instance, in things like medical or forensic study, pigs are far more like humans than are the great apes.
    If you want to go by actions, though, it gets a bit weird. By action, a dolphin is more closely related to a tuna than to a human, even though we're both mammals.
     
  8. Jan 25, 2008 #7

    jim mcnamara

    User Avatar
    Science Advisor
    Gold Member

    Danger -

    Lamarck said that acquired traits are passed on. Not genes.

    So, if you develop a nervous tic, your children will all have a nervous tic. Horrible example, but you get the idea. A lot of this came from attempts at domesticating wild animals. When a wild species is reared in a completely non-thretening environment, adrenaline levels are low compared to their wild cousins. Low adrenaline affects coat coloration of mammals. Since the mammals reared in captivity had spotty coats, and their babies had spotty coats, you can see how somebody might conclude that the spotty coat trait was acquired and passed on.
     
  9. Jan 25, 2008 #8

    Danger

    User Avatar
    Gold Member

    Thanks for the explanation, Jim. Sounds like the old 'Nature vs. Nurture' debate, with a twist.
    The sad truth is that if you raise a lion from birth the same way that you would a regular household tabby, there's still a good chance that at some point in its life it will chew your face off.
    The thing about nervous tics or other quirks is that they might be imitated by an admiring offspring who is trying to emulate a parent. Aside from intensive neurological examination, I'm not too sure how you could determine that. In the case of something like Tourette's (spelling?) Syndrome, then it would be genetic rather than environmental. If it's just an affectation, though, it must be environmental.
     
  10. Jan 25, 2008 #9
    What you ask is well known to biology. Species can be classified according to "functional groups". There are many examples. A "predator", an "omnivore", a "herbivore", etc. Life itself is classified by actions--for example, those forms of life that decompose, those that use anaerobic respiration for energy (fermentation one example), those that carry on photosynthesis (green plants--and let us thank them every day), you get the idea. Ecosystems are classified by actions, those with high primary production vs low (eutrophic vs oligotrophic). The reason biologists use structure rather than function to study evolution of life is because function is not commonly stored as information over time. It is the information contained in nature that allows us to reconstruct the past. Now, consider that ecosystems are cybernetic systems, and you can see how such a system would tend to evolve in such a way to maintain itself in a state of stability--and then we see a way to study natural selection based on study of those species whose "actions" help to maintain ecosystem stability--and that leads to study of such species that are coined "keystone species", e.g., those species who by their ecological "actions" help to maintain ecosystem stability over time. A very interesting aspect of biology--the relationship of structure to function.
     
  11. Jan 28, 2008 #10
    I have a looked at Lamarck's work and although it is a theory of actions it is different to what i am suggesting. i interpreted Lamarck's theory as: the actions of a species, as genarations pass, become more specific and advantageous for the enviroment they are in.
    Now what i am asking is that if we say that each organism is born with a set of possible actions for how it will act in an enviroment, and therefore its chances of survival, can this set of actions be used as structure is in Darwins theory of natural selection?
     
  12. Jan 28, 2008 #11

    Danger

    User Avatar
    Gold Member

    It seems to me that the semantics are too ambiguous to be dealt with scientifically. There is a distinct difference to me, for instance, between 'action', 'structure' and 'structured action'.
    By that same token, I can't see how an ecosystem can be called 'cybernetic' as Rade mentioned. The definition of 'cybernetic' that I grew up with was an interaction of some sort between biological entities and artificially created machines.
     
  13. Jan 28, 2008 #12
    What you describe here is called a "cyborg"--which is a type of cybernetic system--see here: http://en.wikipedia.org/wiki/Cyborg. The field of study called cybernetics is hugh--check out this review:http://en.wikipedia.org/wiki/Cybernetics

    As to ecosystems...there is a very nice book titled " Perspectives in Ecological Theory", 1968, Ramon Margalef, U. Chicago Press. The first chapter is titled, "The Ecosystem as a Cybernetic System". This book is a classic for those that study Ecology. Then, you will want to read the important work of Pattern and Odum from 1981 on this topic:
    http://links.jstor.org/sici?sici=0003-0147(198112)118:6<886:TCNOE>2.0.CO;2-P
     
  14. Jan 28, 2008 #13

    Moonbear

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    That is NOT what Lamarck's theory claimed. Indeed, what you're describing is more Darwinian.

    There is evolution of behavioral traits as well as physical traits, but it's important to keep in mind that those behavioral traits are based on structural traits and genetics as well, at least those that can be passed on to future generations as "innate" behaviors as opposed to learned behaviors.
     
  15. Jan 28, 2008 #14
    The set of "possible actions" that you look for that determines how an organism will act in an environment, as structure, are called genes found on chromosomes. Each organism is born with a set of genes (possible actions) that help determine how it will act to survive and reproduce. Natural selection is defined as the non random reproduction of genotypes.
     
    Last edited by a moderator: Jan 28, 2008
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Action v Structure
  1. Hairpin Structure (Replies: 1)

  2. Flower structure (Replies: 9)

  3. Cells and structure (Replies: 1)

  4. Genetic Structure (Replies: 3)

  5. Chromsome structure (Replies: 1)

Loading...