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

Thoughts on Chloroplasts and Mitochodria

  1. Feb 22, 2007 #1
    I was looking into why chloroplasts and mitochondria have their own DNA seperate from the cells DNA.

    I found an interesting theory; Chloroplasts and Mitochodria were once single celled organisms. Another single celled organism consumes the mitocodria/chloroplast, but they continue to function.
    The cells work in symbiosis together, after millions of years the relationship has now become standard!

    Why do you think chloroplasts and mitochodria have their own DNA?
  2. jcsd
  3. Feb 22, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The endosymbiont theory (the one you outlined above) is the currently accepted theory of the origin of Mitochondria (AFAIK).
    Last edited: Feb 22, 2007
  4. Feb 22, 2007 #3
    Is the theory accepted for chloroplasts aswell?
    Are there any other widely accepted theories or is this the only one?
  5. Feb 22, 2007 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Lynn Margulis certainly thinks so; but I am not sure if other researchers accept her idea with regard to chloroplasts.
  6. Feb 22, 2007 #5
    Fair enough.

    The horrible thing about genetics and evolution is never really being able to prove anything.
  7. Feb 22, 2007 #6
    I'm not very well educated in biology, so do mitochondria do anything else except aerobic respiration?
    Do chloroplasts do anything else except photosynthesis?
    If not why would such organisms have independently evolved?
  8. Feb 22, 2007 #7
    Just to clarify. There is a massive amount of evidence in favor for evolution and genetics, both mathematical and experimental.
  9. Feb 22, 2007 #8
    I wasn't trying to put down genetics or evolution, it's just very difficult to actually prove any theories.

    It's not like we can travel back in time and actually say this evolved from that due to a mutation caused by natural selection.
    We can say such things with a certain degree of acuracy, but the fact remains there is no hard proof.

    Also some of the mathematics seems a bit odd to me e.g. The rate of mutation being recognised as linear.

    How do you prove that an isotope has a half-life of 5700years from 50years research(at most)?

    These points and more are why genetic research needs to be excelled.
  10. Feb 22, 2007 #9


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    How do you prove that an isotope has a half-life of 5700years from 50years research?

    Quite simple:
    The relative rate of decay is a CONSTANT.
    All you need to know in order to determine the half-life of the substance is the amount of stuff at two different instant.
  11. Feb 23, 2007 #10
    Yes I know, but if its really that simple why does such a small half-life (in terms of dating fossils) have a +/- 40 years? What kind of discrepenses can we expect for things such as Potassium with a half-life of 1.25billion years?

    Now can you explain why we would think the rate of mutation to be linear?
  12. Feb 23, 2007 #11
    Back on topic now.
    Why would mitochodria/chloroplasts have independently evolved?
    Can they store the products of their reactions by themselves?
  13. Feb 23, 2007 #12
    Last edited by a moderator: May 2, 2017
  14. Feb 24, 2007 #13
    Thankyou for the links.
    In the first though there is constant reference of billion years!
    The universe is only 6000MYA not 1*10^12, anyone know why this is?
  15. Feb 24, 2007 #14
    Just been reading the endosymbiotic theory link and I'd like to point out;

    "We will never be able to turn back the clocks, thus we will never be absolutely sure of the correct answer."
  16. Mar 20, 2010 #15
    Aye, but there's the rub:

    1) Relative rate of decay is not constant [though current experiments have only shown it varies by a bit]
    2) (More relevant) you said you have to know the "amount of stuff at two different instances," but of course that just gets us back to the original issue... one of those instances (the present) we can do...the other instant (the origin of the substance we care about) we obviously cannot do...because we cannot go back in time.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook