View Poll Results: Is a single celled human zygote an 'organism'?

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  • Yes, a single celled zygote is in fact an organism

    99 51.30%
  • No, a single celled zygote is not in fact an organism

    94 48.70%
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Thread: Is a single celled human zygote an 'organism'?

  1. #161
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    Question Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by iangb View Post
    Post #95!

    The dictionary says that an organism is an individual which is 'capable of independent existence'. The definition of viability says that a zygote is not capable of independent existence.
    Furthermore, the definition of the placenta says that the ZEF is 'a single unit' (united) with the mother, microchimerism shows that the ZEF exchanges cells with the mother (making it even less of an individual), the definition of the reproductive cycle says that a new individual is only produced by parturition (birth), and the definition of a zygote itself says that the single cell 'develops into' an organism, implying that it is not already an organism (because if this was not the case, the entire definition would be grammatically redundant).

    That's... four dictionary definitions and a cited wikipedia link.
    Ian,.. did you bother to also look up the word "existence?"
    Last edited by Chuz Life; 01-29-10 at 04:25 PM.

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    Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by Lakryte View Post
    Of course every cell in the human body is not an individual organism, hence the fact that humans are multicellular organisms. However, a zygote is a new organism. Its DNA is NOT identical to the somatic cells of either the mother or the father. (the claim you made is untrue).
    On average, any cell that divides by mitosis(somatic cells) makes about 100 mistakes per 3 billion base pairs(# of bp's in the human genome) during DNA replication, so even somatic cells most likely willl differ from one cell to another even in the organism's own body. Additionally, unicellular organisms that divide by mitosis are identical to the original cells aside from a few mutated base pairs, yet the one original organism makes two new organisms with nearly identical DNA. My point: DNA is NOT an accurate way to differentiate one organism from another.

    Quote Originally Posted by Tsunami View Post
    I don't know how you got three people to thank you for a post saying human egg cells are not alive. They do react to stimuli, hardening the zona pellucida when a sperm enters. They do develop, from germ cells to oogonia to oocytes, etc. They are part of a system that maintains homeostasis. They can reproduce through fertilization or parthenogenesis.

    Your criteria for life is too specific. Living organisms can be made up of living parts that do not fit all of these criteria independently. Egg and sperm cells are both living parts of the human organism.
    my criteria for life is broad. I said that for something to be living it must reproduce and metabolize (that is a VERY general description).

    Egg and sperms cells are "alive" in contrast to being "dead" cells, but they are not their own living organisms they are just cells that behave like somatic cells do, because they cannot divide by themselves, but rather they need the larger organism to allow them to do so, just as zygotes are not alive because they are apart of the larger organism that is allowing them to divide and grow.

    Place a zygote on a petri dish in womb like conditions, and it won't form a new organism.
    Place an ecoli. bacteria on a petri dish in intestine like conditions, and that colony will have grown exponentially.
    Haha. Panty Hawk. I would watch that show.

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    Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by phildozer9121 View Post
    Place a zygote on a petri dish in womb like conditions, and it won't form a new organism.
    Place an ecoli. bacteria on a petri dish in intestine like conditions, and that colony will have grown exponentially.
    The hell it won't.

    Someone needs to school your arse on "invitro fertilization."

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    Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by Tsunami View Post
    Living organisms can be made up of living parts that do not fit all of these criteria independently. Egg and sperm cells are both living parts of the human organism.
    Exactly.

    Quote Originally Posted by Tsunami View Post
    It is true that new DNA begins after fertilization, during the first mitosis. But if you define an organism by DNA that makes identical twins a part of the same organism. So I don't think DNA can be the defining characteristic.
    I did not mean to say DNA is the primary defining characteristic. I was just responding to a previous post that said the DNA of parent cells was identical to the the DNA of the zygote.

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    Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by phildozer9121 View Post
    On average, any cell that divides by mitosis(somatic cells) makes about 100 mistakes per 3 billion base pairs(# of bp's in the human genome) during DNA replication, so even somatic cells most likely willl differ from one cell to another even in the organism's own body. Additionally, unicellular organisms that divide by mitosis are identical to the original cells aside from a few mutated base pairs, yet the one original organism makes two new organisms with nearly identical DNA. My point: DNA is NOT an accurate way to differentiate one organism from another.
    The somatic cells that may have some mutations are still extremely similar to each other, but are not even close to being identical to the zygote. Unicellular organisms that divide through mitosis and asexual reproduction cannot be compared to human beings. My point about DNA is that human zygotes are not identical to either parent, and are therefore not part of either the mother or father's body.

    Quote Originally Posted by phildozer9121 View Post
    my criteria for life is broad. I said that for something to be living it must reproduce and metabolize (that is a VERY general description).
    A human baby cannot reproduce. Humans do not develop the ability to reproduce until they hit puberty. Does that make them not alive until then? No. Once again, those characteristics of life apply to an organism that will develop those abilities in its lifespan.

    Egg and sperms cells are "alive" in contrast to being "dead" cells, but they are not their own living organisms they are just cells that behave like somatic cells do, because they cannot divide by themselves, but rather they need the larger organism to allow them to do so, just as zygotes are not alive because they are apart of the larger organism that is allowing them to divide and grow.
    Nobody thinks that sperm and egg are separate living organisms. What you say is correct, they are alive. A zygote is not part of a larger organism. It is a different organism. Others have already proved this too you, I do not wish to be redundant.

    Place a zygote on a petri dish in womb like conditions, and it won't form a new organism.
    Not exactly true. In vitro fertilization should prove that to you. And a zygote is already an organism, so what you mean to say is it wont continue to develop.

    Place an ecoli. bacteria on a petri dish in intestine like conditions, and that colony will have grown exponentially.
    Of course it will! Bacteria reproduce asexually and just divide to create new organisms. Human organisms reproduce sexually, require the union of gametes to form a new organism, and that union first results in a zygote which is the first stage of development in human life. A human does not just decide to create another human by splitting in two.

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    Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by phildozer9121 View Post
    Place a zygote on a petri dish in womb like conditions, and it won't form a new organism.
    Why won't it?
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    Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by repeter View Post
    Why won't it?
    Because it already is one.

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    Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by Chuz Life View Post
    Because it already is one.
    I was referring to why it won't continue to further develop into a baby, in womb-like conditions.
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    Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by Lakryte View Post
    The somatic cells that may have some mutations are still extremely similar to each other, but are not even close to being identical to the zygote. Unicellular organisms that divide through mitosis and asexual reproduction cannot be compared to human beings. My point about DNA is that human zygotes are not identical to either parent, and are therefore not part of either the mother or father's body.
    Again I disagree with your using DNA for the criteria for what makes an organism. I can think of multiple examples where a single organism has more than a single DNA type contained in one body, including human chimeras and anyone who has received an organ donation.

    Nobody thinks that sperm and egg are separate living organisms. What you say is correct, they are alive. A zygote is not part of a larger organism. It is a different organism. Others have already proved this too you, I do not wish to be redundant.
    I do think an egg can be considered a separate living organism, depending upon the "separate" part. Sperm I'm not so sure about.

    And the zygote becomes part of the larger organism when it implants, though technically I guess it is a blastocyst rather than a zygote at that point.
    Of course it will! Bacteria reproduce asexually and just divide to create new organisms. Human organisms reproduce sexually, require the union of gametes to form a new organism, and that union first results in a zygote which is the first stage of development in human life. A human does not just decide to create another human by splitting in two.
    A zygote can create another zygote by splitting in two. Thus a zygote is not a human?

    And what makes the zygote the first stage? You can draw the line anywhere and call that "first" if you want to. The human reproductive cycle is just that, a cycle. It neither ends nor begins, it just continues.
    Last edited by Tsunami; 01-29-10 at 05:20 PM.
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    Re: Is a single celled human zygote an 'organism'?

    Quote Originally Posted by Lakryte View Post
    The somatic cells that may have some mutations are still extremely similar to each other, but are not even close to being identical to the zygote. Unicellular organisms that divide through mitosis and asexual reproduction cannot be compared to human beings. My point about DNA is that human zygotes are not identical to either parent, and are therefore not part of either the mother or father's body.


    A human baby cannot reproduce. Humans do not develop the ability to reproduce until they hit puberty. Does that make them not alive until then? No. Once again, those characteristics of life apply to an organism that will develop those abilities in its lifespan.


    Nobody thinks that sperm and egg are separate living organisms. What you say is correct, they are alive. A zygote is not part of a larger organism. It is a different organism. Others have already proved this too you, I do not wish to be redundant.


    Not exactly true. In vitro fertilization should prove that to you. And a zygote is already an organism, so what you mean to say is it wont continue to develop.


    Of course it will! Bacteria reproduce asexually and just divide to create new organisms. Human organisms reproduce sexually, require the union of gametes to form a new organism, and that union first results in a zygote which is the first stage of development in human life. A human does not just decide to create another human by splitting in two.
    The holes in your argument:
    1) Each and every zygote contains nearly identical DNA to the parental cells(differences occurring via mutation). you have 23 sets of chromosomes, each sets contains two homologous chromosomes, one from you father's sperm that is a identical copy of his chromosomes and one from your mother's egg which again, is an exact copy of her chromosomes. They are indeed parts of your mother and parts of your father. What you see in the child depends on allele expression, but i won't bore you with the details of that.

    2)I addressed this exact same point in an earlier post. Yes, babies cannot reproduce, but after birth they are no longer apart of the larger organism that is the mother and become their own organism. They have the means to grow by themselves, independant of the mother and will someday reproduce.

    3) please be redundant, because I have yet to hear an argument that has convinced me that life begins at conception

    4) In-vitro fertilization, if you care to note its name, is just that. Fertilization. Not growth. a fertilized egg won't grow on a petri dish because it's just not an organism, it can't grow by itself. like any other organism would be able too in their respective preferred environments.

    I understand what you're getting at, but I respectfully disagree. Anti-abortionists want zygotes to be new humans so that they can call abortions manslaughter, but all I'm saying is that biology doesn't support that claim. Zygotes can't grow independent of a larger organism, and all I am doing is making the case that because they can't divide or metabolize by
    themselves, as is required by the scientific definition of life.
    Haha. Panty Hawk. I would watch that show.

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