Is a single celled human zygote an 'organism'?

Tsunami said:

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.

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First of all,... there is more to the individuality of a newly formed zygote than just it's DNA. As a matter of physics (for example) two ojects can not be in the same place at the same time,...

Before I digress,...

"In the absense of twinning,... would not not agree that a zygote is in fact an organism? That,... the life it is living is it's own?

Chuz Life said:

First of all,... there is more to the individuality of a newly formed zygote than just it's DNA. As a matter of physics (for example) two ojects can not be in the same place at the same time,...

Before I digress,...

"In the absense of twinning,... would not not agree that a zygote is in fact an organism? That,... the life it is living is it's own?

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I have already pointed out that the answers to this question depend upon the definition of organism. So I assume you are asking for my personal definition. To me, an organism is a separate life form capable of sustaining itself. So:

• Even if viable, a fetus and the mother are still a part of the same living system, and thus are the same organism, until separated at birth.
• Conjoined twins are one organism even if they have two brains and are legally considered separate people, because they are connected and often cannot survive apart. If they are separated by surgery they become individual organisms.
• A male anglerfish is a separate organism until it attaches itself to a female. Afterwards it is unable to self-sustain and they become a single organism.
• A leech remains a separate organism while feeding off a host. In this case the physical attachment is voluntary and doesn't remove either organism's ability to survive independently.
• An ovum in a laboratory test tube is an organism. But if it is implanted and begins to live off someone else they become one organism.

As you can see, my opinion of an organism is independent from my opinion on personhood and would probably not make a good legal distinction. But it makes sense scientifically.

Tsunami said:

I have already pointed out that the answers to this question depend upon the definition of organism. So I assume you are asking for my personal definition. To me, an organism is a separate life form capable of sustaining itself. So:

• Even if viable, a fetus and the mother are still a part of the same living system, and thus are the same organism.
• Conjoined twins are one organism even if they have two brains and are legally considered separate people, because they are connected and often cannot survive apart. If they are separated by surgery they become individual organisms.
• A male anglerfish is a separate organism until it attaches itself to a female. Afterwards it is unable to self-sustain and they become a single organism.
• An ovum in a laboratory test tube is an organism. But if it is implanted and begins to live off someone else they become one organism.

As you can see, my opinion of an organism is independent from my opinion on personhood and would probably not make a good legal distinction. But it makes sense scientifically.

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you could make the argument a fish and the ocean are part of the same living system, or the bacteria in your gut are not organisms.
or perhaps a leach living off someone?
or any type of parasite or mutual symbiotic relationship?

independence is not a requirement for something to be an organism, all it has to do is be alive, which a cell is.

I can answer the entirety of Chuz's most recent post to me (#140) largely by quoting myself from this thread:

Chuz said:

The Poll results on this subject (as of right now) are three to one against your position, Ian. What percentage does it take to have a consensus? A majority? A Genereal agreement?

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iangb said:

If you can show that your 40-person voluntary-response poll of a political debate forum is representative of the scientific community and free from bias, you might have a point. However, I doubt that's going to happen.

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Change that to a '49-person poll' and add in the fact that it's closer to 2-to-one, and that's still an accurate response. Also...

iangb said:

I actually read through the thread itself an noticed something, Chuz. The poll says what it says - but if you look at the responses of the people who have posted here, many of those who voted 'yes' have a definition for 'organism' that differs from both mine and your use of the term - more specifically, they have one that also calls a skin/blood/sperm cell an organism.

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***

Chuz said:

What's say we have a contest? I'll post as many links to as many scientific sources that define a zygote as an organism,... and you provide as many as you can find where scientists say they are not.

(I've posted several, already)

At the end,... we will see which of us can support the notion of a "scientific consensus."

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iangb said:

many of Chuz's sources disagree with the dictionary use shown above. However, the vast majority of them only show scientific opinions, not the consensus which is needed to get a definition into a widely used dictionary as I have been using. The problem with relying on individual people/sites is that to argue based on such sources naturally biases the argument towards false positives - it's far more likely that someone will consider a zygote to be an organism and use that on their website than for someone to consider a zygote not to be an organism and post it - after all, a zygote is not a great many things, why should 'not an organism' be specifically listed unless an agenda is present, making for an easy dismissal of the source? Most of the places to be found where a scientist states that a zygote is 'not an organism' are when they have been directly asked the question

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In short - I posted dictionary links which supported my position, which is far more consensus than you can hope for. Also, it's an unfair 'contest' as it is skewed towards positive returns - there is little point in someone saying 'a zygote is not an organism', even if they consider it to be the case; it's like trying to find someone saying 'a zygote is not a teapot'.

Lakrite said:

No debate is necessary. An organism is a living being that has (or can develop) the ability to act or function independently. A human zygote is a human organism at the earliest stages of development. It is not developing into an organism, it is an organism that is continuing to develop into its full self. Babies and children are developing, but that does not automatically imply they are not organisms.

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A zygote is not 'a living being' in any way that differentiates it from a sperm cell.

Lakrite said:

The pile of ingredients is not analogous to the cake in its earliest stages of development, but rather to the sperm and egg. When they unite the "cake" or zygote (which is the organism) is brought into being.

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So a cake mix is a cake?

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).

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He did say 'almost identical'... Later on in pregnancy, immune cells with the ZEFs DNA often transfer to the mother and persist for quite some time. Given that they too differ from the DNA of the mother, your reasoning so far should claim that they are organisms in their own right.

Spud said:

how's that a contradiction, a single human skin cell is still an organism, even if i is part of a greater whole, amoeba are still organisms, and they're only a single cell, it is because of the actions of individual cells that a human can function, you can respond to stimuli, because the sensory neurons in your skin fire electro-chemical signals to the nerve cells in your brain. it is individual cells working as a whole that hadle everything your body does.

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Ah, apologies, I hadn't realised that you were using a different definition from both me and Chuz. Given your definition, I agree that there is no contradiction - by your definition, every cell in a persons body is an organism.
Out of interest, would you call a person (a collection of billions of organisms) an organism in their own right? If yes: if those billions of organisms are part of the whole person-organism, in what way is a zygote not part of that person-organism?

Maybe I'm just tired from lack of sleep,....

But something tells me we are now just beating some dead horses.

:beatdeadhorse:beatdeadhorse:beatdeadhorse

Quick poll,....

Is anyone still reading this exchange?

Is there any need or benefit for me to respond to Iangb any further in this vein?

Is there any need or benefit for me to respond to Iangb any further in this vein?

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If 'this vein' consists of repeating old arguments which I have already directly adressed - and then refusing to even acknowledge that I have done so - then I would definitely say there isn't much point.

The dictionary disagrees with you. Some scientists agree with you - but some disagree with you, too. You have yet to respond to arguments against your position beyond outright denial without reasoning, and you are repeating several arguments which have already been dealt with. I'd suggest you try a new vein.

iangb said:

If 'this vein' consists of repeating old arguments which I have already directly adressed - and then refusing to even acknowledge that I have done so - then I would definitely say there isn't much point.

The dictionary disagrees with you. Some scientists agree with you - but some disagree with you, too. You have yet to respond to arguments against your position beyond outright denial without reasoning, and you are repeating several arguments which have already been dealt with. I'd suggest you try a new vein.

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As I stated earlier,...

Chuz Life said:

(My philosophical) difference is that I think it's despicable to use the Constitution, the U.S. Code, precident, dictionary definitions and scientific findings to EXCLUDE that which is clearly the offspring of human sexual reproduction from 'personhood',.... rather than using those sources to INCLUDE and to protect them.

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If you posted a dictionary definition that refutes my conclusion (that a zygote is an organism),... it's buried now.

Would you like to repost it or link to it so I (and others) can know what it is you are talking about?

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.

Chuz Life said:

As I stated earlier,...



If you posted a dictionary definition that refutes my conclusion (that a zygote is an organism),... it's buried now.

Would you like to repost it or link to it so I (and others) can know what it is you are talking about?

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Hold on...so you're saying the only thing you will accept is your own view? Well, glad you told us that, we'll stop trying to reason with you :roll:

Chuz Life said:

Maybe I'm just tired from lack of sleep,....

But something tells me we are now just beating some dead horses.

:beatdeadhorse:beatdeadhorse:beatdeadhorse

Quick poll,....

Is anyone still reading this exchange?

Is there any need or benefit for me to respond to Iangb any further in this vein?

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No, he beat you down quite some time ago :lol:

iangb said:

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.

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Ian,.. did you bother to also look up the word "existence?"

Lakryte said:

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).

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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.

Tsunami said:

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.

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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.

phildozer9121 said:

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.

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The hell it won't.

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

Tsunami said:

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.

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Exactly.

Tsunami said:

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.

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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.

phildozer9121 said:

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.

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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.

phildozer9121 said:

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).

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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.

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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.

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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.

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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.

phildozer9121 said:

Place a zygote on a petri dish in womb like conditions, and it won't form a new organism.

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Why won't it?

repeter said:

Why won't it?

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Because it already is one.

Chuz Life said:

Because it already is one.

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I was referring to why it won't continue to further develop into a baby, in womb-like conditions.

Lakryte said:

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.

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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.

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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.

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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.

Lakryte said:

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.

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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.

Chuz said:

Ian,.. did you bother to also look up the word "existence?"

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Yes.
Existence:
–noun
1. the state or fact of existing; being.
2. continuance in being or life; life

Definition #1 would be redundant in the context of biology, as all things that might be confused for an organisms are capable of this - oh, and if you use this context, you have to include sperm and skin cells as being organisms. Hence my use of the second definition; life.

Any comment on the other dictionary bits?

phildozer9121 said:

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.

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[ame="http://en.wikipedia.org/wiki/In_vitro_fertilisation"]Selection[/ame]
Laboratories have developed grading methods to judge oocyte and embryo quality. Typically, embryos that have reached the 6-8 cell stage are transferred three days after retrieval. In many American and Australian programmes[citation needed], however, embryos are placed into an extended culture system with a transfer done at the blastocyst stage at around five days after retrieval, especially if many good-quality embryos are still available on day 3. Blastocyst stage transfers have been shown to result in higher pregnancy rates.[1] In Europe, transfers after 2 days are common. Preimplantation Genetic Diagnosis (PGD) procedures may be performed prior to transfer.[2]

Question: If the zygote (an organism) can't live in a petri dish,... how can it reach the "blastocyst" stage of it's life,... while still being in the petri dish?

Reaching the blastocyst stage isn't exactly baby stage is it? If we could just sprout children why bother with the pains of childbearing? After the food source of the egg is exhausted, it ends up as just a cluster of cells. It can't take in its own food. it can't metabolize, so it can't grow, ergo, it's not an organism.

phildozer9121 said:

Reaching the blastocyst stage isn't exactly baby stage is it? If we could just sprout children why bother with the pains of childbearing? After the food source of the egg is exhausted, it ends up as just a cluster of cells. It can't take in its own food. it can't metabolize, so it can't grow, ergo, it's not an organism.

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If it can't live or grow,... how does it go from a one celled zygote to a multicellular embryo? (again,... while still in the petri dish)

As I see it, it doesn't matter whether a zygote is an organism or not.
It doesn't matter if a zygote, or any form of it before or afterwards is alive, dead, or somewhere in the middle.

Still, no one would know when the future human actually became...human. And I don't mean in the biological sense. I mean in the sense of "sentience", or whatever. It’s biological “aliveness” has little or no effect on that debate.