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Thread: Algae: plant or protist?

  1. #1 Algae: plant or protist? 
    Forum Freshman adamd164's Avatar
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    I've done a bit of reading on this, and seemingly it's a bit of a sticking point for many Biologists. Botanists often classify them as being simple plants, but I had always thought of them as Protists. Anyone care to share their opinions?


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  3. #2 Re: Algae: plant or protist? 
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    Quote Originally Posted by adamd164
    I've done a bit of reading on this, and seemingly it's a bit of a sticking point for many Biologists. Botanists often classify them as being simple plants, but I had always thought of them as Protists. Anyone care to share their opinions?
    Here's mine: 'protist' is not a clade, so I would be against any systematic classification, of any organism as protist.

    Also, algae may themselves not represent a clade, in which case there would be different classifications for different algae - some with the plants, some with rhodophytes(?I know I should look it up) and so on.


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  4. #3 Re: Algae: plant or protist? 
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    Quote Originally Posted by sunshinewarrio
    Quote Originally Posted by adamd164
    I've done a bit of reading on this, and seemingly it's a bit of a sticking point for many Biologists. Botanists often classify them as being simple plants, but I had always thought of them as Protists. Anyone care to share their opinions?
    Here's mine: 'protist' is not a clade, so I would be against any systematic classification, of any organism as protist.

    Also, algae may themselves not represent a clade, in which case there would be different classifications for different algae - some with the plants, some with rhodophytes(?I know I should look it up) and so on.
    Oh absolutely; there is no proper taxonomic kingdom of Protista, what I mean is, in common everyday useage, do more people tend still to refer to them as "protists" or "plants"?
    Knowledge of evolution may not be strictly useful in everyday commerce. You can live some sort of life and die without ever hearing the name of Darwin. But if, before you die, you want to understand why you lived in the first place, Darwinism is the one subject that you must study.

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  5. #4 Re: Algae: plant or protist? 
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by adamd164
    Quote Originally Posted by sunshinewarrio
    Quote Originally Posted by adamd164
    I've done a bit of reading on this, and seemingly it's a bit of a sticking point for many Biologists. Botanists often classify them as being simple plants, but I had always thought of them as Protists. Anyone care to share their opinions?
    Here's mine: 'protist' is not a clade, so I would be against any systematic classification, of any organism as protist.

    Also, algae may themselves not represent a clade, in which case there would be different classifications for different algae - some with the plants, some with rhodophytes(?I know I should look it up) and so on.
    Oh absolutely; there is no proper taxonomic kingdom of Protista, what I mean is, in common everyday useage, do more people tend still to refer to them as "protists" or "plants"?
    Ah, a language post, not a biology one? Perhaps better in the 'humanities' section?

    The reason modern taxonomy is Systematic (deliberate majuscule) is that it eliminates, in principle, inconsistencies. 'Common usage' has nothing to do with precision and hence cannot be prescribed - there's no 'should' about it. But... this is a language issue, then, not a biological one.
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  6. #5 Re: Algae: plant or protist? 
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    Quote Originally Posted by sunshinewarrio
    Ah, a language post, not a biology one? Perhaps better in the 'humanities' section?

    The reason modern taxonomy is Systematic (deliberate majuscule) is that it eliminates, in principle, inconsistencies. 'Common usage' has nothing to do with precision and hence cannot be prescribed - there's no 'should' about it. But... this is a language issue, then, not a biological one.
    Apologies, I know its not really an exact science; it's a pretty subjective issue. I simply wanted to get a flavour of the general consensus amongst those in the field, hence my posting it here.

    Technically, of course, the five kingdom classification paints an incomplete picture, and it's admittedly fallacious to lump all of the so-called "protists" together.
    Knowledge of evolution may not be strictly useful in everyday commerce. You can live some sort of life and die without ever hearing the name of Darwin. But if, before you die, you want to understand why you lived in the first place, Darwinism is the one subject that you must study.

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  7. #6 Re: Algae: plant or protist? 
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    Quote Originally Posted by adamd164
    Quote Originally Posted by sunshinewarrio
    Ah, a language post, not a biology one? Perhaps better in the 'humanities' section?

    The reason modern taxonomy is Systematic (deliberate majuscule) is that it eliminates, in principle, inconsistencies. 'Common usage' has nothing to do with precision and hence cannot be prescribed - there's no 'should' about it. But... this is a language issue, then, not a biological one.
    Apologies, I know its not really an exact science; it's a pretty subjective issue. I simply wanted to get a flavour of the general consensus amongst those in the field, hence my posting it here.

    Technically, of course, the five kingdom classification paints an incomplete picture, and it's admittedly fallacious to lump all of the so-called "protists" together.
    Well, I'm not sure which five kingdom classification you're talking about, but Protista is not an actual taxnomic group, but a term of convenience when talking about eukaryotic organisms that are highly primitive in many of their features (e.g., most are unicellular). Algae are deep within the plant lineage and they split from their common ancestor with land plants a long time ago. Green algae are most closely related to land plants, and most likely it was a green algal-like species that was the common ancestor of all land plants. Here is an article on algal and land plant phylogeny.
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    In no way, shape, or form are algae plants. Call them protists. Perhaps it is easiest to consider the phyla: Chlorophyta (Green algae), Phaeophyta (Brown algae), and Rhodophyta (Red algae). There are others, such as blue-green algae, which are bacteria, and etc, but protist is considered correct enough, generally speaking.

    That said, the five kingdom system is not used much among phylogenists anymore, (except perhaps for expedience on occasion?) It is my understanding that there may be 8, 13, 18 kingdoms or more - and of course the kingdom system is entirely different at the higher levels than the domain system (bacteria, archaea, and eukarya).

    See for example Cavalier-Smith, who proposed the kingdom Chromista for most algaes.

    The Chromista are a paraphyletic eukaryotic supergroup, which may be treated as a separate kingdom or included among the Protista. They include all algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them. These are surrounded by four membranes, and are believed to have been acquired from some red alga.
    http://en.wikipedia.org/wiki/Thomas_Cavalier-Smith
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    Quote Originally Posted by free radical
    In no way, shape, or form are algae plants. Call them protists. Perhaps it is easiest to consider the phyla: Chlorophyta (Green algae), Phaeophyta (Brown algae), and Rhodophyta (Red algae). There are others, such as blue-green algae, which are bacteria, and etc, but protist is considered correct enough, generally speaking.
    Protista is not a taxonomically correct clade. It is a paraphyletic grouping used as a term of convenience. I know algae are not plants but that is the "kingdom"to which they are most closely related.
    Man can will nothing unless he has first understood that he must count on no one but himself; that he is alone, abandoned on earth in the midst of his infinite responsibilities, without help, with no other aim than the one he sets himself, with no other destiny than the one he forges for himself on this earth.
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    By this argument an amoeba is a member of the animal kingdom.

    In any event, the rest of the earlier post, regarding Cavalier-Smith, was more pertinent.
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    Quote Originally Posted by free radical
    By this argument an amoeba is a member of the animal kingdom.
    I don't see why that's such a bad thing. If they fit into a monophyletic clade with animals, then I would find that to be an acceptable kingdom.

    I would not find this Chromista acceptable, however. As was discussed in another thread the purpose of modern taxonomic organization is to represent evolutionary relationships, not just the grouping of similar things together. Thus any clade that is paraphyletic and representative of more than one origin is not a correct or acceptable taxonomic group. Like protista it could be a term of convenience, but little more than that.
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  12. #11  
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    Quote Originally Posted by paralith
    Quote Originally Posted by free radical
    By this argument an amoeba is a member of the animal kingdom.
    I don't see why that's such a bad thing. If they fit into a monophyletic clade with animals, then I would find that to be an acceptable kingdom.

    I would not find this Chromista acceptable, however. As was discussed in another thread the purpose of modern taxonomic organization is to represent evolutionary relationships, not just the grouping of similar things together. Thus any clade that is paraphyletic and representative of more than one origin is not a correct or acceptable taxonomic group. Like protista it could be a term of convenience, but little more than that.
    On this one I'm on paralith's side - I cannot stand messiness in taxonomy and paraphyletic groupings are just wrong wrong wrong! (Putting obsession to work!)

    Here, for instance are some 'common' labels and some seemingly scientific labels, none of which has true cladistic meaning. Some are surprising, some well known:

    protista
    bacteria (probably - else archaea!)
    fish
    reptile
    monkey (!)
    dinosaur (most likely in terms of its common use)

    Dunno what you guys think but I'd rather avoid these unless they're being used in a strictly Systematic sense, and then that would preclude the use of the paraphyletic ones...
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    Quote Originally Posted by paralith
    Quote Originally Posted by free radical
    By this argument an amoeba is a member of the animal kingdom.
    I don't see why that's such a bad thing. If they fit into a monophyletic clade with animals, then I would find that to be an acceptable kingdom.
    I am almost certain this is not the outcome.

    I would not find this Chromista acceptable, however. As was discussed in another thread the purpose of modern taxonomic organization is to represent evolutionary relationships, not just the grouping of similar things together. Thus any clade that is paraphyletic and representative of more than one origin is not a correct or acceptable taxonomic group. Like protista it could be a term of convenience, but little more than that.
    By grouping algae with plants, (I believe) Plantae becomes a paraphyletic grouping.

    Common descent notwithstanding, there is far too much hgt (and such) to allow a strict monophyletic scheme for kingsdoms of life. Hence, 18 kingdoms in some schemes.

    Of course, we could fold it all back together into one kingdom.
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    I do think we tend to fetishise labels like 'kingdom'. Cladistically it has no function and is purely a subjective assessment of the 'importance' we attach to a particular group.

    I agree, however, that a complete monophyletic taxonomic structure is impossible in principle - bacterial DNA exchange would preclude it for one. Nevertheless I would prefer a scheme as close to the cladistic ideal as we can get. 18 kingdoms? I've no problem with 143, if it came to that...
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  15. #14  
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    Quote Originally Posted by free radical
    I am almost certain this is not the outcome.
    If you say so. As I placed algae nearer to plants based on evolutionary relationship and you said by that same reasoning amoeba would be grouped near animals, I assumed that meant that they share a close evolutionary relationship with the ancestors of animals.

    By grouping algae with plants, (I believe) Plantae becomes a paraphyletic grouping.

    Common descent notwithstanding, there is far too much hgt (and such) to allow a strict monophyletic scheme for kingsdoms of life. Hence, 18 kingdoms in some schemes.
    At the very least, green algae would group monophyletically with plants. That much I do know.

    As shanks says, I understand that not everything can be ideally taxonomically defined, but it should most certainly be the ideal we aim towards - and if that involves redefining kingdoms to a much larger number of them, than so be it. Algae do not, as far as I know, engage in any significant horizontal genetic exchange, so I think its quite reasonable to require that they be organized according to phylogenetic relationship.
    Man can will nothing unless he has first understood that he must count on no one but himself; that he is alone, abandoned on earth in the midst of his infinite responsibilities, without help, with no other aim than the one he sets himself, with no other destiny than the one he forges for himself on this earth.
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    I accept that paraphyletic clades can be "messy", but we must also remember that classification is only really a convenience; for this reason, I'd sooner term Algae 'Protists' than Plants to highlight the difference; as long, of course, as one understands that the name just refers to organisms which don't fit into any of the 4 other Kingdoms (Plantae, Monera, Animalia, Fungi). The reason I started this thread is that I see a widespread tendency to simply lump the Algae in with Plants.

    As for Amoebae, they don't form a monphyletic clade with Animals, rather the Flagellates do.
    Knowledge of evolution may not be strictly useful in everyday commerce. You can live some sort of life and die without ever hearing the name of Darwin. But if, before you die, you want to understand why you lived in the first place, Darwinism is the one subject that you must study.

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  17. #16  
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    Quote Originally Posted by adamd164
    I accept that paraphyletic clades can be "messy", but we must also remember that classification is only really a convenience;
    Taxonomy (good taxonomy) is more than just a convenience: bio-chemical similarities can make a huge difference to the ways in which we deal with ourselves and with other living organisms and good cladistic taxonomy makes this identification a lot easier.
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  18. #17  
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    Quote Originally Posted by sunshinewarrio
    protista
    bacteria (probably - else archaea!)
    fish
    reptile
    monkey (!)
    dinosaur (most likely in terms of its common use)
    Dunno what you guys think but I'd rather avoid these unless they're being used in a strictly Systematic sense, and then that would preclude the use of the paraphyletic ones...
    What was your objection to monkey? (I know this is lsightly off-topic, but the thread seems to be going in that different - and interesting- direction.)
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  19. #18  
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    Quote Originally Posted by Ophiolite
    Quote Originally Posted by sunshinewarrio
    protista
    bacteria (probably - else archaea!)
    fish
    reptile
    monkey (!)
    dinosaur (most likely in terms of its common use)
    Dunno what you guys think but I'd rather avoid these unless they're being used in a strictly Systematic sense, and then that would preclude the use of the paraphyletic ones...
    What was your objection to monkey? (I know this is lsightly off-topic, but the thread seems to be going in that different - and interesting- direction.)
    I was hoping someone would take the bait!

    Cladistically, 'Old World' monkeys and Apes (a genuine clade) are more closely related than either is to the 'New World' monkeys, whose lineage split off some time before the Old World monkey/ape lineage split. Thus, if you think a spider monkey is a Monkey (technically speaking) and a mandrill is a Monkey, then definitely all apes are monkeys (despite our being told time and time again at school and elsewhere that apes are not monkeys).

    If you don't accept apes as a sub-group of monkeys then you will have to invent new terms to describe the separate clades of Old World and New World 'monkeys'.

    Just another one of the beautifully counter-intuitive results that a strict application of cladistics produces.
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  20. #19  
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    Quote Originally Posted by sunshinewarrio
    Quote Originally Posted by adamd164
    I accept that paraphyletic clades can be "messy", but we must also remember that classification is only really a convenience;
    Taxonomy (good taxonomy) is more than just a convenience: bio-chemical similarities can make a huge difference to the ways in which we deal with ourselves and with other living organisms and good cladistic taxonomy makes this identification a lot easier.
    Yes, it does, and, in the strictest sense, the type of classification I am referring to is not toxonomic.
    Knowledge of evolution may not be strictly useful in everyday commerce. You can live some sort of life and die without ever hearing the name of Darwin. But if, before you die, you want to understand why you lived in the first place, Darwinism is the one subject that you must study.

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