Is an octopus an animal?
September 27, 2012 8:47 AM Subscribe
Is an octopus an animal?
This question arose in the case of a friendly discussion, and I don't have enough background knowledge to figure it out conclusively.
According to Wikipedia, an octopus is a 'cephalopod', meaning it's a member of the 'molluscan' class which is part of the 'Animalia' kingdom, meaning that is indeed an animal. Is this correct?
I think what I am looking for is a primer on the whole area of classification of living things that will put this into a broader context for me and give me a better intuitive sense of how it all works.
This question arose in the case of a friendly discussion, and I don't have enough background knowledge to figure it out conclusively.
According to Wikipedia, an octopus is a 'cephalopod', meaning it's a member of the 'molluscan' class which is part of the 'Animalia' kingdom, meaning that is indeed an animal. Is this correct?
I think what I am looking for is a primer on the whole area of classification of living things that will put this into a broader context for me and give me a better intuitive sense of how it all works.
Everything that has nerves are animals.
posted by Chocolate Pickle at 8:50 AM on September 27, 2012 [1 favorite]
posted by Chocolate Pickle at 8:50 AM on September 27, 2012 [1 favorite]
it is indeed an animal. You have several kingdoms-plantae (plants), fungi (fungus), protoctista and animalae (animals). I would suggest getting a freshman (college) level biology textbook from the library and start reading-it will cover all the biology basics
posted by bartonlong at 8:51 AM on September 27, 2012
posted by bartonlong at 8:51 AM on September 27, 2012
http://en.wikipedia.org/wiki/Biological_classification
posted by monju_bosatsu at 8:51 AM on September 27, 2012
posted by monju_bosatsu at 8:51 AM on September 27, 2012
This image gives a broad overview.
Here is a brief text description.
posted by Cygnet at 8:52 AM on September 27, 2012
Here is a brief text description.
posted by Cygnet at 8:52 AM on September 27, 2012
By the way, what you're talking about is called "taxonomy", and it's been in kind of a ferment over the last thirty years or so. Used to be a 3-kingdom system (animals, plants, fungi) and then there was a five kingdom system (adding prokaryotes and single-cell eukaryotes), and most recently we seem to be back to a three kingdom system (archaea, prokaryotes, eukaryotes including plants and animals and fungi).
In that latter, animals and plants are no longer "kingdoms" at all; they've been demoted a step. Even so, there's still a category called "animal" and the molluscs are unquestionably in that one.
posted by Chocolate Pickle at 8:54 AM on September 27, 2012 [8 favorites]
In that latter, animals and plants are no longer "kingdoms" at all; they've been demoted a step. Even so, there's still a category called "animal" and the molluscs are unquestionably in that one.
posted by Chocolate Pickle at 8:54 AM on September 27, 2012 [8 favorites]
Animals have several characteristics that set them apart from other living things. Animals are eukaryotic and mostly multicellular,[4] which separates them from bacteria and most protists. They are heterotrophic,[5] generally digesting food in an internal chamber, which separates them from plants and algae.[6] They are also distinguished from plants, algae, and fungi by lacking rigid cell walls.[7] All animals are motile,[8] if only at certain life stages. In most animals, embryos pass through a blastula stage,[9] which is a characteristic exclusive to animals. - Wikipedia
Yes.
posted by General Tonic at 8:56 AM on September 27, 2012
Yes.
posted by General Tonic at 8:56 AM on September 27, 2012
In terms of taxonomy, everything in the kingdom of Animalia is an animal. So yes, an octopus is an animal.
Colloquially, however, some people use the term to mean vertebrates. This is only colloquial and is not a term of classification. A while back, a news site reported that several new species of animal were found in a cave; some comments on the article were from people annoyed that the article had said animals but they'd turned out to be insects and the like. Again, this is only colloquial and varies from person to person.
Sometimes a difference may arise between people who are using the former definition, which is an actual scientific classification, and the latter definition, which is not.
posted by FAMOUS MONSTER at 8:56 AM on September 27, 2012 [1 favorite]
Colloquially, however, some people use the term to mean vertebrates. This is only colloquial and is not a term of classification. A while back, a news site reported that several new species of animal were found in a cave; some comments on the article were from people annoyed that the article had said animals but they'd turned out to be insects and the like. Again, this is only colloquial and varies from person to person.
Sometimes a difference may arise between people who are using the former definition, which is an actual scientific classification, and the latter definition, which is not.
posted by FAMOUS MONSTER at 8:56 AM on September 27, 2012 [1 favorite]
Colloquially, however, some people use the term to mean vertebrates. This is only colloquial and is not a term of classification.
Heck, I've heard people refer to "animals and birds" as if they were two different categories. But yeah, the scientific category of 'animal' most definitely includes the octopus.
I am curious as to what you thought it might be, if not an animal?
posted by showbiz_liz at 9:12 AM on September 27, 2012 [4 favorites]
Heck, I've heard people refer to "animals and birds" as if they were two different categories. But yeah, the scientific category of 'animal' most definitely includes the octopus.
I am curious as to what you thought it might be, if not an animal?
posted by showbiz_liz at 9:12 AM on September 27, 2012 [4 favorites]
Have you heard of the expression "animal, vegetable, or mineral"? That's the very most basic "rule of thumb" to go by when it comes to classifying naturally-occurring things*. Basically, it just means that if something isn't a plant and it isn't a rock, then it's an animal. And an octopus isn't a plant and it isn't a rock, ergo, it's an animal.
* I'm using the term "naturally-occurring things" to mean "things that man didn't make" -- because, obviously, things like tables are none of the above.
posted by EmpressCallipygos at 9:14 AM on September 27, 2012
* I'm using the term "naturally-occurring things" to mean "things that man didn't make" -- because, obviously, things like tables are none of the above.
posted by EmpressCallipygos at 9:14 AM on September 27, 2012
Usually the best definition of animal is that it, one way or another, eats things, and also that it moves. Fish eat things. Bugs eat things. Coral eats things! Now, the eating may be extremely passive at times, and the mobility may be incredibly slow or even strange—but in general, animals both 1. feed and 2. get around. By any remotely reasonable definition, an octopus is definitely an animal! But then so are sponges, corals, sea cucumbers. The fuzzy areas here get pretty remote!
posted by RJ Reynolds at 9:19 AM on September 27, 2012
posted by RJ Reynolds at 9:19 AM on September 27, 2012
Best answer: Lots of folks in this thread have already pretty much answered your question but I'd like to go into a little more detail. I'll be talking (like most people in this thread) about the technical definition of animal, rather than colloquial definitions which are often surprisingly hazy around the edges but which are of course valid in their own contexts. Since I'm a biology guy though and since the technical definition is the only one that's relatively unambiguous, that's the one I'm going to go with.
A concept that has been repeatedly mentioned here is taxonomy. Taxonomy, as others have said, is basically just a way of classifying organisms so that we can group them into useful categories that allow us to have a sense of how similar or how different two organisms are from each other. Nowadays taxonomy is undergoing a bit of a revolution because we're shifting from a purely morphological classification (which groups things based on how physically similar they are) to one that is also informed by genetic data (which often allows us a better sense of how closely related two organisms or groups of organisms are, or specifically how recently they shared a common ancestor). I work in a lab that does a lot of this sort of work and I could talk about it at some length but the relevant bit of information is that taxonomy is a system for classifying organisms based on how similar they are to each other.
One of the key concepts within taxonomy is the concept of hierarchical classification. That means that when classifying a species, we can do it by sorting it into more and more specific boxes, starting with the most general and then working down to the species level. It goes like this, in order of most general to most specific classification: Domain > Kingdom > Phylum > Class > Order > Family > Genus> Species. It actually gets considerably more complicated than that but for our purposes we don't have to care about that right now. Here's the classification for octopuses:
Domain: Eukarya. Any organism with nuclei in its cells belongs here. Octopuses have nuclei in their cells, so they are eukaryotes.
Kingdom: Animalia. Any eukaryote which is multicellular, eats things to obtain energy, and which is multicellular is an animal. Octopuses are eukaryotes and they meet these requirements, so they are animals.
Phylum: Mollusca. Any animal with a mantle, a shell which is made of calcium carbonate, and which also has a nervous system which conforms to a particular basic pattern is a mollusc. Octopuses are animals and they meet these requirements (their shell is modified into a sort of beak, but it was a shell in their ancestors) so they are molluscs.
Class: Cephalopoda. Any mollusc with bilateral symmetry, a well-defined head, and tentacles is a cephalopod. Octopuses are molluscs and the have all of these things, so they are molluscs.
Order: Octopoda. Any cephalopod with eight arms is an octopode. You can call anything in this category an octopus, but that's actually not always the best term because octopus can also refer to more specific groups (such as only the octopodes that fall into the genus Octopus). Either way though octopuses are cephalopods with eight arms, so they are definitely octopodes.
That's basically the classification. Drilling down a little further, most octopuses are found in the family "Octopodidae", and the species which we think of most often are found in the genus "Octopus". But anyway you don't have to go far to find out that octopuses are definitely animals!
I hope that clears things up in terms of shedding a little light on why octopuses are considered animals and how one can go about determining whether an arbitrary organism is an animal or not. Cheers!
posted by Scientist at 9:28 AM on September 27, 2012 [19 favorites]
A concept that has been repeatedly mentioned here is taxonomy. Taxonomy, as others have said, is basically just a way of classifying organisms so that we can group them into useful categories that allow us to have a sense of how similar or how different two organisms are from each other. Nowadays taxonomy is undergoing a bit of a revolution because we're shifting from a purely morphological classification (which groups things based on how physically similar they are) to one that is also informed by genetic data (which often allows us a better sense of how closely related two organisms or groups of organisms are, or specifically how recently they shared a common ancestor). I work in a lab that does a lot of this sort of work and I could talk about it at some length but the relevant bit of information is that taxonomy is a system for classifying organisms based on how similar they are to each other.
One of the key concepts within taxonomy is the concept of hierarchical classification. That means that when classifying a species, we can do it by sorting it into more and more specific boxes, starting with the most general and then working down to the species level. It goes like this, in order of most general to most specific classification: Domain > Kingdom > Phylum > Class > Order > Family > Genus> Species. It actually gets considerably more complicated than that but for our purposes we don't have to care about that right now. Here's the classification for octopuses:
Domain: Eukarya. Any organism with nuclei in its cells belongs here. Octopuses have nuclei in their cells, so they are eukaryotes.
Kingdom: Animalia. Any eukaryote which is multicellular, eats things to obtain energy, and which is multicellular is an animal. Octopuses are eukaryotes and they meet these requirements, so they are animals.
Phylum: Mollusca. Any animal with a mantle, a shell which is made of calcium carbonate, and which also has a nervous system which conforms to a particular basic pattern is a mollusc. Octopuses are animals and they meet these requirements (their shell is modified into a sort of beak, but it was a shell in their ancestors) so they are molluscs.
Class: Cephalopoda. Any mollusc with bilateral symmetry, a well-defined head, and tentacles is a cephalopod. Octopuses are molluscs and the have all of these things, so they are molluscs.
Order: Octopoda. Any cephalopod with eight arms is an octopode. You can call anything in this category an octopus, but that's actually not always the best term because octopus can also refer to more specific groups (such as only the octopodes that fall into the genus Octopus). Either way though octopuses are cephalopods with eight arms, so they are definitely octopodes.
That's basically the classification. Drilling down a little further, most octopuses are found in the family "Octopodidae", and the species which we think of most often are found in the genus "Octopus". But anyway you don't have to go far to find out that octopuses are definitely animals!
I hope that clears things up in terms of shedding a little light on why octopuses are considered animals and how one can go about determining whether an arbitrary organism is an animal or not. Cheers!
posted by Scientist at 9:28 AM on September 27, 2012 [19 favorites]
eats things, and also that it moves
The classical pathological response to that being, "so Fire is alive"? Classification is hard to get right.
posted by jeffamaphone at 9:30 AM on September 27, 2012
The classical pathological response to that being, "so Fire is alive"? Classification is hard to get right.
posted by jeffamaphone at 9:30 AM on September 27, 2012
Oh! I should have said that one of the important things about a hierarchical classification is that as you work your way down the ladder the categories get narrower and more specific and also are nested inside each other. So anything that fits into a specific box (like Cephalopoda) also fits into all the larger ones above it (like Mollusca, Animalia, and Eukarya). So for instance not all animals are molluscs, but all molluscs are animals. Does that make sense?
posted by Scientist at 9:38 AM on September 27, 2012
posted by Scientist at 9:38 AM on September 27, 2012
Correct me if I'm worng, but I believe some of the confusion is cultural - "The birds and the beasts and the fishes" - animals and beasts are sometimes used interchangeably in that sense. An octopus, who swims and breathes water like a fish, yet has limbs like a beast, may cause a bit of confusion as to where it lives in the order of things in that regard.
Scientifically, it's an animal.
Culturally, if you're from Western Europe, it's a fish. If you're a Catholic, you can eat it on Friday during Lent.
posted by Slap*Happy at 9:58 AM on September 27, 2012
Scientifically, it's an animal.
Culturally, if you're from Western Europe, it's a fish. If you're a Catholic, you can eat it on Friday during Lent.
posted by Slap*Happy at 9:58 AM on September 27, 2012
Fish are animals. And my son was sent to the office in grade 5 for insisting that insects are animals and not shutting up about it.
Everyone laughed at him. He was correct, of course.
posted by weapons-grade pandemonium at 10:01 AM on September 27, 2012 [6 favorites]
Everyone laughed at him. He was correct, of course.
posted by weapons-grade pandemonium at 10:01 AM on September 27, 2012 [6 favorites]
Culturally, if you're from Western Europe, it's a fish. If you're a Catholic, you can eat it on Friday during Lent.
Aren't fish animals? I guess this gets in to how some people eat fish, but call themselves vegetarians (instead of pescatarians).
posted by insectosaurus at 10:03 AM on September 27, 2012
Aren't fish animals? I guess this gets in to how some people eat fish, but call themselves vegetarians (instead of pescatarians).
posted by insectosaurus at 10:03 AM on September 27, 2012
I'm not saying octopi are fish. That fish comment was for Slap*Happy.
posted by weapons-grade pandemonium at 10:04 AM on September 27, 2012
posted by weapons-grade pandemonium at 10:04 AM on September 27, 2012
Best answer: I love this question. It's so deceptively simple and yet it highlights a whole host of epistemological issues surrounding the intersection of colloquial/cultural and technical/scientific ways of perceiving the world.
It is just as valid to say that an "animal" is anything that lives on land and has scales, feathers, or fur (which is my stab at the colloquial definition of animal, although really it's super hazy and not even self-consistent and really comes down to an "I know one when I see one" sort of assertion, not that that invalidates it in any way at all -- it's not like people in ancient times didn't know what they meant by the term "animal", they just had a much less precisely-bounded definition than the technical one that is sometimes used today) as it is to say that an "animal" is any eukaryotic organism which eats, has cells which lack rigid walls, and is multicellular.
The two definitions (although it's probably better to acknowledge a myriad of definitions on the colloquial side and at least two or three competing ones on the scientific side) have a coexistence in our society that usually prevents them from fighting or indeed even noticing each other, but then when you try to nail down a consensus once and for all regarding whether an octopus is or is not an animal, you can see the friction and the contradiction.
I love it. I'm a scientist, but I don't want to live in a world where the only definition of an animal is "a multicellular hetertrophic eukaryote whose cells lack rigid walls". I'd prefer it if more people knew that definition and understood why it was a useful one to have, but I'd hardly ask that all the other subjective, hazy, commonsense definitions be erased from the cultural consciousness. We'd all be much poorer for that.
posted by Scientist at 10:32 AM on September 27, 2012 [3 favorites]
It is just as valid to say that an "animal" is anything that lives on land and has scales, feathers, or fur (which is my stab at the colloquial definition of animal, although really it's super hazy and not even self-consistent and really comes down to an "I know one when I see one" sort of assertion, not that that invalidates it in any way at all -- it's not like people in ancient times didn't know what they meant by the term "animal", they just had a much less precisely-bounded definition than the technical one that is sometimes used today) as it is to say that an "animal" is any eukaryotic organism which eats, has cells which lack rigid walls, and is multicellular.
The two definitions (although it's probably better to acknowledge a myriad of definitions on the colloquial side and at least two or three competing ones on the scientific side) have a coexistence in our society that usually prevents them from fighting or indeed even noticing each other, but then when you try to nail down a consensus once and for all regarding whether an octopus is or is not an animal, you can see the friction and the contradiction.
I love it. I'm a scientist, but I don't want to live in a world where the only definition of an animal is "a multicellular hetertrophic eukaryote whose cells lack rigid walls". I'd prefer it if more people knew that definition and understood why it was a useful one to have, but I'd hardly ask that all the other subjective, hazy, commonsense definitions be erased from the cultural consciousness. We'd all be much poorer for that.
posted by Scientist at 10:32 AM on September 27, 2012 [3 favorites]
Response by poster: I am curious as to what you thought it might be, if not an animal?
It was that line of thinking that led to this question :-)
Thanks everyone for the super-helpful answers.
posted by StephenF at 10:35 AM on September 27, 2012
It was that line of thinking that led to this question :-)
Thanks everyone for the super-helpful answers.
posted by StephenF at 10:35 AM on September 27, 2012
Yes, (with the exception of the tree octopus...that does not actually exist) and insects are animals too...fun insect fact...if you take all the ants in the world and put them on a scale, then did the same with ALL of the other insects AND all of the other animals...the ants would weigh more (!)
Also, EmpressCallipygos, I have a lovely marble tabletop that would argue otherwise... :)
posted by sexyrobot at 10:35 AM on September 27, 2012
Also, EmpressCallipygos, I have a lovely marble tabletop that would argue otherwise... :)
posted by sexyrobot at 10:35 AM on September 27, 2012
Best answer: Oh hi! Semanticist here! What's going on is, scientific English and colloquial English define the word "animal" differently.
In a scientific context, yes, you use the word "animal" in a way that includes octopuses. A lot of people get taught in school that this is the One True Correct Way to use the word, and so if you give them time to sit and think about it, they'll tell you "Yes, an octopus is an animal." But in fact, very few people are naturally inclined to use the word "animal" that way on the spur of the moment. Because in colloquial, non-scientific English, that's really not what the word means.
Think about it this way. If a bear or a moose or a rabid squirrel starts chasing you, and you're too flustered to identify it by species, you might well say "Oh god, there's this ANIMAL coming after me!" But if it's a spider or a bee or a centipede, you probably wouldn't say that. (More likely: "Oh god, there's this BUG coming after me!") And similarly with an octopus or a jellyfish; even if you're too flustered to come up with the word "octopus" or "jellyfish," your first reaction wouldn't be to call it an animal. (More likely: "Oh god, there's this THING/CREATURE coming after me!")
And what that tells you is, your gut reaction, when you're speaking colloquially and not worrying about what your science teacher would think, is to use the word "animal" in a way that includes squirrels but not bees or octopuses.
(Interestingly, in other languages, the gut-reaction top-of-the-head categories are put together differently! Right now I'm studying a Mayan language where squirrels and bees go in the same category, and cows go in a different category. If a squirrel or a bee is chasing you you say "Oh god there's this chikop coming after me!", but if a cow is chasing you you say "Oh god there's this awaj coming after me!" And it's the same way with the scientific definitions there: people who have gone to enough school and paid enough attention know that technically, squirrels and bees and cows all go in one category together. But still, in normal conversation, they categorize things according to the colloquial language and not according to the scientific definitions.)
So I mean, if a buddy of yours is telling a story about some "animal," and it turns out that the "animal" is an octopus, it would be totally fair to say "Dude, that's a kind of misleading way to put it." But if a science teacher in a classroom setting is talking about an "animal" that turns out to be an octopus, then that's reasonable and not misleading at all. It all depends on context.
posted by nebulawindphone at 10:58 AM on September 27, 2012 [12 favorites]
In a scientific context, yes, you use the word "animal" in a way that includes octopuses. A lot of people get taught in school that this is the One True Correct Way to use the word, and so if you give them time to sit and think about it, they'll tell you "Yes, an octopus is an animal." But in fact, very few people are naturally inclined to use the word "animal" that way on the spur of the moment. Because in colloquial, non-scientific English, that's really not what the word means.
Think about it this way. If a bear or a moose or a rabid squirrel starts chasing you, and you're too flustered to identify it by species, you might well say "Oh god, there's this ANIMAL coming after me!" But if it's a spider or a bee or a centipede, you probably wouldn't say that. (More likely: "Oh god, there's this BUG coming after me!") And similarly with an octopus or a jellyfish; even if you're too flustered to come up with the word "octopus" or "jellyfish," your first reaction wouldn't be to call it an animal. (More likely: "Oh god, there's this THING/CREATURE coming after me!")
And what that tells you is, your gut reaction, when you're speaking colloquially and not worrying about what your science teacher would think, is to use the word "animal" in a way that includes squirrels but not bees or octopuses.
(Interestingly, in other languages, the gut-reaction top-of-the-head categories are put together differently! Right now I'm studying a Mayan language where squirrels and bees go in the same category, and cows go in a different category. If a squirrel or a bee is chasing you you say "Oh god there's this chikop coming after me!", but if a cow is chasing you you say "Oh god there's this awaj coming after me!" And it's the same way with the scientific definitions there: people who have gone to enough school and paid enough attention know that technically, squirrels and bees and cows all go in one category together. But still, in normal conversation, they categorize things according to the colloquial language and not according to the scientific definitions.)
So I mean, if a buddy of yours is telling a story about some "animal," and it turns out that the "animal" is an octopus, it would be totally fair to say "Dude, that's a kind of misleading way to put it." But if a science teacher in a classroom setting is talking about an "animal" that turns out to be an octopus, then that's reasonable and not misleading at all. It all depends on context.
posted by nebulawindphone at 10:58 AM on September 27, 2012 [12 favorites]
These things can be tricky. I once asked a biology prof what a mammal was, and he replied that if it had hair and milk, it was a mammal. I asked "oh, like a coconut?" and got a dirty look. But at least this proves that octopuses aren't mammals (not, at least, without a fur coat and a bottle of milk).
posted by ubiquity at 11:00 AM on September 27, 2012 [5 favorites]
posted by ubiquity at 11:00 AM on September 27, 2012 [5 favorites]
By the way, if you've never seen an Octopus in person, go to your local friendly aquarium and stare one in the eyes. If this thread hasn't resolved the issue for you, meeting one will.
posted by jeffamaphone at 11:40 AM on September 27, 2012 [1 favorite]
posted by jeffamaphone at 11:40 AM on September 27, 2012 [1 favorite]
I think meeting an octopus might if anything lead one to the conclusion that octopuses are alien colonists whose biology conforms to no know earthly rules or classifications, honestly. Not that one shouldn't go find one, they're super cool. Just don't expect the experience to resolve more questions than it creates. :-)
posted by Scientist at 12:24 PM on September 27, 2012 [1 favorite]
posted by Scientist at 12:24 PM on September 27, 2012 [1 favorite]
Culturally, if you're from Western Europe, it's a fish.
I'm from Western Europe and I don't feel like it's a fish. I feel like even millennia before we sorted it into any sort of mollusc phylum, cephalopoda class, it would have been considered, "culturally" and in people's internal mental/linguistic models, as separate to fish; under some sort of "sea-monster" or "tentacle-y thing" category, perhaps.
But this is total layman speculation and biased by my highly subjective perception of words. I'm struggling to think of anyone I've known who didn't think of fishes and mammals and birds as all subsets of "animals", which seems at odds to most in this thread, so clearly my perception is not that representative. It's an interesting rabbit hole to lose oneself down, anyway.
posted by Slyfen at 12:43 PM on September 27, 2012
I'm from Western Europe and I don't feel like it's a fish. I feel like even millennia before we sorted it into any sort of mollusc phylum, cephalopoda class, it would have been considered, "culturally" and in people's internal mental/linguistic models, as separate to fish; under some sort of "sea-monster" or "tentacle-y thing" category, perhaps.
But this is total layman speculation and biased by my highly subjective perception of words. I'm struggling to think of anyone I've known who didn't think of fishes and mammals and birds as all subsets of "animals", which seems at odds to most in this thread, so clearly my perception is not that representative. It's an interesting rabbit hole to lose oneself down, anyway.
posted by Slyfen at 12:43 PM on September 27, 2012
Kingdom: Animalia. Any eukaryote which is multicellular, eats things to obtain energy, and which is multicellular is an animal. Octopuses are eukaryotes and they meet these requirements, so they are animals.
There are plenty of plant and fungi which are heterotrophs (things that eat other things to obtain energy).
Frankly, when I had to define the distinguishing feature of Animalia as part of my Quals, I was stumped. I waffled a bit on "multicellular eukaryotes with a distinctive body plan" and the professor who'd posed the question suggested the answer was "organisms with homeobox genes". (Homeobox genes are genes which define the basic body plan of animals, and are super conserved across taxa. The same genetic programming underlies your eyes and a fruit fly's. Wackadoodle, I know.)
For MOST cases, we know what are animals and what are not. "I know it when I see it". But it gets really rough at the fringe cases -- sponges are animals, for instance, though they're Metazoa and not Eumetazoa. Which are the animals, except sponges.
And I read once -- maybe in Stephen Jay Gould? -- that under Catholic fast-day taxonomy, fetal rabbits are "fish". Because the amniotic fluid is like seawater. Okidoke!
posted by endless_forms at 1:08 PM on September 27, 2012 [2 favorites]
There are plenty of plant and fungi which are heterotrophs (things that eat other things to obtain energy).
Frankly, when I had to define the distinguishing feature of Animalia as part of my Quals, I was stumped. I waffled a bit on "multicellular eukaryotes with a distinctive body plan" and the professor who'd posed the question suggested the answer was "organisms with homeobox genes". (Homeobox genes are genes which define the basic body plan of animals, and are super conserved across taxa. The same genetic programming underlies your eyes and a fruit fly's. Wackadoodle, I know.)
For MOST cases, we know what are animals and what are not. "I know it when I see it". But it gets really rough at the fringe cases -- sponges are animals, for instance, though they're Metazoa and not Eumetazoa. Which are the animals, except sponges.
And I read once -- maybe in Stephen Jay Gould? -- that under Catholic fast-day taxonomy, fetal rabbits are "fish". Because the amniotic fluid is like seawater. Okidoke!
posted by endless_forms at 1:08 PM on September 27, 2012 [2 favorites]
I think meeting an octopus might if anything lead one to the conclusion that octopuses are alien colonists whose biology conforms to no know earthly rules or classifications, honestly. Not that one shouldn't go find one, they're super cool. Just don't expect the experience to resolve more questions than it creates. :-)
posted by Scientist at 3:24 PM on September 27 [1 favorite +] [!]
Octopuses are the actual chosen of God, for whom this world was created. I mean, jeez louise, how much of this planet is ocean?
posted by endless_forms at 1:11 PM on September 27, 2012
posted by Scientist at 3:24 PM on September 27 [1 favorite +] [!]
Octopuses are the actual chosen of God, for whom this world was created. I mean, jeez louise, how much of this planet is ocean?
posted by endless_forms at 1:11 PM on September 27, 2012
I'm from Western Europe and I don't feel like it's a fish. I feel like even millennia before we sorted it into any sort of mollusc phylum, cephalopoda class, it would have been considered, "culturally" and in people's internal mental/linguistic models, as separate to fish; under some sort of "sea-monster" or "tentacle-y thing" category, perhaps.
Aristotle created the taxon Mollusca for all the soft and squishy things. So it's been in "things that go skoosh" for a long time.
I don't recommend skooshing octopuses. They're probably smarter than you, and besides, you'll make baby octopus Jesus mad.
posted by endless_forms at 1:13 PM on September 27, 2012
Aristotle created the taxon Mollusca for all the soft and squishy things. So it's been in "things that go skoosh" for a long time.
I don't recommend skooshing octopuses. They're probably smarter than you, and besides, you'll make baby octopus Jesus mad.
posted by endless_forms at 1:13 PM on September 27, 2012
By any remotely reasonable definition, an octopus is definitely an animal! But then so are sponges, corals, sea cucumbers. The fuzzy areas here get pretty remote!
And the sea cucumber is much more closely related to you and me than the octopus is.
I mean, assuming you are also a human being. If you're an octopus, disregard.
posted by endless_forms at 1:17 PM on September 27, 2012
And the sea cucumber is much more closely related to you and me than the octopus is.
I mean, assuming you are also a human being. If you're an octopus, disregard.
posted by endless_forms at 1:17 PM on September 27, 2012
Aristotle created the taxon Mollusca for all the soft and squishy things. So it's been in "things that go skoosh" for a long time.
Thanks for the info. Aristotle, eh? I was thinking since my last post, if I were to try and classify sealife based only on what I've seen in the wild, with zero scientific knowledge/reading available to me, and not making any effort to collect samples and rigorously observe and measure them, I'd probably get as far as: fish, shelled things, grey cow things, jellyfish. If I then was presented with an octopus I'd probably put it in with jellyfish. I would personally imagine the most basic humans having "fish" and "not fish" mental buckets for sealife, with octopodes in the latter.
posted by Slyfen at 1:32 PM on September 27, 2012
Thanks for the info. Aristotle, eh? I was thinking since my last post, if I were to try and classify sealife based only on what I've seen in the wild, with zero scientific knowledge/reading available to me, and not making any effort to collect samples and rigorously observe and measure them, I'd probably get as far as: fish, shelled things, grey cow things, jellyfish. If I then was presented with an octopus I'd probably put it in with jellyfish. I would personally imagine the most basic humans having "fish" and "not fish" mental buckets for sealife, with octopodes in the latter.
posted by Slyfen at 1:32 PM on September 27, 2012
I can also see food and not-food being two simple buckets that would naturally occur. So octopi are "not-fish, but food".
posted by jeffamaphone at 1:35 PM on September 27, 2012
posted by jeffamaphone at 1:35 PM on September 27, 2012
endless_forms, I apparently goofed when editing my answer up there, thanks for pointing it out. I intended to write "any eukaryote which is multicellular, eats things to obtain energy, and lacks rigid cell walls belongs in the Kingdom Anamalia" or something to that effect. You rightly point out that some plants and fungi are multicellular and consume things for energy (are heterotrophs) but they all have cell walls made either of cellulose (plants) or chitin (fungi). Animals have squishy cells with no walls, and that's a key distinguishing characteristic. Sorry for messing that up. I meant to put that in but somehow borked it and put "multicellular" twice instead.
posted by Scientist at 2:05 PM on September 27, 2012
posted by Scientist at 2:05 PM on September 27, 2012
Yeah, I noticed that you specified "without rigid cell walls" elsewhere, and I think that covers it. It just goes to show, though, how difficult these defining characters are.
And it looks like *I* goofed -- Aristotle's Mollusca was just the cephalopods; all the other non-arthropod non-vertebrates were Testacea. It was Linneaus, much later, who grouped all the "things that go goosh" under Mollusca.
posted by endless_forms at 2:11 PM on September 27, 2012
And it looks like *I* goofed -- Aristotle's Mollusca was just the cephalopods; all the other non-arthropod non-vertebrates were Testacea. It was Linneaus, much later, who grouped all the "things that go goosh" under Mollusca.
posted by endless_forms at 2:11 PM on September 27, 2012
Best answer: Science (and taxonomy) is so cool!
As someone who works in biology, I can see the use of both common (colloquial) and scientific names. Just this summer I was working with an American team as the official 'fish species identifier'. For the most part we used common names because it was just easier. Everyone who has grown up fishing knows what a largemouth bass is, there was no need to know a bunch of Latin words that may or may not have meaning to you.
That being said, when they started talking about sheepheads and I had no idea what they were talking about, they were able to translate that to Aplodinotus grunniens, which I could then translate to freshwater drum. (Also, whatever you do, do not tell someone from Minnesota that pickeral and walleye are the same species. They will laugh at you for an entire summer)
One of the most important and useful things about scientific names is that it is a standardized system across the entire world. I can read a paper by researchers in Japan or Sweden and know exactly which species they are talking about. It works as a shared language amoung scientists.
That being said, taxonomy can be a highly debated field. Basic concepts that seam obvious like "a species" can be really hard to define. Someone might tell you that if two individuals can interbreed, they are the same species, but what if they can breed, but their offspring are sterile. Likewise, what if two individuals could breed and produce an offspring, but there is some small behavioural trait that stops waht is otherwise physiologically possible? And what about the fact a large amount (most?) of life doesn't even breed?.
And there I go, using an ambiguous term like "life" when scientists can't even produce a universally agreed upon definition.
If you want to delve a little deeper, there are a few resources online that can be fun to poke around on:
- The Tree of Life Project is an attempt to catalogue all known life (which is quite ambitious when you consider that a database containing only fish can be still quite complicated)
- Animal Diversity Web focuses just on Animalia and can be searched by common or scientific name. In the future, if you are curious about a group you can check that out.
- DNA Barcoding is an attempt to look at a standardized part of the DNA of EVERY species and determine a unique sequence (like a barcode) that can identify it.
- Finally, if you want to start at the beginning (of modern scientific classification) you're best to start off with the man himself Carl Linnaeus
posted by Midnight Rambler at 2:15 PM on September 27, 2012 [1 favorite]
As someone who works in biology, I can see the use of both common (colloquial) and scientific names. Just this summer I was working with an American team as the official 'fish species identifier'. For the most part we used common names because it was just easier. Everyone who has grown up fishing knows what a largemouth bass is, there was no need to know a bunch of Latin words that may or may not have meaning to you.
That being said, when they started talking about sheepheads and I had no idea what they were talking about, they were able to translate that to Aplodinotus grunniens, which I could then translate to freshwater drum. (Also, whatever you do, do not tell someone from Minnesota that pickeral and walleye are the same species. They will laugh at you for an entire summer)
One of the most important and useful things about scientific names is that it is a standardized system across the entire world. I can read a paper by researchers in Japan or Sweden and know exactly which species they are talking about. It works as a shared language amoung scientists.
That being said, taxonomy can be a highly debated field. Basic concepts that seam obvious like "a species" can be really hard to define. Someone might tell you that if two individuals can interbreed, they are the same species, but what if they can breed, but their offspring are sterile. Likewise, what if two individuals could breed and produce an offspring, but there is some small behavioural trait that stops waht is otherwise physiologically possible? And what about the fact a large amount (most?) of life doesn't even breed?.
And there I go, using an ambiguous term like "life" when scientists can't even produce a universally agreed upon definition.
If you want to delve a little deeper, there are a few resources online that can be fun to poke around on:
- The Tree of Life Project is an attempt to catalogue all known life (which is quite ambitious when you consider that a database containing only fish can be still quite complicated)
- Animal Diversity Web focuses just on Animalia and can be searched by common or scientific name. In the future, if you are curious about a group you can check that out.
- DNA Barcoding is an attempt to look at a standardized part of the DNA of EVERY species and determine a unique sequence (like a barcode) that can identify it.
- Finally, if you want to start at the beginning (of modern scientific classification) you're best to start off with the man himself Carl Linnaeus
posted by Midnight Rambler at 2:15 PM on September 27, 2012 [1 favorite]
Culturally, if you're from Western Europe, it's a fish. If you're a Catholic, you can eat it on Friday during Lent.
If you're Jewish, it's not a fish and you can't eat it at all.
posted by Pallas Athena at 3:02 PM on September 27, 2012
If you're Jewish, it's not a fish and you can't eat it at all.
posted by Pallas Athena at 3:02 PM on September 27, 2012
I never had any trouble thinking of an octopus as an animal, but I was shocked to learn recently that I feel viscerally different about clams. In my mental model of the world a clam is not an animal at all. How can they possibly be in the same family as octopuses and cuttlefish and slugs and snails? Living things are so bizarre.
posted by fantabulous timewaster at 9:28 PM on October 1, 2012
posted by fantabulous timewaster at 9:28 PM on October 1, 2012
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