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Quiz: why does a cow have 4 stomachs

  1. Dec 5, 2003 #1

    Monique

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    Anyone have an idea?
     
  2. jcsd
  3. Dec 5, 2003 #2

    iansmith

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  4. Dec 5, 2003 #3

    Monique

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    So why does the cow heavily rely on micro-organisms for its digestion? (it is an interesting issue)
     
  5. Dec 5, 2003 #4
    Cows rely on micro-organisms because, unlike "higher organisms", they can digest cellulose (~plant cell walls) and make it available for the cow's metabolic needs. Other herbivores utilize similar systems. I read that cows, like elephants, etc. are large partly because they need to carry around this large vat of digesting bacteria to process large amounts of relatively nutrient-poor grass.
     
  6. Dec 5, 2003 #5

    Monique

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    Don't you think that is strange? Cows don't have the enzyme to digest cellulose! The only thing they eat all day is nutrients with a very thick layer of cellulose around it!

    Didn't evolution do its work?

    Apparently it is much easier to change the body plan of an animal, by making four stomachs out of one, than it is to generate a novel enzyme :)

    I still find it strange though that the enzyme is missing, did we loose it in evolution or did it never exist in eukaryotes? And if it never existed, what did the ancestor live on?

    There is the same issue in humans, we also depend on the enzymes of micro-organisms for the digestion of our food.
     
  7. Dec 5, 2003 #6

    iansmith

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    That is a easy one. Cow cannot break down cellulose because it does not possess cellulase. Cellulase is produce by microorganism. Therefore, bacteria breaks down the cellulose and use it for fermentation. Fermentation produce nutrient for the cow. The cow absorb the fermentation produce and the digeste the dead micro-organism.
     
  8. Dec 5, 2003 #7

    Monique

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    The cow uses the fermentation product? I thought they actually break open a number of the bacteria after which the enzyme leaks into the environment and becomes available for the cow?

    and see my previous post for the other questions
     
  9. Dec 5, 2003 #8

    iansmith

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    Protozoan have the cellulase. There are the major cellulose digester in the cow. It appears that no animal have cellulase but I know there some studies done on grasing insect. There are trying to find if cellulose can be broke down without the micro-organism.


    Probably on the same thing. We eat salad but we don't get much out of it. Horse and rabbit have the fermentative pouch at the end of the G.I. track. They eat the feces to recylce the lost nutrients.

    We do not rely on bacteria and other micro-organism for the digestion of our food. Very few micro-organism in the human digestive track give something back and it is mostly vitamines.
     
  10. Dec 5, 2003 #9

    iansmith

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    What do you mean unlike higher organism? Only lower organism can break down cellulose.


    The cow also digest the dead mirco-organism but the fermentation product appears to be the major source of energy and nutrients.
     
  11. Dec 5, 2003 #10

    Monique

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    How many genes does the cow have? Is it still not strange it can't efficiently break down cellulose?

    It has to depend on lots of chewing, regurgitations, 4 stomachs with bacteria. How is the efficiency of absorbing nutrients with this system? I mean a percentage?
     
  12. Dec 5, 2003 #11

    iansmith

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    I don't know the efficiency of the process but how efficiently could a cow use the break-down cellulose? Also, how would the cow acqire the cellulase enzymes. The strategy employ by the cow is seen in all related animals, the ruminants. It has not been found in any animals so far.
     
  13. Dec 5, 2003 #12

    Monique

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    Euhh... how does an organism become an organism with a metabolism? By somehow modifying genes so to make the correct enzyme.

    So you really are not surprised that animals don't have a cellulase enzyme???

    When do you think that humans started eating meat? Evolutionarily very recent at the time that the Cro-Magnon appeared, some 50-35 ky ago. Only 3000 yrs ago (160 generations) did we start farming animals, we depended largely on plant material, how did we digest it without the help of bacteria?

    Why do we carry more bacteria with us than cells in our body? You are really saying they don't help in breaking down food for us?
     
  14. Dec 5, 2003 #13

    FZ+

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    Perhaps this is an example of co-evolution at work - the cow could have developed with these bacteria in its gut, and thus had little or no selective pressure to adapt its own system. Some other animals "farm" fungi, using them to help digest tough vegetation.

    I am not certain, but I think the appendix had something to do with it.
     
  15. Dec 5, 2003 #14

    Monique

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    Where did the cow come from then? Since none (I assume) of the (higher) eukaryotes have cellulase, we would have had to live in symbiosis with bacteria a very very long time. Then why is it that only the cow (and other remants? (deer, antelopes, cattle, sheep, and goats)) have multiple stomachs?

    Remember, I am also trying to think way back along the evolutionary line, since plants are the primary source of nutrition a eukaryotic cell would have been required to be able to digest it right?

    Ah, wait. I just thought of something: very young leaves contain very little cellulose, maybe way back there was an abundance of these young leaves and thus an enzyme would not be required. Then later on, the young leaves became more scarce and all of a sudden the need was there to digest the tougher older leaves. Since there wasn't enough time to evolve a new enzyme, another faster path was chosen, and that was the symbiosis with bacteria and adaption of the body plan to house these bacteria more efficiently.
     
  16. Dec 5, 2003 #15

    Monique

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    Good hypothesis?
     
  17. Dec 5, 2003 #16

    FZ+

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    You mean a gradual change from browsers to grazers?

    Sounds good to me, though my opinion means little...
     
  18. Dec 5, 2003 #17

    Monique

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    Gradual, but fast enought that it didn't allow for an enzyme to emerge from the chemistry of life. Emergency measures had to be taken, which was symbiosis followed by anatomical changes.

    I then wonder why deer, antelopes, cattle, sheep, and goats? Grass might be the clue.. when did grass start taking over the earth?
     
  19. Dec 5, 2003 #18

    iansmith

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    I am not suprised but if it is not present in any animals than is was probably not required.

    Chimp eat meat. So our ancestor must of eaten meat when they stated to arise. Also, inuit depends on meat only for their survival. Also the plant material that we utilize contain a higher concentration of other sugar than leaf materials. We eat the fruit, the grain and the roots. How much cellulose is present in those parts and what is the ratio digestible sugar to cellulose in those parts? We did not need the enzyme.

    Bacteria are only present in your large intestine. Your food is mostly digested at this point. Technically speaking, the rumen of the cow is a modified oesophagus. Birds also have this kind of pouch. It call the crop but it has another function. Most bacteria that we carry do not help at all. You got some on your skin, respiratory track (some people carry so nasty pathogens)and women have then in their reproductive track. It is theorize that in the intestine most bacteria are blocking the binding site for potential pathogens.

    Ruminants (cattles, sheep and goats) all have multiple stomach. The horse and rabbits have a modifed large intestine which serve the same function but absorbtion of nutrient is not as efficient as in the rumeninants.
     
  20. Dec 5, 2003 #19

    Monique

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    You should be surprised, since that will lead you to form hypotheses on why thing are the way they are.

    Wheeew! That is scientific thinking? First of all, since when are chimps carnivorous? Second: they could have started eating meat occasionally independently from the human line.

    Mostly on fats. This is not a good example of where evolution started with the development of an organism that required to get nutrition from another place than the sun.

    Well, maybe, it is hard to say whether the cave people were eating the leaves or not.

    I don't believe that, humans carry more bacteria in their mouth than a dog does.

    That is a valid argument, but we could just kill all the bacteria right? For some reason we kept them. How come only the good bacteria live inside of you?
     
  21. Dec 5, 2003 #20

    iansmith

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    Chimp eat small monkeys and they are good at it. It is not a major source of energy but they do it.
    http://www.sciam.com/article.cfm?articleID=00060CFC-D2D9-1C6F-84A9809EC588EF21
    We share a common ancestor and they could of had similar eating habits of the chimp. Also meat eating could of independently arise in human and chimp.

    Could a vegeterian adapted human survive so well in this enviroment. It does tell us how the organism started but it give some clues.

    If our ancestor were eating signifcantly large quantity of leaves would we keep the habit. What is the diet of "primitve" tribes? How much leaf component are they eating in their diet. I can give us significant inside to some of the eating habits of our ancestor. Chimp do have 20% of their diet compose of leaf.

    I long does our food stay in our mouth. It is not signficantfor bacteria to digest the food. Any way they will probably die in your stomach and what is left will not have a major impact on the digestion of the food.


    We do not only have good bacteria in inside us. Some peope carry virulent strain of Neisseria meningitis and Staphylococcus aureus in the nasal cavity, some carry Salmonella. Most species of bacteria inside will not harm us or will not be beneficial. We do not kill the bacteria inhabiting us because they adapted to us. Our insides is an excellent enviroment for them.
     
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