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Homework Help: Question about animals' change of number of legs when they grow

  1. Aug 31, 2011 #1
    I recently had a science exam and there is one question I would like to know about.

    Question: Some students noted the number of organisms living in a pond. The table below shows the number of plants and animals:


    Position in pond Number of plants

    Fully Submerged: 124

    Partially Submerged: 186

    Floating: 203



    Legs Number of Animals

    With no legs: 44

    With legs: 36

    One of the students commented that there are at least 6 different populations living in the pond. Is he correct?

    (a) Correct
    (b) Incorrect

    My answer was that he is incorrect since it is not possible to make such a conclusion from the data given as some animals like the tadpole have legs when they are adult frogs but not when they are younger. Also, slightly older tadpoles have legs while newborn ones don't.

    However, I was marked wrong and I would like to confirm here whether I am correct. Thanks.
  2. jcsd
  3. Aug 31, 2011 #2
    In such a scenario, the usage of the word 'population' is incorrect since it is defined for a group of individuals that belong to the same species. Are you sure that this was the exact question?
  4. Aug 31, 2011 #3
    Yes. That is what they meant. They are asking whether the statement is true or false.
  5. Aug 31, 2011 #4


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    Staff: Mentor

    Perhaps I am missing something, but for me it is either poorly worded, or poorly thought problem. Every floating plant I can imagine is partially submerged, yet number of partially submerged plants is lower than the number of floating plants.

    My guess is that it is the differences in numbers of plants that lead to the conclusion that there are at least 4 different species of plants in the pond. There are 203-186 plants that are floating without submerging, perhaps someone thought these are different from all other floating plants (or some similar way of thinking). But I don't think this conclusion was correct.
  6. Aug 31, 2011 #5


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    Staff Emeritus
    Science Advisor

    The term population does not make sense here. If we had a field and in it were 6 herds of cows they would each be a population however there is still one species in the field.

    If that is the question then it is flawed, you cannot answer A or B. From the data we can neither say yes or no.
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