Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question about climax communities.

  1. May 28, 2004 #1
    I'm preparing for my Biology SATII, and I bought one of those review books with practice tests in them. This was one question, and I think that the answer they said was right isn't, can someone try to explain it to me, or confirm my doubts?

    "In a climax community, which of the following will be observed?

    A) The nitrogen cycle ceases to be important for primary producers

    B) There are no changes in seasonal population sizes within the community

    C) Predator-Prey relationships between trphic levels in the food web remain constant from one generation to the next

    D) There is no loss of energy from one trphic level to the next.

    E) There is only one species of primary producer."

    I chose E as the correct answer, the book said it was C.

    My reasoning was that there can only be one primary producer in any situation, because primary either means first or most important, both of which only one entity can hold the title of. Even if you have different species of grasses which feed most of the herbivores, one of them will be more prevalent, and therefore the "primary" producer.

    Perhaps I misread C, but I thought that it meant that the relative amount of animals in each species stays constant throught the generations, meaning that there's no fluxuation with alot of predators, few prey, then the predators dying and prey spawning rapidly, then more predators being born because of so much prey etc.

    I also read it as implying that if C were true, B would also have to be true.

    So is the book wrong, did I misread the question or was I just taught wrong and primary doesn't mean first/most important when talking about producers?
  2. jcsd
  3. May 28, 2004 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    In ecology pimary producer are define as which make up the trophic level of an ecosystem that ultimately supports all other levels. In other words, it is the first one to produce energy. So all plants the are primary producer but to species that is more prevalent is the dominant species not the "primary" species.

    (C) and (B) are not related. Predator-prey relation is usually defined as one organisms consumes a second organism. As define by (C), organism A will always feed on organism B, C, D or E at a given time. Populations will change for any organism at any given period of time. If Population of B decrease, A will consume B at a lower number which will an affect the population A. The predator will not stop eating it prey unless it disapper but it is not a climax community anymore because the system lost its sability.
  4. May 28, 2004 #3
    Ahh, thanks for the explanation, that makes sense, I guess I was just taught poorly or retained my teaching poorly.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook