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Thread: Moss lifecycle, asexual?

  1. #1 Moss lifecycle, asexual? 
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    Hello all, what a great resource! I just found it as I was researching for a unit on plants. Hopefully this is the appropriate place to post this and I can call on your expertise to answer a question that is driving me nuts. I'm a MS science teacher in Alaska and I'm trying to find some info out about the moss life cycle. I've read a lot of info online and even went back to my college text, but I've found some conflicting info.

    I know that moss can reproduce both sexually as well as asexually, but either I'm getting conflicting info or I'm just confusing myself.

    My students' textbook says this: In the other stage, asexual reproduction, a new plant is formed without the joining of an egg and sperm cell. A capsule on the stalk produces spores, or structures that contain cells that can grow into new plants without joining with other cells.

    I thought that the spores were a product of their sexual reproduction? This isn't really asexual reproduction, correct? THe egg and sperm cell had to join together to produce the gametophyte, sporophtye, etc.?

    Thanks in advance,

    WD


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  3. #2  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    My understanding is that asexual reproduction in mosses is simply caused by the separation of one part of the moss from another during the haploid stage.

    I would agree that the spores count as sexual reproduction, I'm not sure if any mosses produce asexual spores. I suppose it could be possible.

    However, there are also asexual reproductive structures called gemmae in some mosses.


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  4. #3  
    Forum Professor Zwirko's Avatar
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    In nature spores are generally haploid. The spores from the sporophyte are haploid and develop in to the male and female gametophytes (which are thus also haploid). The gametophyte then releases gametes for fertilisation - eggs from the female structures (archegonia) and sperm from the males strucures (antheridia). The resultant zygote then forms a new diploid sporophyte which then takes us back to start by using meiosis to produce more haploid spores.

    As I understand it, asexual reproduction in mosses occurs by small fragments of the plant detaching and forming new individuals. If I recall correctly there are also specialised structures for this called brood bodies.
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  5. #4 Asexual? 
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    Thanks guys, so it seems the book is wrong. The production of the spores is NOT an example of asexual reproduction. Correct?
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  6. #5  
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    Dear Broadie,

    I think you are correct. Sporulation in this case, is a pre-requisite to fusion of sperm and egg, and as such is a part of sexual reproduction. As has already been mentioned, some mosses are able to reproduce asexually - by forming brood bodies (small plantlets that detach from the parent plant and grow into a new, genetically-identical copy of their parent). So, it seems that the two processes are distinct. That being the case, it begs the question of why your text claims otherwise? I suppose nobody is infallible.

    All the best,

    Tridimity

    Ref. Campbell/Reece 'Biology' 8th Ed.
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