Meiosis160-page5 - A pollen grain of pine tree or flower,...

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Meiosis and Life Cycles - 5 Alternation of Generations Most plants have both a multicellular haploid stage and a multicellular diploid stage in their life histories. This is called the alternation of generations. In plants, the structure in which meiosis occurs is called a sporangium. Meiosis does not directly produce gametes, but produces haploid cells, called spores that in turn, grow, by mitosis, into multicellular haploid structures called gametophytes (gamete-making plant). Gametophytes eventually produce and contain gametes. (The multicellular diploid structures that produce sporangia are called sporophytes.) Which stage (sporophyte or gametophyte) is predominant in the life of a plant varies with different types of plants. Most "higher" plants have predominant sporophytes.
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Unformatted text preview: A pollen grain of pine tree or flower, for example is the male gametophyte stage of those plants. In ferns, both gametophyte and sporophyte are photosynthetic, but the gametophyte is short-lived and very small. Mosses, in contrast, have predominant gametophyte stages. Alternation of Generations in Plants Fern Sporangia Fern Gametophyte Non-Sexual Reproduction As discussed, many organisms have both sexual and non-sexual means of increasing the numbers of individuals. Asexual reproduction can be a good strategy in an environment that is consistent, if a species is well suited to those conditions. Without sexual reproduction, however, there is no genetic variation to adapt to change....
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This note was uploaded on 12/29/2011 for the course BIO 151 taught by Professor Edwards during the Spring '10 term at SUNY Stony Brook.

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