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Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. The smaller of these, the microspore , is male and the larger megaspore is female. Heterospory evolved during the Devonian period from isospory independently in several plant groups: the clubmosses , the ferns including the arborescent ...
Diagram showing the alternation of generations between a diploid sporophyte (bottom) and a haploid gametophyte (top) A sporophyte (/ ˈ s p ɔːr. ə ˌ f aɪ t /) is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase.
Spores of two distinct sizes (heterospory or anisospory): larger megaspores and smaller microspores. When the two kinds of spore are produced in different kinds of sporangia, these are called megasporangia and microsporangia. A megaspore often (but not always) develops at the expense of the other three cells resulting from meiosis, which abort.
In land plants, anisogamy is universal. As in animals, female and male gametes are called, respectively, eggs and sperm. In extant land plants, either the sporophyte or the gametophyte may be reduced (heteromorphic). [2]
Marsileaceae (/ m ɑːr ˌ s ɪ l i ˈ eɪ s i. iː /) is a small family of heterosporous aquatic and semi-aquatic ferns, though at first sight they do not physically resemble other ferns.
<noinclude>[[Category:Labelled map templates]]</noinclude> to the end of the template code, making sure it starts on the same line as the code's last character. Contents
The idea of a tree of life arose from ancient notions of a ladder-like progression from lower into higher forms of life (such as in the Great Chain of Being).Early representations of "branching" phylogenetic trees include a "paleontological chart" showing the geological relationships among plants and animals in the book Elementary Geology, by Edward Hitchcock (first edition: 1840).
I personally prefer diagrams that are labeled. SVG is a great format that allows translation at any time, and having labels allows the image to stand alone. Otherwise the "user" would have to be going back and forward between the article and the diagram, and if the diagram is a "thumb" that means to be moving between windows in the computer.