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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 ...
Alternation of generations is defined as the alternation of multicellular diploid and haploid forms in the organism's life cycle, regardless of whether these forms are free-living. [6] In some species, such as the alga Ulva lactuca , the diploid and haploid forms are indeed both free-living independent organisms, essentially identical in ...
During the Devonian period several plant groups independently evolved heterospory and subsequently the habit of endospory, in which the gametophytes develop in miniaturized form inside the spore wall. By contrast in exosporous plants, including modern ferns, the gametophytes break the spore wall open on germination and develop outside it.
There is debate as to whether endospory or heterospory evolved first. Some debate centers upon the requirement of endospory to develop before heterospory. [2] Endospory is assumed to follow heterospory but it has been suggested that without endospory, early plant species dependency on water fertilization and environmental impacts on gametophytic gene expression would have reduced the chances ...
Curled up Selaginella tamariscina Wallace's Selaginella (Selaginella wallacei). Selaginella, also known as spikemosses or lesser clubmosses, is a genus of lycophyte.It is usually treated as the only genus in the family Selaginellaceae, with over 750 known species.
Isoetes, commonly known as the quillworts, is a genus of lycopod.It is the only living genus in the family Isoetaceae and order Isoetales.As of 2016, there were about 200 recognized species, [1] with a cosmopolitan distribution mostly in aquatic habitats but with the individual species often scarce to rare.
More than 500 million people have taken a "holy dip" in sacred river waters in north India over the last four weeks as part of the Hindu Maha Kumbh festival, authorities said on Friday, greater ...
Cycads produce strobili, both pollen-producing and seed-producing, that are composed of sporophylls. Ginkgo produces microsporophylls aggregated into a pollen strobilus. Ovules are not born on sporophylls [citation needed]. Gymnosperms, like Ginkgo and cycads, produce microsporophylls, aggregated into pollen strobili. However, unlike these ...