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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 ...
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.
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 ...
The division of human rights into three generations was initially proposed in 1979 by the Czech jurist Karel Vasak at the International Institute of Human Rights in Strasbourg. He used the term at least as early as November 1977. [1] Vasak's theories have primarily taken root in European law.
The Inter-American Commission on Human Rights (the IACHR) is an autonomous organ of the Organization of American States, also based in Washington, D.C. Along with the Inter-American Court of Human Rights, based in San José, Costa Rica, it is one of the bodies that comprise the inter-American system for the promotion and protection of human ...
The Universal Declaration on Human Rights (UDHR), adopted by the UN General Assembly in 1948, is one of the most important sources of economic, social and cultural rights. . It recognizes the right to social security in Article 22, the right to work in Article 23, the right to rest and leisure in Article 24, the right to an adequate standard of living in Article 25, the right to education in ...
On Jan. 12, the American Alliance for Equal Rights sued McDonald's over the HACER program. The alliance, which challenges programs that use race or ethnicity as a factor in their decisions, ...
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]