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Antheridia are structures that produce male sex cells in ferns, mosses, algae, and fungi. They have a thin wall of sterile cells surrounding haploid cells that reproduce to produce sperm. Antheridia are dispersed through water, wind, or plant assistance. They are seen in organisms going through alternation of generations, where the organism goes through several distinct stages. In higher plants, antheridia has changed significantly from the form it takes in lower plants, and the plant has individual pollen grains that contain individual cells.
Antheridia are structures found in some organisms that produce male sex cells, also known as sperm or gametes. Ferns, mosses and other seedless plants use them for reproduction and these structures can also be found in algae and fungi. You need a microscope and some knowledge of anatomy to view these structures, because they are quite small; many microscope images of various species can be found on biology websites. The female counterpart is archegonium, with archegonia producing female sex cells.
The structure of the antheridium comprises a thin wall of sterile cells surrounding the haploid cells, which reproduce to produce sperm. When the wall breaks down, gametes are released and can fertilize female sex cells from the same or other organisms to create zygotes with a complete set of diploid DNA.
Organisms use a variety of ways to spread the sex cells they produce in their antheridia around the world. In some cases, the cells are actually motile and move through water or a film to reach the egg cells and fertilize them. In other cases, they get dispersed by the wind, and sometimes the plant helps out by blowing up the structure to blow them out into the air. In many mosses they are found at the tips of small stems that hang down over the rest of the plant.
These structures can be seen in organisms going through a process known as alternation of generations, where the organism goes through several distinct stages. Antheridia appear in the gametophyte stage, in which the entire organism is haploid and produces gametes through mitosis. When the resulting gametes fuse, they form a diploid zygote that develops into a diploid spore-producing organism. The spores, in turn, develop into a haploid gametophyte stage, which starts the cycle all over again.
In higher plants such as flowering plants, antheridia has changed significantly from the form it takes in lower plants. Instead of having a structure to produce male gametes, the plant has individual pollen grains that contain individual cells, which divide to produce sperm. In these plants, the gametes fuse to form seeds that contain nutrients to support the developing zygote so it has a better chance of maturing. Conversely, plants that use antheridia for reproduction rely on favorable conditions for the zygote to develop, although the spores can also go dormant for a long time while waiting for their opportunity.
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