alternation of generations

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fern: life cycle

moss life cycle

Life cycle of the common jellyfish Aurelia. Eggs released by females pass out through the mouth and become lodged in pits on the tentacles. Sperm released from male jellyfish fertilize the eggs, which remain on the tentacles during early development. A fertilized egg develops into a ciliated larva, or planula, which settles on and attaches to a substrate (such as a rock) and develops into a polyp with a mouth and tentacles. The polyp reproduces asexually by budding off saucer-shaped immature medusae, which develop into mature sexually reproducing forms.

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African Americans demonstrating for voting rights in front of the White House as police and others watch, March 12, 1965. One sign reads, "We demand the right to vote everywhere." Voting Rights Act, civil rights.

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Lake Mead (the impounded Colorado River) at the Hoover Dam. The light-coloured band of rock above the shoreline shows the decrease in water level in the first few years of the 21st century.

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Demystified - Do Lemmings Really Commit Mass Suicide? illustration

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An ancient egyptian hieroglyphic painted carving showing the falcon headed god Horus seated on a throne and holding a golden fly whisk. Before him are the Pharoah Seti and the goddess Isis. Interior wall of the temple to Osiris at Abydos, Egypt.

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Scolex (head) of the tapeworm Taenia solium. The hooks of the scolex enable the tapeworm to attach to the intestinal wall.

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alternation of generations: Facts & Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

Facts

Also Known As	heterogenesis • diplohaplontic life cycle • metagenesis • diplohaplontic cycle

Photos

fern: life cycle

moss life cycle

Life cycle of the common jellyfish Aurelia. Eggs released by females pass out through the mouth and become lodged in pits on the tentacles. Sperm released from male jellyfish fertilize the eggs, which remain on the tentacles during early development. A fertilized egg develops into a ciliated larva, or planula, which settles on and attaches to a substrate (such as a rock) and develops into a polyp with a mouth and tentacles. The polyp reproduces asexually by budding off saucer-shaped immature medusae, which develop into mature sexually reproducing forms.

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Topics

diploid phase haploid phase gametophyte sporophyte microgametophyte gametophore megagametophyte foot spore mother cell spore plant development seed fruit germination annual perennial biennial

Key People

Frederick Orpen Bower, detail of an oil painting by Sir William Orpen; in the University of Glasgow Art Collections

Frederick Orpen Bower

English botanist