metagenesis
/,metə'dʤenisis/
Definition
Noun (Biology) 1. Alternation of Generations: A biological life cycle in which an organism alternates between distinct sexual and asexual reproductive phases across successive generations. This involves a diploid generation (sporophyte) that reproduces asexually via spores and a haploid generation (gametophyte) that reproduces sexually via gametes.
Usage
Metagenesis is a technical term used primarily in biology, specifically in botany, zoology, and marine biology, to describe complex life cycles found in certain plants (e.g., ferns, mosses) and animals (e.g., some cnidarians like jellyfish).
Examples
- The life cycle of a fern is a classic example of metagenesis, involving a large, visible sporophyte and a small, independent gametophyte.
- In studying cnidarians, scientists observed metagenesis, where the polyp stage reproduces asexually and the medusa stage reproduces sexually.
- The textbook chapter on plant reproduction explained metagenesis in detail, contrasting it with simpler life cycles.
Advanced Usage
- Conceptual Usage: The term can be used more broadly to discuss any process or system characterized by a strict, cyclical alternation between two fundamentally different states or modes.
- Example: The novel's structure employs a kind of narrative metagenesis, alternating between prose and verse chapters.
Variants and Related Words
- Alternation of generations: This is the more common descriptive phrase synonymous with metagenesis.
- Heterogenesis: A sometimes synonymous, but less precise, historical term that can also refer to alternation between different forms of reproduction.
- Sporophyte (n): The diploid, asexual spore-producing phase in a life cycle characterized by metagenesis.
- Gametophyte (n): The haploid, sexual gamete-producing phase in a life cycle characterized by metagenesis.
Synonyms
- Alternation of generations
- Heterogenesis (in specific contexts)
Antonyms
- Direct development: A life cycle without an alternation between distinct sexual and asexual generations; the organism develops directly from the fertilized egg to a juvenile form resembling the adult.
Noun
-
alternation of sexual and asexual generations
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