class hydrozoa
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Definition
- Noun (Biology): A class of coelenterates (cnidarians) characterized by a life cycle that typically involves alternation of generations. This cycle usually includes a sessile, often colonial, polyp stage (the hydroid phase) that reproduces asexually by budding to produce a free-swimming medusa stage (the medusoid phase). The class includes organisms such as hydras, Portuguese man o' war, and many types of jellyfishes.
Usage
- Noun:
- The class Hydrozoa is distinguished by its complex life cycle.
- Many organisms in the class Hydrozoa are marine.
Examples
- Noun:
- Hydra vulgaris is a well-studied freshwater genus within the class Hydrozoa.
- The Portuguese man o' war, often mistaken for a jellyfish, is actually a colonial organism belonging to the class Hydrozoa.
- The life cycle of a typical hydrozoan involves both a polyp and a medusa stage.
Advanced Usage
- "Hydrozoan" (adj/n): Pertaining to or a member of the class Hydrozoa.
- The hydrozoan polyp colony was attached to the rock.
- In taxonomic context: Used to specify a rank within the phylum Cnidaria.
- The order Siphonophora falls under the class Hydrozoa.
Variants and Related Words
- Hydrozoan (noun): An individual organism belonging to the class Hydrozoa.
- The biologist studied the feeding habits of a hydrozoan.
- Hydroid (noun): Refers specifically to the polyp stage of a hydrozoan life cycle.
- The hydroid stage is often colonial and sessile.
Synonyms
- Hydroid class (less common, contextual synonym in taxonomy).
Notes
- The term "class Hydrozoa" is a formal taxonomic classification. In general scientific writing, it is often not capitalized ("hydrozoans," "the hydrozoan class").
- While many jellyfishes are in the class Scyphozoa, some true jellyfishes, like those in the order Trachylina, are classified under Hydrozoa.
Noun
- coelenterates typically having alternation of generations; hydroid phase is usually colonial giving rise to the medusoid phase by budding: hydras and jellyfishes