metazoa
Definition
- Noun:
- A major division of the animal kingdom: Metazoa refers to all multicellular animals whose bodies are composed of cells differentiated into distinct tissues and organs. This group excludes single-celled and simple colonial organisms like protozoans and sponges (which are sometimes placed in a separate subkingdom, Parazoa).
- Characterized by specialized structure: Organisms classified as Metazoa typically possess a digestive cavity and a nervous system, representing a fundamental level of complexity in animal life.
Usage Examples
- Noun:
- All vertebrates and insects are members of the Metazoa.
- The evolution of the Metazoa from simpler ancestors was a pivotal event in the history of life.
Advanced Usage
- In taxonomic context: The term is often used in scientific classification to distinguish complex animals from other life forms.
- The kingdom Animalia is often subdivided into the Parazoa (sponges) and the Eumetazoa (true Metazoa).
- As a conceptual group: Used to discuss biological features common to complex animals.
- The development of specialized germ layers is a defining feature of the Metazoa.
Variants and Related Words
- Metazoan (noun): An individual animal belonging to the Metazoa.
- A typical metazoan has cells organized into tissues.
- Metazoan (adjective): Of or pertaining to the Metazoa.
- Metazoan development involves complex cellular differentiation.
- Eumetazoa (noun): A clade within Metazoa comprising all major animal groups except sponges, characterized by true tissues.
Synonyms
- Multicellular animals
- Animalia (in a broad taxonomic sense, though Animalia technically includes all animals)
Notes on Meaning
The term "Metazoa" is primarily used in zoological and evolutionary biology contexts. In modern phylogenetic classification, it is often synonymous with the kingdom Animalia, though historically it was used to specifically exclude the most primitive, non-tissue-grade animals like sponges. Its usage implies a level of biological organization beyond that of single-celled organisms.
Noun
-
multicellular animals having cells differentiated into tissues and organs and usually a digestive cavity and nervous system
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