Flagellate
Organisms with whip-like flagella for motion and feeding.
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The term describes a particular level of organization characteristic of many prokaryotes and eukaryotes and their means of motion, though it does not imply any specific relationship or classification. Flagellates are major consumers of primary and secondary production in aquatic ecosystems, consuming bacteria and other protists, and many parasites affecting human health or economy are flagellates in at least one life stage.
- definition
- Cell or organism with one or more flagella
- occurrence
- Eukaryotes, some prokaryotes
- ecological role
- Major consumers in aquatic ecosystems
- human relevance
- Includes parasites such as Naegleria, Trichomonas, Plasmodium
- flagella structure
- Eukaryotic flagella have nine fused pairs surrounding two central singlets, arising from a basal body
Lore & Background
Flagella in eukaryotes are supported by microtubules in a characteristic arrangement, with nine fused pairs surrounding two central singlets, arising from a basal body. In some flagellates, flagella direct food into a cytostome or mouth. Flagella are generally used for propulsion, but may also create a current that brings in food. In most such organisms, one or more flagella are located at or near the anterior of the cell, often with one directed forwards and one trailing behind.
Reader's Guide
The term 'flagellate' remains in use as a description of a level of organization and as an ecological functional group, even though the taxonomic group Flagellata was abandoned. In older classifications, flagellated protozoa were grouped in Flagellata (Mastigophora), sometimes divided into Phytoflagellata (mostly autotrophic) and Zooflagellata (heterotrophic). These groups are now known to be highly polyphyletic. Modern classifications place principal flagellated taxa in groups such as Archaeplastida, Stramenopiles, Alveolata, Rhizaria, Amoebozoa, Opisthokonta, and Excavata, which also include non-flagellated forms. The amoeboflagellates and helioflagellates represent peculiar types of organization combining flagella with pseudopods or heliozoan structures.
Did You Know?
- Flowering plants do not produce flagellate cells, but ferns, mosses, green algae, and some gymnosperms do.
- Most fungi do not produce cells with flagella, but the primitive fungal chytrids do.
- Many parasites that affect human health or economy are flagellates in at least one stage of their life cycle, such as Naegleria, Trichomonas, and Plasmodium.
- The term 'flagellate' does not imply any specific relationship or classification of the organisms that possess flagella.
Frequently Asked Questions
What is a flagellate in the Algae And Protists 1-24 entry?
A flagellate is any single cell or organism that propels itself using one or more whip-like tails called flagella. The label spans a broad swath of life, from certain prokaryotes to many eukaryotic protists, and it describes a locomotion strategy rather than a single evolutionary lineage.
What ecological role do flagellates fill in aquatic ecosystems?
Flagellates serve as major consumers of both primary and secondary production in water bodies, preying on bacteria and other protists. By linking microbial producers to higher trophic levels, they are a critical link in the aquatic food web.
Does the term 'flagellate' imply a single taxonomic group?
No. The word is purely functional, describing how an organism moves rather than where it sits on the tree of life. Flagellated cells appear across multiple kingdoms and phyla, so the label carries no implication of shared ancestry.
How do flagellates connect to human health and economy?
Several parasites that cause disease or economic loss are flagellates at some stage of their life cycle. Notable examples include Naegleria, Trichomonas, and Plasmodium, all of which can produce serious illness in humans.
What is the internal structure of a eukaryotic flagellum?
A eukaryotic flagellum contains nine fused microtubule pairs arranged around a central pair of singlets, a pattern often summarized as the 9+2 arrangement. It is anchored to the cell by a basal body, which also serves as the site where the flagellum assembles.
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