alveolära

Alveolata, or alveolates, is a major supergroup of unicellular eukaryotes within the SAR clade. It includes three well-established lineages often treated as phyla: Ciliophora (ciliates), Dinophyta (dinoflagellates), and Apicomplexa (apicomplexans). The group is named for cortical alveoli, small membrane-bound sacs beneath the plasma membrane in many alveolates, which are thought to provide structural support and may affect membrane processes. Alveolates show substantial diversity in form and ecology, ranging from free-living photosynthetic organisms to intracellular parasites.

Key features vary among lineages. Ciliates have cilia for movement and feeding and display nuclear dimorphism with micronuclei and macronuclei. Dinoflagellates typically possess two flagella and, in many species, a cellulose plate covering called the theca; many are photosynthetic, others are heterotrophic. Apicomplexans are mostly parasites and possess an apical complex of organelles that enables host cell invasion.

Reproduction and ecology: Ciliates reproduce mainly by fission and can exchange genes during conjugation; dinoflagellates reproduce by division with sexual phases in some groups; apicomplexans have complex life cycles with sexual and asexual stages. Alveolates occur in marine and freshwater environments, soils, and animal guts. Dinoflagellate blooms affect water quality; ciliates are central to microbial food webs; apicomplexans include important parasites such as Plasmodium and Toxoplasma.

Systematics and research: molecular data continue to refine alveolate relationships, but the three-lineage framework remains a common reference point for understanding this ecologically important group.