Biological Sciences
Chromalveolata
Chromalveolata is a supergroup of protists that includes a diverse range of organisms such as brown algae, diatoms, and ciliates. It is characterized by the presence of chlorophyll c and a unique type of flagellar hairs called mastigonemes. This group is of significant interest in evolutionary biology and has important ecological and economic implications due to its members' roles in marine and freshwater ecosystems.
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eBook - PDFUnravelling the algae
the past, present, and future of algal systematics
- Juliet Brodie, Jane Lewis, Juliet Brodie, Jane Lewis(Authors)
- 2007(Publication Date)
- CRC Press(Publisher)
181 ABSTRACT The chlorarachniophytes are one of the most evolutionarily interesting algal groups. Their cells have small organelles, called nucleomorphs, which provide us with direct evidence for the lateral transfer of plastids through a secondary endosymbiosis. Advances in molecular phylogenetics have proved that the chlorarachniophytes originated from a cercozoan protist that engulfed a green alga and retained it as a plastid. The focus of chlorarachniophyte research has now shifted to tackling the question “how did the endosymbiont become an organelle?” In addition to this evolutionary research, the recognition of the chlorarachniophytes as a group and their diversity has also pro-gressed in the past decade. Currently, five genera and nine species make up the chlorarachniophytes and several new taxa are waiting to be described. Remarkable diversity in life cycle and ultrastruc-ture and fascinating cell behaviour are beginning to be revealed. INTRODUCTION In a bright shallow lagoon of a coral reef, among the bushes of tropical green seaweeds, such as Halimeda and Caulerpa species, microscopic filose amoebae with green plastids are crawling around. In the middle of the Atlantic Ocean, among the drifting seaweeds, tiny green single-flagellated plankton swim. These are members of the chlorarachniophytes. Among the many groups of algae, the chlo-rarachniophytes are particularly interesting and enigmatic due to their unique evolutionary history, cellular structure, and genetic organization. Research has revealed that the chlorarachniophytes are one of the groups that acquired plastids via a secondary endosymbiosis in which an eukaryotic alga was engulfed and retained by a protozoan host (Hibberd and Norris, 1984; Ludwig and Gibbs, 1989; McFadden et al., 1994). The chlorarachniophytes are, like cryptophytes, unique among those
eBook - PDF- Tamar Berner(Author)
- 2014(Publication Date)
- CRC Press(Publisher)
The principal ultrastructural evidence for this association, which has been dignified with the taxonomic designation of' 'Infrakingdom Alveolata, 9 is the presence of cortical alveoli. Roberts and Roberts 79 were unable to confirm this rela-tionship on the basis of a phylogenetic analysis of ultrastructural features. However, two genera of zooflagellates, Perkinsus and Colpodella (Spiro-monas sensu auct. 19 ) are known to have apical complexes similar to those of apicomplexans, 29 -47 and structural similarities exist between the apical pore complex of apicomplexans and certain dinoflagellates. 89 Moreover, the al-veolate flagellate genus Katablepharis, which previously, but in my opinion doubtfully (Katablepharis mitochondrial cristae are tubular, not flattened), has been assigned to the cryptomonads, has feeding apparatus features similar in many respects to those of suctorian ciliates. 90 Further studies on these flagellates may provide new insights on the validity of the Infrakingdom Alveolata concept and on the origin of the dinoflagellates. VII. GREEN ALGAE, RED ALGAE, GLAUCOPHYTES: MONOPHYLETIC OR POLYPHYLETIC? Green algae, red algae, and glaucophytes have some features in common, including the presence of plastids with only two bounding membranes, mi-tochondria with flattened cristae, and storage of an a-linked polyglucan (starch). Until very recently, and after the discovery of phagotrophic and mixotrophic cryptomonads, they could also be considered the only eukaryotic algal groups with no phagotrophic species among them. Cavalier-Smith 9,9192 has proposed that these three groups share a single common photosynthetic ancestor, most nearly allied with the dinoflagellates, despite the fact that, apart from the features listed above, the red, green, and glaucophytic algae are very different ultrastructurally and biochemically.
eBook - PDFMarine Algae
A survey of research and utilization
- Tore Levring, Heinz August Hoppe, Otto J. Schmid(Authors)
- 2019(Publication Date)
- De Gruyter(Publisher)
Classification of the Algae B y T o r e L e v r i n g The algae constitute no uniform or systematic group. Rather, they comprise various divisions of primitive plants of a low order which have undergone a more or less parallel evolution. Formerly a distinction was made between flagellates and algae. Flagellates were then so defined as to include coloured unicellular organisms moving by means of cilia but lacking cell walls. However, several colourless species, too, were classified among the flagellates. Several of them are closely related to the coloured species: they have only lost their photosynthetically active pigments. The coloured flagellates resemble several motile stages of certain algae (zoospores, gametes). Already KLEBS ( 1 8 9 3 ) had drawn attention to the close relationship between colour-ed flagellates and algae. In this century many scientists have clarified this relationship with greater precision. The flagellate-like forms occur as primitive stages in various parallel lines of development. In the older systematic classification of algae colour was not allowed for as a feature of distinction. H A R V E Y ( 1 8 3 6 ) was the first to distinguish between these various groups: Chlorospermeae (green algae), Melanospermeae (brown algae), and Rhodospermeae (red algae). These names were subsequently altered into Chlorophyceae (KOTZING, 1 8 4 5 ) , Phaeophyceae (KJELLMAN, 1 8 9 1 ) , and Rhodophyceae ( R U P P R E C H T , 1 8 5 5 ) , respectively. H A R V E Y had classi-fied the blue-green algae amongst the CHLOROPHYCEAE. The blue-green algae were called M Y X O P H Y C E A E by STITZENBERGER ( 1 8 6 0 ) and CYANOPHYCEAE by SACHS ( 1 8 7 4 ) . From the grass-green algae L U T H E R ( 1 8 9 0 ) separated the yellow-green species as Heterokontae. Later they were called Xanthophyceae by ALLORGE ( 1 9 3 0 ) . The different groups of algae, accor-ding to STRAIN ( 1 9 4 4 ) , contain special types of chlorophyll, carotene, and xanthophyll.
eBook - PDFBiology
Concepts and Applications
- Cecie Starr, Christine Evers, Lisa Starr, , Cecie Starr, Christine Evers, Lisa Starr(Authors)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
Ciliates use cilia to move and to feed. Most are aquatic predators, but some are parasites. All apicomplexans are parasitic alveolates that live in animal cells. The disease malaria is caused by the apicomplexan parasite Plas- modium and transmitted by mosquitoes. The parasite lives in human liver and blood cells. Untreated malaria is deadly, but drugs can prevent and cure it. Members of the third SAR lineage, the rhizaria, are single- celled heterotrophs with a perforated shell. Cytoplasmic projec- tions extend through openings in the shell. Foraminifera have a calcium carbonate shell and most live on the seafloor. Radiolaria have a silica shell and float as part of the zooplankton. Section 20.6 The Archaeplastida super- group includes plants and their protist relatives: red algae and green algae. All have cell walls of cellulose and chloroplasts derived from cyano- bacteria. Red algae are multicelled and marine. Accessory pigments called phycobilins allow them to carry out photosynthesis in deep waters. Green algae may be single cells, colonial, or multicelled. The charophyte green algae are the closest living relatives of land plants. Like all land plants, some algae have an alternation of generations, a life cycle that includes two kinds of multicelled bodies: a diploid, spore-producing sporophyte and a haploid, gamete-producing gametophyte. Sections 20.7, 20.8 The supergroup Amoebozoa includes amoebas and slime molds. The plasmodial slime molds feed as a multinu- cleated mass. Cells of cellular slime molds aggre- gate when food is scarce. Both form resting spores when conditions do not favor growth. A related supergroup, the Opisthokonta, includes fungi, animals, and the protist relatives of these groups. The closest rela- tives of animals are choanoflagellates, a groups of heterotrophic protists that can be solitary or colonial.
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