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Sarcomonadia
The sarcomonads () or class Sarcomonadea are a group of amoeboid biciliate protists in the phylum Cercozoa. They are characterized by a propensity to move through gliding on their posterior cilium or through filopodia, a lack of scales or external theca, a soft cell surface without obvious cortical filamentous or membranous skeleton, two cilia without scales or hairs, tubular mitochondrial cristae, near-spherical extrusomes, and a microbody (probably a peroxisome) attached to the nucleus. History In 1993 Cavalier-Smith described the sarcomonads as a subclass known as “Sarcomonadia”, an assemblage of unrelated cercozoans ( thaumatomonads, proteomyxids, cercomonads...) and excavates (jakobids), in the now defunct class “Heteromitea”, in the old phylum “Opalozoa”. This subclass was created to lump together protozoa that have an anisokont type of zoospore (i.e. two cilia of different lengths), are non-thecate and have isodiametric extrusomes. Sarcomonadia was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opalozoa
Opalozoa is a subphylum of heterotrophic protists of the phylum Bigyra, and is the sister group to Sagenista. Opalozoans are non-photosynthetic heterokonts that are ancestrally phagotrophic but many times have evolved to be osmotrophic saprotrophs in the gut of vertebrate animals. Taxonomy History: phylum Opalozoa In 1993 the name “Opalozoa” referred to a group of protists that was very different from what it is now. It was a phylum composed of many unrelated zooflagellates, grouped together because of the common presence of tubular mitochondrial cristae and the lack of cortical alveoli or rigid tubular ciliary hairs ( retronemes). It also included the opalinids, proteomyxids and plasmodiophorids. Modern classification The modern taxonomy of Opalozoa, down to order level, is as follows: * Subphylum Opalozoa ** Infraphylum Bikosia *** Class Bikosea ****Subclass Bicosidia *****Superorder Cyathobodoniae ******Order Bicoecida ******Order Anoecida ******Order Pseud ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cercomonas
Cercomonads are small flagellates, widespread in aqueous habitats and common in soils. Characteristics The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do not use them for locomotion, which usually takes place by gliding along surfaces. Most members have two flagella, one directed forward and one trailing under the cell, inserted at right angles near its anterior. The nucleus is connected to the flagellar bases and accompanied by a characteristic paranuclear body. Classification Genetic studies place the cercomonads among the Cercozoa, a diverse group of amoeboid and flagellate protozoans. They are divided into two families. * The Heteromitidae tend to be relatively rigid, and produce only temporary pseudopods. * The Cercomonadidae are more plastic, and when food supplies are plentiful may become amoeboid and even multinucleate. The classification of genera and species continues to u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crista
A crista (; plural cristae) is a fold in the inner membrane of a mitochondrion. The name is from the Latin for ''crest'' or ''plume'', and it gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area for chemical reactions to occur on. This aids aerobic cellular respiration, because the mitochondrion requires oxygen. Cristae are studded with proteins, including ATP synthase and a variety of cytochromes. Background With the discovery of the dual-membrane nature of mitochondria, the pioneers of mitochondrial ultrastructural research proposed different models for the organization of the mitochondrial inner membrane. Three models proposed were: *Baffle model – According to Palade (1953), the mitochondrial inner membrane is convoluted in a baffle-like manner with broad openings towards the intra-cristal space. This model entered most textbooks and was widely believed for a long time. *Septa model – Sjöstrand (1953) suggested that she ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dictyosome
The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles inside the cell before the vesicles are sent to their destination. It resides at the intersection of the secretory, lysosomal, and endocytic pathways. It is of particular importance in processing proteins for secretion, containing a set of glycosylation enzymes that attach various sugar monomers to proteins as the proteins move through the apparatus. It was identified in 1897 by the Italian scientist Camillo Golgi and was named after him in 1898. Discovery Owing to its large size and distinctive structure, the Golgi apparatus was one of the first organelles to be discovered and observed in detail. It was discovered in 1898 by Italian physician Camillo Golgi during an investigation of the nervous system. After first observing it under his micr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zoospore
A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or more distinct types of flagella - tinsel or "decorated", and whiplash, in various combinations. *Tinsellated (straminipilous) flagella have lateral filaments known as mastigonemes perpendicular to their main axis, which allow for more surface area, and disturbance of the medium, giving them the property of a rudder, that is, used for steering. *Whiplash flagella are straight, to power the zoospore through its medium. Also, the "default" zoospore only has the propelling, whiplash flagella. Both tinsel and whiplash flagella beat in a sinusoidal wave pattern, but when both are present, the tinsel beats in the opposite direction of the whiplash, to give two axes of control of motility. Morphological types In eukaryotes, the four main types ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protozoa
Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Historically, protozoans were regarded as "one-celled animals", because they often possess animal-like behaviours, such as motility and predation, and lack a cell wall, as found in plants and many algae. When first introduced by Georg Goldfuss (originally spelled Goldfuß) in 1818, the taxon Protozoa was erected as a class within the Animalia, with the word 'protozoa' meaning "first animals". In later classification schemes it was elevated to a variety of higher ranks, including phylum, subkingdom and kingdom, and sometimes included within Protoctista or Protista. The approach of classifying Protozoa within the context of Animalia was widespread in the 19th and early 20th century, but not universal. By the 1970s, it became usual to require th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jakobid
Jakobids are an order of free-living, heterotrophic, flagellar eukaryotes in the supergroup Excavata. They are small (less than 15 μm), and can be found in aerobic and anaerobic environments. The order Jakobida, believed to be monophyletic, consists of only twenty species at present, and was classified as a group in 1993. There is ongoing research into the mitochondrial genomes of jakobids, which are unusually large and bacteria-like, evidence that jakobids may be important to the evolutionary history of eukaryotes. Molecular phylogenetic evidence suggests strongly that jakobids are most closely related to Heterolobosea (Percolozoa) and Euglenozoa. Structure and Biology Jakobids have two flagella, inserted in the anterior end of the cell, and, like other members of order Excavata, have a ventral feeding groove and associated cytoskeleton support. The posterior flagella has a dorsal vane and is aligned within the ventral groove, where it generates a current that the cell uses f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Excavata
Excavata is a major supergroup of unicellular organisms belonging to the domain Eukaryota. It was first suggested by Simpson and Patterson in 1999 and introduced by Thomas Cavalier-Smith in 2002 as a formal taxon. It contains a variety of free-living and symbiotic forms, and also includes some important parasites of humans, including ''Giardia'' and ''Trichomonas''. Excavates were formerly considered to be included in the now obsolete Protista kingdom. They are classified based on their flagellar structures, and they are considered to be the most basal flagellate lineage. Phylogenomic analyses split the members of Excavata into three different and not all closely related groups: Discobids, Metamonads and Malawimonads. Except for Euglenozoa, they are all non-photosynthetic. Characteristics Most excavates are unicellular, heterotrophic flagellates. Only the Euglenozoa are photosynthetic. In some (particularly anaerobic intestinal parasites), the mitochondria have been greatly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cercomonad
Cercomonads are small flagellates, widespread in aqueous habitats and common in soils. Characteristics The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do not use them for locomotion, which usually takes place by gliding along surfaces. Most members have two flagella, one directed forward and one trailing under the cell, inserted at right angles near its anterior. The nucleus is connected to the flagellar bases and accompanied by a characteristic paranuclear body. Classification Genetic studies place the cercomonads among the Cercozoa, a diverse group of amoeboid and flagellate protozoans. They are divided into two families. * The Heteromitidae tend to be relatively rigid, and produce only temporary pseudopods. * The Cercomonadidae are more plastic, and when food supplies are plentiful may become amoeboid and even multinucleate. The classification of genera and species continues to un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteomyxidea
Proteomyxidea is a class of Cercozoa. Although it is known to be paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ..., further research is needed before its classification can be improved. References External links Cercozoa classes {{Cercozoa-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
