|
Zooflagellate
Zooflagellates are single-celled eukaryotes with flagella (i.e., flagellates). They are heterotrophic flagellates, as opposed to phytoflagellates, which are photosynthetic. The term "zooflagellate" is also used to refer to reproductive cells or zoospores belonging to multicellular organisms, such as fungi. History In historical systems of classification during the 20th century, zooflagellates were grouped as a single taxon Zoomastigophora or Zoomastigophorea within the kingdom Protista. It included protists that lack chloroplasts and cell walls and have one or more flagella, but not many as in ciliates or opalines, namely: *Bicosoecids, composing the order ''Bicosoecida'', distinguished by two unequal flagella. They are currently known as a lineage of Stramenopiles, more closely related to algae such as diatoms than to other zooflagellates. *Choanoflagellates, then treated as order ''Choanoflagellida'', distinguished by one anterior flagellum surrounded by a collar. They ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-celled
A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell (biology), cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and eukaryotic organisms. Most prokaryotes are unicellular and are classified into bacteria and archaea. Many eukaryotes are multicellular, but some are unicellular such as protozoa, unicellular algae, and unicellular fungi. Unicellular organisms are thought to be the oldest form of life, with early organisms emerging 3.5–3.8 billion years ago. Although some prokaryotes live in Colony (biology), colonies, they are not specialised cells with differing functions. These organisms live together, and each cell must carry out all life processes to survive. In contrast, even the simplest multicellular organisms have cells that depend on each other to survive. Most multicellular organisms have a unicellular life-cycle stage. Gam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opaline
The opalines are a small group of peculiar heterokonts, currently assigned to the family Opalinidae, in the order Slopalinida. Their name is derived from the opalescent appearance of these microscopic organisms when illuminated with full sunlight. Most opalines live in the large intestine and cloaca of anurans (frogs and toads), though they are sometimes found in fish, reptiles, molluscs and insects; whether they are parasitic is not certain. The unusual features of the opalines, first observed by Antonie van Leeuwenhoek in 1683, has led to much debate regarding their phylogenetic position among the protists. Taxonomy and phylogeny The relationship between opalines and other protists has been a subject of great controversy since the late 19th century, and is not completely resolved at present. Initially, microscopists believed that the thousands of rhythmically beating hair-like structures which cover their surface were cilia, and they placed the opalines in Ciliophora. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kinetoplastid
Kinetoplastida (or Kinetoplastea, as a class) is a group of flagellated protists belonging to the phylum Euglenozoa, and characterised by the presence of a distinctive organelle called the kinetoplast (hence the name), a granule containing a large mass of DNA. The group includes a number of parasites responsible for serious diseases in humans and other animals, as well as various forms found in soil and aquatic environments. The organisms are commonly referred to as "kinetoplastids" or "kinetoplasts". The kinetoplastids were first defined by Bronislaw M. Honigberg in 1963 as the members of the flagellated protozoans. They are traditionally divided into the biflagellate Bodonidae and uniflagellate Trypanosomatidae; the former appears to be paraphyletic to the latter. One family of kinetoplastids, the trypanosomatids, is notable as it includes several genera which are exclusively parasitic. ''Bodo'' is a typical genus within kinetoplastida, which also includes various common f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trichomonadida
Trichomonadida is an order of anaerobic protists, included with the parabasalids. Members of this order are referred to as trichomonads. Some organisms in this order include: *''Trichomonas vaginalis'', an organism living inside the vagina of humans *'' Dientamoeba fragilis'', parasitic ameboid in humans *''Histomonas meleagridis'', parasite that causes blackhead disease in poultry *'' Mixotricha paradoxa'', a symbiotic organism inside termites, host of endosymbionts Anatomy Species in this order typically have four to six flagella at the cell's apical pole, one of which is recurrent - that is, it runs along a surface wave, giving the aspect of an undulating membrane. Like other parabasalids, they typically have an axostyle, a pelta, a costa, and parabasal bodies. In '' Histomonas'' only one flagellum and a reduced axostyle are found, and in '' Dientamoeba'', both are absent. Behavior Most species are either parasites or other endosymbionts of animals. Trichomonads ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retortamonadida
The retortamonads are a small group of flagellates, most commonly found in the intestines of animals as commensals, although a free-living species called the ''Chilomastix cuspidata'' exists. They are grouped under the taxon Archezoa. They are usually around 5-20 μm in length, and all of their small subunit ribosomal RNA gene sequences are very similar to each other. There are two genera: '' Retortamonas'' with two flagella, and '' Chilomastix'' with four. In both cases there are four basal bodies anterior to a prominent feeding groove, and one flagellum is directed back through the cell, emerging from the groove. The retortamonads lack mitochondria, golgi apparatus, dictyosomes, and peroxisomes. They are close relatives of the diplomonads, and are placed among the metamonad The metamonads are a large group of flagellate amitochondriate microscopic eukaryotes. They include the retortamonads, diplomonads, parabasalids, oxymonads, and a range of more poorly studied taxa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxymonadida
The Oxymonads (or Oxymonadida) are a group of flagellated protists found exclusively in the intestines of animals, mostly termites and other wood-eating insects. Along with the similar parabasalid flagellates, they harbor the symbiotic bacteria that are responsible for breaking down cellulose. There is no evidence for presence of mitochondria (not even anaerobic mitochondrion-like organelles like hydrogenosomes or mitosomes) in oxymonads and three species have been shown to completely lack any molecular markers of mitochondria. It includes e.g. '' Dinenympha'', '' Pyrsonympha'', '' Oxymonas'', ''Streblomastix'', ''Monocercomonoides'', and '' Blattamonas''. Characteristics Most Oxymonads are around 50 μm in size and have a single nucleus, associated with four flagella. Their basal bodies give rise to several long sheets of microtubules, which form an organelle called an axostyle, but different in structure from the axostyles of parabasalids. The cell may use the axostyle to s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diplomonadida
The diplomonads (Greek for "two units") are a group of flagellates, most of which are parasitic. They include ''Giardia duodenalis'', which causes giardiasis in humans. They are placed among the metamonads, and appear to be particularly close relatives of the retortamonads. Morphology Most diplomonads are double cells: they have two nuclei, each with four associated flagella, arranged symmetrically about the body's main axis. Like the retortamonads, they lack both mitochondria and Golgi apparatuses. However, they are now known to possess modified mitochondria, in the case of ''G. duodenalis'', called mitosomes. These are not used in ATP synthesis the way mitochondria are, but are involved in the maturation of iron-sulfur proteins. Possible sexual reproduction in ''Giardia'' The common intestinal parasite ''Giardia duodenalis'' (synonyms ''Giardia lamblia'', ''G. intestinalis'') was once considered to be a descendant of a protist lineage that predated the emergence of mei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypermastigida
Hypermastigia (hypermastigids) within microbiology, is the name used for a group of flagellate endosymbionts which were placed under the Excavata Excavata is an obsolete, extensive and diverse paraphyletic group of unicellular Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smith in 2002. It contains ... class. They are now treated as belonging to one of the groups Tritrichomonadea, Hypotrichomonadea, or Trichomonadea within the Parabasalia. References Metamonads {{Microbiology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamonad
The metamonads are a large group of flagellate amitochondriate microscopic eukaryotes. They include the retortamonads, diplomonads, parabasalids, oxymonads, and a range of more poorly studied taxa, most of which are free-living flagellates. All metamonads are anaerobic (many being aerotolerant anaerobes), and most members of the four groups listed above are symbiotes or parasites of animals, as is the case with ''Giardia lamblia'' which causes diarrhea in mammals. Characteristics A number of parabasalids and oxymonads are found in termite guts, and play an important role in breaking down the cellulose found in wood. Some other metamonads are parasites. These flagellates are unusual in lacking aerobic mitochondria. Originally they were considered among the most primitive eukaryotes, diverging from the others before mitochondria appeared. However, they are now known to have lost aerobic mitochondria secondarily, and retain both organelles and nuclear genes derived ultimate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Animal
Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, have myocytes and are motility, able to move, can reproduce sexually, and grow from a hollow sphere of Cell (biology), cells, the blastula, during embryonic development. Animals form a clade, meaning that they arose from a single common ancestor. Over 1.5 million extant taxon, living animal species have been species description, described, of which around 1.05 million are insects, over 85,000 are molluscs, and around 65,000 are vertebrates. It has been estimated there are as many as 7.77 million animal species on Earth. Animal body lengths range from to . They have complex ecologies and biological interaction, interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anterior
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and axes. The meaning of terms that are used can change depending on whether a vertebrate is a biped or a quadruped, due to the difference in the neuraxis, or if an invertebrate is a non-bilaterian. A non-bilaterian has no anterior or posterior surface for example but can still have a descriptor used such as proximal or distal in relation to a body part that is nearest to, or furthest from its middle. International organisations have determined vocabularies that are often used as standards for subdisciplines of anatomy. For example, '' Termin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Choanoflagellate
Choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of animals. The name refers to the characteristic funnel-shaped "collar" of interconnected microvilli and the presence of a flagellum. Choanoflagellates are found globally in aquatic environments, and they are of particular interest to evolutionary biologists studying the origins of multicellularity in animals. The flagellum of choanoflagellates is surrounded by microvilli at its base. Movement of the flagellum creates water currents that can propel free-swimming choanoflagellates through the water column and trap bacteria and detritus against the microvilli, where these foodstuffs are engulfed. This feeding plays an ecological role in the carbon cycle by linking different trophic levels. Choanoflagellates bear morphological similarities to the choanocyte, a type of cell in sponges. As the proposed sister group to Animalia, choanoflagellate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
