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Evolution Of Flagella
The evolution of flagella is of great interest to biologists because the three known varieties of flagella – (eukaryotic, bacterial, and archaeal) each represent a sophisticated cellular structure that requires the interaction of many different systems. Eukaryotic flagellum There are two competing groups of models for the evolutionary origin of the eukaryotic flagellum (referred to as cilium below to distinguish it from its bacterial counterpart). Recent studies on the microtubule organizing center suggest that the most recent ancestor of all eukaryotes already had a complex flagellar apparatus. Endogenous, autogenous and direct filiation models These models argue that cilia developed from pre-existing components of the eukaryotic cytoskeleton (which has tubulin and dynein also used for other functions) as an extension of the mitotic spindle apparatus. The connection can still be seen, first in the various early-branching single-celled eukaryotes that have a microtubule b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biologist
A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual Cell (biology), cell, a multicellular organism, or a Community (ecology), community of Biological interaction, interacting populations. They usually specialize in a particular Outline of biology#Subdisciplines, branch (e.g., molecular biology, zoology, and evolutionary biology) of biology and have a specific research focus (e.g., studying malaria or cancer). Biologists who are involved in basic research have the aim of advancing knowledge about the natural world. They conduct their research using the scientific method, which is an empirical method for testing hypothesis, hypotheses. Their discoveries may have Applied science#Applied research, applications for some specific purpose such as in biotechnology, which has the goal of developing medically useful products for humans. In modern times, most biologists have one or more academic degre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable traits characteristic of a population over generations. Charles Darwin popularised the term "natural selection", contrasting it with selective breeding, artificial selection, which is intentional, whereas natural selection is not. Genetic diversity, Variation of traits, both Genotype, genotypic and phenotypic, exists within all populations of organisms. However, some traits are more likely to facilitate survival and reproductive success. Thus, these traits are passed the next generation. These traits can also become more Allele frequency, common within a population if the environment that favours these traits remains fixed. If new traits become more favoured due to changes in a specific Ecological niche, niche, microevolution occurs. If new traits become more favoured due to changes in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trichonympha
''Trichonympha'' is a genus of single-celled, anaerobic parabasalids of the order Hypermastigia that is found exclusively in the hindgut of lower termites and wood roaches. ''Trichonympha''’s bell shape and thousands of flagella make it an easily recognizable cell. The symbiosis between lower termites/wood roaches and ''Trichonympha'' is highly beneficial to both parties: ''Trichonympha'' helps its host digest cellulose and in return receives a constant supply of food and shelter. ''Trichonympha'' also has a variety of bacterial symbionts that are involved in sugar metabolism and nitrogen fixation. Etymology The word ''Trichonympha'' is a compound of the New Latin word ‘tricho’ and the word ‘nympha’. ‘Tricho’ in its simplest form refers to hair, and in this case makes reference to the many flagella of ''Trichonympha''. The ending ‘nympha’ was chosen by Joseph Leidy in 1877 when he first observed ''Trichonympha'' because their flagella reminded him of nymphs f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mixotricha
''Mixotricha paradoxa'' is a species of protozoan that lives inside the gut of the Australian termite species ''Mastotermes darwiniensis''. It is composed of five different organisms: three bacterial ectosymbionts live on its surface for locomotion and at least one endosymbiont lives inside to help digest cellulose in wood to produce acetate for its host(s). ''Mixotricha'' mitochondria degenerated in hydrogenosomes and mitosomes and lost the ability to produce energy aerobically by oxidative phosphorylation. The mitochondria-derived nuclear genes were however conserved. Discovery The name was given by the Australian biologist J.L. Sutherland, who first described ''Mixotricha'' in 1933. The name means "the paradoxical being with mixed-up hairs" because this protist has both cilia and flagella, which was not thought to be possible for protists. Behavior ''Mixotricha'' is a species of protozoan that lives inside the gut of the Australian termite species ''Mastotermes darwin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Termite
Termites are a group of detritivore, detritophagous Eusociality, eusocial cockroaches which consume a variety of Detritus, decaying plant material, generally in the form of wood, Plant litter, leaf litter, and Humus, soil humus. They are distinguished by their moniliform antennae and the soft-bodied, unpigmented worker caste for which they have been commonly termed "white ants"; however, they are not ants but highly Apomorphy and synapomorphy, derived cockroaches. About 2,997 extant species are currently described, 2,125 of which are members of the family Termitidae. Termites comprise the infraorder Isoptera, or alternatively the Taxonomic rank#All ranks, epifamily Termitoidae, within the order Blattodea (the cockroaches). Termites were once classified in a separate Order (biology), order from cockroaches, but recent phylogenetic studies indicate that they evolved from cockroaches, as they are deeply nested within the group, and the sister group to wood-eating cockroaches of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parabasalid
The parabasalids are a group of flagellated protists within the supergroup Excavata. Most of these eukaryotic organisms form a symbiosis, symbiotic relationship in animals. These include a variety of forms found in the intestines of termites and cockroaches, many of which have symbiotic bacteria that help them digest cellulose in woody plants. Other species within this supergroup are known parasites, and include human pathogens. Characteristics The flagella are arranged in one or more clusters near the anterior of the cell. Their basal bodies are linked to parabasal fibers that are associated with a prominent Golgi apparatus, Golgi complex, together forming a parabasal apparatus distinctive to the group. Attachment of a parabasal fiber to the first Golgi cisterna by thin filaments has been reported in ''Tritrichomonas foetus''. Usually they also give rise to a sheet of cross-like microtubules that runs down the center of the cell and in some cases projects past the end. This i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organelle
In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as Organ (anatomy), organs are to the Human body, body, hence ''organelle,'' the suffix ''-elle'' being a diminutive. Organelles are either separately enclosed within their own lipid bilayers (also called membrane-bounded organelles) or are spatially distinct functional units without a surrounding lipid bilayer (non-membrane bounded organelles). Although most organelles are functional units within cells, some functional units that extend outside of cells are often termed organelles, such as cilia, the flagellum and archaellum, and the trichocyst (these could be referred to as membrane bound in the sense that they are attached to (or bound to) the membrane). Organelles are identified by microscopy, and can also be purified by cell fractionation. There are many types of organe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motility
Motility is the ability of an organism to move independently using metabolism, metabolic energy. This biological concept encompasses movement at various levels, from whole organisms to cells and subcellular components. Motility is observed in animals, microorganisms, and even some plant structures, playing crucial roles in activities such as foraging, reproduction, and cellular functions. It is genetically determined but can be influenced by environmental factors. In multicellular organisms, motility is facilitated by systems like the Nervous system, nervous and Human musculoskeletal system, musculoskeletal systems, while at the cellular level, it involves mechanisms such as amoeboid movement and flagellar propulsion. These cellular movements can be directed by external stimuli, a phenomenon known as taxis. Examples include chemotaxis (movement along chemical gradients) and phototaxis (movement in response to light). Motility also includes physiological processes like gastroi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endosymbiotic Theory
Symbiogenesis (endosymbiotic theory, or serial endosymbiotic theory) is the leading evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms. The theory holds that mitochondria, plastids such as chloroplasts, and possibly other organelles of eukaryotic cells are descended from formerly free-living prokaryotes (more closely related to the Bacteria than to the Archaea) taken one inside the other in endosymbiosis. Mitochondria appear to be phylogenetically related to Rickettsiales bacteria, while chloroplasts are thought to be related to cyanobacteria. The idea that chloroplasts were originally independent organisms that merged into a symbiotic relationship with other one-celled organisms dates back to the 19th century, when it was espoused by researchers such as Andreas Schimper. The endosymbiotic theory was articulated in 1905 and 1910 by the Russian botanist Konstantin Mereschkowski, and advanced and substantiated with microbiological evidence by Lyn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lynn Margulis
Lynn Margulis (born Lynn Petra Alexander; March 5, 1938 – November 22, 2011) was an American evolutionary biologist, and was the primary modern proponent for the significance of symbiogenesis, symbiosis in evolution. In particular, Margulis transformed and fundamentally framed current understanding of the evolution of Eukaryote, cells with nuclei by proposing it to have been the result of symbiotic mergers of bacteria. Margulis was also the co-developer of the Gaia hypothesis with the British chemist James Lovelock, proposing that the Earth functions as a single self-regulating system, and was the principal defender and promulgator of the Five kingdoms, five kingdom classification of Robert Whittaker (ecologist), Robert Whittaker. Throughout her career, Margulis' work could arouse intense objections, and her formative paper, "On the Origin of Mitosing Cells", appeared in 1967 after being rejected by about fifteen journals. Still a junior faculty member at Boston University at t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prosthecobacter
''Prosthecobacter'' is a genus of bacteria from the phylum Verrucomicrobiota with a distinctive characteristic; the presence of tubulin-like genes. Tubulins, which are components of the microtubule, have never been observed in Gracilicutes before. Tubulin was long thought to be specific to eukaryotes. More recently, however, several prokaryotic proteins have been shown to be related to tubulin. Most bacteria have a homologous structure, FtsZ. ''Prosthecobacter'' are the exception to this, containing genes that have higher sequence homology to eukaryotic tubulin than FtsZ. These genes are called bacterial tubulin a (BtubA) and bacterial tubulin b (BtubB). The properties are not exactly same. However, surface loops and microtubules are extremely similar. Phylogeny The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI) See also * List of bacterial orders * List ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spirochete
A spirochaete () or spirochete is a member of the phylum Spirochaetota (also called Spirochaetes ), which contains distinctive diderm (double-membrane) Gram-negative bacteria, most of which have long, helically coiled (corkscrew-shaped or spiraled, hence the name) cells. Spirochaetes are chemoheterotrophic in nature, with lengths between 3 and 500 μm and diameters around 0.09 to at least 3 μm. Spirochaetes are distinguished from other bacterial phyla by the location of their flagella, called endoflagella, or periplasmic flagella, which are sometimes called ''axial filaments''. Endoflagella are anchored at each end (pole) of the bacterium within the periplasmic space (between the inner and outer membranes) where they project backwards to extend the length of the cell. These cause a twisting motion which allows the spirochaete to move. When reproducing, a spirochaete will undergo asexual transverse binary fission. Most spirochaetes are free-living and anaerob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
