Basic Web Pages
EUKARYOTA
The most diverse group of living organisms, dominant in most ecosystems, with the exception of anaerobic zones. Includes autotrophic and heterotrophic groups of protists, plants, animals, fungi. Characteristic features of eukaryotes are the nucleus, delimited from the cytoplasm by a nuclear membrane, a linear (rarely circular) genome based on DNA, organized with the participation of histones in the form of chromosomes, cytoplasmic ribosomes with a sedimentation coefficient of 80S, the presence of cytoplasmic endomembrane complexes as the endoplasmic reticulum, the Golgi apparatus, vacuoles, lysosomes, peroxisomes, glyoxisomes, spherosomes. Most species have mitochondria, and their absence is always of secondary nature. Autotrophic eukaryotes have plastids. Eukaryotic membranes are bilayered and consist of phospholipids. The cell wall, if present, has a cellulose or chitin base and a pectin or glucan (or heteroglican) matrix. The eukaryotic flagellum (undulipodia) is organized as axoneme surrounded by a membrane — a complex of two free microtubules and nine microtubule triplets connected to each other by dynein handles and nexin bridges, and to the axoneme by radial spokes.
Both in all multicellulars and a part of unicellular eukaryotes, the flagellum is present only at the motile stage of their life cycle, wereas in some groups (most of fungi, rhodophytes, some groups of amoebae) it is secondarily absent. In non-flagellated cells, the system of microtubules and microfilaments associated with the flagellum, called the cytoskeleton, remains. The cytoskeleton is involved in the amoeboid movement of eukaryotic cells, phagocytosis and pinocytosis, the movement of cytoplasmic organelles and vesicles, and most importantly, in mitotic and meiotic division. Most eukaryotes are aerobes with oxidative enzymes localized in mitochondria. Aerobic, less often anaerobic glycolysis is also known. Holozoic nutrition – by swallowing small particles and other cells from forms lacking a cell wall, osmotrophy – nutrition by absorption of products of extracellular destruction of the substrate by heterotrophs with a cell wall, and phototrophic (autotrophic) – by photosynthesis in plastid-bearing forms.
In different groups of eukaryotes, the sexual process independently arose, convergently similar in essential details. The cause of the sexual process is the presence in the eukaryotic cell of additional mitochondrial DNA, the recombination of which is undesirable, in contrast to the recombination of nuclear DNA. Various eukaryotes have developed mechanisms that ensure the fusion of nuclei (karyogamy), but at the same time hinder the fusion of mitochondria: usually these are preserved along the line of stationary (mother) gametes, which are called oogametes if they are expressed morphologically.
The emergence of eukaryotes is attributed to the period 1.5–2 billion years ago. Comparison of the nucleotide sequences of rRNA genes in representatives of the main domains of life suggests that eukaryotes differ less from archaebacteria than from other groups of prokaryotes, although the differences between eukaryotes and archaebacteria are also significant.
A eukaryotic cell is a symbiotic ensemble, somewhat super-cell, the basic property of which is the production and secretion of an “outside product” (biopolymers, enzymes, signal molecules). Eukaryotes represent a kind of mill for the biomass production and extracellular secretion with a huge biotechnological potential.
The biotechnological community is in demand for a stable macrosystem of organisms with the maximum current heuristic power (primarily for exploratory screening studies). However its creation is hampered both by the chronic incompleteness of current systems and their competition in scientific media. The time has come to create a taxonomic/biotechnological interface that allows a user-biotechnologist to quickly select the classification solution that is most adequate to modern data in order to optimization of the search for new nests of technologically significant organisms from various eukaryotic supergroups that have certain properties already studied.
In different groups of eukaryotes, the sexual process independently arose, convergently similar in essential details. The cause of the sexual process is the presence in the eukaryotic cell of additional mitochondrial DNA, the recombination of which is undesirable, in contrast to the recombination of nuclear DNA. Various eukaryotes have developed mechanisms that ensure the fusion of nuclei (karyogamy), but at the same time hinder the fusion of mitochondria: usually these are preserved along the line of stationary (mother) gametes, which are called oogametes if they are expressed morphologically.
The emergence of eukaryotes is attributed to the period 1.5–2 billion years ago. Comparison of the nucleotide sequences of rRNA genes in representatives of the main domains of life suggests that eukaryotes differ less from archaebacteria than from other groups of prokaryotes, although the differences between eukaryotes and archaebacteria are also significant.
A eukaryotic cell is a symbiotic ensemble, somewhat super-cell, the basic property of which is the production and secretion of an “outside product” (biopolymers, enzymes, signal molecules). Eukaryotes represent a kind of mill for the biomass production and extracellular secretion with a huge biotechnological potential.
The biotechnological community is in demand for a stable macrosystem of organisms with the maximum current heuristic power (primarily for exploratory screening studies). However its creation is hampered both by the chronic incompleteness of current systems and their competition in scientific media. The time has come to create a taxonomic/biotechnological interface that allows a user-biotechnologist to quickly select the classification solution that is most adequate to modern data in order to optimization of the search for new nests of technologically significant organisms from various eukaryotic supergroups that have certain properties already studied.