47-608: Leca or LECA may refer to: Acronyms [ edit ] Last eukaryotic common ancestor Lightweight expanded clay aggregate Lutheran Evangelical Church in Africa—Zambia Diocese Places [ edit ] Leča , a village in Novi Pazar, Serbia Leça da Palmeira a former civil parish in the Greater Porto area, Portugal Leça Lighthouse Leca,
94-420: A bacterium came together to create the first eukaryotic common ancestor ( FECA ). This cell had a new level of complexity and capability, with a nucleus, at least one centriole and cilium , facultatively aerobic mitochondria , sex ( meiosis and syngamy ), a dormant cyst with a cell wall of chitin and/or cellulose and peroxisomes . It evolved into a population of single-celled organisms that included
141-405: A microtubular spindle during nuclear division, in the distinctively eukaryotic process of mitosis . Eukaryotes differ from prokaryotes in multiple ways, with unique biochemical pathways such as sterane synthesis. The eukaryotic signature proteins have no homology to proteins in other domains of life, but appear to be universal among eukaryotes. They include the proteins of the cytoskeleton,
188-513: A "symbiosis-based phylogeny", giving the description "Eukarya (symbiosis-derived nucleated organisms)". By 2014, a rough consensus started to emerge from the phylogenomic studies of the previous two decades. The majority of eukaryotes can be placed in one of two large clades dubbed Amorphea (similar in composition to the unikont hypothesis) and the Diphoda (formerly bikonts), which includes plants and most algal lineages. A third major grouping,
235-430: A body, with its cells dividing by mitosis , and at some stage produce haploid gametes through meiosis , a division that reduces the number of chromosomes and creates genetic variability . There is considerable variation in this pattern. Plants have both haploid and diploid multicellular phases . Eukaryotes have lower metabolic rates and longer generation times than prokaryotes, because they are larger and therefore have
282-479: A bundle of microtubules arising from a centriole , characteristically arranged as nine doublets surrounding two singlets. Flagella may have hairs ( mastigonemes ), as in many stramenopiles . Their interior is continuous with the cell's cytoplasm . Centrioles are often present, even in cells and groups that do not have flagella, but conifers and flowering plants have neither. They generally occur in groups that give rise to various microtubular roots. These form
329-502: A football club in Leça da Palmeira, Portugal Battle of Leça , a 1684 military encounter between Portuguese and Castilian forces See also [ edit ] [REDACTED] Search for "leca" , "le-ca" , "l-ec-a" , "lec-a" , or "l-eca" on Misplaced Pages. All pages with titles beginning with LECA All pages with titles beginning with Leca All pages with titles containing leca Lecca ,
376-655: A given name and surname Lecka (disambiguation) Leka (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Leca . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Leca&oldid=1229323174 " Categories : Disambiguation pages Place name disambiguation pages Disambiguation pages with given-name-holder lists Disambiguation pages with surname-holder lists Hidden categories: Short description
423-559: A membrane-bound nucleus . All animals , plants , fungi , and many unicellular organisms are eukaryotes. They constitute a major group of life forms alongside the two groups of prokaryotes : the Bacteria and the Archaea . Eukaryotes represent a small minority of the number of organisms, but given their generally much larger size, their collective global biomass is much larger than that of prokaryotes. The eukaryotes seemingly emerged within
470-460: A more complex process, it gained all three in short order, then other capabilities. Other models have been proposed. Whatever happened, many lineages must have been created, but the LECA either out-competed or came together with the other lineages to form a single point of origin for the eukaryotes. Nick Lane and William Martin have argued that mitochondria came first, on the grounds that energy had been
517-406: A primary component of the cytoskeleton, and are often assembled over the course of several cell divisions, with one flagellum retained from the parent and the other derived from it. Centrioles produce the spindle during nuclear division. The cells of plants, algae, fungi and most chromalveolates , but not animals, are surrounded by a cell wall. This is a layer outside the cell membrane , providing
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#1733086094591564-510: A smaller surface area to volume ratio. The evolution of sexual reproduction may be a primordial characteristic of eukaryotes. Based on a phylogenetic analysis, Dacks and Roger have proposed that facultative sex was present in the group's common ancestor. A core set of genes that function in meiosis is present in both Trichomonas vaginalis and Giardia intestinalis , two organisms previously thought to be asexual. Since these two species are descendants of lineages that diverged early from
611-417: A system of domains rather than kingdoms as top level rank being put forward by Carl Woese , Otto Kandler , and Mark Wheelis in 1990, uniting all the eukaryote kingdoms in the domain "Eucarya", stating, however, that " 'eukaryotes' will continue to be an acceptable common synonym". In 1996, the evolutionary biologist Lynn Margulis proposed to replace kingdoms and domains with "inclusive" names to create
658-797: A village in Antonești, Cantemir , Moldova People [ edit ] Leca of Cătun (before 1599–1616), Wallachian political figure Béatrice Leca (born 1970), French writer Daniel Leca (born 1985), French politician Francine Leca (1938-2024), French surgeon and professor Grégory Leca (born 1980), French footballer Haralamb Lecca (or Leca), (1873–1920), Romanian poet and playwright Jean-Louis Leca (born 1985), French footballer Marius Leca (born 2000), Romanian footballer Mickaël Leca (born 1994), French footballer Mihai Leca (born 1992), Romanian footballer Ricangel de Leça (born 1981), Aruban football referee and former player Other uses [ edit ] Leça F.C. ,
705-482: Is believed to have been a protist with a nucleus, at least one centriole and cilium , facultatively aerobic mitochondria, sex ( meiosis and syngamy ), a dormant cyst with a cell wall of chitin and/or cellulose , and peroxisomes . It had been proposed that the LECA fed by phagocytosis , engulfing other organisms. However, in 2022, Nico Bremer and colleagues confirmed that the LECA had mitochondria, and stated that it had multiple nuclei, but disputed that it
752-610: Is closer in structure to bacterial RNA than to eukaryote RNA. Some eukaryotes, such as the metamonads Giardia and Trichomonas , and the amoebozoan Pelomyxa , appear to lack mitochondria, but all contain mitochondrion-derived organelles, like hydrogenosomes or mitosomes , having lost their mitochondria secondarily. They obtain energy by enzymatic action in the cytoplasm. Plants and various groups of algae have plastids as well as mitochondria. Plastids, like mitochondria, have their own DNA and are developed from endosymbionts , in this case cyanobacteria . They usually take
799-434: Is different from Wikidata All article disambiguation pages All disambiguation pages Last eukaryotic common ancestor Eukaryogenesis , the process which created the eukaryotic cell and lineage, is a milestone in the evolution of life, since eukaryotes include all complex cells and almost all multicellular organisms. The process is widely agreed to have involved symbiogenesis , in which an archeon and
846-532: Is that their cells have nuclei . This gives them their name, from the Greek εὖ ( eu , "well" or "good") and κάρυον ( karyon , "nut" or "kernel", here meaning "nucleus"). Eukaryotic cells have a variety of internal membrane-bound structures, called organelles , and a cytoskeleton which defines the cell's organization and shape. The nucleus stores the cell's DNA , which is divided into linear bundles called chromosomes ; these are separated into two matching sets by
893-659: The Asgard archaea , and are closely related to the Heimdallarchaeia . This implies that there are only two domains of life , Bacteria and Archaea, with eukaryotes incorporated among the Archaea. Eukaryotes first emerged during the Paleoproterozoic , likely as flagellated cells. The leading evolutionary theory is they were created by symbiogenesis between an anaerobic Asgard archaean and an aerobic proteobacterium , which formed
940-467: The animals , plants , and fungi . According to the theory of symbiogenesis (also known as the endosymbiotic theory ) championed by Lynn Margulis , a member of the archaea gained a bacterial cell as a component. The archaeal cell was a member of the Asgard group. The bacterium was one of the Alphaproteobacteria , which had the ability to use oxygen in its respiration. This enabled it – and
987-518: The archaea —having a volume of around 10,000 times greater. Eukaryotes represent a small minority of the number of organisms , but, as many of them are much larger, their collective global biomass (468 gigatons) is far larger than that of prokaryotes (77 gigatons), with plants alone accounting for over 81% of the total biomass of Earth . The eukaryotes are a diverse lineage, consisting mainly of microscopic organisms . Multicellularity in some form has evolved independently at least 25 times within
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#17330860945911034-583: The blue whale , weighing up to 190 tonnes and measuring up to 33.6 metres (110 ft) long, or plants like the coast redwood , up to 120 metres (390 ft) tall. Many eukaryotes are unicellular; the informal grouping called protists includes many of these, with some multicellular forms like the giant kelp up to 200 feet (61 m) long. The multicellular eukaryotes include the animals, plants, and fungi , but again, these groups too contain many unicellular species . Eukaryotic cells are typically much larger than those of prokaryotes —the bacteria and
1081-471: The last eukaryotic common ancestor ( LECA ), gaining capabilities along the way, though the sequence of the steps involved has been disputed, and may not have started with symbiogenesis. In turn, the LECA gave rise to the eukaryotes' crown group , containing the ancestors of animals , fungi , plants , and a diverse range of single-celled organisms. Life arose on Earth once it had cooled enough for oceans to form. The last universal common ancestor (LUCA)
1128-740: The mitochondria . A second episode of symbiogenesis with a cyanobacterium created the plants, with chloroplasts . Eukaryotic cells contain membrane-bound organelles such as the nucleus , the endoplasmic reticulum , and the Golgi apparatus . Eukaryotes may be either unicellular or multicellular . In comparison, prokaryotes are typically unicellular. Unicellular eukaryotes are sometimes called protists . Eukaryotes can reproduce both asexually through mitosis and sexually through meiosis and gamete fusion ( fertilization ). Eukaryotes are organisms that range from microscopic single cells , such as picozoans under 3 micrometres across, to animals like
1175-510: The taxonomic rank of kingdom by Linnaeus in the 18th century. Though he included the fungi with plants with some reservations, it was later realized that they are quite distinct and warrant a separate kingdom. The various single-cell eukaryotes were originally placed with plants or animals when they became known. In 1818, the German biologist Georg A. Goldfuss coined the word Protozoa to refer to organisms such as ciliates , and this group
1222-528: The RNA into proteins, were separated, permitting extensive RNA processing and allowing the expression of genes to become more complex. It had mechanisms for reshuffling its genetic material, and possibly for manipulating its own evolvability . All of these gave the LECA "a compelling cohort of selective advantages". Sex in eukaryotes is a composite process, consisting of meiosis and fertilisation , which can be coupled to reproduction . Dacks and Roger proposed on
1269-512: The ability to move, including the ability to pull chromosomes into two sets during mitosis , cell division. More recently, the Asgard archaean has been identified as belonging to the Heimdallarchaeota . The last eukaryotic common ancestor (LECA) is the hypothetical last common ancestor of all living eukaryotes, around 2 billion years ago, and was most likely a biological population . It
1316-431: The archaeal cells that included it – to survive in the presence of oxygen, which was poisonous to other organisms adapted to reducing conditions. The endosymbiotic bacteria became the eukaryotic cell's mitochondria , providing most of the energy of the cell. Lynn Margulis and colleagues have suggested that the cell also acquired a Spirochaete bacterium as a symbiont, providing the cell skeleton of microtubules and
1363-524: The basis of a phylogenetic analysis that facultative sex was likely present in the common ancestor of all eukaryotes. Early in eukaryotic evolution, about 2 billion years ago, organisms needed a solution to the major problem that oxidative metabolism releases reactive oxygen species that damage the genetic material, DNA . Eukaryotic sex provides a process, homologous recombination during meiosis, for using informational redundancy to repair such DNA damage . Biologists have proposed multiple scenarios for
1410-709: The cell to move, change shape, or transport materials. The motor structures are microfilaments of actin and actin-binding proteins , including α- actinin , fimbrin , and filamin are present in submembranous cortical layers and bundles. Motor proteins of microtubules, dynein and kinesin , and myosin of actin filaments, provide dynamic character of the network. Many eukaryotes have long slender motile cytoplasmic projections, called flagella , or multiple shorter structures called cilia . These organelles are variously involved in movement, feeding, and sensation. They are composed mainly of tubulin , and are entirely distinct from prokaryotic flagella. They are supported by
1457-404: The cell with structural support, protection, and a filtering mechanism. The cell wall also prevents over-expansion when water enters the cell. The major polysaccharides making up the primary cell wall of land plants are cellulose , hemicellulose , and pectin . The cellulose microfibrils are linked together with hemicellulose, embedded in a pectin matrix. The most common hemicellulose in
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1504-427: The complex transcription machinery, the membrane-sorting systems, the nuclear pore , and some enzymes in the biochemical pathways. Eukaryote cells include a variety of membrane-bound structures, together forming the endomembrane system. Simple compartments, called vesicles and vacuoles , can form by budding off other membranes. Many cells ingest food and other materials through a process of endocytosis , where
1551-423: The creation of the eukaryotes. While there is broad agreement that the LECA must have had a nucleus, mitochondria, and internal membranes, the order in which these were acquired has been disputed. In the syntrophic model, the first eukaryotic common ancestor (FECA, around 2.2 gya ) gained mitochondria, then membranes, then a nucleus. In the phagotrophic model, it gained a nucleus, then membranes, then mitochondria. In
1598-622: The cytoplasm. Mitochondria are organelles in eukaryotic cells. The mitochondrion is commonly called "the powerhouse of the cell", for its function providing energy by oxidising sugars or fats to produce the energy-storing molecule ATP . Mitochondria have two surrounding membranes , each a phospholipid bilayer , the inner of which is folded into invaginations called cristae where aerobic respiration takes place. Mitochondria contain their own DNA , which has close structural similarities to bacterial DNA , from which it originated, and which encodes rRNA and tRNA genes that produce RNA which
1645-422: The early eukaryotic cell, while the cell wall was lost. In the same way, mitochondrial acquisition must not be regarded as the end of the process, for still new complex families of genes had to be developed after or during the endosymbiotic exchange. In this way, from FECA to LECA, we can think of organisms that can be considered as protoeukaryotes. At the end of the process, LECA was already a complex organism with
1692-406: The eukaryotes. Complex multicellular organisms, not counting the aggregation of amoebae to form slime molds , have evolved within only six eukaryotic lineages: animals , symbiomycotan fungi , brown algae , red algae , green algae , and land plants . Eukaryotes are grouped by genomic similarities, so that groups often lack visible shared characteristics. The defining feature of eukaryotes
1739-484: The eukaryotic evolutionary tree, core meiotic genes, and hence sex, were likely present in the common ancestor of eukaryotes. Species once thought to be asexual, such as Leishmania parasites, have a sexual cycle. Amoebae, previously regarded as asexual, may be anciently sexual; while present-day asexual groups could have arisen recently. In antiquity , the two lineages of animals and plants were recognized by Aristotle and Theophrastus . The lineages were given
1786-646: The form of chloroplasts which, like cyanobacteria, contain chlorophyll and produce organic compounds (such as glucose ) through photosynthesis . Others are involved in storing food. Although plastids probably had a single origin, not all plastid-containing groups are closely related. Instead, some eukaryotes have obtained them from others through secondary endosymbiosis or ingestion. The capture and sequestering of photosynthetic cells and chloroplasts, kleptoplasty , occurs in many types of modern eukaryotic organisms. The cytoskeleton provides stiffening structure and points of attachment for motor structures that enable
1833-405: The late Paleoproterozoic , include acritarch microfossils with relatively robust ornate carbonaceous vesicles of Tappania from 1.63 gya and Shuiyousphaeridium from 1.8 gya. Eukaryote The eukaryotes ( / j uː ˈ k ær i oʊ t s , - ə t s / yoo- KARR -ee-ohts, -əts ) constitute the domain of Eukaryota or Eukarya , organisms whose cells have
1880-429: The limiting factor on the size of the prokaryotic cell. The phagotrophic model presupposes the ability to engulf food, enabling the cell to engulf the aerobic bacterium that became the mitochondrion. Eugene Koonin and others, noting that the archaea share many features with eukaryotes, argue that rudimentary eukaryotic traits such as membrane-lined compartments were acquired before endosymbiosis added mitochondria to
1927-449: The outer membrane invaginates and then pinches off to form a vesicle. Some cell products can leave in a vesicle through exocytosis . The nucleus is surrounded by a double membrane known as the nuclear envelope , with nuclear pores that allow material to move in and out. Various tube- and sheet-like extensions of the nuclear membrane form the endoplasmic reticulum , which is involved in protein transport and maturation. It includes
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1974-595: The presence of protein families involved in cellular compartmentalization. In turn, the LECA gave rise to the eukaryotes' crown group , containing the ancestors of animals , fungi , plants , and a diverse range of single-celled organisms with the new capabilities and complexity of the eukaryotic cell. Single cells without cell walls are fragile and have a low probability of being fossilised . If fossilised, they have few features to distinguish them clearly from prokaryotes: size, morphological complexity, and (eventually) multicellularity . Early eukaryote fossils, from
2021-417: The primary cell wall is xyloglucan . Eukaryotes have a life cycle that involves sexual reproduction , alternating between a haploid phase, where only one copy of each chromosome is present in each cell, and a diploid phase, with two copies of each chromosome in each cell. The diploid phase is formed by fusion of two haploid gametes, such as eggs and spermatozoa , to form a zygote ; this may grow into
2068-498: The rough endoplasmic reticulum, covered in ribosomes which synthesize proteins; these enter the interior space or lumen. Subsequently, they generally enter vesicles, which bud off from the smooth endoplasmic reticulum. In most eukaryotes, these protein-carrying vesicles are released and further modified in stacks of flattened vesicles ( cisternae ), the Golgi apparatus . Vesicles may be specialized; for instance, lysosomes contain digestive enzymes that break down biomolecules in
2115-503: Was an organism which had ribosomes and the genetic code ; it lived some 4 billion years ago. It gave rise to two main branches of prokaryotic life, the bacteria and the archaea . From among these small-celled, rapidly-dividing ancestors arose the Eukaryotes, with much larger cells, nuclei, and distinctive biochemistry. The eukaryotes form a domain that contains all complex cells and most types of multicellular organism , including
2162-498: Was expanded until Ernst Haeckel made it a kingdom encompassing all single-celled eukaryotes, the Protista , in 1866. The eukaryotes thus came to be seen as four kingdoms: The protists were at that time thought to be "primitive forms", and thus an evolutionary grade , united by their primitive unicellular nature. Understanding of the oldest branchings in the tree of life only developed substantially with DNA sequencing , leading to
2209-583: Was phagotrophic. This would mean that the ability found in many eukaryotes to engulf materials developed later, rather than being acquired first and then used to engulf the alphaproteobacteria that became mitochondria. The LECA has been described as having "spectacular cellular complexity". Its cell was divided into compartments. It appears to have inherited a set of endosomal sorting complex proteins that enable membranes to be remodelled, including pinching off vesicles to form endosomes . Its apparatuses for transcribing DNA into RNA , and then for translating
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