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Mating Type
Mating types are the microorganism equivalent to sexes in multicellular lifeforms and are thought to be the ancestor to distinct sexes. They also occur in multicellular organisms such as fungi. Definition Mating types are the microorganism equivalent to sex in higher organisms and occur in isogamous species. Depending on the group, different mating types are often referred to by numbers, letters, or simply "+" and "−" instead of "male" and "female", which refer to " sexes" or differences in size between gametes. Syngamy can only take place between gametes carrying different mating types. Mating types are extensively studied in fungi. Among fungi, mating type is determined by chromosomal regions called mating-type loci. Furthermore, it is not as simple as "two different mating types can mate", but rather, a matter of combinatorics. As a simple example, most '' basidiomycete'' have a "tetrapolar heterothallism" mating system: there are two loci, and mating between two individua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microorganism
A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in Jain literature authored in 6th-century BC India. The scientific study of microorganisms began with their observation under the microscope in the 1670s by Anton van Leeuwenhoek. In the 1850s, Louis Pasteur found that microorganisms caused food spoilage, debunking the theory of spontaneous generation. In the 1880s, Robert Koch discovered that microorganisms caused the diseases tuberculosis, cholera, diphtheria, and anthrax. Microorganisms are extremely diverse, representing most unicellular organisms in all three domains of life: two of the three domains, Archaea and Bacteria, only contain microorganisms. The third domain, Eukaryota, includes all multicellular o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fungus
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one of the kingdom (biology)#Six kingdoms (1998), traditional eukaryotic kingdoms, along with Animalia, Plantae, and either Protista or Protozoa and Chromista. A characteristic that places fungi in a different kingdom from plants, bacteria, and some protists is chitin in their cell walls. Fungi, like animals, are heterotrophs; they acquire their food by absorbing dissolved molecules, typically by secreting digestive enzymes into their environment. Fungi do not photosynthesize. Growth is their means of motility, mobility, except for spores (a few of which are flagellated), which may travel through the air or water. Fungi are the principal decomposers in ecological systems. These and other differences place fungi in a single group of related o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleodorina Starrii
''Pleodorina starrii'' is a species of algae that resides in freshwater in Japan. The name ''starri'' is in honor of phycologist Richard C. Starr. Since 2006 it has provided molecular genetic evidence for an evolutionary link between sexes and mating types. It was later confirmed to be the first reportedly trioecious haploid species. Description ''Pleodorina starrii'' is a colonial organism. The colonies are spherical or ellipsoidal and consist of 32 or 64 biflagellate cells embedded in the periphery of a gelatinous matrix, thus forming a hollow sphere. Cells are differentiated into somatic and reproductive cells; in 32-celled colonies, 8–12 of the cells are somatic while in 64-celled colonies, 18–20 of the cells are somatic. Somatic cells are nearly spherical, up to 13 μm in diameter, having a cup-shaped chloroplast with a single pyrenoid. Two contractile vacuoles are present near the base of the flagella, as well as several others near the cell surface. Reproductive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Green Algae
The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep within the charophytes as a sister of the Zygnematophyceae. Since the realization that the Embryophytes emerged within the green algae, some authors are starting to include them. The completed clade that includes both green algae and embryophytes is monophyletic and is referred to as the clade Viridiplantae and as the kingdom Plantae. The green algae include unicellular and colonial flagellates, most with two flagella per cell, as well as various colonial, coccoid (spherical), and filamentous forms, and macroscopic, multicellular seaweeds. There are about 22,000 species of green algae, many of which live most of their lives as single cells, while other species form coenobia (colonies), long filaments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convergent Evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The cladistic term for the same phenomenon is Cladogram#Homoplasies, homoplasy. The recurrent evolution of flight is a classic example, as flying pterygota, insects, birds, pterosaurs, and bats have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are ''analogous'', whereas ''homology (biology), homologous'' structures or traits have a common origin but can have dissimilar functions. Bird, bat, and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions. The opposite of convergence is divergent evolution, where related species evolve different trai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anisogamy
Different forms of anisogamy: A) anisogamy of motile cells, B) 283x283px Anisogamy is a form of sexual reproduction">egg cell">oogamy (egg cell and sperm cell), C) anisogamy of non-motile cells (egg cell and spermatia).">283x283px Anisogamy is a form of sexual reproduction that involves the union or fusion of two gametes that differ in size and/or form. The smaller gamete is male, a ''microgamete'' or sperm cell, whereas the larger gamete is female, a larger ''macrogamete'' or typically an egg cell. Anisogamy is predominant among multicellular organisms. In both plants and animals, gamete size difference is the fundamental difference between females and males. Anisogamy most likely evolved from isogamy. Since the biological definition of male and female is based on gamete size, the evolution of anisogamy is viewed as the evolutionary origin of male and female sexes. Anisogamy is an outcome of both natural selection and sexual selection, and led the sexes to different prima ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Complementation (genetics)
Complementation refers to a genetics, genetic process when two strain (biology), strains of an organism with different homozygous recessive mutations that produce the same mutant phenotype (for example, a change in wing structure in flies) have offspring that express the wild-type phenotype when mated or crossed. Complementation will ordinarily occur if the mutations are in different genes (intergenic complementation). Complementation may also occur if the two mutations are at different sites within the same gene (intragenic complementation), but this effect is usually weaker than that of intergenic complementation. When the mutations are in different genes, each strain's genome supplies the wild-type allele to "complement" the mutated allele of the other strain's genome. Since the mutations are recessive, the offspring will display the wild-type phenotype. A complementation test (sometimes called a "Cistron, cis-trans" test) can test whether the mutations in two strains are in d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurospora Crassa
''Neurospora crassa'' is a type of red bread mold of the phylum Ascomycota. The genus name, meaning 'nerve spore' in Greek, refers to the characteristic striations on the spores. The first published account of this fungus was from an infestation of French bakeries in 1843. ''Neurospora crassa'' is used as a model organism because it is easy to grow and has a haploid life cycle that makes genetics, genetic analysis simple since recessive traits will show up in the offspring. Analysis of genetic recombination is facilitated by the ordered arrangement of the products of meiosis in ''Neurospora'' ascospores. Its entire genome of seven chromosomes has been sequenced. ''Neurospora'' was used by Edward Tatum and George Wells Beadle in their experiments for which they won the Nobel Prize in Physiology or Medicine in 1958. Beadle and Tatum exposed ''N. crassa'' to x-rays, causing mutations. They then observed failures in metabolic pathways caused by errors in specific enzymes. This led ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basidiomycete
Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basidiomycota includes these groups: agarics, puffballs, stinkhorns, bracket fungi, other polypores, jelly fungi, boletes, chanterelles, earth stars, smuts, bunts, rusts, mirror yeasts, and '' Cryptococcus'', the human pathogenic yeast. Basidiomycota are filamentous fungi composed of hyphae (except for basidiomycota-yeast) and reproduce sexually via the formation of specialized club-shaped end cells called basidia that normally bear external meiospores (usually four). These specialized spores are called basidiospores. However, some Basidiomycota are obligate asexual reproducers. Basidiomycota that reproduce asexually (discussed below) can typically be recognized as members of this division by gross similarity to others, by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homothallic
In fungi and algae, homothallism refers to the condition in which a single individual or thallus carries the genetic determinants (i.e., both mating types or sexes) required to undergo sexual reproduction without the need for a distinct mating partner. The opposite sexual functions are performed by different cells of a single mycelium. It can be contrasted to heterothallic. It is often used to categorize fungi. In yeast, heterothallic cells have mating types a and α. An experienced mother cell (one that has divided at least once) will switch mating type every cell division cycle because of the ''HO'' allele. Sexual reproduction commonly occurs in two fundamentally different ways in fungi. These are outcrossing (in heterothallic fungi) in which two different individuals contribute nuclei to form a zygote, and self-fertilization or selfing (in homothallic fungi) in which both nuclei are derived from the same individual. Homothallism in fungi can be defined as the capability of an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fertilisation
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or offspring. While processes such as insemination or pollination, which happen before the fusion of gametes, are also sometimes informally referred to as fertilisation, these are technically separate processes. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms, the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation. History In antiquity, Aristotle conceived the formation of new individuals through fusion of male and female fluids, with form and function emerging gradually, in a mode called by him as epigenetic. In 1784, Spallanzani established the need of in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterothallic
Heterothallic species have sexes that reside in different individuals. The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of sexual reproduction from a single organism. In heterothallic fungi, two different individuals contribute nuclei to form a zygote. Examples of heterothallism are included for ''Saccharomyces cerevisiae, Aspergillus fumigatus, Aspergillus flavus'', '' Penicillium marneffei'' and ''Neurospora crassa''. The heterothallic life cycle of ''N. crassa'' is given in some detail, since similar life cycles are present in other heterothallic fungi. Certain heterothallic species (such as ''Neurospora tetrasperma'') are called "pseudo-homothallic". Instead of separating into four individual spores by two meiosis events, only a single meiosis occurs, resulting in two spores, each with two haploid nuclei of different mating types (those of its parent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
