|
Mixed Mating Systems
A mixed mating system (in plants), also known as “variable inbreeding” a characteristic of many hermaphroditic seed plants, where more than one means of mating is used. Mixed mating usually refers to the production of a mixture of self-fertilized (selfed) and outbred (outcrossed) seeds. Plant mating systems influence the distribution of genetic variation within and among populations, by affecting the propensity of individuals to self-fertilize or cross-fertilize (or reproduce asexually). Mixed mating systems are generally characterized by the frequency of selfing vs. outcrossing, but may include the production of asexual seeds through agamospermy. The trade offs for each strategy depend on ecological conditions, pollinator abundance and herbivory and parasite load. Mating systems are not permanent within species; they can vary with environmental factors, and through domestication when plants are bred for commercial agriculture. Occurrence Although practiced by a mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morning Glory Flowers
Morning is the period from sunrise to noon. There are no exact times for when morning begins (also true of evening and night) because it can vary according to one's lifestyle and the hours of daylight at each time of year. However, morning strictly ends at noon, which is when afternoon starts. Morning can also be defined as starting from midnight to noon. Morning precedes afternoon, evening, and night in the sequence of a day. Originally, the term referred to sunrise. Etymology The Modern English words "morning" and "tomorrow" began in Middle English as , developing into , then , and eventually . English, unlike some other languages, has separate terms for "morning" and "tomorrow", despite their common root. Other languages, like Dutch, Scots and German, may use a single wordto signify both "morning" and "tomorrow". Significance Greeting Some languages that use the time of day in greeting have a special greeting for morning, such as the English good morning. The appropri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bamboos
Bamboos are a diverse group of evergreen perennial flowering plants making up the subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family. The origin of the word "bamboo" is uncertain, but it probably comes from the Dutch or Portuguese language, which originally borrowed it from Malay or Kannada. In bamboo, as in other grasses, the internodal regions of the stem are usually hollow and the vascular bundles in the cross-section are scattered throughout the stem instead of in a cylindrical arrangement. The dicotyledonous woody xylem is also absent. The absence of secondary growth wood causes the stems of monocots, including the palms and large bamboos, to be columnar rather than tapering. Bamboos include some of the fastest-growing plants in the world, due to a unique rhizome-dependent system. Certain species of bamboo can grow within a 24-hour period, at a rate of almost an hour (equivalent to 1 mm every 90 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cleistogamy
Cleistogamy is a type of automatic self-pollination of certain plants that can propagate by using non-opening, self-pollinating flowers. Especially well known in peanuts, peas, and pansies, this behavior is most widespread in the grass family. However, the largest genus of cleistogamous plants is ''Viola''. The more common opposite of cleistogamy, or "closed marriage", is called chasmogamy, or "open marriage". Virtually all plants that produce cleistogamous flowers also produce chasmogamous ones.Meeuse, Bastiaan and Sean Morris. 1984. The sex life of flowers. New York, NY: Facts on File Publishers. pp 110-111. The principal advantage of cleistogamy is that it requires fewer plant resources to produce seeds than does chasmogamy, because development of petals, nectar and large amounts of pollen is not required. This efficiency makes cleistogamy particularly useful for seed production on unfavorable sites or adverse conditions. ''Impatiens capensis,'' for example, has been o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autonomous
In developmental psychology and moral, political, and bioethical philosophy, autonomy, from , ''autonomos'', from αὐτο- ''auto-'' "self" and νόμος ''nomos'', "law", hence when combined understood to mean "one who gives oneself one's own law" is the capacity to make an informed, uncoerced decision. Autonomous organizations or institutions are independent or self-governing. Autonomy can also be defined from a human resources perspective, where it denotes a (relatively high) level of discretion granted to an employee in his or her work. In such cases, autonomy is known to generally increase job satisfaction. Self-actualized individuals are thought to operate autonomously of external expectations. In a medical context, respect for a patient's personal autonomy is considered one of many fundamental ethical principles in medicine. Sociology In the sociology of knowledge, a controversy over the boundaries of autonomy inhibited analysis of any concept beyond relative autonom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Load
Genetic load is the difference between the fitness of an average genotype in a population and the fitness of some reference genotype, which may be either the best present in a population, or may be the theoretically optimal genotype. The average individual taken from a population with a low genetic load will generally, when grown in the same conditions, have more surviving offspring than the average individual from a population with a high genetic load. Genetic load can also be seen as reduced fitness at the population level compared to what the population would have if all individuals had the reference high-fitness genotype. High genetic load may put a population in danger of extinction. Fundamentals Consider n genotypes \mathbf _1, \dots, \mathbf _n, which have the fitnesses w_1, \dots, w_n and frequencies p_1, \dots, p_n, respectively. Ignoring frequency-dependent selection, the genetic load L may be calculated as: :L = where w_\max is either some theoretical optimum, or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inbreeding Depression
Inbreeding depression is the reduced biological fitness which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. Inbreeding depression is often the result of a population bottleneck. In general, the higher the genetic variation or gene pool within a breeding population, the less likely it is to suffer from inbreeding depression, though inbreeding and outbreeding depression can simultaneously occur. Inbreeding depression seems to be present in most groups of organisms, but varies across mating systems. Hermaphroditic species often exhibit lower degrees of inbreeding depression than outcrossing species, as repeated generations of selfing is thought to purge deleterious alleles from populations. For example, the outcrossing nematode (roundworm) ''Caenorhabditis remanei'' has been demonstrated to suffer severely from inbreeding depression, unlike i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David Lloyd (botanist)
David Graham Lloyd (20 June 1937 – 30 May 2006) was an evolutionary biologist and the seventh New Zealander to be elected as a fellow of the Royal Society in London. He did pioneering work in the field of plant reproduction. In December 1992, Lloyd fell victim to an apparent poisoning by acrylamide, a common laboratory chemical. As a result, he lay in a coma for three months and was left blind, mute, and quadriplegic. His former partner and fellow molecular biologist Vicki Calder was tried twice for his attempted murder. The first trial ended with a hung jury and the second acquitted her. AP News Archive, 19 April 1996 Research Lloyd's major contribution to |
Ronald Fisher
Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. For his work in statistics, he has been described as "a genius who almost single-handedly created the foundations for modern statistical science" and "the single most important figure in 20th century statistics". In genetics, his work used mathematics to combine Mendelian genetics and natural selection; this contributed to the revival of Darwinism in the early 20th-century revision of the theory of evolution known as the modern synthesis. For his contributions to biology, Fisher has been called "the greatest of Darwin’s successors". Fisher held strong views on race and eugenics, insisting on racial differences. Although he was clearly a eugenist and advocated for the legalization of voluntary sterilization of those with heritable mental disabilities, there is some debate as to whether Fisher supported ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mixed-mating Model
The mixed-mating model is a mathematical model that describes the mating system of a plant population in terms of degree of self-fertilisation. It is a fairly simplistic model, employing several simplifying assumptions, most notably the assumption that every fertilisation event may be classed as either self-fertilisation, or outcrossing with a completely random mate. Thus the only model parameter to be estimated is the probability of self-fertilisation. The mixed mating model originated in the 1910s, with plant breeders who were seeking evidence of outcrossing contamination of self-pollinating crops, but a formal description of the model and its parameter estimation was not published until 1951. The model is still in common use today, though a number of more complex models are also now in use. For example, a weakness of the model lies in its assumption that inbreeding occurs only as a result of self-fertilisation; in reality, inbreeding may also occur through outcrossing between clo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gossypium Hirsutum
''Gossypium hirsutum'', also known as upland cotton or Mexican cotton, is the most widely planted species of cotton in the world. Globally, about 90% of all cotton production is of cultivars derived from this species. In the United States, the world's largest exporter of cotton, it constitutes approximately 95% of all cotton production. It is native to Mexico, the West Indies, northern South America, Central America and possibly tropical Florida. Archeological evidence from the Tehuacan Valley in Mexico shows the cultivation of this species as long ago as 3,500 BC, although there is as yet no evidence as to exactly where it may have been first domesticated. This is the earliest evidence of cotton cultivation in the Americas found thus far. ''Gossypium hirsutum'' includes a number of varieties or cross-bred cultivars with varying fiber lengths and tolerances to a number of growing conditions. The longer length varieties are called "long staple upland" and the shorter length varie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sorghum
''Sorghum'' () is a genus of about 25 species of flowering plants in the grass family (Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species is grown for grain, while many others are used as fodder plants, either cultivated in warm climates worldwide or naturalized in pasture lands. Taxonomy ''Sorghum'' is in the Poaceae (grass) subfamily Panicoideae and the tribe Andropogoneae (the same as maize, big bluestem and sugarcane). Species Accepted species recorded include: Distribution and habitat Seventeen of the 25 species are native to Australia, with the range of some extending to Africa, Asia, Mesoamerica, and certain islands in the Indian and Pacific Oceans. Toxicity In the early stages of the plants' growth, some species of sorghum can contain levels of hydrogen cyanide, hordenine, and nitrates, which are lethal to grazing animals. Plants stressed by drought or heat can also contain toxic level ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avocado
The avocado (''Persea americana'') is a medium-sized, evergreen tree in the laurel family ( Lauraceae). It is native to the Americas and was first domesticated by Mesoamerican tribes more than 5,000 years ago. Then as now it was prized for its large and unusually oily fruit. The tree likely originated in the highlands bridging south-central Mexico and Guatemala. Its fruit, sometimes also referred to as an alligator or avocado pear, is botanically a large berry containing a single large seed. Avocado trees are partially self-pollinating, and are often propagated through grafting to maintain consistent fruit output. Avocados are presently cultivated in the tropical and Mediterranean climates of many countries. Mexico is the world's leading producer of avocados as of 2020, supplying nearly 30% of the global harvest in that year. The fruit of domestic varieties have smooth, buttery, golden-green flesh when ripe. Depending on the cultivar, avocados have green, brown, pu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
