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Disassortative Sexual Selection
Disassortative mating (also known as negative assortative mating or heterogamy) is a mating pattern in which individuals with dissimilar phenotypes mate with one another more frequently than would be expected under random mating. Disassortative mating reduces the mean genetic similarities within the population and produces a greater number of heterozygotes. The pattern is character specific, but does not affect allele frequencies. This nonrandom mating pattern will result in deviation from the Hardy-Weinberg principle (which states that genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences, such as "mate choice" in this case). Disassortative mating is different from outbreeding, which refers to mating patterns in relation to genotypes rather than phenotypes. Due to homotypic preference (bias toward the same type), assortative mating occurs more frequently then disassortative mating. This is due to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenotypes
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological properties, its behavior, and the products of behavior. An organism's phenotype results from two basic factors: the expression of an organism's genetic code, or its genotype, and the influence of environmental factors. Both factors may interact, further affecting phenotype. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented example of polymorphism is Labrador Retriever coloring; while the coat color depends on many genes, it is clearly seen in the environment as yellow, black, and brown. Richard Dawkins in 1978 and then again in his 1982 book ''The Extended Phenotype'' suggested that one can regard bird nests and other built structures such as cad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heliconius
''Heliconius'' comprises a colorful and widespread genus of brush-footed butterflies commonly known as the longwings or heliconians. This genus is distributed throughout the tropical and subtropical regions of the New World, from South America as far north as the southern United States. The larvae of these butterflies eat passion flower vines (Passifloraceae). Adults exhibit bright wing color patterns which signal their distastefulness to potential predators. Brought to the forefront of scientific attention by Victorian naturalists, these butterflies exhibit a striking diversity and mimicry, both amongst themselves and with species in other groups of butterflies and moths. The study of ''Heliconius'' and other groups of mimetic butterflies allowed the English naturalist Henry Walter Bates, following his return from Brazil in 1859, to lend support to Charles Darwin, who had found similar diversity amongst the Galápagos finches. Model for evolutionary study ''Heliconius'' b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mating Systems
A mating system is a way in which a group is structured in relation to sexual behaviour. The precise meaning depends upon the context. With respect to animals, the term describes which males and females mate under which circumstances. Recognised systems include monogamy, polygamy (which includes polygyny, polyandry, and polygynandry), and promiscuity, all of which lead to different mate choice outcomes and thus these systems affect how sexual selection works in the species which practice them. In plants, the term refers to the degree and circumstances of outcrossing. In human sociobiology, the terms have been extended to encompass the formation of relationships such as marriage. In plants The primary mating systems in plants are outcrossing (cross-fertilisation), autogamy (self-fertilisation) and apomixis (asexual reproduction without fertilization, but only when arising by modification of sexual function). Mixed mating systems, in which plants use two or even all three mating s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mating
In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization. Mating may also lead to external fertilization, as seen in amphibians, fishes and plants. For most species, mating is between two individuals of opposite sexes. However, for some hermaphroditic species, copulation is not required because the parent organism is capable of self-fertilization (autogamy); for example, banana slugs. The term ''mating'' is also applied to related processes in bacteria, archaea and viruses. Mating in these cases involves the pairing of individuals, accompanied by the pairing of their homologous chromosomes and then exchange of genomic information leading to formation of recombinant progeny (see mating systems). Animals For animals, mating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White-throated Sparrow
The white-throated sparrow (''Zonotrichia albicollis'') is a passerine bird of the New World sparrow family Passerellidae. Etymology The genus name ''Zonotrichia'' is from Ancient Greek (, ) and (, ). The specific ''albicollis'' is from Latin (), and (). Description The white-throated sparrow is a passerine bird of the New World sparrow family Passerellidae. It measures in length with a wingspan of . Typical weight is , with an average of . Among standard measurements, the wing chord is , the tail is , the bill is and the tarsus is . They are similar in appearance to the white-crowned sparrow, but with white throat markings and yellow lores. There are two adult plumage variations known as the tan-striped and white-striped forms. On the white-striped form the crown is black with a white central stripe. The supercilium is white as well. The auriculars are gray with the upper edge forming a black eye line. On the tan form, the crown is dark brown with a tan central s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alcohol Dehydrogenase
Alcohol dehydrogenases (ADH) () are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide (NAD+) to NADH. In humans and many other animals, they serve to break down alcohols that otherwise are toxic, and they also participate in generation of useful aldehyde, ketone, or alcohol groups during biosynthesis of various metabolites. In yeast, plants, and many bacteria, some alcohol dehydrogenases catalyze the opposite reaction as part of fermentation to ensure a constant supply of NAD+. Evolution Genetic evidence from comparisons of multiple organisms showed that a glutathione-dependent formaldehyde dehydrogenase, identical to a class III alcohol dehydrogenase (ADH-3/ADH5), is presumed to be the ancestral enzyme for the entire ADH family. Early on in evolution, an effective method for eliminating both endogenous and exogenous formaldehyde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coelopa Frigida
''Coelopa frigida'' is a species of seaweed fly or kelp fly. It is the most widely distributed species of seaweed fly. It can be found on most shorelines in the temperate Northern Hemisphere. Other species of seaweed flies include ''Coelopa nebularum'' and ''Coelopa pilipes''. ''C. frigida'' feeds primarily on seaweed, and groups of ''C. frigida'' flies tend to populate near bodies of water. Climate change has led to an increase in ''C. frigida'' blooms along shores, which creates a pest problem for human beach-goers. ''C. frigida'' is also an important organism for the study of sexual selection, particularly female choice, which is influenced by genetics. Description ''C. frigida'' are the most common seaweed fly. They tend to aggregate on beaches with an abundance of stranded algae, but occasionally swarm inland. Their physical features include a dark brown to black body, a set of lighter colored legs, and large, translucent wings. Males are typically larger than females, though ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perissodus Microlepis
''Perissodus microlepis'' is a species of cichlid endemic to Lake Tanganyika. This species reaches a length of TL. This species can also be found in the aquarium trade. It is a scale-eating 'parasite' on other fish species. It occurs in two distinct morphological forms. One morph has mouth parts twisted to the left, enabling it to eat scales off its victim's right flank. In contrast, the other morph, whose mouth is twisted to the right, eats scales off its victim's left flank. The relative abundance of the two morphs in populations is regulated by frequency-dependent selection Frequency-dependent selection is an evolutionary process by which the fitness (biology), fitness of a phenotype or genotype depends on the phenotype or genotype composition of a given population. * In positive frequency-dependent selection, the fit ....Stewart, T. A. and Albertson, R. C. (2010"Evolution of a unique predatory feeding apparatus: functional anatomy, development and a genetic locus for jaw l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphidromus Inversus
''Amphidromus inversus'' is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Camaenidae. MolluscaBase eds. (2020). MolluscaBase. Amphidromus inversus (O. F. Müller, 1774). Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=1245795 on 2020-05-17 Like most members of the subgenus ''Amphidromus'', it is chirally dimorphic: within the same populations, both dextral (clockwise-coiled) and sinistral (anticlockwise-coiled) individuals co-exist. This is one of the very few cases of genetic antisymmetry known in nature. Among the subgenus ''Amphidromus'', ''A. inversus'' stands out because since c. 2004, it has been the focus of studies aimed at understanding the evolution of chiral dimorphism. Most of these studies have taken place on the Malaysian island of Kapas. Subspecies * ''Amphidromus inversus andamensis'' (L. Pfeiffer, 1871) * ''Amphidromus inversus annamiticus'' (Crosse & ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Major Histocompatibility Complex
The major histocompatibility complex (MHC) is a large locus on vertebrate DNA containing a set of closely linked polymorphic genes that code for cell surface proteins essential for the adaptive immune system. These cell surface proteins are called MHC molecules. This locus got its name because it was discovered via the study of transplanted tissue compatibility. Later studies revealed that tissue rejection due to incompatibility is only a facet of the full function of MHC molecules: binding an antigen derived from self-proteins, or from pathogens, and bringing the antigen presentation to the cell surface for recognition by the appropriate T-cells. MHC molecules mediate the interactions of leukocytes, also called white blood cells (WBCs), with other leukocytes or with body cells. The MHC determines donor compatibility for organ transplant, as well as one's susceptibility to autoimmune diseases. In a cell, protein molecules of the host's own phenotype or of other biologic entities ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random Mating
Panmixia (or panmixis) means random mating. A panmictic population is one where all individuals are potential partners. This assumes that there are no mating restrictions, neither genetic nor behavioural, upon the population and that therefore all recombination is possible. The Wahlund effect assumes that the overall population is panmictic. In genetics, random mating involves the mating of individuals regardless of any physical, genetic or social preference. In other words, the mating between two organisms is not influenced by any environmental, hereditary or social interaction. Hence, potential mates have an equal chance of being selected. Random mating is a factor assumed in the Hardy–Weinberg principle and is distinct from lack of natural selection: in viability selection for instance, selection occurs ''before'' mating. Description In simple terms, panmixia (or panmicticism) is the ability of individuals in a population to interbreed without restrictions; individuals are ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Balancing Selection
Balancing selection refers to a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone. Balancing selection is rare compared to purifying selection. It can occur by various mechanisms, in particular, when the heterozygotes for the alleles under consideration have a higher fitness than the homozygote. In this way genetic polymorphism is conserved. Evidence for balancing selection can be found in the number of alleles in a population which are maintained above mutation rate frequencies. All modern research has shown that this significant genetic variation is ubiquitous in panmictic populations. There are several mechanisms (which are not exclusive within any given population) by which balancing selection works to maintain polymorphism. The two major and most studied are heterozygote advantage and frequency-dependent selection. Mech ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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