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Mottled Duck
The mottled duck (''Anas fulvigula'') or mottled mallard is a medium-sized species of dabbling duck. It is intermediate in appearance between the female mallard and the American black duck. It is closely related to those species, and is sometimes erroneously considered a subspecies of the former. Along the Gulf of Mexico coast, the mottled duck is one of the most frequently banded waterfowl. This is due in part to the fact that it is mostly non-migratory. Approximately one out of every 20 mottled ducks is banded, making it an extremely prized and sought after bird among hunters. Subspecies There are two distinct subspecies of the mottled duck. One subspecies, the Gulf Coast mottled duck (''A. f. maculosa''), lives on the Gulf of Mexico coast between Alabama and Tamaulipas (Mexico); outside the breeding season, individual birds may venture as far south as Veracruz. The other, the Florida mottled duck (''A. f. fulvigula''), is resident in central and southern Florida and occasiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Ridgway
Robert Ridgway (July 2, 1850 – March 25, 1929) was an American ornithologist specializing in systematics. He was appointed in 1880 by Spencer Fullerton Baird, secretary of the Smithsonian Institution, to be the first full-time curator of birds at the United States National Museum, a title he held until his death. In 1883, he helped found the American Ornithologists' Union, where he served as officer and journal editor. Ridgway was an outstanding descriptive taxonomist, capping his life work with ''The Birds of North and Middle America'' (eight volumes, 1901–1919). In his lifetime, he was unmatched in the number of North American bird species that he described for science. As technical illustrator, Ridgway used his own paintings and outline drawings to complement his writing. He also published two books that systematized color names for describing birds, ''A Nomenclature of Colors for Naturalists'' (1886) and ''Color Standards and Color Nomenclature'' (1912). Orni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speculum Feathers
The speculum is a patch, often distinctly coloured, on the secondary wing feathers, or ''remiges'', of some birds. Examples of the colour(s) of the speculum in a number of ducks are: * Common teal and green-winged teal: Iridescent green edged with buff. * Blue-winged teal: Iridescent green. The species' common name comes from the sky-blue wing coverts. * Crested duck and bronze-winged duck: Iridescent purple-bronze, edged white. * Pacific black duck: Iridescent green, edged light buff. * Mallard: Iridescent purple-blue with white edges. * American black duck: Iridescent violet bordered in black and may have a thin white trailing edge. * Northern pintail: Iridescent green in male and brown in female, both are white on trailing edge. * Gadwall: Both sexes have white inner secondaries. * Yellow-billed duck: Iridescent green or blue, bordered white. Bright wing speculums are also known from a number of other birds; among them are several parrots from the genus Genus ( plura ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules. The theory of evolut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylogeny
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical or genetic characteristics. All life on Earth is part of a single phylogenetic tree, indicating common ancestry. In a ''rooted'' phylogenetic tree, each node with descendants represents the inferred most recent common ancestor of those descendants, and the edge lengths in some trees may be interpreted as time estimates. Each node is called a taxonomic unit. Internal nodes are generally called hypothetical taxonomic units, as they cannot be directly observed. Trees are useful in fields of biology such as bioinformatics, systematics, and phylogenetics. ''Unrooted'' trees illustrate only the relatedness of the leaf nodes and do not require the ancestral r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sample Size
Sample size determination is the act of choosing the number of observations or replicates to include in a statistical sample. The sample size is an important feature of any empirical study in which the goal is to make inferences about a population from a sample. In practice, the sample size used in a study is usually determined based on the cost, time, or convenience of collecting the data, and the need for it to offer sufficient statistical power. In complicated studies there may be several different sample sizes: for example, in a stratified survey there would be different sizes for each stratum. In a census, data is sought for an entire population, hence the intended sample size is equal to the population. In experimental design, where a study may be divided into different treatment groups, there may be different sample sizes for each group. Sample sizes may be chosen in several ways: *using experience – small samples, though sometimes unavoidable, can result in wide co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Flow
In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent allele frequencies and therefore can be considered a single effective population. It has been shown that it takes only "one migrant per generation" to prevent populations from diverging due to drift. Populations can diverge due to selection even when they are exchanging alleles, if the selection pressure is strong enough. Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants change the distribution of genetic diversity among populations, by modifying allele frequencies (the proportion of members carrying a particular variant of a gene). High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity. For this reason, gene flow has been thought to c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Caribbean Sea, and to the west and south by the Pacific Ocean. Because it is on the North American Tectonic Plate, Greenland is included as a part of North America geographically. North America covers an area of about , about 16.5% of Earth's land area and about 4.8% of its total surface. North America is the third-largest continent by area, following Asia and Africa, and the fourth by population after Asia, Africa, and Europe. In 2013, its population was estimated at nearly 579 million people in 23 independent states, or about 7.5% of the world's population. In human geography and in the English-speaking world outside the United States, particularly in Canada, "North America" and "North American" can refer to just Canada and the Uni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hybrid (biology)
In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in blending inheritance), but can show hybrid vigor, sometimes growing larger or taller than either parent. The concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are. Species are reproductively isolated by strong barriers to hybridisation, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. Some act before fertilization and others after it. Similar barriers exist in plants, with differences in flowering t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, the equivalent Latin term ''cladus'' (plural ''cladi'') is often used in taxonomical literature. The common ancestor may be an individual, a population, or a species (extinct or extant). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic. Some of the relationships between org ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mottled Duck
The mottled duck (''Anas fulvigula'') or mottled mallard is a medium-sized species of dabbling duck. It is intermediate in appearance between the female mallard and the American black duck. It is closely related to those species, and is sometimes erroneously considered a subspecies of the former. Along the Gulf of Mexico coast, the mottled duck is one of the most frequently banded waterfowl. This is due in part to the fact that it is mostly non-migratory. Approximately one out of every 20 mottled ducks is banded, making it an extremely prized and sought after bird among hunters. Subspecies There are two distinct subspecies of the mottled duck. One subspecies, the Gulf Coast mottled duck (''A. f. maculosa''), lives on the Gulf of Mexico coast between Alabama and Tamaulipas (Mexico); outside the breeding season, individual birds may venture as far south as Veracruz. The other, the Florida mottled duck (''A. f. fulvigula''), is resident in central and southern Florida and occasiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Sequence
DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. The advent of rapid DNA sequencing methods has greatly accelerated biological and medical research and discovery. Knowledge of DNA sequences has become indispensable for basic biological research, DNA Genographic Projects and in numerous applied fields such as medical diagnosis, biotechnology, forensic biology, virology and biological systematics. Comparing healthy and mutated DNA sequences can diagnose different diseases including various cancers, characterize antibody repertoire, and can be used to guide patient treatment. Having a quick way to sequence DNA allows for faster and more individualized medical care to be administered, and for more organisms to be identified and cataloged. The rapid speed of sequencing attained with modern D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MtDNA Control Region
The mtDNA control region is an area of the mitochondrial genome which is non-coding DNA. This region controls RNA and DNA synthesis. It is the most polymorphic region of the human mtDNA genome, with polymorphism concentrated in hypervariable regions. The average nucleotide diversity in these regions is 1.7%. Despite this variability, an RNA transcript from this region has a conserved secondary structure (''pictured'') which has been found to be under selective pressure. The mtDNA control region contains the origin of replication of one strand, and the origin of transcription for both strands. There is also an open reading frame thought to code for 7s ribosomal RNA in humans but not in mice or cows, where it has been deleted. Distinction from D-loop The control region and mtDNA D-loop are sometimes used synonymously in the literature; specifically the control region includes the D-loop along with adjacent transcription promoter regions. For this reason, the control reg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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