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Wild Ancestor
Wild ancestors are the original species from which domesticated plants and animals are derived. Examples include dogs which are derived from wolves and flax which is derived from ''Linum bienne''. In most cases the wild ancestor species still exists, but some domesticated species, such as camels, have no surviving wild relatives. In many cases there is considerable debate in the scientific community about the identity of the wild ancestor or ancestors, as the process of domestication involves natural selection, artificial selection, and hybridization. Wild ancestors have gone through genetic changes to achieve biological mutualism with humans. This is due to humans selectively breeding those species. Theory All living creatures are derived from a common wild ancestor. With time and the help of humans or nature, living beings adapt to their surroundings by gradual changes whether visible or not. According to Darwin, there are two different categories that may cause wild ances ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. However, only about 14% of these had been described by 2011. All species (except viruses) are given a two-part name, a "binomial". The first part of a binomial is the genus to which the species belongs. The second part is called the specific name or the specific epithet (in botanical nomenclature, also sometimes i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Pressure
Any cause that reduces or increases reproductive success in a portion of a population potentially exerts evolutionary pressure, selective pressure or selection pressure, driving natural selection. It is a quantitative description of the amount of change occurring in processes investigated by evolutionary biology, but the formal concept is often extended to other areas of research. In population genetics, selective pressure is usually expressed as a selection coefficient. Amino acids selective pressure It has been shown that putting an amino acid bio-synthesizing gene like ''HIS4'' gene under amino acid selective pressure in yeast causes enhancement of expression of adjacent genes which is due to the transcriptional co-regulation of two adjacent genes in Eukaryota. Antibiotic resistance Drug resistance in bacteria is an example of an outcome of natural selection. When a drug is used on a species of bacteria, those that cannot resist die and do not produce offspring, while th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homo Habilis
''Homo habilis'' ("handy man") is an extinct species of archaic human from the Early Pleistocene of East and South Africa about 2.31 million years ago to 1.65 million years ago (mya). Upon species description in 1964, ''H. habilis'' was highly contested, with many researchers recommending it be synonymised with '' Australopithecus africanus'', the only other early hominin known at the time, but ''H. habilis'' received more recognition as time went on and more relevant discoveries were made. By the 1980s, ''H. habilis'' was proposed to have been a human ancestor, directly evolving into '' Homo erectus'' which directly led to modern humans. This viewpoint is now debated. Several specimens with insecure species identification were assigned to ''H. habilis'', leading to arguments for splitting, namely into "''H. rudolfensis''" and "'' H. gautengensis''" of which only the former has received wide support. Like contemporary ''Homo'', ''H. habilis'' brain size generally varied from . ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continuous Breeder
Continuous breeders are animal species that can breed or mate throughout the year. This includes humans and apes ( bonobos, chimpanzees, gorillas, orangutans, and gibbons), who can have a child at any time of year. In continuous breeders, females are sexually receptive during estrus, at which time ovarian follicles are maturing and ovulation can occur. Evidence of ovulation, the phase during which conception is most probable, is advertised to males among many non-human primates via swelling and redness of the genitalia. See also * Opportunistic breeder * Seasonal breeder Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and ch ... References Attribution Animal breeding Fertility Reproduction in animals {{zoology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seasonal Breeder
Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and changes in the predation behaviors of other species. Related sexual interest and behaviors are expressed and accepted only during this period. Female seasonal breeders will have one or more estrus cycles only when she is "in season" or fertile and receptive to mating. At other times of the year, they will be anestrus, or have a dearth of their sexual cycle. Unlike reproductive cyclicity, seasonality is described in both males and females. Male seasonal breeders may exhibit changes in testosterone levels, testes weight, and fertility depending on the time of year. Seasonal breeders are distinct from opportunistic breeders, that mate whenever the conditions of their environment become favorable, and continuous breeders that mate year-round. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Matter
White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribution of action potentials, acting as a relay and coordinating communication between different brain regions. White matter is named for its relatively light appearance resulting from the lipid content of myelin. However, the tissue of the freshly cut brain appears pinkish-white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color in prepared specimens is due to its usual preservation in formaldehyde. Structure White matter White matter is composed of bundles, which connect various grey matter areas (the locations of nerve cell bodies) of the brain to each other, and carry nerve impulses between neurons. Myelin acts as an insulator, which allows electrical signals to jump, rather than c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prefrontal Cortex
In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA46, and BA47. The basic activity of this brain region is considered to be orchestration of thoughts and actions in accordance with internal goals. Many authors have indicated an integral link between a person's will to live, personality, and the functions of the prefrontal cortex. This brain region has been implicated in executive functions, such as planning, decision making, short-term memory, personality expression, moderating social behavior and controlling certain aspects of speech and language. Executive function relates to abilities to differentiate among conflicting thoughts, determine good and bad, better and best, same and different, future consequences of current activities, working toward a defined goal, prediction of outcomes, e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amygdala
The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex vertebrates, including humans. Shown to perform a primary role in the processing of memory, decision making, and emotional responses (including fear, anxiety, and aggression), the amygdalae are considered part of the limbic system. The term "amygdala" was first introduced by Karl Friedrich Burdach in 1822. Structure The regions described as amygdala nuclei encompass several structures of the cerebrum with distinct connectional and functional characteristics in humans and other animals. Among these nuclei are the basolateral complex, the cortical nucleus, the medial nucleus, the central nucleus, and the intercalated cell clusters. The basolateral complex can be further subdivided into the lateral, the basal, and the accessory basal nucle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toy Dog
Toy dog traditionally refers to a very small dog or a grouping of small and very small breeds of dog. A toy dog may be of any of various dog types. Types of dogs referred to as toy dogs may include spaniels, pinschers and terriers that have been bred down in size. Not all toy dogs are lap dogs. Small dogs Dogs found in the Toy Group of breed registries may be of the very ancient lapdog type, or they may be small versions of hunting dogs or working dogs, bred down in size for a particular kind of work or to create a pet of convenient size. In the past, very small dogs not used for hunting were kept as symbols of affluence, as watchdogs, and for the health function of attracting fleas away from their owners. Breeds Most major dog clubs in the English-speaking world have a toy group, under one exact name or another, in which they place breeds of dog that the kennel club categorizes as ''toy'', based on size and tradition. The Kennel Club (UK), the Canadian Kennel Clu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brachycephaly
Brachycephaly (derived from the Ancient Greek '' βραχύς'', 'short' and '' κεφαλή'', 'head') is the shape of a skull shorter than typical for its species. It is perceived as a desirable trait in some domesticated dog and cat breeds, notably the pug and Persian, and can be normal or abnormal in other animal species. In humans, the cephalic disorder is known as flat head syndrome, and results from premature fusion of the coronal sutures, or from external deformation. The coronal suture is the fibrous joint that unites the frontal bone with the two parietal bones of the skull. The parietal bones form the top and sides of the skull. This feature can be seen in Down syndrome. In anthropology, human populations have been characterized as either dolichocephalic (long-headed), mesaticephalic (moderate-headed), or brachycephalic (short-headed). The usefulness of the cephalic index was questioned by Giuseppe Sergi, who argued that cranial morphology provided a better mean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Betta
''Betta'' is a large genus of small, active, often colorful, freshwater ray-finned fishes, in the gourami family (Osphronemidae). The best known ''Betta'' species is ''B. splendens,'' commonly known as the Siamese fighting fish and often kept as an aquarium pet. Characteristics All ''Betta'' species are small fishes, but they vary considerably in size, ranging from under 2.5 cm (1 in) total length in ''B. chanoides'' to 14 cm (5.5 in) in the Akar betta (''B. akarensis''). Bettas are anabantoids, which means they can breathe atmospheric air using a unique organ called the labyrinth. This accounts for their ability to thrive in low-oxygen water conditions that would kill most other fish, such as rice paddies, slow-moving streams, drainage ditches, and large puddles. The bettas exhibit two kinds of spawning behaviour: some build bubble nests, such as ''B. splendens'', while others are mouthbrooders, such as ''B. picta''. The mouthbrooding species are sometim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dmitry Belyayev (zoologist)
Dmitry Konstantinovich Belyayev (Russian: Дми́трий Константи́нович Беля́ев, 17 July 1917 – 14 November 1985) was a Soviet geneticist and academician who served as director of the Institute of Cytology and Genetics (IC&G) of the USSR Academy of Sciences, Novosibirsk, from 1959 to 1985. His decades-long effort to breed domesticated silver foxes was described by ''The New York Times'' as “arguably the most extraordinary breeding experiment ever conducted.” A 2010 article in Scientific American stated that Belyayev “may be the man most responsible for our understanding of the process by which wolves were domesticated into our canine companions.” Beginning in the 1950s, in order to uncover the genetic basis of the distinctive behavioral and physiological attributes of domesticated animals, Belyayev and his team spent decades breeding the silver fox (''Vulpes vulpes'') and selecting for reproduction only those individuals in each generation that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
