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Allochronic Speciation
Allochronic speciation (also known as allochronic isolation, or temporal isolation) is a form of speciation (specifically ecological speciation) arising from reproductive isolation that occurs due to a change in breeding time that reduces or eliminates gene flow between two populations of a species. The term allochrony is used to describe the general ecological phenomenon of the differences in phenology that arise between two or more species—speciation caused by allochrony is effectively allochronic speciation. Environmental changes acting on a species population or populations can drive isolation. An important form of isolation is when populations are separated, not geographically, but temporally (by time). Genetic changes (mutations) over time can cause the two populations to differ—notably in phenology (events in a species life dictated by time such as breeding seasons); exhibiting unique phenotypes (the observable characteristics or traits of an organism). Scientists have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speciation
Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages. Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book ''On the Origin of Species''. He also identified sexual selection as a likely mechanism, but found it problematic. There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric speciation, allopatric, peripatric speciation, peripatric, parapatric speciation, parapatric, and sympatric speciation, sympatric. Whether genetic drift is a minor or major contributor to speciation is the subject of much ongoing discussion. Rapid sympatric speciation can take place through polyploidy, such as by doubling of chromosome number; the result is progeny wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoperiodism
Photoperiod is the change of day length around the seasons. The rotation of the earth around its axis produces 24 hour changes in light (day) and dark (night) cycles on earth. The length of the light and dark in each phase varies across the seasons due to the tilt of the earth around its axis. The photoperiod defines the length of the light, for example a summer day the length of light could be 16 hours while the dark is 8 hours, whereas a winter day the length of day could be 8 hours, whereas the dark is 16 hours. Importantly, the seasons are different in the northern hemisphere than the southern hemisphere. Photoperiodism is the physiological reaction of organisms to the length of light or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods. They are classified under three groups according to the photoperiods: short-day plants, long-day plants, and day ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cline (biology)
In biology, a cline is a measurable gradient in a single characteristic (or biological trait) of a species across its geographical range. Clines usually have a genetic (e.g. allele frequency, blood type), or phenotypic (e.g. body size, skin pigmentation) character. They can show either smooth, continuous gradation in a character, or more abrupt changes in the trait from one geographic region to the next. A cline is a spatial gradient in a single specific trait, rather than in a collection of traits; a single population can therefore have as many clines as it has traits, at least in principle. Additionally, as Julian Huxley recognised, these multiple independent clines may not act in concordance with each other. For example, it has been observed that in Australia, birds generally become smaller the further towards the north of the country they are found. In contrast, the intensity of their plumage colouration follows a different geographical trajectory, being most vibrant where ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenotype
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological properties, and its behavior. An organism's phenotype results from two basic factors: the expression of an organism's genetic code (its genotype) and the influence of environmental factors. Both factors may interact, further affecting the 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 again in his 1982 book '' The Extended Phenotype'' suggested that one can regard bird nests and other built structures such as caddisfly larva cases and beaver dams ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bamboo
Bamboos are a diverse group of mostly evergreen perennial plant, perennial flowering plants making up the subfamily (biology), subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family, in the case of ''Dendrocalamus sinicus'' having individual stalks (Culm (botany), culms) reaching a length of , up to in thickness and a weight of up to . The internodes of bamboos can also be of great length. ''Kinabaluchloa, Kinabaluchloa wrayi'' has internodes up to in length. and ''Arthrostylidium schomburgkii'' has internodes up to in length, exceeded in length only by Cyperus papyrus, papyrus. By contrast, the stalks of the tiny bamboo Raddiella, ''Raddiella vanessiae'' of the savannas of French Guiana measure only in length by about in width. The origin of the word "bamboo" is uncertain, but it most likely comes from the Dutch language, Dutch or Portuguese language, Portuguese language, which originally borrowed it from Malay langua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Periodical Cicadas
The term periodical cicada is commonly used to refer to any of the seven species of the genus ''Magicicada'' of eastern North America, the 13- and 17-year cicadas. They are called periodical because nearly all individuals in a local population are developmentally synchronized and emerge in the same year. Although they are sometimes called "locusts", this is a misnomer, as cicadas belong to the taxonomic order Hemiptera (true bugs), suborder Auchenorrhyncha, while locusts are grasshoppers belonging to the order Orthoptera. ''Magicicada'' belongs to the cicada tribe Lamotialnini, a group of genera with representatives in Australia, Africa, and Asia, as well as the Americas. ''Magicicada'' species spend around 99.5% of their long lives underground in an immature state called a nymph. While underground, the nymphs feed on xylem fluids from the roots of broadleaf forest trees in the eastern United States. In the spring of their 13th or 17th'' ''year, mature cicada nymphs emerge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sockeye Salmon
The sockeye salmon (''Oncorhynchus nerka''), also called red salmon, kokanee salmon, blueback salmon, or simply sockeye, is an anadromous species of salmon found in the Northern Pacific Ocean and rivers discharging into it. This species is a Pacific salmon that is primarily red in hue during spawning. They can grow up to in length and weigh . Juveniles remain in freshwater until they are ready to migrate to the ocean, over distances of up to . Their diet consists primarily of zooplankton. Sockeye salmon are semelparous, dying after they spawn. Some populations, referred to as kokanee, do not migrate to the ocean and live their entire lives in fresh water. Classification and name origin The sockeye salmon is the third-most common Pacific salmon species, after pink and chum salmon. ''Oncorhynchus'' comes from Ancient Greek ὄγκος (''ónkos''), meaning "bend", and ῥύγχος (''rhúnkhos''), meaning "snout". The specific name ''nerka'' is the Russian name for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salmon Run
A salmon run is an annual fish migration event where many salmonid species, which are typically hatched in fresh water and live most of their adult life downstream in the ocean, swim back against the stream to the upper reaches of rivers to spawn (biology), spawn on the gravel beds of small stream, creeks. After spawning, most Atlantic salmon and all species of Oncorhynchus, Pacific salmon die, and the salmon biological life cycle, life cycle starts over again with the new generation of hatchlings. Salmon are anadromous, spending their juvenile fish, juvenile life in rivers or lakes, and then migrating out to sea where they spend adult lives and gain most of their body mass. When they reach sexual maturity, the adults return to the upstream rivers to reproduce. Usually they natal homing, return with uncanny precision to the natal river where they were born, and even to the very spawning ground of their birth. It is thought that, when they are in the ocean, they use magnetorece ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbicella
''Orbicella'' is a genus of stony corals in the Merulinidae family. The ''Orbicella'' species complex comprises three sister species, namely '' Orbicella faveolata'', '' Orbicella annularis'' and '' Orbicella franksi'', all of which are shallow-water, zooxanthellate species and are native to the tropical western Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. These corals are ubiquitous and major reef-builders in the Caribbean. Their similar colony morphologies misled scientists to historically lump them into a single species, ''Montastraea annularis'', which included three morphotypes “bumpy”, “columnar” and “massive”. These growth forms were believed to arise as a response to abiotic factors (e.g., depth, light availability). This taxonomic classification was challenged by further ecological, reproductive, genetic, and morphologic evidence, which led to the re-description of three separate species, ''Montastraea faveolata'' (massive), ''M. annularis'' ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acropora
''Acropora'' is a genus of small polyp stony coral in the phylum Cnidaria. Some of its species are known as table coral, elkhorn coral, and staghorn coral. Over 149 species are described. ''Acropora'' species are some of the major reef corals responsible for building the immense calcium carbonate substructure that supports the thin living skin of a reef. Anatomy and distribution Depending on the species and location, ''Acropora'' species may grow as plates or slender or broad branches. Like other corals, ''Acropora'' corals are colonies of individual polyps, which are about 2 mm across and share tissue and a nerve net. The polyps can withdraw back into the coral in response to movement or disturbance by potential predators, but when undisturbed, they protrude slightly. The polyps typically extend further at night to help capture plankton and organic matter from the water. The species are distributed in the Indo-Pacific (over 100 species) and Caribbean (3 species). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reinforcement (speciation)
Reinforcement is a process of speciation where natural selection increases the reproductive isolation (further divided to pre-zygotic isolation and post-zygotic isolation) between two populations of species. This occurs as a result of selection acting against the production of hybrid individuals of low fitness. The idea was originally developed by Alfred Russel Wallace and is sometimes referred to as the Wallace effect. The modern concept of reinforcement originates from Theodosius Dobzhansky. He envisioned a species separated allopatrically, where during secondary contact the two populations mate, producing hybrids with lower fitness. Natural selection results from the hybrid's inability to produce viable offspring; thus members of one species who do not mate with members of the other have greater reproductive success. This favors the evolution of greater prezygotic isolation (differences in behavior or biology that inhibit formation of hybrid zygotes). Reinforcement ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
