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Migration (ecology)
Migration, in ecology, is the large-scale movement of members of a species to a different environment. Migration is a natural behavior and component of the life cycle of many species of mobile organisms, not limited to animals, though animal migration is the best known type. Migration is often cyclical, frequently occurring on a seasonal basis, and in some cases on a daily basis. Species migrate to take advantage of more favorable conditions with respect to food availability, safety from predation, mating opportunity, or other environmental factors. While members of some species learn a migratory route on their first journey with older members of their group, other species genetically pass on information regarding their migratory paths. Despite many differences in organisms’ migratory cues and behaviors, “considerable similarities appear to exist in the cues involved in the different phases of migration.” Migratory organisms use environmental cues like photoperiod and weath ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wildebeest Crossing River - Stefan Swanepoel
Wildebeest ( , , ), also called gnu ( or ), are antelopes of the genus ''Connochaetes'' and native to Eastern and Southern Africa. They belong to the family Bovidae, which includes true antelopes, cattle, goats, sheep, and other even-toed horned ungulates. There are two species of wildebeest: the black wildebeest or white-tailed gnu (''C. gnou''), and the blue wildebeest or brindled gnu (''C. taurinus''). Fossil records suggest these two species diverged about one million years ago, resulting in a northern and a southern species. The blue wildebeest remained in its original range and changed very little from the ancestral species, while the black wildebeest changed more as adaptation to its open grassland habitat in the south. The most obvious ways of telling the two species apart are the differences in their colouring and in the way their horns are oriented. In East Africa, the blue wildebeest is the most abundant big-game species; some populations perform an annual mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olfaction
The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, it occurs when an odor binds to a receptor within the nasal cavity, transmitting a signal through the olfactory system. Glomeruli aggregate signals from these receptors and transmit them to the olfactory bulb, where the sensory input will start to interact with parts of the brain responsible for smell identification, memory, and emotion. There are many different causes for alteration, lack, or disturbance to a normal sense of smell, and can include damage to the nose or smell receptors, or central problems affecting the brain. Some causes include upper respiratory infections, traumatic brain injury, and neurodegenerative disease. History of study Early scientific study of the sense of smell includes the extensive doctoral dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ecology
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps with the closely related sciences of biogeography, evolutionary biology, genetics, ethology, and natural history. Ecology is a branch of biology, and it is not synonymous with environmentalism. Among other things, ecology is the study of: * The abundance, biomass, and distribution of organisms in the context of the environment * Life processes, antifragility, interactions, and adaptations * The movement of materials and energy through living communities * The successional development of ecosystems * Cooperation, competition, and predation within and between species * Patterns of biodiversity and its effect on ecosystem processes Ecology has practical applications in conservation biology, wetland management, natural resour ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Migration
Human migration is the movement of people from one place to another with intentions of settling, permanently or temporarily, at a new location (geographic region). The movement often occurs over long distances and from one country to another (external migration), but internal migration (within a single country) is also possible; indeed, this is the dominant form of human migration globally. Migration is often associated with better human capital at both individual and household level, and with better access to migration networks, facilitating a possible second move. It has a high potential to improve human development, and some studies confirm that migration is the most direct route out of poverty.Age is also important for both work and non-work migration. People may migrate as individuals, in family units or in large groups. There are four major forms of migration: invasion, conquest, colonization and emigration/ immigration. Persons moving from their home due to forced di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great American Interchange
The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which land and freshwater fauna migrated from North America via Central America to South America and vice versa, as the volcanic Isthmus of Panama rose up from the sea floor and bridged the formerly separated continents. Although earlier dispersals had occurred, probably over water, the migration accelerated dramatically about 2.7 million years ( Ma) ago during the Piacenzian age. It resulted in the joining of the Neotropic (roughly South American) and Nearctic (roughly North American) biogeographic realms definitively to form the Americas. The interchange is visible from observation of both biostratigraphy and nature ( neontology). Its most dramatic effect is on the zoogeography of mammals, but it also gave an opportunity for reptiles, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Top-down And Bottom-up Design
Top-down and bottom-up are both strategies of information processing and knowledge ordering, used in a variety of fields including software, humanistic and scientific theories (see systemics), and management and organization. In practice, they can be seen as a style of thinking, teaching, or leadership. A top-down approach (also known as ''stepwise design'' and stepwise refinement and in some cases used as a synonym of ''decomposition'') is essentially the breaking down of a system to gain insight into its compositional sub-systems in a reverse engineering fashion. In a top-down approach an overview of the system is formulated, specifying, but not detailing, any first-level subsystems. Each subsystem is then refined in yet greater detail, sometimes in many additional subsystem levels, until the entire specification is reduced to base elements. A top-down model is often specified with the assistance of "black boxes", which makes it easier to manipulate. However, black boxes may ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of California Press
The University of California Press, otherwise known as UC Press, is a publishing house associated with the University of California that engages in academic publishing. It was founded in 1893 to publish scholarly and scientific works by faculty of the University of California, established 25 years earlier in 1868, and has been officially headquartered at the university's flagship campus in Berkeley, California, since its inception. As the non-profit publishing arm of the University of California system, the UC Press is fully subsidized by the university and the State of California. A third of its authors are faculty members of the university. The press publishes over 250 new books and almost four dozen multi-issue journals annually, in the humanities, social sciences, and natural sciences, and maintains approximately 4,000 book titles in print. It is also the digital publisher of Collabra and Luminos open access (OA) initiatives. The University of California Press publishes i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forest Migration
Forest migration or assisted migration is the movement of large seed plant dominated communities in geographical space over time. The emphasis of forest migration is placed on the movement of the populations that make up the forest community. Though an individual tree is permanently fixed in a location, tree populations may migrate over the landscape through successful dispersal and establishment into new regions and/or a lack of regeneration in a portion of its previous habitat range over the course of generations. Tree migration is controlled by two overlying forces: environmental suppression and dispersal capacity of the population by seed. Though the true rate of forest expansion is difficult to quantify, efforts are being made to evaluate and predict past, current, and future rates and extents of forest movements. Forces controlling forest migrations Forest migration happens by the occurrence of two processes: population expansion into new habitat range and population retr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seed Dispersal
In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, such as the wind, and living (biotic) vectors such as birds. Seeds can be dispersed away from the parent plant individually or collectively, as well as dispersed in both space and time. The patterns of seed dispersal are determined in large part by the dispersal mechanism and this has important implications for the demographic and genetic structure of plant populations, as well as migration patterns and species interactions. There are five main modes of seed dispersal: gravity, wind, ballistic, water, and by animals. Some plants are serotinous and only disperse their seeds in response to an environmental stimulus. These modes are typically inferred based on adaptations, such as wings or fleshy fruit. However, this simplified view may ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insect Migration
Insect migration is the seasonal movement of insects, particularly those by species of dragonflies, beetles, butterflies and moths. The distance can vary with species and in most cases, these movements involve large numbers of individuals. In some cases, the individuals that migrate in one direction may not return and the next generation may instead migrate in the opposite direction. This is a significant difference from bird migration. Definition All insects move to some extent. The range of movement can vary from within a few centimeters for some sucking insects and wingless aphids to thousands of kilometers in the case of other insects such as locusts, butterflies and dragonflies. The definition of migration is therefore particularly difficult in the context of insects. A behavior-oriented definition proposed is This definition disqualifies movements made in the search of resources and which are terminated upon finding the resource. Migration involves longer distance move ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish Migration
Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres. Such migrations are usually done for better feeding or to reproduce, but in other cases the reasons are unclear. Fish migrations involve movements of schools of fish on a scale and duration larger than those arising during normal daily activities. Some particular types of migration are ''anadromous'', in which adult fish live in the sea and migrate into fresh water to spawn; and ''catadromous'', in which adult fish live in fresh water and migrate into salt water to spawn. Marine forage fish often make large migrations between their spawning, feeding and nursery grounds. Movements are associated with ocean currents and with the availability of food in different areas at different times of year. The migratory movements ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bird Migration
Bird migration is the regular seasonal movement, often north and south along a flyway, between breeding and wintering grounds. Many species of bird migrate. Migration carries high costs in predation and mortality, including from hunting by humans, and is driven primarily by the availability of food. It occurs mainly in the northern hemisphere, where birds are funneled onto specific routes by natural barriers such as the Mediterranean Sea or the Caribbean Sea. Migration of species such as storks, turtle doves, and swallows was recorded as many as 3,000 years ago by Ancient Greek authors, including Homer and Aristotle, and in the Book of Job. More recently, Johannes Leche began recording dates of arrivals of spring migrants in Finland in 1749, and modern scientific studies have used techniques including bird ringing and satellite tracking to trace migrants. Threats to migratory birds have grown with habitat destruction, especially of stopover and wintering sites, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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