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K-selection

K-selection

In ecology, K-selection (note : upper case "K") relates to the selection of traits (in organisms) that allow success in stable or predictable environments. Under these circumstances, the ability to compete successfully for limited resources is crucial, and populations of K-selected organisms are typically very constant and close to the maximum that the environment can bear. Traits that are thought to be characteristic of K-selection include : large size; long life span; and the production of fewer offspring that are well cared for. Organisms whose life history is subject to K-selection are often referred to as "K-strategists". Species with K-selected traits include trees, and large animals such as elephants, humans and whales. The term K-selection itself is derived from standard ecological algebra, as illustrated in the simple Verhulst equation of population dynamics : :\frac=rN\left(1 - \frac\right) \qquad \! Where K is the carrying capacity of the population (N), and r is its growth rate. It should be noted that, although some organisms are primarily r- or K-strategists, the majority of organisms fall between these two ecological extremes, and may display traits considered characteristic of both ends of the r-K spectrum. For instance, trees have traits such as longevity and strong competitiveness that characterise them as K-strategists. However, in reproduction, trees typically produce thousands of offspring and disperse them widely, traits characteristic of r-strategists. Contrast with r-selection.

References


- Pianka, E. R. (1970). On r and K selection. American Naturalist 104, 592-597.
- Verhulst, P. F., (1838). Notice sur la loi que la population pursuit dans son accroissement. Corresp. Math. Phys. 10, 113-121. Category:Ecology Category:Evolutionary biology

Ecology

Ecology, or ecological science, is the scientific study of the distribution and abundance of living organisms and how these properties are affected by interactions between the organisms and their environment. The environment of an organism includes both the physical properties, which can be described as the sum of local abiotic factors like climate and geology, as well as the other organisms that share its habitat. The term oekologie was coined in 1866 by the German biologist Ernst Haeckel; the word is derived from the Greek oikos ("household") and logos ("study")–therefore, "ecology" means the "study of the household of nature".

Scope

Ecology is usually considered a branch of biology, the general science that studies living organisms. Organisms can be studied at many different levels, from proteins and nucleic acids (in biochemistry and molecular biology), to cells (in cellular biology), to individuals (in botany, zoology, and other similar disciplines), and finally at the level of populations, communities, and ecosystems, to the biosphere as a whole; these latter strata are the primary subjects of ecological inquiries. Ecology is a multi-disciplinary science. Because of its focus on the higher levels of the organization of life on earth and on the interrelations between organisms and their environment, ecology draws heavily on many other branches of science, especially geology and geography, meteorology, pedology, chemistry, and physics. Thus, ecology is said to be a holistic science, one that over-arches older disciplines such as biology which in this view become sub-disciplines contributing to ecological knowledge. Agriculture, fisheries, forestry, medicine and urban development are among human activities that would fall within Krebbs' (1972: 4) explanation of his definition of ecology: "where organisms are found, how many occur there, and why". As a scientific discipline, ecology does not dictate what is "right" or "wrong". However, maintaining biodiversity and related ecological goals have provided a scientific basis for expressing the goals of environmentalism and have given scientific methodology, measure, and terminology to environmental issues. Additionally, a holistic view of nature is stressed in both ecology and environmentalism. Consider the ways an ecologist might approach studying the life of honeybees:
- the behavioral relationship between individuals of a species is behavorial ecology — for example, the study of the queen bee, and how she relates to the worker bees and the drones.
- The organized activity of a species is community ecology; for example, the activity of bees assures the pollination of flowering plants. Bee hives additionally produce honey which is consumed by still other species, such as bears.
- The relationship between the environment and a species is environmental ecology — for example, the consequences of environmental change on bee activity. Bees may die out due to environmental changes (see pollinator decline). The environment simultaneously affects and is a consequence of this activity and is thus intertwined with the survival of the species.

Disciplines of ecology

: Main article: Disciplines of ecology Ecology is a broad science which can be subdivided into major and minor sub-disciplines. The major sub-disciplines include (in a nested series from the smallest to the largest in scope):
- Physiological Ecology (or ecophysiology), which studies the influence of the biotic and abiotic environment on the physiology of the individual, and the adaptation of the individual to its environment;
- Behavioral ecology, which studies the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling animals to adapt to their ecological niches;
- Population ecology (or autecology), which deals with the dynamics of populations within species, and the interactions of these populations with environmental factors;
- Community ecology (or synecology) which studies the interactions between species within an ecological community;
- Ecosystem ecology, which studies the flows of energy and matter through ecosystems;
- Landscape ecology, which studies the interactions between discrete elements of a landscape;
- Global ecology, which looks at ecological questions at the global level, often asking macroecological questions. Ecology can also be sub-divided on the basis of target groups:
- Animal ecology, plant ecology, insect ecology; Ecology can also be sub-divided from the perspective of the studied biomes:
- Arctic ecology (or polar ecology), tropical ecology, desert ecology (temperate zone ecology could also exist as a distinct sub-field, but ecology as a whole has an overwhelmingly temperate bias, so the sub-field is redundant). Spanning all of the above is:
- Evolutionary ecology.

History of ecology

: Main article: History of ecology

Fundamental principles of ecology

Biosphere and biodiversity

Main articles: Biosphere, Biodiversity, Unified neutral theory of biodiversity For modern ecologists, ecology can be studied at several levels: population level (individuals of the same species), biocoenosis level (or community of species), ecosystem level, and biosphere level. The outer layer of the planet Earth can be divided into several compartments: the hydrosphere (or sphere of water), the lithosphere (or sphere of soils and rocks), and the atmosphere (or sphere of the air). The biosphere (or sphere of life), sometimes described as "the fourth envelope", is all living matter on the planet or that portion of the planet occupied by life. It reaches well into the other three spheres, although there are no permanent inhabitants of the atmosphere. Relative to the volume of the Earth, the biosphere is only the very thin surface layer which extends from 11,000 meters below sea level to 15,000 meters above. It is thought that life first developed in the hydrosphere, at shallow depths, in the photic zone. Multicellular organisms then appeared and colonized benthic zones. Terrestrial life developed later, after the ozone layer protecting living beings from UV rays formed. Diversification of terrestrial species is thought to be increased by the continents drifting apart, or alternately, colliding. Biodiversity is expressed at the ecological level (ecosystem), population level (intraspecific diversity), species level (specific diversity), and genetic level. Recently technology has allowed the discovery of the deep ocean vent communities. This remarkable ecological system is not dependant on sunlight but bacteria, utilising the chemistry of the hot volcanic vents, are at the base of its food chain. The biosphere contains great quantities of elements such as carbon, nitrogen and oxygen. Other elements, such as phosphorus, calcium, and potassium, are also essential to life, yet are present in smaller amounts. At the ecosystem and biosphere levels, there is a continual recycling of all these elements, which alternate between the mineral and organic states. While there is a slight input of geothermal energy, the bulk of the functioning of the ecosystem is based on the input of solar energy. Plants and photosynthetic microorganisms convert light into chemical energy by the process of photosynthesis, which creates glucose (a simple sugar) and releases free oxygen. Glucose thus becomes the secondary energy source which drives the ecosystem. Some of this glucose is used directly by other organisms for energy. Other sugar molecules can be converted to other molecules such as amino acids. Plants use some of this sugar, concentrated in nectar to entice pollinators to aid them in reproduction. Cellular respiration is the process by which organisms (like mammals) break the glucose back down into its constituents, water and carbon dioxide, thus regaining the stored energy the sun originally gave to the plants. The proportion of photosynthetic activity of plants and other photosynthesizers to the respiration of other organisms determines the specific composition of the Earth's atmosphere, particularly its oxygen level. Global air currents mix the atmosphere and maintain nearly the same balance of elements in areas of intense biological activity and areas of slight biological activity. Water is also exchanged between the hydrosphere, lithosphere, atmosphere and biosphere in regular cycles. The oceans are large tanks, which store water, ensure thermal and climatic stability, as well as the transport of chemical elements thanks to large oceanic currents. For a better understanding of how the biosphere works, and various dysfunctions related to human activity, American scientists simulated the biosphere in a small-scale model, called Biosphere II.

The ecosystem concept

: Main article: Ecosystem The first principle of ecology is that each living organism has an ongoing and continual relationship with every other element that makes up its environment. An ecosystem can be defined as any situation where there is interaction between organisms and their environment. The ecosystem is composed of two entities, the entirety of life (called the biocoenosis) and the medium that life exists in (the biotope). Within the ecosystem, species are connected and dependent upon one another in the food chain, and exchange energy and matter between themselves and with their environment. The concept of an ecosystem can apply to units of variable size, such as a pond, a field, or a piece of deadwood. A unit of smaller size is called a microecosystem. For example, an ecosystem can be a stone and all the life under it. A mesoecosystem could be a forest, and a macroecosystem a whole ecoregion, with its watershed. The main questions when studying an ecosystem are:
- How could the colonization of a barren area be carried out?
- What are the ecosystem's dynamics and changes
- How does an ecosystem interact at local, regional and global scale
- Is the current state stable?
- What is the value of an ecosystem? How does the interaction of ecological systems provide benefit to humans, especially in the provision of healthy water? Ecosystems are often classified by reference to the biotopes concerned. The following ecosystems may be defined:
- As continental ecosystems (or terrestrial), such as forest ecosystems, meadow ecosystems (meadows, steppes, savannas), or agro-ecosystems (agricultural systems).
- As ecosystems of inland waters, such as lentic ecosystems (lakes, ponds) or lotic ecosystems (rivers)
- As oceanic ecosystems (seas, oceans). Another classification can be done by reference to its communities (for example a human ecosystem).

Dynamics and stability

: Main articles: biogeochemistry, Homeostasis, Population dynamics Ecological factors which can affect dynamic change in a population or species in a given ecology or environment are usually divided into two groups: abiotic and biotic. Abiotic factors are geological, geographical, hydrological and climatological parameters. A biotope is an environmentally uniform region characterized by a particular set of abiotic ecological factors. Specific abiotic factors include:
- Water, which is at the same time an essential element to life and a milieu
- Air, which provides oxygen, nitrogen, and carbon dioxide to living species and allows the dissemination of pollen and spores
- Soil, at the same time source of nutriment and physical support
  - Soil pH, salinity, nitrogen and phosphorus content, ability to retain water, and density are all influential
- Temperature, which should not exceed certain extremes, even if tolerance to heat is significant for some species
- Light, which provides energy to the ecosystem through photosynthesis
- Natural disasters can also be considered abiotic Biocenose, or community, is a group of populations of plants, animals, micro-organisms. Each population is the result of procreations between individuals of same species and cohabitation in a given place and for a given time. When a population consists of an insufficient number of individuals, that population is threatened with extinction; the extinction of a species can approach when all biocenoses composed of individuals of the species are in decline. In small populations, consanguinity (inbreeding) can result in reduced genetic diversity that can further weaken the biocenose. Biotic ecological factors also influence biocenose viability; these factors are considered as either intraspecific and interspecific relations. : Intraspecific relations are those which are established between individuals of the same species, forming a population. They are relations of co-operation or competition, with division of the territory, and sometimes organization in hierarchical societies. : Interspecific relations— interactions between different species—are numerous, and usually described according to their beneficial, detrimental or neutral effect (for example, mutualism (relation ++) or competition (relation --)). The most significant relation is the relation of predation (to eat or to be eaten), which leads to the essential concepts in ecology of food chains (for example, the grass is consumed by the herbivore, itself consumed by a carnivore, itself consumed by a carnivore of larger size). A high predator to prey ratio can have a negative influence on both the predator and prey biocenoses in that low availability of food and high death rate prior to sexual maturity can decrease (or prevent the increase of) populations of each, respectively. Selective hunting of species by humans which leads to population decline is one example of a high predator to prey ratio in action. Other interspecific relations include parasitism, infectious disease and competition for limiting resources, which can occur when two species share the same ecological niche. The existing interactions between the various living beings go along with a permanent mixing of mineral and organic substances, absorbed by organisms for their growth, their maintenance and their reproduction, to be finally rejected as waste. These permanent recyclings of the elements (in particular carbon, oxygen and nitrogen) as well as the water are called biogeochemical cycles. They guarantee a durable stability of the biosphere (at least when unchecked human influence and extreme weather or geological phenomena are left aside). This self-regulation, supported by negative feedback controls, ensures the perenniality of the ecosystems. It is shown by the very stable concentrations of most elements of each compartment. This is referred to as homeostasis. The ecosystem also tends to evolve to a state of ideal balance, reached after a succession of events, the climax (for example a pond can become a peat bog).

Spatial relationships and subdivisions of land

: Main articles: Biome, ecozone Ecosystems are not isolated from each other, but are interrelated. For example, water may circulate between ecosystems by the means of a river or ocean current. Water itself, as a liquid medium, even defines ecosystems. Some species, such as salmon or freshwater eels move between marine systems and fresh-water systems. These relationships between the ecosystems lead to the concept of a biome. A biome is a homogeneous ecological formation that exists over a vast region, such as tundra or steppes. The biosphere comprises all of the Earth's biomes -- the entirety of places where life is possible -- from the highest mountains to the depths of the oceans. Biomes correspond rather well to subdivisions distributed along the latitudes, from the equator towards the poles, with differences based on to the physical environment (for example, oceans or mountain ranges) and to the climate. Their variation is generally related to the distribution of species according to their ability to tolerate temperature and/or dryness. For example, one may find photosynthetic algae only in the photic part of the ocean (where light penetrates), while conifers are mostly found in mountains. Though this is a simplification of more complicated scheme, latitude and altitude approximate a good representation of the distribution of biodiversity within the biosphere. Very generally, the richness of biodiversity (as well for animal than plant species) is decreasing most rapidly near the equator (as in Brazil) and less rapidly as one approaches the poles. The biosphere may also be divided into ecozone, which are very well defined today and primarily follow the continental borders. The ecozones are themselves divided into ecoregions, though there is not agreement on their limits.

Ecosystem productivity

In an ecosystem, the connections between species are generally related to food and their role in the food chain. There are three categories of organisms:
- Producers -- plants which are capable of photosynthesis
- Consumers -- animals, which can be primary consumers (herbivorous), or secondary or tertiary consumers (carnivorous).
- Decomposers -- bacteria, mushrooms which degrade organic matter of all categories, and restore minerals to the environment. These relations form sequences, in which each individual consumes the preceding one and is consumed by the one following, in what are called food chains or food network. In a food network, there will be fewer organisms at each level as one follows the links of the network up the chain. These concepts lead to the idea of biomass (the total living matter in a given place), of primary productivity (the increase in the mass of plants during a given time) and of secondary productivity (the living matter produced by consumers and the decomposers in a given time). These two last ideas are key, since they make it possible to evaluate the load capacity -- the number of organisms which can be supported by a given ecosystem. In any food network, the energy contained in the level of the producers is not completely transferred to the consumers. Thus, from an energy point of view, it is more efficient for humans to be primary consumers (to get nourishment from grains and vegetables) than as secondary consumers (from herbivores such as beef and veal), and more still than as a tertiary consumer (from eating carnivores). The productivity of ecosystems is sometimes estimated by comparing three types of land-based ecosystems and the total of aquatic ecosystems:
- The forests (1/3 of the Earth's land area) contain dense biomasses and are very productive. The total production of the world's forests corresponds to half of the primary production.
- Savannas, meadows, and marshes (1/3 of the Earth's land area) contain less dense biomasses, but are productive. These ecosystems represent the major part of what humans depend on for food.
- Extreme ecosystems in the areas with more extreme climates -- deserts and semi-deserts, tundra, alpine meadows, and steppes -- (1/3 of the Earth's land area) have very sparse biomasses and low productivity
- Finally, the marine and fresh water ecosystems (3/4 of Earth's surface) contain very sparse biomasses (apart from the coastal zones). Humanity's actions over the last few centuries have seriously reduced the amount of the Earth covered by forests (deforestation), and have increased agro-ecosystems (agriculture). In recent decades, an increase in the areas occupied by extreme ecosystems has occurred (desertification).

Ecological crisis

Generally, an ecological crisis is what occurs when the environment of a species or a population evolves in a way unfavourable to that species survival. It may be that the environment quality degrades compared to the species needs, after a change in an abiotic ecological factor (for example, an increase of temperature, less significant rainfalls).
It may be that the environment becomes unfavourable for the survival of a species (or a population) due to an increased pressure of predation (for example overfishing).
Lastly, it may be that the situation becomes unfavourable to the quality of life of the species (or the population) due to a rise in the number of individuals (overpopulation). Ecological crises may be more or less brutal (occurring within a few months or taking as long as a few million years). They can also be of natural or anthropic origin. They may relate to one unique species or to many species (see the article on Extinction event). Lastly, an ecological crisis may be local (as an oil spill) or global (a rise in the sea level due to global warming). According to its degree of endemism, a local crisis will have more or less significant consequences, from the death of many individuals to the total extinction of a species. Whatever its origin, disappearance of one or several species often will involve a rupture in the food chain, further impacting the survival of other species. In the case of a global crisis, the consequences can be much more significant; some extinction events showed the disappearance of more than 90% of existing species at that time. However, it should be noted that the disappearance of certain species, such as the dinosaurs, by freeing an ecological niche, allowed the development and the diversification of the mammals. An ecological crisis thus paradoxically favored biodiversity. Sometimes, an ecological crisis can be a specific and reversible phenomenon at the ecosystem scale. But more generally, the crises impact will last. Indeed, it rather is a connected series of events, that occur till a final point. From this stage, no return to the previous stable state is possible, and a new stable state will be set up gradually (see homeorhesy). Lastly, if an ecological crisis can cause extinction, it can also more simply reduce the quality of life of the remaining individuals. Thus, even if the diversity of the human population is sometimes considered threatened (see in particular indigenous people), few people envision human disappearance at short span. However, epidemic diseases, famines, impact on health of reduction of air quality, food crises, reduction of living space, accumulation of toxic or non degradable wastes, threats on keystone species (great apes, panda, whales) are also factors influencing the well-being of people. During the past decades, this increasing responsibility of humanity in some ecological crises has been clearly observed. Due to the increases in technology and a rapidly increasing population, humans have more influence on their own environment than any other ecosystem engineer. Some usually quoted examples as ecological crises are:
- Permian-Triassic extinction event 250 million of years ago
- Cretaceous-Tertiary extinction event 65 million years ago
- Global warming related to the Greenhouse effect. Warming could involve flooding of the Asian deltas (see also ecorefugees), multiplication of extreme weather phenomena and changes in the nature and quantity of the food resources (see Global warming and agriculture). See also international Kyoto Protocol.
- Ozone layer hole issue
- Deforestation and desertification, with disappearance of many species.
- The nuclear meltdown at Chernobyl in 1986 caused the death of many people and animals from cancer, and caused mutations in a large number of animals and people. The area around the plant is now abandoned because of the large amount of radiation generated by the meltdown.

See also


- ELDIS, a database on ecological aspects of economical development.
- Ecology movement
- List of ecologists
- List of ecology topics
- List of biology topics
- Important publications in ecology Category:Environmental science Category:Agronomy als:Ökologie ko:생태학 ms:Ekologi ja:生態学 simple:Ecology th:นิเวศวิทยา

Organism

In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. The origin of life and the relationships between its major lineages are controversial. Two main grades may be distinguished, the prokaryotes and eukaryotes. The prokaryotes are generally considered to represent two separate domains, called the Bacteria and Archaea, which are not closer to one another than to the eukaryotes. The gap between prokaryotes and eukaryotes is widely considered a major missing link in evolutionary history. Two eukaryotic organelles, namely mitochondria and chloroplasts, are generally considered to be derived from endosymbiotic bacteria. The phrase complex organism describes any organism with more than one cell.

Organizational terminology

Biological Organization

Viruses

Viruses are not typically considered to be organisms because they are not capable of independent reproduction or metabolism. However, according to the United States Code, they are considered to be microorganisms in the sense of biological weaponry and malicious use. This controversy is problematic, though, since some parasites and endosymbionts are incapable of independent life either. Although viruses do have enzymes and molecules characteristic of living organisms, they are incapable of surviving outside a host cell and most of their metabolic processes require a host and its 'genetic machinery'. The origin of such parasites is uncertain, but it appears most likely that they are derived from their host.

Life span

One of the basic parameters of organism is its life span. Some animals live as short as one day, while some plants can live thousands of years. Aging is important when determining life span of most organisms, bacterium, a virus or even a prion.

See also


- superorganism

External links


- [http://news.bbc.co.uk/1/hi/sci/tech/944790.stm BBCNews: 27 September, 2000, When slime is not so thick] Citat: "...It means that some of the lowliest creatures in the plant and animal kingdoms, such as slime and amoeba, may not be as primitive as once thought...."
  - [http://www.spaceref.com/news/viewpr.html?pid=4742 SpaceRef.com, July 29, 1997: Scientists Discover Methane Ice Worms On Gulf Of Mexico Sea Floor]
    - [http://www.science.psu.edu/iceworms/iceworms.html The Eberly College of Science: Methane Ice Worms discovered on Gulf of Mexico Sea Floor] download Publication quality photos
  - [http://www.sb-roscoff.fr/Ecophy/PDF/00-Fisher-NatWis.pdf Artikel, 2000: Methane Ice Worms: Hesiocaeca methanicola. Colonizing Fossil Fuel Reserves]
  - [http://www.spaceref.com/news/viewnews.html?id=339 SpaceRef.com, May 04, 2001: Redefining "Life as We Know it"] Hesiocaeca methanicola In 1997, Charles Fisher, professor of biology at Penn State, discovered this remarkable creature living on mounds of methane ice under half a mile of ocean on the floor of the Gulf of Mexico.
- [http://news.bbc.co.uk/1/hi/sci/tech/2585235.stm BBCNews, 18 December, 2002, 'Space bugs' grown in lab] Citat: "...Bacillus simplex and Staphylococcus pasteuri...Engyodontium album...The strains cultured by Dr Wainwright seemed to be resistant to the effects of UV - one quality required for survival in space...."
- [http://news.bbc.co.uk/1/hi/sci/tech/3003946.stm BBCNews, 19 June, 2003, Ancient organism challenges cell evolution] Citat: "..."It appears that this organelle has been conserved in evolution from prokaryotes to eukaryotes, since it is present in both,"..."
- [http://www.anselm.edu/homepage/jpitocch/genbios/bi04syllabsu03.html Interactive Syllabus for General Biology - BI 04, Saint Anselm College, Summer 2003]
- [http://www.personal.psu.edu/users/j/s/jsf165/Bio110.html Jacob Feldman: Stramenopila]
- [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Root NCBI Taxonomy entry: root] (rich)
- [http://www.anselm.edu/homepage/jpitocch/genbios/surveybi04.html Saint Anselm College: Survey of representatives of the major Kingdoms] Citat: "...Number of kingdoms has not been resolved...Bacteria present a problem with their diversity...Protista present a problem with their diversity...",
- [http://www.species2000.org/ Species 2000 Indexing the world's known species]. Species 2000 has the objective of enumerating all known species of plants, animals, fungi and microbes on Earth as the baseline dataset for studies of global biodiversity. It will also provide a simple access point enabling users to link from here to other data systems for all groups of organisms, using direct species-links.
- [http://www.abc.net.au/science/news/enviro/EnviroRepublish_828525.htm The largest organism in the world may be a fungus carpeting nearly 10 square kilometers of an Oregon forest, and may be as old as 8500 years.]
- [http://tolweb.org/tree/phylogeny.html The Tree of Life]. zh-min-nan:Seng-bu̍t ko:생물 ja:生物 th:สิ่งมีชีวิต

Competition

Competition is the act of striving against another force for the purpose of achieving dominance or attaining a reward or goal, or out of a biological imperative such as survival. Competition is a term widely used in several fields, including biochemistry, ecology, economics, business, politics, and sports. Competition may be between two or more forces, life forms, agents, systems, individuals, or groups, depending on the context in which the term is used. Competition may yield various results to the participants, including both intrinsic and extrinsic rewards. Some, such as survival advantages, including favorable territory, are intrinsic biological factors that occur as a result of ecological competition between organisms. Others, such as business dominance and political power, involve competition between humans. In addition, extrinsic symbols, such as trophies, plaques, ribbons, prizes, or laudations, may be given to the winner(s). Such symbolic rewards are commonly used wherever the rewards inherent in the competition are primarily intrinsic, such as at human sporting and academic competitions. In general, the rewards range widely but usually help reinforce the advantage that one participant has over the other participant(s).

Sizes and levels of competition

Competition may also exist at different sizes; some competitions may be between two members of a species, while other competitions can involve entire species. In an example in economics, a competition between two local stores would be considered small compared to competition between several mega-giants. As a result, the consequences of the competition would also vary- the larger the competition, the larger the effect. In addition, the level of competition can also vary. At some levels, competition can be informal and be more for pride or fun. However, other competitions can be extreme and bitter; for example, some human wars have erupted because of the intense competition between two nations or nationalities.

Consequences of competition

nationalities Competition can result in both beneficial and detrimental results. For example, inter-species competition, including between humans, is the driving force of adaptation and ultimately, evolution. Social darwinists claim that competition also serves as a mechanism for determining the best-suited group, politically, economically, and ecologically, however this belief is very questionable. However, competition can also have negative consequences, particularly on the human species. Potential detrimental effects include the injury of other organisms and the drain of valuable resources and energy for competition. In addition, human competition may also require large amounts of money (such as in political elections, international sports competitions, and advertising wars) and can also lead to the compromising of ethical standards in order to gain an advantage in the competition. For example, several athletes have been caught using banned steroids in professional sports in order to boost their own chances of success or victory. Finally, competitive striving can also be harmful for the participants. Examples include athletes that injure themselves because they exceed the physical tolerances of their bodies, and companies that pursue unprofitable paths while engaging in competitive rivalries.

Competition in different fields

Economics and business competition

Seen as the pillar of capitalism in that it may stimulate innovation, encourage efficiency, or drive down prices, competition is touted as the foundation upon which capitalism is justified. According to microeconomic theory, no system of resource allocation is more efficient than pure competition. Competition, according to the theory, causes commercial firms to develop new products, services, and technologies. This gives consumers greater selection and better products. The greater selection typically causes lower prices for the products compared to what the price would be if there was no competition (monopoly) or little competition (oligopoly). However, competition may also lead to wasted (duplicated) effort and to increased costs (and prices) in some circumstances. Similarly, the psychological effects of competition may result in harm as well as good. Three levels of economic competition have been classified. The most narrow form is direct competition (also called category competition or brand competition), where products that perform the same function compete against each other. For example, a brand of pick-up trucks competes with several different brands of pick-up trucks. Sometimes two companies are rivals and one adds new products to their line so that each company distributes the same thing and they compete. The next form is substitute competition, where products that are close substitutes for one another compete. For example, butter competes with margarine, mayonnaise, and other various sauces and spreads. The broadest form of competition is typically called budget competition. Included in this category is anything that the consumer might want to spend their available money on. For example, a family that has $20,000 available may choose to spend it on many different items, which can all be seen as competing with each other for the family's available money. Competition does not necessarily have to be between companies. For example, business writers sometimes refer to "internal competition". This is competition within companies. The idea was first introduced by Alfred Sloan at General Motors in the 1920s. Sloan deliberately created areas of overlap between divisions of the company so that each division would be competing with the other divisions. For example, the Chevy division would compete with the Pontiac division for some market segments. Also, in 1931, Proctor and Gamble initiated a deliberate system of internal brand versus brand rivalry. The company was organized around different brands, with each brand allocated resources, including a dedicated group of employees willing to champion the brand. Each brand manager was given responsibility for the success or failure of the brand and was compensated accordingly. This form of competition thus pitted a brand against another brand. Finally, most businesses also encourage competition between individual employees. An example of this is a contest between sales representatives. The sales representative with the highest sales (or the best improvement in sales) over the a period of time would gain benefits from the employer. It should also be noted that business and economical competition in most countries is often limited or restricted. Competition often is subject to legal restrictions, which usually provide for fair and equal business competition. Such laws may include the banning of monopolies and price gouging. Depending on the respective economic policy, the pure competition is to a greater or lesser extent regulated by competition policy and competition law. Competition between countries is quite subtle to detect, but is quite evident in the World economy, where countries like the US, Japan, the European Union and the East Asian Tigers each try to outdo the other in the quest for economic supremacy in the global market, harkening to the concept of Kiasuism.Such competition is evident by the policies undertaken by these countries to educate the future workforce. For example, East Asian economies like Singapore, Japan and South Korea tend to emphasize education by allocating a large portion of the budget to this sector, and by implementing programmes such as gifted education, which some detractors criticise as indicative of academic elitism.

Competition in biology and ecology

Competition is also present in biology, and more specifically, ecology. Competition between members of a species is the driving force of evolution and natural selection- the competition for resources, such as food, water, territory, and sunlight, results in the ultimate survival and dominance of the variation of the species best suited for survival. According to Darwin's Theory of Evolution, this intraspecies competition results in the organisms best suited for survival producing the most offspring. As a result, the species would evolve over time and adapt to the environment in which the organisms lived. Competition is also present between species. First, a limited amount of resources are available, and several species may depend on these resources. Thus, each of the species competes with the others to gain the resources. As a result, several species less suited to compete for the resources may either adapt or die out. In addition, competition is also prominent in predator-prey relationships. Both the predator and prey are competing against one another for survival; the predator is seeking food, and the prey is seeking to survive.

Competition in politics

Competition is also found in politics. In democracies, an election is a competition for an elected office. In other words, two or more candidates strive and compete against one another to attain a position of power. The winner gains the seat of the elected office for a set amount of time, when another election is usually held to determine the next holder of the office. In addition, there is inevitable competition inside a government. Because several offices are appointed, potential candidates compete against the others in order to gain the particular office. Departments may also compete for a limited amount of resources, such as for funding. Finally, where there are party systems, elected leaders of different parties will ultimately compete against the other party for laws, funding, and power. Finally, competition is also imminent between governments. Each country or nationality struggles for world dominance, power, or military strength. For example, the United States competed against the Soviet Union in the Cold War for world power, and the two also struggled over the different types of government (in this case, representative democracy and communism). The result of this type of competition often leads to worldwide tensions and may sometimes erupt into warfare.

Sports competition

While some sports, such as fishing, have been viewed as primarily recreational, most sports are considered competitive. The majority involve the competition between two or more persons, (or animals and/or mechanical devices typically controlled by humans as in horse racing or auto racing). For example, in a game of basketball, two teams compete against one another to determine who can score the most points. While there is no set reward for the winning team, many players gain an internal sense of pride. In addition, extrinsic rewards may also be given. Athletes, besides competing against other humans, also compete against nature in sports such as kayaking or mountain climbing, where the goal is to reach a destination, with only natural barriers impeding the process. While professional sports have been usually viewed as intense and extremely competitive, recreational sports, which are often less intense, are considered a healthy option for the competitive urges in humans. Sport provides a relatively safe venue for converting unbridled competition into harmless competition, because sports competition is not unrestrained. On the contrary, the competitions are governed by codified rules ageed upon by the participants. Violating these rules is considered to be unfair competition. Sports, in addition, is also considered artificial and not natural competition; for example, competing for control of a ball or defending territory on a playing field is not an innate biologal factor in humans. Athletes in sports like gymnastics and competitive diving actually compete against a conceptual ideal of a perfect performance, which incorporates measurable criteria and standards that are translated into numerical ratings and scores. Sports competition is generally broken down into three categories: individual sports, such as archery, dual sports, such as doubles tennis, or team sports competition, such as soccer. While most sports competitions are recreation, there exists several major and minor professional sports leagues throughout the world, and the Olympic Games, held every four years, is a pinnacle of sports competition.

Competition in education

Competition is also very evident in education. On a global scale, national education systems, intending to bring out the best in the next generation, encourage competitiveness among students by scholarships. Countries like Singapore and the United Kingdom have a gifted education programme which caters to gifted students, prompting charges of academic elitism. Upon receipt of their academic results, students tend to compare their grades to see who is better. For severe cases, the pressure to perform in some countries is so high that it results in stigmatisation of intellectually deficient students or even suicide as consequence of failing the exams, Japan being a prime example (see Education in Japan). This resulted in critical revaluation of examinations as a whole by educationists (see Exam). Competitions also make up a large proponent of extracurricular activities that students partake in. Such competitions include TVO's broadcasted Reach for the Top competition, FIRST Robotics and the University of Toronto Space Design Contest.

The study of competition

Competition has been studied in several fields, including psychology, sociology, and anthropology. Social psychologists, for instance, study the nature of competition. They investigate the natural urge of competition and its circumstances. They also study group dynamics to detect how competition emerges and what its effects are. Sociologists, meanwhile, study the effects of competition on society as a whole. In addition, anthropologists study the history and prehistory of competition in various cultures. They also investigate how competition manifested itself in various cultural settings in the past, and how competition has developed over time.

Competitiveness

Many philosophers and psychologists have identified a trait in most living organisms that drive the particular organism to compete. This trait, called competitiveness, is viewed as an innate biological trait that coexists along with the urge for survival. Competitiveness, or the inclination to compete, though, has become synonymous with aggressiveness and ambitiousness in the English language.

See also


- Biological interaction
- Competitor analysis
- Cooperative
- Co-operation
- Ecological model of competition
- Microeconomics
- Perfect competition
- Planned economy
- Monopolistic competition
- Imperfect competition
- Perverse competition
- "Winning isn't everything; it's the only thing." Category:Ecology ja:競技



Whale

Whales are the largest species of exclusively aquatic placental mammals, members of the order Cetacea, which also includes dolphins and porpoises. They are the largest mammals, the largest vertebrates, and the largest animals in the world. The term whale is ambiguous: it can refer to all cetaceans, to just the larger ones, or only to members of particular families within the order Cetacea. The latter definition is the one followed here. Whales are those cetaceans which are neither dolphins (i.e. members of the families Delphinidae or Platanistoidea), nor porpoises. This can lead to some confusion because Orcas ("Killer Whales") and Pilot Whales have "whale" in their name, but they are dolphins for the purpose of classification.

Origins and taxonomy

Whales, along with most dolphins and porpoises, are descendants of land-living mammals, most likely of the Artiodactyl order. They entered the water roughly 50 million years ago. See evolution of cetaceans for the details [http://news.bbc.co.uk/1/hi/sci/tech/1974869.stm]. Cetaceans are divided into two suborders:
- The baleen whales are characterized by the baleen, a sieve-like structure in the upper jaw made of keratin, which they use to filter plankton from the water. They are the largest whales.
- The toothed whales have teeth and prey on fish and/or squid. An outstanding ability of this group is to sense their surrounding environment through echolocation. A complete up-to-date taxonomical listing of all cetacean species, including all whales, is maintained at the Cetacea article.

Anatomy

Like all mammals, whales breathe air into lungs, are warm-blooded (that is, endothermic), breast-feed their young, and have some (although very little) hair. The whales' ancestors lived on land, and their adaptions to a fully aquatic life are quite striking: The body is fusiform, resembling the streamlined form of a fish. The forelimbs, also called flippers, are paddle-shaped. The end of the tail holds the fluke, or tail fins, which provide propulsion by vertical movement. Although whales generally do not possess hind limbs, some whales (such as sperm whales, baleen whales, and humpback whales) have been seen having rudimentary hind limbs; some even with feet and digits. Most species of whale bear a fin on their backs known as a dorsal fin. Beneath the skin lies a layer of fat, the blubber. It serves as an energy reservoir and also as insulation. Whales have a four-chambered heart. The neck vertebrae are fused in most whales, which provides stability during swimming at the expense of flexibility. Whales breathe through blowholes, located on the top of the head so the animal can remain submerged. Baleen whales have two; toothed whales have one. When exhaling after a dive, a spout can be seen from the right perspective, the shape of which differs among the species. Whales have a unique respiratory system that lets them stay underwater for long periods of time without taking in any oxygen. Some whales, such as the Sperm Whale, can stay underwater for up to two hours holding a single breath. Especially noteworthy is the Blue Whale, the largest known animal that has ever lived. It may be up to 30 meters long and weigh 180 tons.

Behaviour

Blue Whale Main article: Whale behaviour Whales are broadly classed as predators, but their food ranges from microscopic plankton to very large fish. Males are called bulls; females, cows. The young are called calves. Because of their environment (and unlike many animals), whales are conscious breathers: They have to decide when to breathe. So how do they sleep? All mammals sleep, and so do whales, but they cannot afford to fall into an unconscious state for too long, since they need to be conscious in order to breathe. The solution is that only one hemisphere of their brains sleeps at the time, so that whales are never completely asleep, but still get the rest they need. Whales "sleep" around 8 hours a day. Whales also communicate with each other using beautiful lyrical type sounds. Being so large and powerful these sounds are also extremely loud and can be heard for many miles. They have been known to generate about 20,000 acoustic watts of sound at 163 decibels.
- [http://www.makeitlouder.com/Decibel%20Level%20Chart.txt table of sound decibel levels] Whale females give birth to a single calf. Nursing time is long (more than one year in many species), which is associated with a strong bond between mother and young. In most whales reproductive maturity occurs late, typically at seven to ten years. This strategy of reproduction spawns few offspring, but provides each with a high rate of survival. The genital organs are retracted into cavities of the body during swimming, so as to be streamlined and reduce drag. Most whales do not maintain fixed partnerships during mating; in many species the females have several mates each season. At birth the newborn is delivered tail-first, so the risk of drowning is minimized. Whale mothers nurse the young by actively squirting the fatty milk into their mouths, a milk that according to German naturalist Dieffenbach, bears great similarities to cow's milk.

Whale intelligence

For more material in this area, focusing more on dolphins, see cetacean intelligence. Many people believe that cetaceans in general, and whales in particular, are highly intelligent animals. This belief has become a central argument against whaling (killing whales for food or other commercial reasons). There is no universally agreed definition of "intelligence." One commonly used definition is "the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience." Proponents of whale intelligence cite the social behavior of whales and their apparent capacity for language as evidence of a sophisticated intellect. Given the radically different environment of whales and humans, and the size of whales compared to (say) dolphins or chimpanzees, it is extremely difficult to test these views experimentally. One traditional indicator of intelligence is brain capacity, since humans have bigger brains than most other animals. Whales have the largest brain of any animal. A typical sperm whale brain weighs about 7.8 kg, whereas a typical human brain weighs about 1.5 kg. While it may seem that this would indicate that five times greater intelligence, in mammals brain size is in approximate ratio to body size, and most of the extra capacity is used to manage the larger body. A more precise indicator is the brain-body ratio: the size of the brain compared to body mass. Here humans have a decisive advantage. A human brain comprises about 2% of the human body mass, while the sperm whale's brain comprises only 0.02% of its body mass. A cow's brain is four times as large as a whale's on this measurement. On the other hand, a large proportion of a whale's body mass is blubber, which requires no brain power, and this distorts the ratio somewhat. Nevertheless, it is clear that brain size is not a decisive criterion. Hummingbirds have an even higher brain-to-body ratio than humans. The next consideration is the structure of the brain. It is generally agreed that the growth of the neocortex, both absolutely and relative to the rest of the brain, during human evolution, has been responsible for the evolution of intelligence, however defined. In most mammals the neocortex has six layers, and its different functional areas (vision, hearing, etc) are sharply differentiated. The whale neocortex, on the other hand, has only five layers, and there is little differentiation of these layers according to function. This has led some to argue that the whale brain has not significantly evolved since the distant ancestors of the whale took to a marine lifestyle about 50 million years ago. From an evolutionary point of view, this is consistent with the principles of natural selection. Intelligence does not arise spontaneously: like any other animal capacity, it evolves under the pressure of the animal's environment. The human brain has evolved under the pressure of natural selection in a hostile terrestrial environment. The key primate characteristics - bipedalism and the opposable thumb - gave the early hominids the ability to manipulate their environment through the use of technology (by making tools). This unique adaptation created a virtuous cycle: tool-making gave those hominids with larger brains a decisive evolutionary advantage, leading to larger and more sophisticated brains, and thus to more tool-making. This process explains the exponential growth of hominid intelligence over the past million years. By contrast, the whale has faced no such environmental stimuli to brain evolution. Whales live in an unchanging and benign environment with few natural predators. Their sole adaptation to their marine environment has been increasing size. The whale's lifestyle consists of swimming and eating, tasks which fish perform perfectly competently with very small brains. From an evolutionary point of view, there is no reason for whales to have evolved intelligence, since their survival does not require them to perform any tasks for which intelligence is necessary. It is certainly true that whales have a sophisticated social system, and that their communication system may contain some of the elements of true language, although our knowledge of whale communications is not very advanced. These capacities are sometimes confused with intelligence. But many other animals, including insects, have complex social systems, and many others, such as birds, have sophisticated communications. Whales also have very acute hearing, which gives them advanced echo-location capacities analogous to sonar - but so do bats. All this has led many (though far from all) zoologists to the conclusion that there is no convincing evidence for superior whale intelligence.

Whales and Humans

Main article Whaling Most species of large whales are endangered as a result of large-scale whaling during the nineteenth and twentieth centuries. For centuries large whales have been hunted for oil, meat, baleen and ambergris (a perfume ingredient from the intestine of sperm whales). Until the middle of the 20th century, whaling left many populations nearly or fully extinct. The International Whaling Commission introduced an open ended moratorium on all commercial whaling in 1986. For various reasons some exceptions to this moratorium exist; current whaling nations are Norway, Iceland and Japan and the aboriginal communities of Siberia, Alaska and northern Canada. For details, see whaling. Several species of small whales are caught as bycatch in fisheries for other species. In the tuna fishery in the Eastern Tropical Pacific thousands of dolphins used to drown in purse-seine nets, until measures to prevent this were introduced. Fishing gear and deployment modifications, and eco-labelling (dolphin-safe brands of canned tuna), have contributed to an estimated 96% reduction in the mortality of dolphins by tuna fishing vessels in recent years. In many countries, small whales are still hunted for food, oil, meat or bait. Environmentalists have long argued that some cetaceans including whales are endangered by sonar used by advanced navies. In 2003 British and Spanish scientists have suggested in Nature that the sonar is connected to whale beachings and to signs that the beached whales have experienced decompression sickness (see [http://news.bbc.co.uk/2/hi/science/nature/3173942.stm a BBC report about the Nature article] or [http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v425/n6958/full/425575a_fs.html the Nature article itself (requires subscription)]). Mass whale beachings do occur amongst many species (most of them are beaked whales that make use of echolocation system for deep diving). The frequency and size of beachings around the world, recorded over the last 1000 years in religious tracts and more recently in scientific surveys, has been used to estimate the changing population size of various whale species by assuming that the proportion of the total whale population beaching in any one year is constant (reference?). Despite the concerns raised about sonar which may invalidate this assumption, this population estimate technique is still popular today. Researchers in the area (Talpalar & Grossman, 2005) support that is the combination between high pressure environment of deep-diving together with the disturbing effect of the sonar which causes decompression sickness and stranding of whales. Thus, an exaggerated startle response occurring during deep diving may alter orientation cues and produce rapid ascension. This hypothesis is based on direct effect of high pressure in the central nervous system of mammals: depression of synaptic activity and increased neural excitability. Following public concern, the US Defense department has been ordered by the US judiciary to strictly limit use of its Low Frequency Active Sonar during peacetime. Attempts by the UK-based Whale and Dolphin Conservation Society to obtain a public inquiry into the possible dangers of the Royal Navy's equivalent (the "2087" sonar launched in December 2004) have so far failed. The European Parliament on the other hand has requested that EU members resist using the powerful sonar system until an environmental impact study has been carried out. [http://home.businesswire.com/portal/site/google/index.jsp?ndmViewId=news_view&newsId=20041206005421&newsLang=en] Conservationists are also concerned that seismic testing used for oil and gas exploration may also damage the hearing and echolocation capabilities of whales. They also suggest that disturbances in magnetic fields caused by the testing may also be responsible for beaching. [http://www.sustainability.ca/Docs/Impact%20of%20Seismic%20Surveys%20on%20Whales.pdf?CFID=9951883&CFTOKEN=72165442 See e.g. Seismic testing and the impacts of high intensity sound on whales, Lindy Weilgart, Department of Biology Dalhouise University (PDF format)] or a [http://whales.greenpeace.org/news/3aug2001.html typical press release from Greenpeace on the issue]

Whales in culture

The King James Version of the Bible mentions whales four times: "And God created great whales" (Genesis 1:21); "Am I a sea, or a whale, that thou settest a watch over me? (Job 7:12); "Thou art like a young lion of the nations, and thou art as a whale in the seas (Ezekiel 32:2); and "For as Jonas [sic] was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth" (Matthew 12:40). Nevertheless, the passages in question do not unambiguously refer to whales; modern translations tend to use other terms; for example the New International Version uses "creatures of the sea"; "monster of the deep"; "monster"; and "huge fish" respectively. The Book of Jonah (in the King James and some other translations) does not use the word "whale" at all, referring throughout to a "fish" or a "great fish": "Now the LORD had prepared a great fish to swallow up Jonah. And Jonah was in the belly of the fish three days and three nights." (Jonah 1:17). This detail was used to dramatic effect in Clarence Darrow's cross-examination of fundamentalist William Jennings Bryan in the 1925 Scopes Trial, as depicted in the drama "Inherit the Wind" by Jerome Lawrence and Robert E. Lee. The hunting of whales is the subject of one of the classics of the English language literary canon, Herman Melville's Moby-Dick. Melville classed whales as "a spouting fish with a horizontal tail", despite science suggesting otherwise the previous century. Melville acknowledged "the grounds upon which Linnaeus would fain have banished the whales from the waters" but says that when he presented them to "my friends Simeon Macey and Charley Coffin, of Nantucket ... they united in the opinion that the reasons set forth were altogether insufficient. Charley profanely hinted they were humbug." Melville's book is an extraordinary work, part adventure story, part metaphysical allegory, and part natural history; it is essentially a complete summary of nineteenth-century knowledge about the biology, ecology and cultural significance of whales. Some cultures associate some level of divinity with the whale, such as in some places in Ghana and the Vietnamese, who occasionally hold funerals for beached whales, a throwback to Vietnam's ancient sea-based Austroasiatic culture. Festivals celebrating whales have sprung in both Sitka and Kodiak Alaska. They feature speakers on marine biology and celebrate the creatures with art, music, whale-watching cruises, and symposiums.

See also


- Cetacea (contains a species list)
- Baleen whale
- Toothed whale
- Dorsal fin
- Whaling
- International Whaling Commission
- Exploding whale
- Whale fall
- List of whale species
- Sitka Whale Fest

Further reading


- Whales, Dolphins and Porpoises by Mark Carwardine, published by Dorling Kindersley, 2000. ISBN 0-7513-2781-6. Introductory guide to cetaceans.

External links


- [http://www.bigvolcano.com.au/human/whaling.htm Australian Whaling History]
- [http://news.bbc.co.uk/1/hi/sci/tech/239966.stm Oldest whale fossil confirms amphibious origins]
- [http://whales.greenpeace.org/ Greenpeace] - anti-whaling site
- [http://www.highnorth.no/Default.asp High North Alliance] - pro-whaling site
- [http://www.cetacea.org/ Cetacea]
- [http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html Whale Evolution]
- [http://www.whale-images.com Whale and Dolphin images]
- [http://whaleofatime.com/forum Whale Of A Time Forum] Whales, Dolphins, Porpoises and Cetaceans. Category:Cetaceans ja:クジラ目 ms:Ikan paus

Population dynamics

Population dynamics is the study of marginal and long-term changes in the numbers, individual weights and age composition of individuals in one or several populations, and biological and environmental processes influencing those changes. Population dynamics has tradionally been the dominant branch of mathematical biology, which has a history of more than 200 years, although more recently the scope of mathematical biology has greatly expanded. The early period was dominated by demographic studies such as the work of Benjamin Gompertz and Pierre François Verhulst in the early 19th century, who refined and adjusted the Malthusian demographical model. A more general model formulation was proposed by F.J. Richards in 1959, by which the models of Gompertz, Verhulst and also Ludwig von Bertalanffy are covered as special cases of the general formulation. The computer game SimCity and the MMORPG Ultima Online, among others, tried to simulate some of these population dynamics. Population dynamics also attempts to study topics such as aging populations or population decline. In Fisheries and Wildlife management, population is affected by three dynamic rate functions. Density of individuals in a population affects all three rate functions.
- Natality or birth rate, often recruitment, which means reaching a certain size or reproductive stage. Usually refers to the age a fish can be caught and counted in nets
- Growth rate, which measures the growth of individuals in size and length. More important in fisheries, where population is often measured in biomass.
- Mortality, which includes harvest mortality and natural mortality. Natural mortality includes non-human predation, disease and old age. Immigration and emigration are present, but are usually not measured. All of these are measured to determine the Harvestable surplus, which is the number of individuals that can be harvested from a population without affecting long term stability, or average population size. The harvest within the harvestable surplus is considered Compensatory Mortality, where the harvest deaths are substituting for the deaths that would occur naturally. Harvest beyond that is Additive Mortality, harvest in addition to all the animals that would have died naturally. These terms are not the universal good and evil of population management, for example, in deer, the DNR are trying to reduce deer population size overall to an extent, since hunters have reduced buck competition and increased deer population unnaturally.

See also:


- System dynamics
- Volterra-Lotka equations
- population genetics Category:Population Category:Fisheries science Category:Ecology

Carrying capacity

In ecology, carrying capacity is the measure of an environment, or habitat, to indefinitely sustain the population of a particular species in a steady-state population density. An alternative definition for carrying capacity is: the maximum population of a particular species a particular region can support without hindering future generations' ability to maintain the same population. The carrying capacity of an environment will vary for different species in different habitats, and can change over time due to a species impact on its environment, as well as other environmental factors. Species typically adopt one of two strategies:
- Strategy r-selected : the species has a high reproduction rate, but is very sensitive to environmental factors, in particular predation. Therefore, the populations do exceed the carrying capacity. This strategy is typical of insects.
- Strategy K-selected : the species has a low reproduction rate and usually a long life span. They are submitted to low predation rate and population may grow over the carrying capacity. Environmental stress usually lead to hormonal disrupting to prevent ovulation, or to abortions. This strategy is typical of mammals. Humans have demonstrated an ability to increase the short term carrying capacity of their environment through use of Earth's available resources, most notably the wide scale use of ancient deposits of hydrocarbons, also known as fossil fuels. Exploitation of these resources has allowed massive short term inputs of energy into human population growth, but at the potential cost of reducing long term carrying capacity through environmental degradation and depletion of non-renewable resources. When a population exceeds the long term carrying capacity of its environment, also known as overshoot, then famine and disease tend to reduce the size of that population. See also Ecological yield, Sexual selection, Overpopulation. Category:Ecology

Population growth rate

Population growth rate is a term used in demographics and ecology which refers to the rate at which the number of individuals in a population increases. Simple models of population growth include the exponential model and the logistic model.

See also


- Population growth
- Growth rate (group theory) Category:Ecology

R-selection

In ecology, r-selection (note: lower case "r") relates to the selection of traits (in organisms) that allow success in unstable or unpredictable environments. Under these circumstances, the ability to reproduce quickly is crucial, and there is little advantage in adaptations that permit successful competition with other organisms (since the environment is likely to change again). Traits that are thought to be characteristic of r-selection include : high fecundity; small size; short generation time; and the ability to disperse offspring widely. Organisms whose life history is subject to r-selection are often referred to as "r-strategists". Species with r-selected traits include bacteria, diatoms, many insects and plants labelled weeds. The term r-selection itself is derived from standard ecological algebra, as illustrated in the simple Verhulst equation of population dynamics: :\frac=rN\left(1 - \frac\right) \qquad \! Where r is the growth rate of the population (N), and K is its carrying capacity. It should be noted that, although some organisms are primarily r- or K-strategists, the majority of organisms fall between these two ecological extremes, and may display traits considered characteristic of both ends of the r-K spectrum. For instance, trees have traits such as longevity and strong competitiveness that characterise them as K-strategists. However, in reproduction, trees typically produce thousands of offspring and disperse them widely, traits characteristic of r-strategists. Contrast with K-selection.

References


- Pianka, E. R. (1970). On r and K selection. American Naturalist 104, 592-597.
- Verhulst, P. F. (1838). Notice sur la loi que la population pursuit dans son accroissement. Corresp. Math. Phys. 10, 113-121. Category:Ecology Category:Evolutionary biology

Category:Ecology

Ecology is the branch of science that studies the distribution and interactions between living things and between living things and the physical environment. This category does not cover environmentalism, or ethics topics. Category:Earth sciences Category:Environmental science ecology Category:Academic disciplines category:Agronomy ko:분류:생태학 ja:Category:生態学

Category:Evolutionary biology

Evolutionary biology is a subfield of biology concerned with the origin and descent of species, as well as their change over time. evolutionary biology Category:Evolution ko:분류:진화생물학

Autodromo Nazionale di Monza

L'Autodromo Nazionale Monza (o Circuito di Monza) è il circuito automobilistico di Monza, situato all'interno del Parco. Ospita molti eventi motoristici, sia automobilistici sia motociclistici, durante tutto l'anno ma è famoso internazionalmente per aver ospitato il Gran Premio d'Italia di Formula 1, quasi ininterrottamente, fin dalla sua nascita dal 1922.

Storia

L'idea

L'idea del circuito automobilistico, nasce dall'Automobile Club di Milano nel gennaio del 1922, per celebrare il 25° anniversario dell'organizzazione. Il primo Gran Premio d'Italia si era disputato l'anno prima in un circuito semipermanente a Montichiari. Il successo dell'esperimento, portò alla ricerca di una sede stabile per un circuito ad alta velocità. Le bozze di progetto presentate indicavano tre diverse località:
- una zona di brughiera presso Gallarate (dove oggi sorge l'Aeroporto internazionale Milano-Malpensa
- un'area nel rione di Cagnola (che allora era alla periferia di Milano)
- il Parco Reale di Monza (affidato al tempo all'Opera Nazionale Combattenti). La scelta cadde su Monza. L'area disponibile era ampia, vicina a Milano e con possibilità di facili collegamenti. Il progetto prevedeva un circuito ad anello perimetrale, con la possibilità di creare ulteriori tracciati complementari interni.

La SIAS

L'Automobile Club crea una società a capitale privato, la SIAS (Società Incremento Automobilismo e Sport, che si assunse l'incarico di costruire e gestire l'attività sportiva del circuito. La società viene presieduta da Silvio Crespi e il progetto viene affidato all'architetto Alfredo Rosselli.

La costruzione

Felice Nazzaro e Vincenzo Lancia collocarono la prima pietra del circuito verso la fine del febbraio del 1922. Il progetto incontrò subito perplessità, a causa del valore paesaggistico in cui il circuito andava inserendosi. Per essere accettato, a parità di area occupata (340 ettari), lo sviluppo complessivo del circuito fu ridotto a 10 km. I lavori ripresero il 15 maggio.
Il circuito fu completato in 110 giorni: il 28 luglio, Felice Nazzaro e Pietro Bordino, su una FIAT 570, collaudano il circuito in tutto il suo sviluppo.

Il circuito

Il circuito comprendeva un anello di 4,5 km, con due curve (320 m di raggio) sopraelevate fino ad un'altezza di 2,60 m, con un angolo di pendenza di 21 gradi; i due rettilinei che collegano le curve erano lunghi 1.070 m. La pista stradale era invece lunga 5,5 km, con curve di raggio diverso.
L'anello di velocità e la pista stradale si intersecavano su due livelli mediante un sottopassaggio.
L'inclinazione delle curve paraboliche permetteva alle macchine in competizione di raggiungere medie vicine ai 180-190 kmh, velocità mai raggiunte all'epoca.

Le prime gare

Il 3 settembre 1922, il circuito di Monza ospitò la prima competizione, una gara di vetturette sport vinta da Pietro Bordino su FIAT 501.
Il Gran Premio motociclistico della Nazioni si svolse l'8 settembre dello stesso anno e fu vinto da Amedeo Ruggieri (Harley Davidson 1000.
Due giorni dopo, il 10 settembre, il primo Gran Premio automobilistico d'Italia, vinto da Bordino (FIAT 804).

Tracciati alternativi

Vincenzo Florio studiò un nuovo tracciato che lasciava comunque inalterate le strutture del circuito, utilizzando la pista stradale e la curva sopraelevata a sud, collegate da due curve a 90° e da un breve tratto rettilineo. Questo tracciato fu chiamato il "circuito Florio" ed aveva una lunghezza di 10 km.
Nel 1933, un grave incidente mortale coinvolse Campari, Czaykowski e Borzacchini, costringendo gli organizzatori a modificare il tracciato. Nel 1934 fu così disegnato un tracciato che comprendeva la curvetta sud, la sopraelevata sud, il raccordo del circuito Florio e metà rettilineo delle tribune, furono anche inserite due chicanes, il tutto al fine di ridurre le velocità di punta. Nel 1935 e nel 1936 si tornò a gareggiare sul circuito Florio, anche se riempito di chicanes, mentre nel 1937 si gareggiò sul circuito di Livorno, per tornare l'anno successivo a Monza, con l'ultimo utilizzo del circuito Florio.

Modifiche all'impianto (1938)

Nel 1938, terminato il Gran Premio d'Italia, fu modicata la pista stradale: il rettilineo centrale fu spostato verso ovest, raccordandolo al rettilineo delle tribune con due curve con un raggio di 60 m, pavimentate con porfido, seguendo un progetto di Aldo Di Rienzo. La pista di velocità non venne quasi più utilizzata. Il nuovo tracciato aveva una lunghezza di 6,3 km.
Le novita del circuito non poterono essere provate in gara, a causa della guerra, che bloccò ogni attività. Nel periodo bellico, l'autodromo fu utilizzato nei modi più diversi: uffici dell'Automobile Club, archivio del Pubblico Registro Automobilistico, rifugio per gli animali del giardino zoologico di Milano.
Finita la guerra, una parata di mezzi cingolati alleati (1945), distrusse il fondo della pista. Successivamente venne adibito a deposito di automezzi militari. Il ripristino del circuito avvenne nei primi mesi del 1948, nel frattempo le competizioni programmate si disputarono sul circuito del Valentino a Torino (auto) e a Faenza (moto). Il 17 ottobre tutto era pronto per un nuovo Gran Premio di Formula I a Monza. Il tracciato fu utilizzato fino al 1954.

Il nuovo anello di velocità

Il nuovo progetto di circuito di velocità, voluto da Giuseppe Bacciagaluppi, fu realizzato da Antonino Berti e Aldo Di Rienzo. Nel 1955 si ripristinò il tracciato di 10 km, seguendo il progetto del 1922, con un settore stradale e un settore per la velocità denominato "catino". L'anello di velocità era simile a quello precendente, ma leggermente spostato verso sud. Le curve sopraelevate furono costruite in cemento armato, con un raggio di 320 m ed una pendenza progressiva fino ad un massimo dell'80%. Per sostenere le curve sopraelevate, furono utilizzati piloni, mentre la struttura delle curve fu realizzata con calcestruzzo additivato per consentire una resa omogenea dell'asfaltatura.
La pista stradale fu leggermente accorciata, riducendo il rettilineo centrale e quello delle tribune e collegandoli con una curva a raggio crescente, la "parabolica", che sostituiva le curve in profido.
La lunghezza diveniva così di 5.750 m per la pista stradale e di 4.250 per quella di velocità.
Il nuovo circuito fu inaugurato nel 1955 ed ospitò le gare Indy, le 1.000 chilometri e diverse gare di rally e di turismo. Il catino di velocità fu abbandonato con la costruzione del nuovo tracciato.

Tracciato per la formula junior

Il successo della formula addestrativa junior portò alla creazione di un circuito corto, "pista junior" (1959), realizzato raccordando a nord, con un percorso sinuoso, il rettilineo delle tribune con quello centrale. Il tracciato ottenuto misurava 2.385 m (oggi a causa di lievi modifiche ne misura 2.405 m). Nel 1965, questo tracciato fu dotato di un impianto di illuminazione per pemettere prove in notturna.

Sistemi di protezione

Nel 1961 fu attuato un programma di protezione che comprese l'utilizzo di reti rinforzate e di guard-rails. Nel 1963 furono anche ricostruiti i box, separando la corsia di servizio dalla pista per mezzo di un muretto.

Le "varianti"

Per ridurre le velocità delle Formula 1, furono realizzate due chicanes (1972), una al "curvone" e una alla "Curva Ascari". Le chicanes si rivelarono inefficienti, rallentavano si la velocità, ma provocavano continui incidenti. Nel 1976 la chicanes del rettilineo dopo l'inizio della curva nord, fu sostituta da una vera e propria "variante" costituita da due curve a sinistra e da due curve a destra alternate; un'altra variante fu costruita a 300 m dalla "prima curva di Lesmo", con una curva a sinistra seguita da una a destra.

Modifiche alla seconda curva di Lesmo e alla curva grande

Nel 1994 la seconda curva di Lesmo viene ridefinita, con una configurazione "a gomito" (il raggio diviene di 36 m). Nel 1995 la curva Grande viene spostata all'interno di circa dieci metri, i suoi due raggi passano a 290 e 395 m (erano, rispettivamente, 325 e 450 m). La variante della Roggia viene anticipata di 50 m. L'intero tratto delle curve di Lesmo viene spostato verso l'interno di 15 metri; la prima curva risulta ristretta, 75 m invece di 98 m di raggio, mentre la seconda rimane praticamente identica a quella disegnata l'anno prima.
Dopo tutte queste modifiche il tracciato risulta diminuito di 30 m ed ora ha una lunghezza di 5.770 m.

Modifiche alle varianti

In occasione del Gran Premio d'Italia del 2000, un'importante modifica coinvolge la prima variante (o variante Goodyear). Al posto della doppia curva sinistra-destra, viene inserita una variante più semplice, una singola destra-sinistra, raccordata poi all'ingresso della Curva Grande da un tratto con raggio di curvatura molto ampio. Scopo di questa modifica è soprattutto di evitare i frequenti incidenti che si verificano alla partenza, a causa del tratto di ingresso alla vecchia variante, che formava una specie di "imbuto". Nella nuova configurazione, la frenata per la variante avviene senza deviazioni rispetto al rettilineo principale. Questa modifica porta il tracciato ad una lunghezza complessiva di 5.793 m. Successive modifiche coinvolgono la seconda curva della variante della Roggia, allo scopo di rallentare le vetture. Questa modifica non altera la lunghezza della pista.

Competizioni

Gran Premio automobilistico d'Italia

Formula 3

Campionato italiano Formula 3000

Prototipi

Collegamenti esterni


- [http://www.monzanet.it/ita/ sito ufficiale]
- [http://www.monzasport.it Monzasport.it] Monza ja:アウトドローモ・ナツィオナーレ・ディ・モンツァ

Dorota Rabczewska NLP aminokwasy NLP jelenia gra ogoszenia










































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