:: wikimiki.org ::

Ecology

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

Interaction
:Interaction is also a Science fiction convention Interaction is a kind of action which occurs as two or more objects have an effect upon one another. The idea of a two-way effect is essential in the concept of interaction instead of a one-way causal effect. Combinations of many simple interactions can lead to surprising emergent phenomena. It has different tailored meanings in various sciences. Casual examples of interaction outside of science include:
- communication of any sort, for example two or more people talking to each other, or communication among groups, organisations, nations or states: trade, migration, foreign relations, transportation; etc.
- the feedback during operation of a machines such as a computer or a tool, for example the interaction between a driver and the position of his or her car on the road: by steering the driver influences this position, by looking this information returns to the driver;
Chemistry and medicine
In medicine, most medications can be safely used with other medicines but particular combinations of medicines need to be monitored for interactions, often by the pharmacist. Interactions between drugs fall generally into one of two main categories; pharmacodynamic (involving the actions of the two interacting drugs), and pharmacokinetic (involving the absorption, distribution, metabolism, and excretion of one or both of the interacting drugs upon the other). Sometimes two or medications are used together to create an extra effect - e.g. two different pain killers to provide more complete pain control. These interactions are usually intentional but need to be monitored by the doctor because patients can end up with more effect than is actually required. Sometimes two or more medications work against each other. These interactions are usually well-known and avoided unless both medicines are essential. Careful monitoring is used to prevent problems from the results of the interaction. Other interactions may cause one medicine to have less or more effect than expected and these are usually managed by a dosage adjustment.
Communications
In communications, interactive communication occurs when sources take turns transmitting messages between one another. This should be distinguished from transactive communication, in which sources transmit messages simultaneously.
Media
In media, interactivity is a feature of the media in question. As a result of digitalization and convergence the consumption of media is becoming more interactive. In media the strive for interaction is also a cultural trend.
Physics
In physics, an interaction specifically refers to the action of one physical object upon another and results in an interaction energy - the physical objects under consideration may range from point particles to quantum fields. For example, the interaction of charged particles takes place through the mediation of electromagnetic fields, whereas beta decay occurs by means of the weak interaction. There are believed to be four fundamental interactions in Nature.
Sociology
In sociology, social interaction is a dynamic, changing sequence of social actions between individuals (or groups) who modify their actions and reactions due to the actions by their interaction partner(s). Social interactions can be differentiated into:
- accidental - not planned and likely not repeated. For example, asking a stranger for directions or shopkeeper for product availabity.
- repeated - not planned, bound to happen from time to time. For example, accidentaly meeting a neighbour from time to time when walking on your street;
- regular - not planned, but very common, likely to raise questions when missed. Meeting a doorman or a security guard every workday in your workplace, dining every day in the same restaurant, etc.
- regulated - planned and regulated by customs or law, will definitely raise questions when missed. Interaction in a workplace (coming to work, staff meetings, etc.), family, etc. Social interactions form the basis for social relations.
See also

- Computability logic
- Game semantics
- Interaction Design
- Interactive computation
- Interactivity
- Transaction Category:Communication Category:Sociology Category:Pharmacology ja:相互作用

Natural environment

The natural environment comprises all living and non-living things that occur naturally on Earth. In its purest sense, it is thus an environment that is not the result of human activity or intervention. The natural environment may be contrasted to "the built environment." For some, there is a difficulty with the term "natural environment" in that nearly all environments have been directly or indirectly influenced by humans at some point in time. In order to address this concern, some level of human influence is thus allowable without the status of any particular landscape ceasing to be "natural." The term's meaning, however, is usually dependent more on context than a set definition. Many natural environments are the product of the interaction between nature and humans. For this reason, the term ecosystem has been used to describe an environment that contains nature, and includes people. It follows then that environmental problems are human or social problems. Some also consider it dangerously misleading to regard "environment" as separate from "people." It is the common understanding of natural environment that underlies environmentalism—a broad political, social, and philosophical movement that advocates various actions and policies in the interest of protecting what nature remains in the natural environment, or restoring or expanding the role of nature in this environment. While wilderness is increasingly rare, wild nature (e.g., unmanaged forests, uncultivated grasslands, wildlife, wildflowers) can be found in many locations previously inhabited by humans. Goals commonly expressed by environmentalists include: reduction and clean up of man-made pollution, with future goals of zero pollution; reducing societal consumption of non-renewable fuels, development of alternative, green, low carbon or renewable energy sources; conservation and sustainable use of scarce resources such as water, land and air; protection of representative or unique or pristine ecosystems; preservation and expansion of threatened or endangered species or ecosystems from extinction; the establishment of nature and biosphere reserves under various types of protection, and, most generally, the protection of biodiversity and ecosystems upon which all human and other life on earth depends. More recently, there has been a strong concern about climatic changes caused by anthroprogenic releases of greenhouse gases, most notably carbon dioxide, and their interactions with human uses and the natural environment. Efforts here have focused on the mitigition of greenhouse gases that are causing climatic changes (i.e., through the Climate Change Convention and the Kyoto Protocol), and ondeveloping adaptative strategies to assist species, ecosystems, humans, nations and regions in adjusting to these climatic changes.

Climate

The climate (ancient Greek: κλίμα) is the weather averaged over a long period of time. The Intergovernmental Panel on Climate Change (IPCC) glossary definition is: : Climate in a narrow sense is usually defined as the “average weather”, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period is 30 years, as defined by the World Meteorological Organization (WMO). These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system.[http://www.grida.no/climate/ipcc_tar/wg1/518.htm]

Climate vs weather

In the most succinct words, weather is the combination of events in the atmosphere and climate is the overall accumulated weather in a certian location. The exact boundaries of what is climate and what is weather are not well defined and depend on the application. For example, in some senses an individual El Niño event could be considered climate; in others, as weather. When the original conception of climate as a long-term average came to be considered, perhaps towards the end of the 19th century, the idea of climate change was not current, and a 30 year average seemed reasonable (but see note 1). Given the current availability of long-term trends in the temperature record, it is harder to give a precise contradiction-free definition of climate: over a 30 year period, averages may shift; over a shorter period, the statistics are less stable.

Climate determinants

In a given geographical region, the climate generally does not vary over time on the scale of a human life span. However, over geological time, climate can vary considerably for a given place on the Earth. For example, Scandinavia has been through a number of ice ages over hundreds of thousands of years (the last one ending about 10,000 years ago). Paleoclimatology is the study of these past climates, their origin, and by extension, the origin of today's climate. Over historic time spans there are a number of static variables that determine climate including: altitude, proportion of land to water, and proximity to oceans and mountains. Other climate determinants are more dynamic: The Thermohaline circulation of the ocean distributes heat energy between the equatorial and polar regions; other ocean currents do the same between land and water on a more regional scale. Degree of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level. Alterations in the quantity of atmospheric greenhouse gases determines the amount of solar energy retained by the planet, leading to global warming (or cooling). The variables which determine climate are numerous and the interactions complex but there is general agreement that the broad outlines are understood, at least in so far as the determinates of historical climate change are concerned.

Climate indices

Scientists use climate indices in their attempt to characterize and understand the various climate mechanisms that culminate in our daily weather. Much in the way the Dow Jones Industrial Average, which is based on the stock prices of 30 companies, is used to represent the fluctuations in the stock market as a whole, climate indices are used to represent the essential elements of climate. Climate indices are generally identified or devised with the twin objectives of simplicity and completeness, and each typically represents the status and timing of the climate factor they represent. By their very nature, indices are simple, and combine many details into an generalized, overall description of the atmosphere or ocean which can be used to characterize the factors which impact the global climate system. Because the climate indices are generally determined from measurements made in a localized area, they can have impacts in other areas around the globe, through processes sometimes called teleconnections. References:
- [http://www.arctic.noaa.gov/essay_bond.html Why and how do scientists study climate change in the Arctic? What are the Arctic climate indices?]
- [http://www.arctic.noaa.gov/climate.html Climate index and mode information]

Classifications

In the original sense, climate is a concept used to divide the world into regions sharing similar climatic parameters. Climate regions can be classified on the basis of temperature and precipitation alone. Examples of such climate schemes are the Köppen climate classification or the Thornthwaite climate classification schemes. For more details about specific climates, please see:
- Tropical climate
- Subtropical climate
- Arid climate
- Semiarid climate
- Mediterranean climate
- Temperate climate
- Oceanic climate
- Continental climate
- Alpine climate
- Subarctic climate
- Polar climate
- Climate of Antarctica To understand a climate of a specific place or area, please see the article on that place or area.

Historical climates

- Climate changes of 535-536
- Medieval climate optimum

National climates

- Climate of the Alps
- Climate of India
- Climate of the United Kingdom

External links

- [http://climateapps2.oucs.ox.ac.uk/cpdnboinc/ Climate Prediction Project]
- [http://www.worldclimate.com WorldClimate]
- [http://www.atmosphere.mpg.de/enid/1442 ESPERE Climate Encyclopaedia]
- [http://www.weatherbase.com Weatherbase]
- [http://www.climate-zone.com Global Climate Data]
- [http://www.limaperunet.com/climate/climateall.html The Climate of Peru]
- [http://www.arctic.noaa.gov/climate.html Climate index and mode information]
- [http://www.arctic.noaa.gov/essay_bond.html Why and how do scientists study climate change in the Arctic? What are the Arctic climate indices?]
- [http://www.arctic.noaa.gov/detect/ A near-realtime Arctic Change Indicator Website]
- [http://www.beringclimate.noaa.gov/ A current view of the Bering Sea Ecosystem and Climate]

Notes

# In "Climatology" by W G Kendrew (OUP; 3rd edition 1949; chapter 38; page 359) we find: "A well-known cycle is one with a mean period of about 35 years... which was worked out by Bruckner... the reality of this cycle seems to be well established, though it is of little use for actual forecasting; it is a basis of the choice of 35 years as the period estimated to give true mean values of climate elements." Category:Ecology ko:기후 ja:気候 simple:Climate

Geology

Geology (from Greek γη- (ge-, "the earth") and λογος (logos, "word", "reason")) is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it. It is one of the Earth sciences. Geologists have helped establish the age of the Earth at about 4.5 billion (4.5x10⁹) years, and have determined that the Earth's lithosphere, which includes the crust, is fragmented into tectonic plates that move over a rheic upper mantle (asthenosphere) via processes that are collectively referred to as plate tectonics. Geologists help locate and manage the earth's natural resources, such as petroleum and coal, as well as metals such as iron, copper, and uranium. Additional economic interests include gemstones and many minerals such as asbestos, perlite, mica, phosphates, zeolites, clay, pumice, quartz, and silica, as well as elements such as sulfur, chlorine, and helium. Astrogeology refers to the application of geologic principles to other bodies of the solar system. However, specialised terms such as selenology (studies of the Moon), areology (of Mars), etc., are also in use. The word "geology" was first used by Jean-André Deluc in the year 1778 and introduced as a fixed term by Horace-Bénédict de Saussure in the year 1779. An older meaning of the word was first used by Richard de Bury. He used it to distinguish between earthly and theological jurisprudence.

History

In China, the polymath Shen Kua (1031 - 1095) formulated a hypothesis for the process of land formation: based on his observation of fossil shells in a geological stratum in a mountain hundreds of miles from the ocean, he inferred that the land was formed by erosion of the mountains and by deposition of silt. The work on rocks Peri lithon by Theophrastus, a student of Aristotle, remained authoritative for millennia. However, its interpretation of fossils was not overturned until after the Scientific Revolution. It was translated into Latin and the other languages of Europe such as French. Georg Bauer (Georg Agricola), a physician, summarised the knowledge of mining and metallurgy in 1556. Georg Agricola (1494-1555) wrote the first systematic treatise about mining and smelting works, De re metallica libri XII, with an appendix Buch von den Lebewesen unter Tage (book of the creatures beneath the earth). He covered subjects like wind energy, hydrodynamic power, melting cookers, transport of ores, extraction of soda, sulfur and alum, and administrative issues. The book was published in 1556. By the 1700s Jean-Etienne Guettard and Nicolas Desmarest hiked central France and recorded their observations on geological maps; Guettard recorded the first observation of the volcanic origins of this part of France. James Hutton recorded his Theory of the Earth in the 1788 Transactions of the Royal Society of Edinburgh, later called uniformitarianism. William Smith (1769-1839) drew some of the first geological maps and began the process of ordering rock strata (layers) by examining the fossils contained in them. James Hutton is often viewed as the first modern geologist. In 1785 he presented a paper entitled Theory of the Earth to the Royal Society of Edinburgh. In his paper, he explained his theory that the Earth must be much older than had previously been supposed in order to allow enough time for mountains to be eroded and for sediment to form new rocks at the bottom of the sea, which in turn were raised up to become dry land. Followers of Hutton were known as Plutonists because they believed that some rocks were formed by vulcanism which is the deposition of lava from volcanoes, as opposed to the Neptunists, who believed that all rocks had settled out of a large ocean whose level gradually dropped over time. In 1811 Georges Cuvier and Alexandre Brongniart published their explanation of the antiquity of the Earth, inspired by Cuvier's discovery of fossil elephant bones in Paris. To prove this, they formulated the principle of stratigraphic succession of the layers of the earth. They were independently anticipated by William Smith's stratigraphic studies on England and Scotland. Sir Charles Lyell first published his famous book, Principles of Geology, in 1830 and continued to publish new revisions until he died in 1875. He successfully promoted the doctrine of uniformitarianism. This theory states that slow geological processes have occurred throughout the Earth's history and are still occurring today. In contrast, catastrophism is the theory that Earth's features formed in single, catastrophic events and remained unchanged thereafter. Though Hutton believed in uniformitarianism, the idea was not widely accepted at the time. catastrophism illustrated on relief globe of the Field Museum ]] By 1827 Charles Lyell's Principles of Geology reiterated Hutton's uniformitarianism, which influenced the thought of Charles Darwin. 19th Century geology revolved around the question of the Earth's exact age. Estimates varied from a few 100,000 to billions of years. The most significant advance in 20th century geology has been the development of the theory of plate tectonics in the 1960s. Plate tectonic theory arose out of two separate geological observations: seafloor spreading and continental drift. The theory revolutionised the Earth sciences. The theory of continental drift was proposed by Alfred Wegener in 1912 and by Arthur Holmes, but wasn't broadly accepted until the 1960s when the theory of plate tectonics was developed.

Important principles of geology

There are a number of important principles in geology. Many of these involve the ability to provide the relative ages of strata or the manner in which they were formed. The Principle of Intrusive Relationships concerns crosscutting intrusions. In geology, when an igneous intrusion cuts across a formation of sedimentary rock, it can be determined that the igneous intrusion is younger than the sedimentary rock. There are a number of different types of intrusions, including stocks, laccoliths, batholiths, sills and dikes. The Principle of Cross-cutting Relationships pertains to the formation of faults and the age of the sequences through which they cut. Faults are younger than the rocks they cut; accordingly, if a fault is found that penetrates some formations but not those on top of it, then the formations that were cut are older than the fault, and the ones that are not cut must be younger than the fault. Finding the key bed in these situations may help determine whether the fault is a normal fault or a thrust fault. The Principle of Inclusions and Components states that, with sedimentary rocks, if inclusions (or clasts) are found in a formation, then the inclusions must be older than the formation that contains them. For example, in sedimentary rocks, it is common for gravel from an older formation to be ripped up and included in a newer layer. A similar situation with igneous rocks occurs when xenoliths are found. These foreign bodies are picked up as magma or lava flows, and are incorporated, later to cool in the matrix. As a result, xenoliths are older than the rock which contains them. The Principle of Uniformitarianism states that, the geologic processes observed in operation that modify the Earth's crust at present have worked in much the same way over geologic time. A fundamental principle of geology advanced by the 18th century Scottish physician and geologist James Hutton, is that "The Present is the Key to the Past." In Hutton's words: "the past history of our globe must be explained by what can be seen to be happening now." The Principle of Original Horizontality states that, the deposition of sediments occurs as essentially horizontal beds. Observation of modern marine and nonmarine sediments in a wide variety of environments supports this generalisation (although cross-bedding is inclined, the overall orientation of cross-bedded units is horizontal). The Principle of Superposition states that, a sedimentary rock layer in a tectonically undisturbed sequence is younger than the one beneath it and older than the one above it. Logically a younger layer cannot slip beneath a layer previously deposited. This principle allows sedimentary layers to be viewed as a form of vertical time line, a partial or complete record of the time elapsed from deposition of the lowest layer to deposition of the highest bed. The Principle of Faunal Succession is based on the appearance of fossils in sedimentary rocks. As organisms exist at the same time period throughout the world, their presence or (sometimes) absence may be used to provide a relative age of the formations in which they are found. Based on principles laid out by William Smith almost a hundred years before the publication of Charles Darwin's theory of evolution, the principles of succession were developed independently of evolutionary thought. The principle becomes quite complex, however, given the uncertainties of fossilisation, the localisation of fossil types due to lateral changes in habitat (facies change in sedimentary strata), and that not all fossils may be found globally at the same time.

Fields or related disciplines

- Earth science
- Economic geology
- Mining geology
- Petroleum geology
- Engineering geology
- Environmental geology
- Geoarchaeology
- Geochemistry
- Biogeochemistry
- Isotope geochemistry
- Geochronology
- Geodetics
- Geomicrobiology
- Geomorphology
- Geophysics
- Glaciology
- Historical geology
- Hydrogeology or geohydrology
- Marine geology
- Mineralogy
- Paleoclimatology
- Paleontology
- Micropaleontology
- Palynology
- Petrology
- Plate tectonics
- Sedimentology
- Seismology
- Soil science
- Pedology (soil study)
- Speleology
- Stratigraphy
- Biostratigraphy
- Structural geology
- Volcanology

Regional geology

- Geology of the Alps
- Geology of the Himalaya
- Geology of Victoria (Australia)

United Kingdom

- Geology of Dorset
- Geology of Hampshire
- Geology of Hertfordshire

United States

- Geology of the Bryce Canyon area(Utah)
- Geology of the Canyonlands area (Utah)
- Geology of the Capitol Reef area (Utah)
- Geology of Connecticut
- Geology of the Death Valley area (California)
- Geology of the Grand Canyon area (Arizona)
- Geology of the Grand Teton area (Wyoming)
- Geology of the Lassen area (California)
- Geology of Mount Shasta (California)
- Geology of the Yosemite area (California)
- Geology of the Zion and Kolob canyons area (Utah)
- Glacial geology of the Genesee River (New York, Pennsylvania)

National geology

- Geology of Australia
- Geology of Victoria
- Geology of Iran
- Geology of India
- Geology of Sikkim
- Geology of the United States of America
- Geology of California
- Geology of the Grand Canyon area
- Geology of the United Kingdom
- Geology of Japan

Planetary geology

- Geology of Mars
- Geology of the Moon

External links

- James Hutton's [http://www.mala.bc.ca/~johnstoi/essays/Hutton.htm Theory of the Earth]
- James Hutton's [http://www.uwmc.uwc.edu/geography/hutton/hutton.htm Theory of the Earth & Abstract of the Theory of the Earth] Category:Geology ko:??? ja:??? th:?????????

1866

1866 is a common year starting on Monday.

Events

January – June

- January 6 – Ottoman troops clash with men of a Maronite leader Karam in St. Doumit in Lebanon - Turks are defeated
- January 12 - Royal Aeronautical Society is formed (London)
- January 28 - 800 Maronite troops clash with Ottoman troops in Karem Saddah, modern-day Lebanon - more battles between nationalist Maronites and Ottoman army follow
- February 13 - The first daylight robbery in United States history during peacetime takes place in Liberty, Missouri. This is considered to be the first robbery committed by Jesse James and his gang, although James's role is disputed.
- February 26 - The Calaveras Skull is discovered. Purported to be evidence of humans during the Pliocene Age, it turns out to be a hoax.
- April 4 - Alexander II of Russia narrowly escapes an assassination attempt in the city of Kiev. A design for a city gate to commemorate his escape was the inspiration for Mussorgsky's The Great Gate of Kiev from Pictures at an Exhibition.
- April 10 - The American Society for the Prevention of Cruelty to Animals (ASPCA) is founded in New York City by Henry Bergh.
- May - Student Choen Blind fails to assassinate Otto von Bismarck in Unter den Linden in Berlin
- May 2 - Peruvian defenders fight off Spanish fleet at the Battle of Callao.
- May 16 - The U.S. Congress eliminates the half dime coin and replaces it with the five cent piece, or nickel.
- May 16 - Charles Elmer Hires invents root beer.
- May 24 - Battle of Tuyuti - 32.000 soldiers of the Triple Alliance defeat 24.000 Paraguayan soldiers few miles north of the Parana - 18.000 dead
- June 2 - Fenian forces skirmish with Canadian militia at Ridgeway and Fort Erie
- June 5 - Calculations indicate Pluto reached its most recent aphelion (furthest point from Sun) on this day. The next aphelion will occur in August 2113.
- June 8 - The Canadian Parliament meets for the first time in Ottawa.
- June 11 - Agra High Court established (later shifted to Allahabad High Court.
- June 14 - Beginning of the Austro-Prussian War, when the Austrians and most of the medium German states declare war on Prussia.
- June 20 - The Kingdom of Italy declares war on Austria.
- June 24 - At the Second Battle of Custozza, the Austrian army under Archduke Albert defeats the main Italian army, commander by King Victor Emmanuel.
- June 27-29 - The Prussians defeat the Hanoverian army at the Battle of Langensalza.

July – December

- July 3 - At the Battle of Königgratz, the Prussian army under King Wilhelm and Helmuth von Moltke defeats the Austrian army of Ludwig von Benedek, leading to a decisive Prussian victory in the Austro-Prussian War.
- July 5 - Marriage of Princess Helena of the United Kingdom, third daughter of Queen Victoria to Prince Christian of Schleswig-Holstein-Sonderburg-Augustenburg
- July 20 - At the Naval Battle of Lissa, the Austrian fleet under Wilhelm von Tegetthoff defeats the Italian fleet of Carlo di Persano.
- July 24 - Reconstruction: Tennessee becomes the first U.S. state to be readmitted to the Union following the American Civil War.
- July 25 - The U.S. Congress passes legislation authorizing the rank of General of the Army (now called "5-star general") Lieutenant General Ulysses S. Grant becomes the first to have this rank.
- July 27 - The Atlantic Cable is successfully completed, allowing transatlantic telegraph communication for the first time.
- July 28 - The Metric Act of 1866 becomes law and legalizes the standardization of weights and measures in the United States.
- August 23 - Treaty of Prague ends the Austro-Prussian War
- September 22 - Paraguay successfully defends Curupaity against the Triple Alliance, scoring more than 5000 with just about 50 casualties.
- October 12 - The Treaty of Vienna ends the war between Austria and Italy. It formalizes the annexation of Venetia by Italy.
- December 21 - Fetterman's massacre - Sioux ambush and wipe out 79 cavalrymen under lieutenant colonel William J. Fetterman
- Federalist revolts in Argentina
- In Sweden the Riksdag of the Estates is replaced by an elected two chamber assembly, the Riksdag.
- Alfred Nobel invents dynamite.
- First historical mention of gerbils, "yellow rats" sent to Museum of Natural History (Musée d'Histoire Naturelle) in Paris, by father Armand David from northern China
- First use of the term Ecology

Births

- January 13 - Vasily Kalinnikov, Russian composer (d. 1901)
- January 15 - Nathan Söderblom, Swedish archbishop, recipient of the Nobel Peace Prize (d. 1931)
- January 29 - Romain Rolland, French writer, Nobel Prize laureate (d. 1944)
- March 30 - George Van Haltren, baseball player (d. 1945)
- April 1 - Ferruccio Busoni, Italian pianist and composer (d. 1924)
- April 6 - Butch Cassidy, American outlaw (d. 1909)
- April 17 - Ernest Starling, British physiologist (d. 1927)
- May 17- Erik Satie, French composer (d. 1925)
- June 26 - George Herbert, 5th Earl of Carnarvon, English financier of Egyptian excavations (d. 1923)
- July 28 - Beatrix Potter, English children's author (d. 1943)
- August 12 - Jacinto Benavente, Spanish writer, Nobel Prize laureate (d. 1954)
- September 1 - James J. Corbett, American boxer (d. 1933)
- September 7 - Tristan Bernard, French writer (d. 1947)
- September 10 - Jeppe Aakjaer, Danish poet and novelist

Ernst Haeckel

Ernst Heinrich Philipp August Haeckel (February 16, 1834 — August 8, 1919), also written von Haeckel, was a German biologist and philosopher who popularized Charles Darwin's work in Germany. Haeckel was a physician, an accomplished artist and illustrator, and later a professor of comparative anatomy. He was one of the first to consider psychology as a branch of physiology. He also proposed many now ubiquitous terms including "phylum" and "ecology." His chief interests lay in evolution and life development processes in general, including development of nonrandom form, which culminated in the beautifully illustrated Kunstformen der Natur (Art forms of nature). Haeckel advanced the "recapitulation theory" which proposed a link between ontogeny (development of form) and phylogeny (evolutionary descent), summed up in the phrase "ontogeny recapitulates phylogeny". He supported the theory with embryo drawings that have been shown to be inaccurate and the theory has been largely discredited. Haeckel was also known for his "biogenic theory", in which he suggested that the development of races paralleled the development of individuals. He advocated the idea that "primitive" races were in their infancies and needed the "supervision" and "protection" of more "mature" societies. He extrapolated a new religion or philosophy called Monism from evolutionary science. In Monism, all economics, politics, and ethics are reduced to "applied biology." His writings and lectures on Monism provided scientific (or quasi-scientific) justifications for racism, nationalism and social darwinism. It has even been argued that monism thus became the de facto religion of Nazi Germany. Some scholars disagree, arguing that Nazi ideology was not comfortable with evolutionary theory, which argues for a common descent of all human races. Haeckel was a flamboyant figure whose popularity with the public was substantially greater than it was with his scientific peers. He sometimes took great (and non-scientific) leaps from available evidence. For example, at the time that Darwin first published On the Origin of Species by Means of Natural Selection, no remains of human ancestors had yet been found. Haeckel postulated that evidence of human evolution would be found in the Dutch East Indies (now Indonesia), and described these theoretical remains in great detail. He even named the as-of-yet unfound species, Pithecanthropus alalus, and charged his students to go find it. Remarkably, one of them did so — a young Dutchman named Eugene Dubois went to the East Indies and dug up the remains of Java Man, the first human ancestral remains ever found. (These remains originally carried Haeckel's Pithecanthropus label, though they were later reclassified as Homo erectus.) Although Haeckel's ideas are important to the history of evolutionary theory, and he was a competent invertebrate anatomist most famous for his work on radiolaria, most of the speculative concepts that he championed are now seen as incorrect. For example, Haeckel described and named hypothetical ancestral micro-organisms that have not been found as of date. His concept of recapitulation called "strong recapitulation" has been disputed. Haeckel did not support Darwin's "survival of the fittest", rather believing in a Lamarckian inheritance of acquired characteristics. Richard and Oskar Hertwig were Haeckel´s most important students. Mount Haeckel is a 4090 m (13,418') summit in the Eastern Sierra Nevada, overlooking the Evolution Basin, named in honor of Ernst Haeckel. So is the asteroid 12323 Häckel.

Sources

Richard Milner, "The Encyclopedia of Evolution: Humanity's Search for Its Origins", Henry Holt, 1993

External links

- [http://www.ucmp.berkeley.edu/history/haeckel.html Ernst Haeckel biography]
- [http://www.slate.com/id/2124625/ Ernst Haeckel – Evolution's controversial artist.] A slide-show essay about Ernst Haeckel.
- [http://caliban.mpiz-koeln.mpg.de/~stueber/haeckel/kunstformen/natur.html Kunstformen der natur, scanned] (from [http://www.biolib.de/] Stuebers Online Library)
- [http://draves.org/pix/kdn/ PNG alpha-transparencies of Haeckel's "Kustformen der natur"]

Books

- Art Forms from the Ocean: The Radiolarian Atlas of 1862, by Ernst Haeckel, Prestel Verlag, 2005 ISBN 3791333275
- Haeckel, Ernst Haeckel, Ernst Haeckel ja:エルンスト・ヘッケル

Biology

Biology is the study, or science, of life. It is concerned with the characteristics and behaviors of organisms, how species and individuals come into existence, and the interactions they have with each other and with the environment. Biology encompasses a broad spectrum of academic fields that are often viewed as independent disciplines. However, together they address the phenomenon of life over a wide range of scales. At the atomic and molecular scale, life is studied in the disciplines of molecular biology, biochemistry, and molecular genetics. At the level of the cell, it is studied in cell biology, and at multicellular scales, it is examined in physiology, anatomy, and histology. Developmental biology studies life at the level of an individual organism's development or ontogeny. Moving up the scale towards more than one organism, genetics considers how heredity works between parent and offspring. Ethology considers group behavior of more than one individual. Population genetics looks at the level of an entire population, and systematics considers the multi-species scale of lineages. Interdependent populations and their habitats are examined in ecology and evolutionary biology. A speculative new field is astrobiology (or xenobiology), which examines the possibility of life beyond the Earth.

Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle

Principles of biology

Unlike physics, biology does not usually describe systems in terms of objects which obey immutable physical laws described by mathematics. Nevertheless, the biological sciences are characterized and unified by several major underlying principles and concepts: universality, evolution, diversity, continuity, homeostasis, and interactions.

Universality: Biochemistry, cells, and the genetic code

mathematics]] Main articles: Life The most salient example of biological universality is that all living things share a common carbon-based biochemistry and in particular pass on their characteristics via genetic material, which is based on nucleic acids such as DNA and which uses a common genetic code with only minor variations. Another universal principle is that all organisms (that is, all forms of life on Earth except for viruses) are made of cells. Similarly, all organisms share common developmental processes. For example, in most metazoan organisms, the basic stages of early embryonic development share similar morphological characteristics and include similar genes.

Evolution: The central principle of biology

Main article: Evolution The central organizing concept in biology is that all life has a common origin and has changed and developed through the process of evolution (see Common descent). This has led to the striking similarity of units and processes discussed in the previous section. Charles Darwin established evolution as a viable theory by articulating its driving force, natural selection (Alfred Russell Wallace is recognized as the co-discoverer of this concept). Genetic drift was embraced as an additional mechanism of evolutionary development in the modern synthesis of the theory. The evolutionary history of a species— which describes the characteristics of the various species from which it descended— together with its genealogical relationship to every other species is called its phylogeny. Widely varied approaches to biology generate information about phylogeny. These include the comparisons of DNA sequences conducted within molecular biology or genomics, and comparisons of fossils or other records of ancient organisms in paleontology. Biologists organize and analyze evolutionary relationships through various methods, including phylogenetics, phenetics, and cladistics (The major events in the evolution of life, as biologists currently understand them, are summarized on this evolutionary timeline).

Diversity: The variety of living organisms

evolutionary timeline, based on rRNA gene data, showing the separation of the three domains bacteria, archaea, and eukaryotes as described initially by Carl Woese. Trees constructed with other genes are generally similar, although they may place some early-branching groups very differently, presumably owing to rapid rRNA evolution. The exact relationships of the three domains are still being debated.]] Despite its underlying unity, life exhibits an astonishingly wide diversity in morphology, behavior, and life histories. In order to grapple with this diversity, biologists attempt to classify all living things. Scientific classification seeks to reflect the evolutionary trees (phylogenetic trees) of the organism being classified. Classification is the province of the disciplines of systematics and taxonomy. Taxonomy places organisms in groups called taxa, while systematics seeks to define their relationships with each other. This clasification technique has evolved to reflect advances in cladistics and genetics, shifting the focus from physical similarities and shared characteristics to phylogenetics. Traditionally, living things have been divided into five kingdoms: :Monera -- Protista -- Fungi -- Plantae -- Animalia However, many scientists now consider this five-kingdom system to be outdated. Modern alternative classification systems generally begin with the three-domain system: :Archaea (originally Archaebacteria) -- Bacteria (originally Eubacteria) -- Eukaryota These domains reflect whether the cells have nuclei or not, as well as differences in the cell exteriors. There is also a series of intracellular parasites that are progressively "less alive" in terms of metabolic activity: :Viruses -- Viroids -- Prions

Continuity: The common descent of life

Main article: Common descent Up into the 19th century, it was commonly believed that life forms could appear spontaneously under certain conditions (see abiogenesis). This misconception was challenged by William Harvey's diction that "all life [is] from [an] egg" (from the Latin "Omne vivum ex ovo"), a foundational concept of modern biology. It simply means that there is an unbroken continuity of life from its initial origin to the present time. A group of organisms is said to share a common descent if they share a common ancestor. All organisms on the Earth have been and are descended from a common ancestor or an ancestral gene pool. This last universal common ancestor of all organisms is believed to have appeared about 3.5 billion years ago. Biologists generally regard the universality of the genetic code as definitive evidence in favor of the theory of universal common descent (UCD) for all bacteria, archaea, and eukaryotes (see: origin of life).

Homeostasis: Adapting to change

Main article: Homeostasis Homeostasis is the ability of an open system to regulate its internal environment to maintain a stable condition by means of multiple dynamic equilibrium adjustments controlled by interrelated regulation mechanisms. All living organisms, whether unicellular or multicellular, exhibit homeostasis. Homeostasis manifests itself at the cellular level through the maintenance of a stable internal acidity (pH); at the organismic level, warm-blooded animals maintain a constant internal body temperature; and at the level of the ecosystem, as when atmospheric carbon dioxide levels rise and plants are theoretically able to grow healthier and remove more of the gas from the atmosphere. Tissues and organs can also maintain homeostasis.

Interactions: Groups and environments

organ of the genus Amphiprion that dwell among the tentacles of tropical sea anemones. The territorial fish protects the anemone from anemone-eating fish, and in turn the stinging tentacles of the anemone protects the anemone fish from its predators]] Every living thing interacts with other organisms and its environment. One reason that biological systems can be difficult to study is that so many different interactions with other organisms and the environment are possible, even on the smallest of scales. A microscopic bacterium responding to a local sugar gradient is responding to its environment as much as a lion is responding to its environment when it searches for food in the African savannah. For any given species, behaviors can be co-operative, aggressive, parasitic or symbiotic. Matters become more complex when two or more different species interact in an ecosystem. Studies of this type are the province of ecology.

Scope of biology

Main article: List of biology disciplines Biology has become such a vast research enterprise that it is not generally regarded as a single discipline, but as a number of clustered sub-disciplines. This article considers four broad groupings. The first group consists of those disciplines that study the basic structures of living systems: cells, genes etc.; the second group considers the operation of these structures at the level of tissues, organs, and bodies; the third group considers organisms and their histories; the final constellation of disciplines focuses on their interactions. It is important to note, however, that these boundaries, groupings, and descriptions are a simplified characterization of biological research. In reality, the boundaries between disciplines are fluid, and most disciplines frequently borrow techniques from each other. For example, evolutionary biology leans heavily on techniques from molecular biology to determine DNA sequences, which assist in understanding the genetic variation of a population; and physiology borrows extensively from cell biology in describing the function of organ systems.

Structure of life

DNA sequences and structures]] Main articles: Molecular biology, Cell biology, Genetics, Developmental biology Molecular biology is the study of biology at a molecular level. This field overlaps with other areas of biology, particularly with genetics and biochemistry. Molecular biology chiefly concerns itself with understanding the interactions between the various systems of a cell, including the interrelationship of DNA, RNA, and protein synthesis and learning how these interactions are regulated. Cell biology studies the physiological properties of cells, as well as their behaviors, interactions, and environment. This is done both on a microscopic and molecular level. Cell biology researches both single-celled organisms like bacteria and specialized cells in multicellular organisms like humans. Understanding cell composition and how they function is fundamental to all of the biological sciences. Appreciating the similarities and differences between cell types is particularly important in the fields of cell and molecular biology. These fundamental similarities and differences provide a unifying theme, allowing the principles learned from studying one cell type to be extrapolated and generalized to other cell types. Genetics is the science of genes, heredity, and the variation of organisms. In modern research, genetics provides important tools in the investigation of the function of a particular gene, or the analysis of