Radiocarbon Dating

a method of dating ORGANIC material up to 8000 years old. There is a small amount of radioactive carbon 14 in the atmosphere which is taken up naturally by plants and animals during life. When the organism dies there is no more uptake of ¹⁴C and it starts to decay, with a HALF-LIFE of 5730 years. A date for the sample is arrived at by comparing the amount of ¹⁴C left with known standards.

Taken from Dictionary of Science

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Radiocarbon dating, or carbon dating, is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 (¹⁴C) to determine the age of carbonaceous materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" (BP), "Present" being defined as AD 1950. Such raw ages can be calibrated to give calendar dates.

One of the most frequent uses of radiocarbon dating is to estimate the age of organic remains from archaeological sites. When plants fix atmospheric carbon dioxide (CO₂) into organic material during photosynthesis they incorporate a quantity of ¹⁴C that approximately matches the level of this isotope in the atmosphere (a small difference occurs because of isotope fractionation, but this is corrected after laboratory analysis). After plants die or they are consumed by other organisms (for example, by humans or other animals) the ¹⁴C fraction of this organic material declines at a fixed exponential rate due to the radioactive decay of ¹⁴C. Comparing the remaining ¹⁴C fraction of a sample to that expected from atmospheric ¹⁴C allows the age of the sample to be estimated.

The technique of radiocarbon dating was developed by Willard Libby and his colleagues at the University of Chicago in 1949. Emilio Segrè asserted in his autobiography that Enrico Fermi suggested the concept to Libby in a seminar at Chicago that year. Libby estimated that the steady state radioactivity concentration of exchangeable carbon-14 would be about 14 disintegrations per minute (dpm) per gram. In 1960, he was awarded the Nobel Prize in chemistry for this work. He first demonstrated the accuracy of radiocarbon dating by accurately estimating the age of wood from an ancient Egyptian royal barge for which the age was known from historical documents.

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Ecology

the study of the relationship between plants and animals and their environment. Ecology is also known as bionomics and is concerned with, for example, predator-prey relationships, population dynamics and competition between species.

Taken from Dictionary of Science

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Ecology (from Greek: οἶκος, "house" ; -λογία, "study of") is the interdisciplinary scientific study of the interactions between organisms and their environment. Ecology is also the study of ecosystems. Ecosystems describe the web or network of relations among organisms at different scales of organization. Since ecology refers to any form of biodiversity, ecologists can conduct research on the smallest bacteria to the global flux of atmospheric gases that are regulated by photosynthesis and respiration as organisms breath in and out of the biosphere.

Ecology is a recent discipline that emerged from the natural sciences in the late 19th century. Ecology is not synonymous with environment, environmentalism, or environmental science. Ecology is closely related to the disciplines of physiology, evolution, genetics and behavior.

Like many of the natural sciences, a conceptual understanding of ecology is found in the broader details of study, including:

• life processes explaining adaptations

• distribution and abundance of organisms

• the movement of materials and energy through living communities

• the successional development of ecosystems, and

• the abundance and distribution of biodiversity in context of the environment.

Ecology is distinguished from natural history, which deals primarily with the descriptive study of organisms. It is a sub-discipline of biology, which is the study of life.

There are many practical applications of ecology in conservation biology, wetland management, natural resource management (agriculture, forestry , fisheries), city planning (urban ecology), community health, economics, basic & applied science and it provides a conceptual framework for understanding and researching human social interaction (human ecology).

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Darwinism

the theory of evolution devised by the British naturalist, Charles Robert Darwin (1809-1882), in order to explain the great variety of plants and animals which exist on Earth. He arrived at his theories as a result of a five year voyage around the world (the voyage of the Beagle) and when he returned to England in 1859, he published a scientific paper with the title Origin of Species. Darwin proposed that some individuals in a species are more successful than others and hence better adapted to their environment. They are more likely to reproduce successfully and some of the characteristics which enable them to do so are inherited by their offspring. Hence these characteristics eventually become more widespread within a species. Gradually, new species can emerge that will adapt to new environments. Old species, which are no longer suited to the surrounding environment, will eventually die out.

Taken from Dictionary of Science

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Darwinism is a term used for various movements or concepts related to ideas of transmutation of species or evolution, including ideas with no connection to the work of Charles Darwin. The meaning of Darwinism has changed over time, and varies depending on who is using the term. In the United States, Darwinism is often used by creationists as a pejorative term but in the United Kingdom the term has no negative connotations, being freely used as a short hand for evolutionary theory.

The term was coined by Thomas Henry Huxley in April 1860, and was used to describe evolutionary concepts, including earlier concepts such as Malthusianism and Spencerism. In the late 19th century it came to mean the concept that natural selection was the sole mechanism of evolution, in contrast to Lamarckism, then around 1900 it was eclipsed by Mendelism until the modern evolutionary synthesis unified Darwin's and Gregor Mendel's ideas. As modern evolutionary theory has developed, the term has been associated at times with specific ideas.

While the term has remained in use amongst scientific authors, it is increasingly regarded as an inappropriate description of modern evolutionary theory. For example, Darwin was unfamiliar with the work of Gregor Mendel, having as a result only a vague and inaccurate understanding of heredity, and knew nothing of genetic drift.

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Dark Reaction

a stage in PHOTOSYNTHESIS which is not directly dependent on light. It takes place within the CHLOROPLASTS of the cells of green plants.

Taken from Dictionary of Science

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Photosynthesis, or the light-independent reactions, are chemical reactions that convert carbon dioxide and other compounds into glucose. The reactions occur in the stroma, the fluid-filled area of a chloroplast outside of the thylakoid membranes. These reactions take the products of the light-dependent reactions and perform further chemical processes on them. There are three phases to the light-independent reactions, collectively called the Calvin Cycle: carbon fixation, reduction reactions, and ribulose 1,5-diphosphate (RuDP) regeneration.

The light-independent reactions are sometimes referred to as the dark reactions, though that term may be misleading as they do not actually require darkness to proceed. The term "light-independent" is used to emphasize that the reactions continue even in the absence of light as long as the proper substrate compounds are available. However, because the availability of substrates in plants depends on photosynthesis, the reactions cannot be said to be entirely "light-independent." The term "dark reactions" may be more accurate in CAM (Crassulacean acid metabolism) plants, which only take up CO₂, which is necessary for the reactions to proceed, at night.

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Calcium

a metallic substance with the symbol Ca which is common in nature being found in both plants and animals. It is essential for the normal growth and development of animals, being found in bones, teeth, blood and nerves.

Taken from Dictionary of Science

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Calcium (pronounced /ˈkælsiəm/, KAL-see-əm) is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust. Calcium is also the fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate.

Calcium is essential for living organisms, particularly in cell physiology, where movement of the calcium ion Ca²⁺ into and out of the cytoplasm functions as a signal for many cellular processes. As a major material used in mineralization of bones and shells, calcium is the most abundant metal by mass in many animals.

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Caffeine

a naturally-occurring chemical substance that is found in tea leaves, coffee beans and other plants. It acts as a weak stimulant on the central nervous system so after drinking a cup of coffee or tea, a person may feel more alert.

Taken from Dictionary of Science

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Caffeine is a bitter, white crystalline xanthine alkaloid that is a psychoactive stimulant drug. Caffeine was discovered by a German chemist, Friedrich Ferdinand Runge, in 1819. He coined the term kaffein, a chemical compound in coffee, which in English became caffeine.

Taken from Wikipedia