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.

Taken from Wikipedia

Radical

a group of atoms within a compound, which are not able to exist on their own and are not changed when the substance is involved in chemical reactions.

Taken from Dictionary of Science
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In chemistry, radicals (often referred to as free radicals) are atoms, molecules, or ions with unpaired electrons on an open shell configuration. The unpaired electrons cause them to be highly chemically reactive. Radicals play an important role in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes, including human physiology. For example, superoxide and nitric oxide regulate many biological processes, such as controlling vascular tone. "Radical" and "free radical" are frequently used interchangeably, although a radical may be trapped within a solvent cage or be otherwise bound. The first organic free radical identified was triphenylmethyl radical, by Moses Gomberg in 1900 at the University of Michigan.

Historically, the term radical has also been used for bound parts of the molecule, especially when they remain unchanged in reactions. These are now called functional groups. For example, methyl alcohol was described as consisting of a methyl "radical" and a hydroxyl "radical". Neither are radicals in the modern chemical sense, as they are permanently bound to each other, and have no unpaired, reactive electrons. They can, however, be observed as radicals in mass spectrometry when broken apart by irradiation with energetic electrons.

Taken from Wikipedia