charles_darwin

Glossary of Selected Terms
Scientists using this technique can ensure that specific character traits
of the parents are passed on or eliminated from their offspring.
Progressionism. An idea developed in the eighteenth and nineteenth centuries
to explain the relationship between different species. The species
were fixed, they did not mutate or change, but they were all related to
each other. The species belonged in an order that progressed from the
simplest to the most complex. For example, a vertebrate animal such
as a dog was a higher order of species than an invertebrate such a
worm. Humans were the highest of species. Progressionism was a similar
idea to Aristotle’s Scale of Being.
Punctuated Equilibrium. An alternative explanation for the process of evolution.
Scientists favoring punctuated equilibrium argue that evolution
does not occur slowly and uniformly. The gaps in the fossil record are
not gaps but a reflection of what occurred. Evolution occurs rapidly
at some periods—hence the large number of fossil remains dating to
particular era. Evolution does not occur or species change very little
at other periods, hence the lack of fossils for some era. The American
scientists Nils Eldredge (1943–) and Stephen Jay Gould (1941–2002)
proposed the idea in 1971 because they were dissatisfied with the
Neo-Darwinist explanation of evolution.
RNA (ribose nucleic acid). Related to DNA (deoxyribose nucleic acid),
RNA carries the information about cell proteins from DNA, thus enabling
new proteins and new cells to be built.
Saltationism. An alternative theory of evolution to Darwin’s. Saltationists
argue that species can arise suddenly as a result of significant mutation.
Thomas Huxley favored a saltationist approach to evolution: he
thought Darwin’s theory of slow, gradual transformation was too restrictive.
The early geneticists such as William Bateson (1861–1926)
and Hugo de Vries (1848–1935) were the strongest proponents of
saltationism.
Scale of Being. Aristotle’s idea about the progression of species from the
simplest to the most complex. Each species had a particular place in
the hierarchy of nature that did not and could not change. Also
known as the Chain of Being.
Sexual Selection. One of Darwin’s explanations for evolution. Individuals of
a species, usually females, chose a mate who is best able to help
produce the most offspring. This selection enables species best
adapted to their surroundings to survive. Darwin argued that natural
selection played a much more significant role in evolution than sexual
selection.
Social Biologists. Biologists who study the behavior of groups of animals.
Pioneered by the American entomologist Edward O. Wilson (1929–),
social biologists examine the relationship between the behavior of
insects such as ants and that of other animal species such as humans.
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