A large polynucleotide
(about 1500 bases) which functions as a part of the small subunit of the
ribosome of prokaryotes
and from whose sequence evolutionary
information can be obtained; the eukaryotic
counterpart is 18S rRNA.
Darwin, Charles
Definition:
An English naturalist who lived from 1809 to 1882; he studied and documented
the flora and fauna of parts of coastal South America, including the Galapagos
Islands, but is most famous for developing the theories of evolution
and natural selection.
Haldane's evolutionary unit
Definition:
A unit of measurement, given in darwins, which measures the increase
in body size of a chronospecies
over evolutionary time.
HeLa cells
Definition:
A line of tissue
culturecells
which originated from some human cervical cancer
cells and which was established in 1951 by Gey, Coffman, and Kubicek. The
line is named after the woman who donated the tumor,
Henrietta Lacks, and is the first tissue culture made from human epithelial-like
cells. The line is used to study life processes and the cultivation of
viruses.
(It is also interesting to note that the woman who donated the cells has
since died, but that the line from her tumor lives on in scientific laboratories.
In some respects, the establishment of these cells in a line is not unlike
instant macroevolution
from human to protozoan.)
Jordan's rule
Definition:
An evolutionary
rule that states that the closest genetic relatives of a given species
are found very near it, but the two groups are isolated by some kind of
natural barrier (such as a river) that neither species can cross easily.
adaptive radiation
Definition:
The evolution
of new species or sub-species to fill unoccupied ecological niches.
allopatric speciation (geographic speciation)
Definition:
The evolutionary
process through which two geographically separated (and therefore non-interbreeding)
populations of
the same species
become less and less similar to each other over time (via mutation
or the success of different traits in each environment) and eventually
become distinctly different species.
allopatrically
Definition:
An adverb refering to a specific mechanism of evolutionary divergence.
A species which arose allopatrically from another diverged from the other
because of evolutionary
changes occurring in two different geographically separated populations.
Also see allopatric
and speciation.
analogy (adj. analogous)
Definition:
Two anatomical structures or behavioral traits within different and
unrelated organisms which perform the same functions in each organism but
which did not originate from an ancestral structure or trait that the organisms'
ancestors had in common. Instead, the structures or traits arose separately
and then later evolved to perform the same function (or similar functions).
See also convergent
evolution. Compare homology.
anaplasia (anaplastia; adj. anaplastic)
Definition:
The loss of cellular organization and differentiation; typical of a tumor.
A phase in the evolutionary
development of a species characterized by increase hardiness and diversification.
biogenetic law (recapitulation theory)
Definition:
The theory that
"ontogeny recapitulates
phylogeny," which
means that one can trace the evolutionary development of a species
by studying the development of an individual embryo
or young of that species. The theory is still used, especially in paleontology,
but has been found to not be strictly true when applied to problems in
biology.
bioseries
Definition:
A series of recognizable evolutionary
changes in a single inheritable characteristic.
catagenesis (katagenesis)
Definition:
Evolutionary
change toward simpler, more general forms, and away from complex forms
which are highly-specialized for a particular set of environmental conditions.
chronospecies
Definition:
A chronospecies is a species
which changes physically, morphologically,
genetically, and/or
behaviorally over time on an evolutionary scale (experiences a phyletic
shift) such that the species from the early point in time and the species
it becomes at the later point in time could not be classified as the same
species had they existed at the same point in time. Throughout the change,
there is only one species at any point in time and diversity does not increase.
Evolutionary computation, genetic algorithms, and genetic programming
are all computer disciplines involved with modeling genetic inheritance
and/or biological evolution in computers.
In phylogenetic
trees, the sum of the physical distance on a tree separating organisms;
this distance is inversely proportional to evolutionary relatedness.
fixation
Definition:
An attachment. Being affixed. Immobilization by being glued to something
solid.
Evolutionarily,
a state where every single individual within a population
is homozygous for
a particular allele
(and therefore the phenotype
that the allele confers). For example, in a population where everyone
has blue eyes, the allele for blue eye color is fixed and everyone will
continue to have blue eyes in the future, as long as no new individuals
come into the population from elsewhere.
Psychologically, an obsessive amount of attention toward something.
The conversion of an inorganic source of an element (like nitrogen or carbon)
into an organically useful form.
genetic distance
Definition:
A way of measuring the amount of evolutionary
divergence in two separated populations
of a species by counting
the number of allelic
substitutions per locus
that have cropped up in each population.
homoplasy (adj. homoplasic)
Definition:
Organs or other bodily structures within different species
which resemble each other and have the same functions, but which did not
have a common ancestral origin and development. Instead, the parts arose
via convergent evolution
and are thus analogies.
hypertely
Definition:
An evolutionary term describing a state in which an organism's body
size or body structure becomes overspecialized such that it becomes a disadvantage.
For example, overly large body size, or color/marking imitations of another
species such that camouflage is no longer possible. Also, many traits which
arise from sex selection tend to be disadvantageous overall to the organism
(in terms of survival) but advantageous when the organism wants to attract
a mate.
index fossils
Definition:
Fossils (or groups of fossils) which are used by geologists and paleontologists
to help correlate different events or processes in different parts of the
world which happened at the same time. Species
which make good index fossils are able to tolerate a wide range of ecological
conditions, are geographically widespread, common, easy to find, and evolutionarily
short-lived (that is, they speciated and then quickly became extinct).
In general, they are also planktonic
and very small.
inheritance of acquired characteristics (Lamarckism, Lamarckian inheritance)
Definition:
The obsolete theory
that offspring can inherit
physical or behavioral characteristics from a parent that the parent acquired
during its life. For example, a giraffe which stretches its neck to reach
leaves at the top of a tall tree and thus ends up with a slightly longer
neck can pass on the long neck trait so that its offspring also have long
necks and can stretch it even longer. The theory, now known to be incorrect,
was popularized by Jean-Baptiste Lamarck (1744-1829) and played an important
role in the history of the study of evolutionary biology.
k selection
Definition:
In evolution,
the selection* of traits that aid an organism's
competitive capability when the population is at or near its carrying capacity.
Evolutionary
change in the chromosome
set, expressed as changes in number and gross structure of the chromosomes;
(more broadly), evolutionary relationships between taxa
as indicated by karyotype
differences.
The evolutionary
process of a single population of a species
splitting into two or more species, where the new species end up in areas
that are right next to each other (but not overlapping) and which do not
have any geographic barriers in between. Parapatric speciation is intermediate
between allopatric
and sympatric speciation.
Composed of members that originated, independently, from more than
one evolutionary line. Compare monophyletic
and paraphyletic.
quantum evolution
Definition:
An extremely rapid evolutionary
change in a single genetic lineage, thought to result from a sudden and
radical change in the species' environment.
quantum speciation (saltational speciation)
Definition:
The rapid evolution
of a new species from a small population that is partially or totally isolated
from the parent population; the rapid speciation occurs due to genetic
drift and founder effect and usually involves a few mutations
that have a big impact on the organisms' observable physical traits.
radiation
Definition:
In evolution, the
process through which a group of species diverge from a single ancestral
form.
General term referring to the emission of electromagnetic waves (e.g. heat,
light. etc.) or particles (e.g. neutrons) from from a material.
sickle-cell trait
Definition:
This condition occurs in people who have one of two possible genes
(i.e., they are heterozygous
for the allele) that
code for the defective hemoglobin
responsible for sickle-cell
anemia. The codition is diagnosed by exposing an individual's red
blood cells to a low oxygen environment; if the trait is present, the
cells will turn to a sickle shape. People with this trait may suffer milder
symptoms of sickle-cell anemia, or may have no symptoms. Some scientists
believe the trait actually provides an evolutionary
advantage in tropical environments because the slightly altered shape of
the blood cells causes a person to be more resistant to malaria.
species
Definition:
Groups of populations
(which are groups of individuals living together that are separated from
other such groups) which can potentially interbreed or are actually interbreeding,
that can successfully produce viable, fertile offspring (without the help
of human technology). [Ernst Mayr, 1969] The species is the most fundamental
unit of evolution
and is the most specific taxonomic
level.
spontaneous mutation
Definition:
A mutation which
occurs by itself without first being affected by a mutagen,
for example during the process of DNAreplication.
Spontaneous mutations arise at a remarkably constant rate. The rate that
spontaneous mutations arise has been used as an evolutionary clock to estimate
how closely related two (or more) separate species
are to each other.
sympatric speciation
Definition:
The evolutionary
process of a single population of a species splitting into two populations
which gradually evolve into two different species (as a result of genetic
mutation and variation)
while both diverging populations still occupy the same geographic area.
uniform rate hypothesis
Definition:
This states that any two evolving
organismal lineages diverge from a common ancestor at a constant rate with
respect to each other.
zoogenesis
Definition:
The origin of animal life on the planet.
The origin and evolution
of a particular animal species.
END
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1995-97 by their respective authors or, if no author is listed, by BioTech
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