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objective piece: The
rock or artifact being modified by the removal of detached pieces.
Objective pieces may be cores that are used solely as sources of
raw material or they may be tools such as bifaces or flake tools.
obsidian: A volcanic
rock formed into natural glass. This rock is usually black but may
be found in greenish and reddish colors or banded.
obsidian hydration
dating: This technique involves the absorption of water on exposed
surfaces of obsidian; when the local hydration rate is known, the
thickness of the hydration layer, if accurately measured, can be
used to provide an absolute date.
obstetrical: Of or
relating to childbirth.
obturator foramen:
A space at the front of the pelvis enclosed by the pubis and ischium.
occiptal bone: The
bone forming the vault posterior and much of the basicranium.
occipital bun: A backward
extension of the cranial rear in the form of a protuberance bounded
by the nuchal plane below, a shaft vertical face for the occiput
behind, and a flat surface above (lambdoidal flattening). See also
chignon.
occipital condyles:
Raised, elongated-oval, convex articular eminences on either side
of the foramen magnum of the occiptal bone, for the junction of
the head and the uppermost neck vertebra occiptal lobes: Back part
of the cerebral hemispheres of the brain.
occipital plane (upper
scale): The portion of the occiput above the superior nuchal line,
and for the most part above the nuchal muscles.
occipitomastoid: A
process, usually in the form of a crest, paralleling or straddling
the occipitomastoid suture and separated from the most lateral paramastoid
process, if there is one, by an occipital grove. See juxtamastoid
eminence.
occlusal: The surfaces
of the opposing teeth that meet for chewing; in an occlusal view
the crowns of the teeth are shown.
occlusal force: The
force produced between the teeth during chewing.
occlusion: The positions
of the teeth when the jaws are closed and their biting surfaces
touch.
oestrus: See estrus.
Okazaki fragments:
The relatively short, single-stranded DNA fragments in discontinuous
DNA replication that are synthesized during DNA replication and
that are subsequently covalently joined to make a continuous strand.
Olduwan industry: One
of the earliest toolkits, comprising flake and pebble tools, used
by hominids in the Olduvai Gorge, East Africa.
Old World primate:
Any primate from Africa or Eurasia.
olecranon fossa: A
depression at the posterior side of the distal humerus, at the elbow,
for the accommodating the olecranon process of the ulna when the
elbow is extended.
olecranon process:
A beak-like projection on the proximal end of the ulna, at the elbow,
for articulation with the humerus and attachment of the triceps
muscles.
olfaction: The sense
of smell.
oligomers: Short DNA
molecules.
oligopithecine: Member
of the family Oligopithecinae.
omnivore: An organism
that eats a diversity of food types, including animals and plants.
oncogene: A gene whose
action promotes cell proliferation. Oncogenes are altered forms
of proto-oncogenes.
oncogenesis: Tumor
(cancer) initiation in an organism.
one gene-one enzyme
hypothesis: The hypothesis, based on Beadle and Tatum's studies
in biochemical genetics, that each gene controls the synthesis of
one enzyme.
one gene-one polypeptide
hypothesis: Updated version of the one gene-one enzyme hypothesis,
which states that each gene controls the synthesis of a polypeptide
chain.
ontogeny: The developmental
history of an individual from egg to adult.
oogenesis: The development
in the gonad of the female germ cell (egg cell) of animals.
opal: An amorphous
form of quartz unstable at temperatures and pressures found on the
surface of the earth.
open-area excavation:
The opening up of large horizontal areas for excavation, used especially
where single period deposits lie close to the surface.
open reading frame:
In a segment of DNA, a potential protein-coding-sequence identified
by an initiator codon in frame with a chain-terminating codon.
operational sequence:
The stages of artifact production, reflecting the technological
decisions of the toolmakers that are assumed to be technical traditions
(they are unlikely to be genetically encoded). The operational sequence
is divided into three stages: raw material procurement, core reduction,
and tool manufacture and use.
operator: The controlling
site, that is adjacent to a promoter, that is responsible for controlling
the transcription of genes that are contiguous to the promoter.
operon: A cluster of
genes whose expressions are regulated together by operator-regulator
protein interactions, plus the operator region itself and the promoter.
opisthion: The midline
point of the posterior margin of the foramen magnum.
opisthocranion: The
back of the school, located as far from the center of the brows
as is possible to get on the midline.
opportunistic evolution:
Species adapt to fill in all available niches.
opposability: The ability
to touch the thumb tip to the fingertips of the same hand.
optical emission spectrometry
(OES): A technique used in the analysis of artifact composition,
based on the principle that electrons, when excited (i.e. heated
to a high temperature), release light of a particular wavelength.
The presence or absence of various elements is established by examining
the appropriate spectral line of their characteristic wavelengths.
Generally, this method gives an accuracy of only 25 percent and
has been superseded by ICPS (inductively coupled plasma emission
spectrometry).
oral: Pertaining to
the mouth.
orbit: Bony socket
for the eye.
orbital pillar: The
outer bony rim found on orbits that face anteriorly, made up of
the zygomatic process of the frontal and the frontal process of
the zygomatic bone.
order: A monophyletic
higher-level taxon (made up of suborders, superfamilies, etc.) whose
members generally share a basic structural pattern.
ordered tetrads: A
structure resulting from meiosis in which the fouor meiotic products
are in an order reflecting exactly the orientation of the four chromatids
at the metaphase plate in meiosis I.
origin: A specific
site on a chromosome at which the double helix denatures into single
strands and continues to unwind as the replication fork(s) migrates.
origin of replication:
A specific DNA sequence that is required for the initiation of DNA
replication in prokaryotes.
orthognathous: Having
a relatively vertical, nonprotruding face (cf. prognathic).
orthoquartzite: A sandstone
converted to quartzite with grains cemented only through infiltration
and pressure. The cementing agent is usually quartz.
ossicle: Very small
bone, such as the ear ossicles or the finger joint sesamoid bones.
ossification: The process
of forming new bone.
osteo: Pertaining to
bone.
Osteodontokeratic:
Artifacts made of bone, tooth, or horn, as in the Osteodontokeratic
"culture" of the Makapansgat australopithecines.
osteology: The study
of bones and their variation.
outbreeding: Preferential
mating between nonrelated individuals.
overdominance (heterozygote
advantage): Condition in which the heterozygote has higher fitness
than either of the homozygotes.
overshot termination:
See plunging termination.
overspecialized: Adapted
to a particular niche so specifically that the genetic variation
necessary to meet changing conditions has been lost.
ovulation: Release
of an unfertilized gamete (egg) from the ovary.
ovum: A mature egg
cell. In the second meiotic division, the secondary oocyte produces
two haploid cells; the large cell rapidly matures into the ovum.
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