imago
The adult and sexually
mature insect.
immediate hypersensitivity
Inflammatory
reaction based primarily on humoral
immunity.
immunity
Ability by tissues in an organism to
recognize and defend against nonself
invaders. Innate immunity is a mechanism
of defense that does not depend on prior
exposure to the invader; acquired immunity is specific to a nonself material, requires time
for development, and occurs more quickly
and vigorously on secondary response.
immunoglobulin
(L.
immunis, free, + globus, globe). Any of a
group of plasma proteins, produced by
plasma cells, that participates in the immune
response by combining with the antigen
that stimulated its production. Antibody.
imprinting
(im´print-ing) (L. imprimere, to
impress, imprint). Rapid and usually stable
learning pattern appearing early in the life of
a member of a social species and involving
recognition of its own species; may involve
attraction to the first moving object seen.
inbreeding
The tendency among members of
a population to mate preferentially with
close relatives.
incomplete
dominance See intermediate
inheritance
incus
(L. incus, anvil). The middle of
a chain of three bones of the mammalian
middle ear.
indeterminate cleavage
A type of embryonic
development in which the fate of the
blastomeres is not determined very early as
to tissues or organs, for example, in
echinoderms and vertebrates; regulative
cleavage.
indigenous
(L. indigena,
native). Pertains to organisms that are native
to a particular region; not introduced.
induction
(L. inducere, inductum, to lead).
Reasoning from the particular to the
general, that is, deriving a general statement
(hypothesis) based on individual
observations. In embryology, the alteration
of cell fates as the result of interaction with
neighboring cells.
inductor
(L. inducere, to
introduce, lead in). In embryology, a tissue
or organ that causes the differentiation of
another tissue or organ.
inflammation
(L. inflammare, from flamma, flame). The
complicated physiological process in
mobilization of body defenses against
foreign substances and infectious agents and
repair of damage from such agents.
infraciliature
(L. infra,
below, + cilia, eyelashes). The organelles
just below the cilia in ciliate protozoa.
infundibulum
(L. funnel).
Stalk of the neurohypophysis linking the
pituitary to the diencephalon.
innate
(L. innatus, inborn). A
characteristic based partly or wholly on
genetic or epigenetic constitution.
instar
(L. form). Stage in the life of an
insect or other arthropod between molts.
instinct
(L. instinctus, impelled). Stereotyped,
predictable, genetically programmed
behavior. Learning may or may not be
involved.
integument
(L. integumentum, covering). An external
covering or enveloping layer.
intercellular
(L. inter, among, + cellula, chamber). Occurring
between body cells.
interferons
Several cytokines encoded by
different genes, important in mediation of
natural immunity and inflammation.
interleukin-1
A cytokine produced by
macrophages that stimulates T helper
lymphocytes.
interleukin-2
A lymphokine produced by T
helper lymphocytes that leads to
proliferation of T helper cells and other T
lymphocytes.
interleukins
A series of cytokines produced
primarily by various leukocytes, such as macrophages and T cells, whose target
cells are various leukocytes and other
cells. Given the name "interleukins" when
it was believed that they were produced
only by leukocytes and their target cells
were limited to leukocytes.
intermediary meiosis
Meiosis that occurs
neither during gamete formation nor
immediately after zygote formation,
resulting in both haploid and diploid
generations, such as in foraminiferan
protozoa.
intermediate host
A host in which some
development of a symbiont occurs, but in
which maturation and sexual reproduction
do not take place.
intermediate inheritance
Neither of
alternate alleles of a gene are completely
dominant, and heterozygote shows a
condition intermediate between or
different from homozygotes for each allele.
interstitial
(L. inter,
among, + sistere, to stand). Situated
in the interstices or spaces between
structures such as cells, organs, or
grains of sand.
intracellular
(L. intra,
inside, + cellula, chamber). Occurring
within a body cell or within body cells.
intrinsic growth rate
Exponential growth
rate of a population, that is, the difference
between the density-independent
components of the birth and death rates
of a natural population with stable age
distribution.
intron
(L. intra, within). Portion of
mRNA as transcribed from DNA that will
not form part of mature mRNA, and
therefore does not encode an amino-acid
sequence in the protein product.
introvert
(L. intro, inward, + vertere, to
turn). The anterior narrow portion that can
be withdrawn (introverted) into the trunk
of a sipunculid worm.
invagination
(L. in, in, + vagina, sheath). An infolding of a layer of
tissue to form a sac-like structure.
inversion
(L. invertere, to turn upside
down). A turning inward or inside out, as
in embryogenesis of sponges; also,
reversal in order of genes or reversal of a
chromosome segment.
ion
An atom or group of atoms with a net
positive or negative electrical charge
because of the loss or gain of electrons.
ionicn bond
A chemical bond formed by
transfer of one or more electrons
from one atom to another; characteristic
of salts.
iridophore
(Gr. iris, rainbow, or
iris of eye). Iridescent or silvery
chromatophores containing crystals or
plates of guanine or other purine.
irritability
(L. irritare, to provoke). A
general property of all organisms
involving the ability to respond to stimuli
or changes in the environment.
isogametes
(Gr. isos, equal, + gametes, spouse). Gametes of a species in
which gametes of both sexes are alike in
size and appearance.
isolecithal
(Gr. isos, equal, + lekithos, yolk, + al). Pertaining to a
zygote (or ovum) with yolk evenly
distributed. Homolecithal.
isosmotic
A liquid having the same osmotic
pressure as another, reference liquid.
isotonic
(Gr. isos, equal, + tonikos, tension).
Pertaining to solutions having the same or
equal osmotic pressure; isosmotic.
isotope
(Gr. isos, equal, + topos, place). One
of several different forms (species) of a
chemical element, differing from each other
in atomic mass but not in atomic number.
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