eccrine
(Gr. ek, out of, + krinein, to
separate). Applies to a type of mammalian
sweat gland that produces a watery secretion.
ecdysiotropin
(Gr. ekdysis, to strip off, escape, + tropos, a
turn, change). Hormone secreted in brain of
insects that stimulates prothoracic gland to
secrete molting hormone. Prothoracicotropic
hormone; brain hormone.
ecdysis
(Gr. ekdysis, to strip off,
escape). Shedding of outer cuticular layer;
molting, as in insects or crustaceans.
ecdysone
(Gr. ekdysis, to strip off).
Molting hormone of arthropods, stimulates
growth and ecdysis, produced by
prothoracic glands in insects and Y organs
in crustaceans.
ecocline
(Gr. oikos, home, + klino,
to slope, recline). The gradient between
adjacent biomes; a gradient of
environmental conditions.
ecology
(Gr. oikos, house, + logos, discourse).
Part of biology that deals with the
relationship between organisms and their
environment.
ecosystem
(eco[logy] from Gr. oikos, house, + system). An ecological unit
consisting of both the biotic communities
and the nonliving (abiotic) environment,
which interact to produce a stable system.
ecotone
(eco[logy] from Gr. oikos,
home, + tonos, stress). The transition zone
between two adjacent communities.
ectoderm
(Gr. ektos, outside, + derma, skin). Outer layer of cells of an
early embryo (gastrula stage); one of the
germ layers, also sometimes used to include
tissues derived from ectoderm.
ectognathous
(Gr. ektos,
outside, without, + gnathos, jaw). Derived
character of most insects; mandibles and
maxillae not in pouches.
ectolecithal
(Gr. ektos,
outside, + lekithos, yolk). Yolk for nutrition
of the embryo contributed by cells that are
separate from the egg cell and are
combined with the zygote by envelopment
within the eggshell.
ectoneural
(Gr. ektos, outside,
without, + neuron, nerve). Oral (chief)
nervous system in echinoderms.
ectoplasm
(Gr. ektos, outside, + plasma, form). The cortex of a cell or that
part of cytoplasm just under the cell surface;
contrasts with endoplasm.
ectothermic
(Gr. ektos,
outside, + therme, heat). Having a variable
body temperature derived from heat
acquired from the environment; contrasts
with endothermic.
edema
(Gr. oidema, swelling).
Escape of fluid from blood into interstitial
space, causing swelling.
effector
(L. efficere, bring to pass). An organ,
tissue, or cell that becomes active in
response to stimulation.
efferent
(L. ex, out, + ferre, to
bear). Leading or conveying away from
some organ, for example, nerve impulses
conducted away from the brain, or blood
conveyed away from an organ; contrasts
with afferent.
egestion
(L. egestus, to discharge).
Act of casting out indigestible or waste
matter from the body by any normal route.
electron
A subatomic particle with a negative
charge and a mass of 9.1066 × 10−28 gram.
eleocyte
(Gr. elaion, oil, + kytos,
hollow vessel). Fat-containing cells in annelids
that originate from the chlorogogen tissue.
elephantiasis
Disfiguring
condition caused by chronic infection with
filarial worms Wuchereria bancrofti and
Brugia malayi.
embryogenesis
(Gr. embryon, embryo, + genesis, origin). The
origin and development of the embryo;
embryogeny.
emergence
(L. e, out, + mergere, to plunge).
The appearance of properties in a biological
system (at the molecular, cellular,
organismal, or species levels) that cannot be
deduced from knowledge of the component
parts taken separately or in partial
combinations; such properties are termed
emergent properties.
emigrate
(L. emigrare, to move out). To move
from one area to another to take up
residence.
emulsion
(L. emulsus, milked
out). A colloidal system in which both
phases are liquids.
endemic
(Gr. en, in, + demos,
populace). Peculiar to a certain region or
country; native to a restricted area; not
introduced.
endergonic
(Gr. endon,
within, + ergon, work). Used in reference
to a chemical reaction that requires energy;
energy absorbing.
endite
(Gr. endon, within). Medial
process on an arthropod limb.
endochondral
(Gr. endon,
within, + chondros, cartilage). Occurring
with the substance of cartilage, especially
bone formation.
endocrine
(Gr. endon, within, + krinein, to separate). Refers to a gland that
is without a duct and that releases its
product directly into the blood or lymph.
endocytosis
(Gr. endon,
within, + kytos, hollow vessel). The
engulfment of matter by phagocytosis,
potocytosis, receptor-mediated endocytosis,
and by bulk-phase (nonspecific)
endocytosis.
endoderm
(Gr. endon, within, + derma, skin). Innermost germ layer of an
embryo, forming the primitive gut; also may
refer to tissues derived from endoderm.
endognathous
(Gr. endon,
within, + gnathous, jaw). Ancestral
character in insects, found in orders Diplura,
Collembola, and Protura, in which the
mandibles and maxillae are located in
pouches.
endolecithal
(Gr. endon,
within, + lekithos, yolk). Yolk for nutrition
of the embryo incorporated into the egg cell
itself.
endolymph
(Gr. endon, within, + lympha, water). Fluid that fills most of
the membranous labyrinth of the vertebrate
ear.
endometrium
(Gr. endon,
within, + metra, womb). The mucous
membrane lining the uterus.
endoplasm
(Gr. endon, within, + plasma, mold or form). The portion of
cytoplasm that immediately surrounds the
nucleus.
endoplasmic reticulum
A complex of
membranes within a cell; may bear
ribosomes (rough) or not (smooth).
endopod, endopodite
(Gr. endon, within, + pous, podos,
foot). Medial branch of a biramous
crustacean appendage.
endopterygote
(Gr. endon,
within, + pteron, feather, wing). Insect in
which the wing buds develop internally; has
holometabolous metamorphosis.
endorphin
(contraction of
endogenous morphine). Group of opiatelike
brain neuropeptides that modulate pain
perception and are implicated in many
other functions.
endoskeleton
(Gr. endon, within, + skeletos,
hard). A skeleton or supporting framework
within the living tissues of an organism;
contrasts with exoskeleton.
endosome
(Gr. endon, within, + soma, body). Nucleolus in nucleus of some
protozoa that retains its identity through
mitosis.
endostyle
(Gr. endon, within, + stylos, a pillar). Ciliated groove(s) in the
floor of the pharynx of tunicates,
cephalochordates, and larval jawless fishes
useful for accumulating and moving food
particles to the stomach.
endothelium
(Gr. endon,
within, + thele, nipple). Squamous
epithelium lining internal body cavities such
as heart and blood vessels. Adj.,
endothelial.
endothermic
(Gr. endon,
within, + therme, heat). Having a body
temperature determined by heat derived
from the animal’s own oxidative
metabolism; contrasts with ectothermic.
enkephalin
(Gr. endon, within, + kephale, head). Group of small brain
neuropeptides with opiate-like qualities.
enterocoel
(Gr. enteron, gut, + koilos, hollow). A type of coelom formed by
the outpouching of a mesodermal sac from
the endoderm of the primitive gut.
enterocoelic
mesoderm formation
Embryonic formation of mesoderm by a
pouchlike outfolding from the archenteron,
which then expands and obliterates the
blastocoel, thus forming a large cavity, the
coelom, lined with mesoderm.
enterocoelomate
(Gr. enteron, gut, + koiloma, cavity, + Eng. ate,
state of). An animal having an enterocoel,
such as an echinoderm or a vertebrate.
enteron
(Gr. intestine). The
digestive cavity.
entomology
(Gr. entoma, an
insect, + logos, discourse). Study of insects.
entozoic
(Gr. entos, within, + zoon, animal). Living within another
animal; internally parasitic (chiefly parasitic
worms).
entropy
(Gr. en, in, on, + tropos,
turn, change in manner). A quantity that is the measure of energy in a system not
available for doing work.
enzyme
(Gr. enzymos, leavened,
from en, in, + zyme, leaven). A substance,
produced by living cells, that is capable of
speeding up specific chemical
transformations, such as hydrolysis,
oxidation, or reduction, but is unaltered
itself in the process; a biological catalyst.
eocytes
(Gr. eos, the dawn, + kytos,
hollow vessel). A group of prokaryotes
currently classified among the
Archaebacteria but possibly a sister
group of eukaryotes.
ephyra
(Gr. Ephyra, Greek city).
Refers to castlelike appearance. Medusa bud
from a scyphozoan polyp.
epidermis
(Gr. epi, on, upon, + derma, skin). The outer, nonvascular
layer of skin of ectodermal origin; in
invertebrates, a single layer of ectodermal
epithelium.
epididymis
(Gr. epi, on,
upon, + didymos, testicle). Part of the sperm
duct that is coiled and lying near the testis.
epigenesis
(Gr. epi, on, upon, + genesis, birth). The embryological (and
generally accepted) view that an embryo is
a new creation that develops and
differentiates step by step from an initial
stage; the progressive production of new
parts that were nonexistent as such in the
original zygote.
epigenetics
(Gr. epi, on,
upon, + genesis, birth). Study of the
relationship between genotype and
phenotype as mediated by developmental
processes.
epipod, epipodite
(Gr. epi, on, upon, + pous, podos, foot). A lateral
process on the protopod of a crustacean
appendage, often modified as a gill.
epistasis
(Gr. epi, on, upon, + stasis, standing). Prevention of expression
of an allele at one locus by an allele at
another locus.
epistome
(Gr. epi, on, upon, + stoma, mouth). Flap over the mouth in
some lophophorates bearing the protocoel.
epithelium
(Gr. epi, on,
upon, + thele, nipple). A cellular tissue
covering a free surface or lining a tube or
cavity.
epitoke
(Gr. epitokos, fruitful).
Posterior part of a marine polychaete when
swollen with developing gonads during the
breeding season; contrast with atoke.
epitope
That portion of an antigen to which
an antibody or T-cell receptor binds. Also
called antigenic determinant.
erythroblastosis fetalis
(Gr. erythros, red, + blastos, germ, + osis, a disease; L. fetalis, relating to a
fetus). A disease of newborn infants caused
when Rh-negative mothers develop
antibodies against the Rh-positive blood of
the fetus. See blood type.
erythrocyte
(Gr. erythros, red, + kytos, hollow vessel). Red blood cell; has
hemoglobin to carry oxygen from lungs or
gills to tissues; during formation in
mammals, erythrocytes lose their nuclei,
those of other vertebrates retain the nuclei.
esthete
(Gr. esthes, a garment). Light
sensory receptor on a shell of a chiton
(phylum Mollusca).
estrus
(L. oestrus, gadfly, frenzy).
The period of heat, or rut, especially
of the female during ovulation of the egg.
Associated with maximum sexual receptivity.
estuary (es+ch‰-we+re) (L. aestuarium,
estuary). An arm of the sea where the tide
meets the current of a freshwater drainage.
ethology
(Gr. ethos, character, + logos, discourse). The study of animal
behavior in natural environments.
euchromatin
(Gr. eu, good,
well, + chroma, color). Part of the
chromatin that takes up stain less than
heterochromatin, contains active genes.
eukaryotic, eucaryotic
(Gr. eu,
good, true, + karyon, nut, kernel).
Organisms whose cells characteristically
contain a membrane-bound nucleus or
nuclei; contrasts with prokaryotic.
euploidy
(Gr. eu, good, well, + ploid, multiple of). Change in chromosome
number from one generation to the next
in which there is an addition or deletion
of a complete set of chromosomes in the
progeny; the most common type is
polyploidy.
euryhaline
(Gr. eurys, broad, + hals, salt). Able to tolerate wide ranges of
saltwater concentrations.
euryphagous
(Gr. eurys, broad, + phagein, to eat). Eating a large variety of
foods.
eurytopic
(Gr. eurys, broad, + topos, place). Refers to an organism with
a wide environmental range.
eutely
(Gr. euteia, thrift). Condition of
a body composed of a constant number of
cells or nuclei in all adult members of a
species, as in rotifers, acanthocephalans,
and nematodes.
evagination
(L. e, out, + vagina, sheath). An outpocketing from a
hollow structure.
evolution
(L. evolvere, to unfold). Organic
evolution encompasses all changes in the
characteristics and diversity of life on earth
throughout its history.
evolutionary
duration
The length of time that
a species or higher taxon exists in
geological time.
evolutionary species concept
A single
lineage of ancestral-descendant populations
that maintains its identity from other such
lineages and has its own evolutionary
tendencies and historical fate; differs from
the biological species concept by explicitly
including a time dimension and including
asexual lineages.
evolutionary taxonomy
A system of
classification, formalized by George Gaylord
Simpson, that groups species into Linnean
higher taxa representing a hierarchy of
distinct adaptive zones; such taxa may be
monophyletic or paraphyletic but not
polyphyletic.
excision repair
Means by which cells are able
to repair certain kinds of damage (dimerized
pyrimidines) in their DNA.
exergonic
(Gr. exo, outside of, + ergon, work). An energy-yielding
reaction.
exite
(Gr. exo, outside). Process from
lateral side of an arthropod limb.
exocrine
(Gr. exo, outside, + krinein, to separate). A type of gland
that releases its secretion through a duct;
contrasts with endocrine.
exocytosis
(Gr. exo, outside, + kytos, hollow vessel). Transport of a
substance from inside a cell to the outside.
exon
(Gr. exo, outside). Part of the
mRNA as transcribed from the DNA that
contains a portion of the information
necessary for final gene product.
exopod, exopodite
(Gr. exo, outside, + pous, podos, foot).
Lateral branch of a biramous crustacean
appendage.
exopterygote
(Gr. exo,
without, + pteron, feather, wing). Insect in
which the wing buds develop externally
during nymphal instars; has
hemimetabolous metamorphosis.
exoskeleton
(Gr. exo,
outside, + skeletos, hard). A supporting
structure secreted by ectoderm or epidermis;
external, not enveloped by living tissue, as
opposed to endoskeleton.
experiment
A trial made
to support or disprove a hypothesis.
exteroceptor
(L. exter,
outward, + capere, to take). A sense organ
excited by stimuli from the external world.
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