Glossary ❮ 325increases the likelihood that two deleterious, reces-
sive alleles will end up in the same offspring.
hydrolysis reaction A reaction that breaks down
compounds by the addition of H 2 O.
hydrophilic Water-loving.
hydroxyl groupA hydrophilic and polar functional
group (—OH) that is present in compounds known
asalcohols.
hypercholesterolemiaRecessive disorder (hh) that
causes cholesterol levels to be many times higher
than normal and can lead to heart attacks in chil-
dren as young as two years old.
hypertonic Characterizes a solution that has a higher
solute concentration than does a neighboring
solution.
hypha Filament found in fungi made of chitin that
separates fungi into multicellular compartments.
hypoblast Forms the yolk sac, which produces the
embryo’s first blood cells.
hypothalamus The thermostat and “hunger meter”
of the body, regulating temperature, hunger, and
thirst.
hypotonic Characterizes a solution that has a lower
solute concentration than a neighboring solution.
immigration rate Rate at which individuals relocate
intoa given population.
imprintingInnate behavior that is learned during a
critical period early in life.
inclusive fitness An individual’s fitness gain that is a
direct result of his or her contribution to the repro-
ductive effort of closely related kin. This results from
the fact that close kin share copies of identical genes.
incomplete dominance Blending inheritance. The
heterozygous genotype produces an intermediate
phenotype rather than the dominant phenotype;
neither allele dominates the other.
induced-fit modelTheory that suggests that when an
enzyme and a substrate bind together, the enzyme
isinducedto alter its shape for a tighter active-
site/substrate attachment, which places the sub-
strate in a favorable position to react more quickly.
inducer Molecule that binds to and inactivates a
repressor.
induction The ability of one group of cells to influence
the development of another. This influence can be
through physical contact or chemical signaling.
inner cell mass Portion of the blastula that develops
into the embryo.
inorganic compounds For the most part, compounds
containing no carbon. There are some exceptions
such as carbon dioxide, carbon monoxide, and
others.
insight learningThe ability to do something cor-
rectly the first time even with no prior experience.
insulinHormone secreted in response to high blood
glucose levels to promote glycogen formation.
integral proteins Proteins that are implanted within
the bilayer and can extend part way or all the way
across the membrane.
intermediate filamentsSubstances constructed
from a class of proteins called keratins; function as
reinforcement for the shape and position of
organelles in a cell.
intermediate inheritance An individual heterozy-
gous for a trait (Yy) shows characteristics not
exactly like those of eitherparent. The phenotype
is a “mixture” of both of the parents’ genetic input.
interneuronsFunction to make synaptic connec-
tions with other neurons. They work to integrate
sensory input and motor output.
interphase The first three stages of the cycle, G 1 , S,
and G 2. Accounts for approximately 90 percent of
the cell cycle.
interspecific competition Competition between
different species that rely on the same resources for
survival.
interstitial cells The structures that produce the hor-
mones involved in the male reproductive system.
intraspecific competition Within-species competition
that occurs because members of the same species rely
on the same valuable resources for survival.
introns Noncoding regions produced during tran-
scription that are cut out of the mRNA.
invertebrate Animal without a backbone.
ion An atom with a positive or negative charge.
isotonic solution Solution that has the same solute
concentration as surrounding solutions.
karyotypeA chart that organizes chromosomes in
relation to number, size, and type.
ketone Carbonyl group in which both Rs are carbon
chains; hydrophilic and polar.
kinesisA random change in the speed of movement in
response to a stimulus. Organisms speed up in places
they don’t like and slow down in places they do like.
kingdomThe broadest of the classification groups.http://www.ebook3000.com