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OCR for page 449
Glossary
allele: any of several particular forms of a gene.
adverse effects: any change in the information on known risks of pesticide
use; must be reported to EPA as part of FIFRA requirements.
antitrust: a body of laws making illegal various actions that have the effect
of changing prices, allocating sales, or otherwise restraining trade.
competition: the interaction between populations in which there is mutual
inhibition of each other's growth due to the sharing of common re-
source(s).
criticalfrequency: the frequency of resistance within a population at which
specific strategies should be enacted in order to manage resistance suc-
cessfully. It is important to recognize that critical frequencies have not
been established for the vast majority of pest/pesticide situations.
theme: a local population of closely related organisms.
density dependence: situations in which the rate of growth of populations
or relative fitness of individuals varies with the standing density of the
population.
density independence: situations in which the rate of growth of populations
or relative fitness of individuals is independent of the density of the
population.
dtiploi`: individual organisms or cells with two separate sets of genes (chro-
mosomes).
dominance: situations in which the expression of one allelic form of a gene
determines the phenotype of heterozygous individuals and obliterates
the expression of recessive alleles of that gene.
ecology: the study of the distribution and abundance of organisms and their
interactions with their physical and biotic environment.
449
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450
GLOSSARY
economic efficacy: "acceptable" pest control from the user's perspective,
under field conditions. Many variables influence the user's impression
of what is "acceptable." They include effectiveness, cost of the pes-
ticide and its alternatives, commodity value, perception of pest severity,
injury or public health standards, etc. The fact that a pest population
has a verified level and frequency of resistance does not necessarily
mean that there has been a loss of economic efficacy, or that use of the
pesticide should be discontinued. Conversely, it is possible to have a
loss of economic efficacy without resistance (i.e., the introduction of a
more effective pesticide, cultivar, or cultural practice; the microbial
degradation of the pesticide before it reaches the pest).
economic threshold: that pest population density or damage level at which
control measures should be taken to prevent economic injury from oc-
curring.
efflux: passing out, flow out, or pumping out from a cell.
epistasis: the nonadditive interactions between genes where the phenotypic
expression of alleles of one gene affects the expression of alleles of
other genefs).
emergency use permits: pesticide-use permits granted under section 18 of
FIFRA for specific locations and time periods; granted if unusual pest
or pesticide availability conditions arise.
genomic shock: an environmental effect that causes movement of genetic
elements (e.g., a transposition of genes within a chromosome).
genotype: the combination of genes borne by an individual organism.
genetically elective component (of migrationJ: the contribution of immi-
grants to the genetic makeup of the population in the succeeding gen-
eration.
fitness: the relative probability of survival and reproductive yield of indi-
viduals of a particular genotype.
haploid: having only one complete set of chromosomes.
heterokaryotic: containing genetically different nuclei (in cells).
JR-4: an interregional project supported by USDA and the land-grant col-
leges to provide efficacy and safety data necessary for receiving a tol-
erance and registration of a pesticide for a minor-use market.
linkage disequilibrium: a nonrandom association of alleles at two or more
loci.
locus: a synonym for gene; the position of a gene on a chromosome (pi.
loci).
market structure: a description of a group of buyers and sellers in a market
that emphasizes number of participants, numbers and types of substitute
products, information exchange, and other features affecting level of
competition.
minor-use: a pesticide market that is small in sales volume because the
OCR for page 451
GLOSSARY
451
pesticide is only used on infrequently occurring pests or on pests of a
crop that has a small number of acre-applications per year.
multinucleate: having two or more nuclei per cell.
neolamarckian: the process by which the genotype of individual organisms
is changed due to the directed action of the environment. After the
French zoologist, J. G. Lamarck (1744-1829), who proposed a theory
of evolution operating through the inheritance of acquired characters.
phenotype: the physical manifestation of the genes borne by an individual
organism.
plasmid: short, circular segment of nonchromosomal DNA.
plastic: a cytoplasmic organelle concerned with photosynthesis and/or stor-
age of food.
plastome: the complex of genes in the plastic (also: plastic genome).
pleiotropy: multiple phenotypic expressions of a single gene.
population biology: the study of the genetic and ecological behavior of
populations of organisms.
population genetics: the study of genetic diversity and the mechanisms of
genetic change (evolution) in populations of organisms.
refuge: a place or period of time in which organisms are free from the
action of predators or substances that inhibit their growth and repro-
duction.
relative reproductive rate: the numbers of progeny produced by an indi-
vidual of a particular genotype in the course of a generation compared
to those produced by other individuals in the population.
resistance: the inherited ability in a strain of pest to tolerate doses of toxicant
that would prove lethal to a majority of individuals in a normal popu-
lation of that species. This definition implies a statistically significant
shift in LCX (or LDX) values that are normally established through lab-
oratory bioassays. Laboratory documentation of resistance, however,
does not necessarily indicate a current or impending loss of economic
efficacy in the field.
selection: changes in the genetic composition of populations resulting from
the differential survival or reproduction of specific genotypes.
selective advantage: the extent to which the relative fitness of individuals
of a particular genotype exceeds the mean fitness of all genotypes in
the population.
selective disadvantage: the extent to which the relative fitness of individuals
of a particular genotype is less than the mean fitness of all genotypes
in the population.
thylakoid: flattened membrane sacs within chloroplastids in which chlo-
rophyll molecules are incorporated.
tubulin: a protein that is a subunit of microtubules, which are found in
structures such as the mitotic spindle.
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452
GLOSSARY
user fees: taxes or fees that are proportional to use level and are charged
to users of public services.
variance: the average value of the squared deviations of observations from
their mean. It is a measure of the magnitude of variation in a character.
In the study of inheritance of continuously distributed characters (Quan-
titative Genetics), primary concern is the proportion of the variance in
the phenotype ("phenotypic variance") that is due to underlying vari-
ation in the genotypes of individuals in the population.
additive genetic variance: the proportion of the phenotypic variance that
is due to cumulative expression of alleles of the same gene or different
genes that are acting independently in the determination of the value of
a continuously distributed character, e.g., height.
nonadditive genetic variance: the proportion of the phenotypic variance
that is due to cumulative expression of alleles of the same gene or
different genes that are not independent in their determination of the
phenotype, e.g., the contributions of dominance and epistasis.
(geneticJ covariance: the average value of the product of the differences
between an array of observations taken in pairs and their means. It is
used as a measure of the direction and extent a character varies among
pairs of individuals and as a measure of how two different characters
vary within individuals. As used in Chapter 3, the genetic covariance
is the direction and extent of variation in the expression of the same set
of genes on two different characters, e.g., tolerance to two different
pesticides.
Vo~terra principle: The prediction (and observation) that in cases where a
prey population is held in check by a predator, the killing of predators
and prey (e.g., by the use of pesticides) is likely to result in an increase
in the numbers of prey (pests).
xenobiotic: foreign chemical (such as a pesticide).
Representative terms from entire chapter:
relative fitness
