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National Research Council (US) Committee on Population; Wachter KW, Finch CE, editors. Between Zeus and the Salmon: The Biodemography of Longevity. Washington (DC): National Academies Press (US); 1997.

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Between Zeus and the Salmon: The Biodemography of Longevity.

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Glossary

Aché

Hunting and gathering group of subtropical Paraguay

Adaptation

The condition of showing fitness for a particular environment, as applied to characteristics of a structure, function, or entire organism; also the process by which such fitness is acquired

Allele

One of two or more alternate forms of a gene found at the same location (locus) in homologous chromosomes

Altruism

Self-destructive behavior performed for the benefit of others; any form of nonselfish behavior

Antagonistic pleiotropy

Multiple gene effects, such that alleles that improve fitness in early life have detrimental effects later in life

Apoptosis

Programmed death of cells during embryogenesis and metamorphosis or during cell turnover in adult tissues

Chromosome

A DNA-containing body in the nucleus of the cell observed during the mitotic phase of cell replication; the carrier of the (nuclear) genes

Cloning

Growing a colony of identical cells or organisms in vivo; a recombinant DNA technique used to produce millions of copies of a DNA fragment. The fragment is spliced into a cloning vehicle (such as a virus, plasmid. or bacteriophage). The cloning vehicle penetrates a bacterial cell or yeast (the host), which is then grown in vitro or in an animal host

Complementation

The restoration of wild-type function by two different mutations brought together in the same cell

Congenic

Referring to members of the same genus

Conspecific

Referring to members of the same species

Cumulative density function

Probability that a variable takes on a value less than a given number; for example, the probability that an individual dies before passing age x

Dominance

Determination of the phenotype of a heterozygote by one allele. Dominant alleles suppress the effects of recessive alleles when the latter are also present in diploid organisms

DNA

Deoxyribonucleic acid; the molecular basis of heredity

Ecdysone

The hormone produced in insects that induces molting and metamorphosis

Electrophoresis

A technique used to separate mixtures of ionic solutes by differences in their rates of migration in an applied electric field

Ethological

Behavioral

Ethology

The scientific study of animal behavior, particularly under natural conditions

Eukaryote

Organism whose cells have a true nucleus (one bound by a nuclear membrane) within which are the chromosomes

Eusociality

Social system in which certain individuals enhance their fitness by aiding their collateral kin to rear their offspring. For example, sterile female worker bees may rear the offspring of their fertile sister queens

F2

Second filial generation; all of the offspring produced by the mating of two individuals of the first filial generation

Fecundity

Ability to produce offspring rapidly and in large numbers. In demography of human populations, the physiological ability to reproduce, as opposed to fertility

Fertility

Reproductive potential. In demography, the number of births per year divided by the number of women of childbearing age, expressed as a rate

Fibroblast

Connective tissue cell that can differentiate into other blastic cells to form fibrous tissues; a fiber-producing cell widely distributed in tissues

Fitness

The ability of a genotype to reproduce its alleles in a particular environment or after some environmental change

Free radical

A highly reactive chemical moiety characterized by unpaired electrons, which can damage the cell fabric and other biological macromolecules.

Gamete

Egg or sperm cell; germ cell

Gene

A unit of inheritance coded by DNA, carried on a chromosome, transmitted from generation to generation by the gametes, and controlling the development and characteristics of an individual

Genetic drift

Genetic changes in populations caused by random phenomena rather than by selection

Genetic marker

A gene mutation that has phenotypic effects useful for tracing the chromosome on which it is located

Genotype

Genetic makeup of an organism or group of organisms, with respect to a single trait or a group of traits; sum total of genes transmitted from parents to offspring

Genome

The total set of genes carried by an individual or cell

Gerontogene

Gene affecting longevity, either reducing average life span of the organism (e.g., as a result of antagonistic pleiotropy) or increasing average life span. ''Longevity assurance gene" is often used for genes that promote survival at older ages. See chapter 7 for discussion.

Germ cell

The egg or sperm cell

Gompertz model

Class of statistical models first proposed by the nineteenth-century British actuary Benjamin Gompertz, in which the hazard rate for death rises exponentially with increasing age of the organism (at least after an initial period of high risk of mortality in infancy and much lower risk in late childhood and adolescence)

Grandmother hypothesis

By ceasing to reproduce, old people (and by extension, old members of other species) can use their time and resources to invest in the survival and reproduction of kin

Hayflick limit

An experimental limit to the number of times a diplosomatic cell is capable of dividing during serial cell culture

Hazard function

Probability that an individual surviving to age x will die at that age. Ratio of the probability density and survival functions; also called "the force of mortality"

Hiwi

Hunting and gathering group of the Venezuelan savanna

Homeostasis

Self-regulation that tends to restore the conditions existing before a disturbance or shift

Homologous

Corresponding in structure and position; allelic chromosomes are homologous. Also, referring to structures or processes that have the same evolutionary origin though their functions may vary widely (as opposed to analogous, referring to structures having a different evolutionary origin but performing the same function)

Inbreeding

Crossing with genetically similar individuals, particularly with close relatives

Iteroparity

The state in an individual organism of reproducing repeatedly or more than once in a lifetime

!Kung San

Hunter and gathering group of the Kalahari in Africa who now practice a mixed economy of hunting, gathering, farming, and wage labor

Knock-out mutation

Deletion of a gene or a portion of a gene from the genome

Life expectancy

Mean life span remaining for individuals of a given age

Life history

Combination of age-specific survival probabilities and fertilities characteristic of a type of organism; the time table of development and aging for each species (for example, puberty, menopause, and longevity in humans)

Life span

Age of death (for individual); maximum potential length of life for most robust member(s) of the species (for species)

Limit-distribution hypothesis

There exists a limiting distribution that mortality curves may approach but not surpass

Limited-life span hypothesis

There exists some age beyond which there can be no survivors

Linkage

Occurrence of genes on the same chromosome. The closer the genes are, the more tightly they are linked—that is, the less likely that crossing over will separate them

Locus, pl. loci

The set of homologous parts of a pair of chromosomes that may be occupied by allelic genes; the locus thus consists of a pair of locations (except in the X chromosome of males)

Longevity genes

Genes that promote survival; most fixed genes are presumed to be of this type

Lotka equation

An identity from mathematical demography developed by Alfred J. Lotka that defines the built-in long-term or "intrinsic" rate of natural increase of a population when age-specific fertility and survivorship rates are held constant

Meiosis

Two consecutive special cell divisions in the developing germ cells characterized by the pairing and segregation of homologous chromosomes; the resulting gametes will have reduced, or haploid, chromosome sets

Mortality trajectory

Plot of death rate against age group over time

Niche

The set of environmental factors into which a species fits; its specific way of using its environment and pattern for association with other species

Oocyte

The developing female gamete before completion and release

Out-crossing

Breeding with genetically different, not closely related individuals, particularly with members of different populations

Phenotype

Physical manifestation of gene function

Pleiotropy

Multiple effects of one gene; the capacity of a gene to affect several aspects of the phenotype

Polygenic

Relating to a normal characterisitic or hereditary disease controlled by the added effects of genes at multiple loci

Polymorphism

Simultaneous occurrence of several discontinuous phenotypes or genes in a population, with the frequency even of the rarest type higher than can be maintained by recurrent mutation, typically > 1%

Positional cloning

A genetic technique for determining the location of a mutation in a small area of the genome

Preadaptation

Presence of previously existing structure, physiological process, or behavior pattern already functional in another context and available as an aid to attainment of a new adaptation

Progeria

A syndrome in which certain characteristics of senescence are compressed. In Werner syndrome, the defect is in gene repair

Quantitative trait

A trait for which phenotypic variation is continuous (rather than discrete)

Quantitative trait locus

One of a group of genes specifying any particular quantitative trait

Recessive gene

Gene that fails to express itself in the phenotype of the heterozygote; that is, its effect is masked in the presence of its dominant allele

Recombinant

Having altered DNA resulting from insertion into the chain by chemical, enzymatic, or biologic means of a sequence not originally present in the chain; an offspring that has received chromosomal parts from different parental strains

Recombination

Reshuffling of parental genes during meiosis due to crossing over, or induced in a test tube by enzymes

Semelparity

A life-history pattern that is characterized by only one burst of reproductive activity and rapid aging

Senescence

Deterioration in performance seen later in the adult life span, associated with increasing mortality rates

Senility

A general term for a variety of mental disorders occurring in old age, consisting of two broad categories, organic and psychological disorders

Somatic

Relating to the body; of cells that are not germ cells

Somatic cell

Any body cell except a germ cell

Speciation

The splitting of a phyletic line; the process of the multiplication of species; the origin of discontinuities between populations caused by the development of reproductive isolating mechanisms

Stochastic

Involving a random variable; involving chance or probability

Survival function

Probability that an individual is still alive at age x

Telomere

Specialized gene sequences found at the ends of chromosomes, which tend to shorten in diploid cells

Territoriality

Occupation of an area that usually contains a scarce resource either by overt defense or advertisement

Wild type

The allele that is most frequent in natural populations, often indicated by the symbol +; this term cannot be applied for a locus that has undergone mutation

Zygote

The cell resulting from the union of a male and female gamete until it divides; the fertilized ovum

Copyright © 1997, National Academy of Sciences.
Bookshelf ID: NBK100415

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