Glossary
A
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
C
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
D
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
E
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
F
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.
G
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
H
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)
I
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
K
!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
L
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
M
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
N
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
O
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
P
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
Q
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
R
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
S
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
T
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
W
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
Z
Zygote.
The cell resulting from the union of a male and female gamete until it divides; the fertilized ovum
