Age Structure

G.C. Myers , in International Encyclopedia of the Social & Behavioral Sciences, 2001

1 Macrolevel Determinants

In the field of demography, age structure is an imbedded concept. Still, it is surprising to learn that in the eighteenth and nineteenth century there was well-nigh nix written most historic period per se or age construction, although considerable attending was devoted to population size and the determinants of population change—fertility, mortality, and migration. In fact, it is not until the beginning of the twentieth century that the Swedish statistician, Gustav Sundbarg (1900), introduced a nomenclature of countries based on the proportions of population nether historic period 15, fifteen to 49, and 50 and over. He observed that the proportions in the working ages for a number of European countries appeared to remain constant over time (roughly fifty percentage), while the relative share of immature and older persons shifted in magnitude from the former to the latter. Thus, he proposed that countries undergo transitions from youthful population structures (that he termed progressive) to stationary and eventually to onetime structures (regressive), developments largely determined by declining fertility and mortality. This remarkable insight, although subsequently found somewhat inadequate, however gave important impetus to studies of the determinants of population modify, specially mortality and fertility, the possibility of transitions in these vital rates and their systematic bear upon on population structure, and time-series cross-national research.

Attention to the determinants of age structure benefited from the original mathematical contributions of Lotka in the early twentieth century and afterwards at midcentury in the development of stable population and demographic bookkeeping models past Coale, Bourgeois-Pichat, and others (Myers 1996b). The of import role played by the succession of cohorts (usually adamant by year/s of birth) over time has been recognized in transforming historic period structures. This has brought attention to the notion of disordered cohorts, in which catastrophic events (e.m., wars, famines, etc.) have produced large deficits in the numbers of persons at subsequent ages.

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Age Structure and Population Dynamics

L.C. Bender , in Encyclopedia of Ecology, 2008

Effects of Male person Age Construction

Historic period construction of males also can influence convenance dynamics of age-structured populations. In polygynous species, populations with greater numbers of older-historic period-course males have been shown to take shorter, before, and less socially disruptive breeding periods. Conversely, where fewer older-age-class males are nowadays, convenance periods tend to exist longer and females are often bred later in the season. Because later convenance may lead to later nativity dates, and after birth dates to lower juvenile survival, the historic period construction of the male population may potentially influence both pregnancy rates and survival of juveniles, thus affecting population rate of increment. Even so, this cascade of furnishings has non been conclusively demonstrated in free-ranging populations. Few studies bespeak that afterwards-bred females accept significantly later parturition dates, while much evidence indicates that female nutritional condition tin override potential effects of male person age structure and breeding date by assuasive females to shorten the length of gestation. Further, ages of males disposed harems may non exist dominated by prime-anile males until male person/female ratios are very loftier even in polygynous species, indicating that younger males may brood a pregnant proportion of females regardless of male historic period structure. Consequently, observed recruitment of juveniles has been shown to be independent of adult sex ratios and male person age structure in several polygynous ungulate species. Thus, whereas theory and modeling frequently advise that male person age and adult sex ratios tin potentially accept a potent influence on population productivity, actual management has driven male age structure and male/female ratios well beneath thresholds theorized to affect population-level productivity, without any pregnant decreases in population productivity being documented in free-ranging populations.

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Population Systems

Timothy D. Schowalter , in Insect Ecology (Second Edition), 2006

D Age structure

Historic period structure reflects the proportions of individuals at dissimilar life stages. This variable is an important indicator of population status. Growing populations generally have larger proportions of individuals in younger historic period-classes, whereas failing populations usually have smaller proportions of individuals in these age classes. Stable populations usually have relatively more individuals in reproductive age-classes. However, populations with larger proportions of individuals in younger age-classes also may reflect low survivorship in these age classes, whereas populations with smaller proportions of individuals in younger historic period-classes may reflect loftier survivorship (see later in this chapter).

For most insect species, life spans are brusk (usually ≦ year) and revolve around seasonal patterns of temperature and rainfall. Oviposition usually is timed to ensure that feeding stages coincide with the nigh favorable seasons and that diapausing stages occur during unfavorable seasons (east.one thousand., winter in temperate regions and dry season in tropical and barren regions). Adults usually dice afterwards reproducing. Although there are many exceptions, almost temperate species have detached, annual generations, whereas tropical species are more than likely to have overlapping generations.

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Population Systems

Timothy D. Schowalter , in Insect Ecology (Fourth Edition), 2016

two.iv Historic period Structure

Age structure reflects the proportions of individuals at dissimilar life stages. This variable is an important indicator of population condition. Growing populations generally accept larger proportions of individuals in younger age classes, whereas failing populations typically have smaller proportions of individuals in these age classes. Stable populations typically have relatively more individuals in reproductive age classes. Still, populations with larger proportions of individuals in younger age classes besides may reflect depression survivorship in these age classes, whereas populations with smaller proportions of individuals in younger historic period classes may reflect loftier survivorship (encounter Section 3.two).

For nigh insect species, life spans are short (usually< one year) and revolve around seasonal patterns of temperature and rainfall. Oviposition typically is timed to ensure that feeding stages coincide with the most favorable seasons and that diapausing stages occur during unfavorable seasons, for example, winter in temperate regions and the dry season in tropical and barren regions. Adults typically die after reproducing. About temperate species have discrete, annual generations, whereas tropical species are more likely to have overlapping generations.

Periodical cicadas, Magicicada spp., represent a major exception. Distinct broods of 13- and 17-year periodical cicadas emerge equally adults following thirteen- or 17-year developmental periods underground. Y. Tanaka et al. (2009) demonstrated that synchronization of prime number-numbered life spans amid these cicadas could be explained by the lower likelihood of hybridization with other circadian patterns and their increased likelihood of persistence and selection nether variable environmental weather that could lead to extinction of low-density populations (see Chapter 6). Emergence densities of these insects tin can exceed 100 m−2 and correspond an important resource for predators (Koenig and Liebhold, 2005; Whiles et al., 2001; Whitford and Jackson, 2007).

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Governmental Support of Research

Sten H. Vermund , Salim Abdool Karim , in Clinical and Translational Science (Second Edition), 2017

AnoPopAge Population age structure and age structure modification via Wolbachia in Anopheles gambiae
ARTEMIP The safe pharmacology of artemisinins when used to contrary pathophysiology of malaria in pregnancy
CHAARM Combined Highly Active Anti-retroviral Microbicides
Chain Collaborative HIV and Anti-HIV Drug Resistance Network
CRIMALDDI The Coordination, Rationalization and Integration of Antimalarial Drug Discovery and Evolution Initiatives
CUT'HIVAC Cutaneous and Mucosal HIV Vaccination
ENAROMaTIC European Network for Advanced Inquiry on Olfaction for Malaria Transmitting Insect Command
ESI-TBVI Establishment, Strategy and Initial activities of the TuBerculosis Vaccine Initiative: Coordination of European efforts with global research initiatives
EUCO-Cyberspace European Network for global cooperation in the field of HIV & TB
EuroCoord European network of HIV/AIDS accomplice studies to coordinate at European and International level clinical research on HIV/AIDS
EuroNeut-41 European consortium on NEUTralising antibodies using gp41
Evimalar Towards the institution of a permanent European Virtual Institute dedicated to Malaria Research
FAST-XDR-Find Development of a two-arroyo plate system for the fast and simultaneous detection of multiple drug resistant (MDR) and extensively drug resistant (XDR) strains of Mycobacterium tuberculosis
HIV-ACE Targeting assembly of infectious HIV particles
HIVIND The antiretroviral curlicue out for HIV in India – generating evidence to promote adherence and patient follow-up
HOMITB Host and mycobacterial molecular autopsy of immunity and pathogenesis of tuberculosis
iNEF Inhibiting Nef: a novel drug target for HIV-host interactions
INYVAX Optimization of the development of Poverty-Related-Diseases (PRD) vaccines past a transversal approach, addressing common gaps and challenges
MALACTRES Multi-drug resistance in malaria under combination therapy: Cess of specific markers and evolution of innovative, rapid and simple diagnostics
MALSIG Signaling in life cycle stages of malaria parasites
MALVECBLOK Population biological science and molecular genetics of vectorial capacity in A. gambiae: targeting reproductive behavior and immunity for transmission-refractory interventions
MEPHITIS Targeting protein synthesis in the apicoplast and cytoplasm of plasmodium
NANOMAL Development of a handheld antimalarial drug resistance diagnostic device using nanowire technology
NATT New Approaches to Target Tuberculosis
NEWTBVAC Discovery and preclinical testing of new vaccine candidates for tuberculosis
NGIN Next Generation HIV-1 Immunogens inducing broadly reactive Neutralizing antibodies
NOstress Unraveling the molecular mechanism of nitrosative stress resistance in tuberculosis
NOVSEC-TB Novel secretion systems of M. tuberculosis and their role in host–pathogen interaction
OPTIMALVAC Initiative on Optimizing malaria Vaccine lab assays evaluation
PENTA LABNET Paediatric European Network Treatment AIDS Laboratory Network
PRD College Poverty Related Diseases-College: International Programme on BioMedicine and Development
PreMalStruct Structural analysis of the placental chondroitin-4-sulfate (CSA) binding interactions involved during pregnancy associated malaria
PregVax Plasmodium vivax Infection in Pregnancy
REDMAL Clinical Evolution of a Pfs48/45 protein-based malaria transmission blocking vaccine
StopLATENT-TB LATENT TUBERCULOSIS: New tools for the detection and clearance of dormant Yard. tuberculosis
STOPPAM Strategies TO Prevent Pregnancy-Associated Malaria
TB PAN-NET TB PAN-NET: Pan-European network for study and clinical direction of drug resistant tuberculosis
TBsusgent Sustaining research momentum over the coming decades: mentoring the next generation of researchers for tuberculosis
TB-EURO-GEN Genetic analysis of the host–pathogen interaction in tuberculosis
TB-VIR M. tuberculosis W-Beijing genetic variety and differential virulence and immune responses
THINC Targeting HIV integration co-factors, targeting cellular proteins during nuclear import or integration of HIV
TransMalariaBloc Blocking Malaria Transmission by vaccines, drugs and immune mosquitoes: Efficacy cess and targets
TM-REST TM-Residuum: a new platform for fast molecular detection of multiple drug resistant (MDR) and extensively drug resistant (XDR) strains of M. tuberculosis and of drug resistant malaria

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Techniques

David Westward. Hagstrum , Bhadriraju Subramanyam , in Fundamentals of Stored-Production Entomology, 2006

Age grading

Knowing the age construction of an insect population can be important in making insect pest management decisions. The behavior and ecology of insect pests and natural enemies and their susceptibility to insect pest management methods tin can vary with age. Age grading also can be an important tool when studying insect life history. It can be used to determine the number of insects in each instar, or stage, and the number of adults that are of pre- or post-reproductive historic period.

2 methods accept unremarkably been used in life history studies to determine the age of internal-feeding stored-product insects. For Sitophilus and several other species of internal-feeding insects (Table 2.four), insect-infested kernels were ten-rayed daily to visually determine the phase of insect evolution. Instar was adamant by measuring the size of the larval feeding cavities. Also, a period when the size of the feeding chamber did not alter indicated the fourth dimension when a larva molted to the next instar. For Sitophilus species, females were allowed to lay eggs on kernels for several days; the egg plugs were stained to determine which kernels were infested; some of the infested kernels were cut open periodically to remove insects; and the widths of the larval heads were measured to determine instar (see recommended reading by Vowotor et al and Table two.5). The heads of external-feeding larvae also have been measured to decide instar. Studies with S. oryzae found that, over fourth dimension, insects killed past fumigation became increasingly more hard to detect with x-rays. This may be a result of the x-rays more than easily penetrating dry, shriveled tissue than water-filled tissue.

Table 2.4. Stored-product insect species for which the instar of insects developing inside grain kernels has been determined using 10-rays

Insect species Source
Callosobruchus maculatus Osuji 1982
Rhyzopertha dominica Stemley 1962
Sitophilus granarius Kirkpatrick and Wilbur 1965
Sitophilus oryzae Dobie 1973, Sharifi and Mills 1971a
Sitophilus zeamais Sharifi and Mills 1971b
Sitotroga cerealella Mills and Wilbur 1967
Theocholax elegans Sharifi 1972a

Table 2.5. Measurements for distinguishing instars of v stored-production insect species a

Species and Instar Mean head width (mm) Range (mm)
Prostephanus truncatus b
  1 0.36 0.32–0.39
  2 0.54 0.45–0.lx
  3 0.80 0.73–0.85
Rhyzopertha commonwealth of dominica
  i 0.thirteen 0.11–0.xviii
  2 0.21 0.19–0.22
  3 0.34 0.25–0.38
  4 0.47 0.40–0.53
Sitophilus granarius
  one 0.24 0.xx–0.28
  2 0.35 0.thirty–0.39
  3 0.51 0.42–0.58
  4 0.68 0.60–0.76
Sitophilus oryzae
  1 0.xx 0.19–0.22
  2 0.28 0.25–0.32
  3 0.38 0.34–0.twoscore
  4 0.53 0.49–0.57
Sitophilus zeamais
  1 0.20 0.17–0.24
  2 0.29 0.25–0.32
  3 0.43 0.37–0.49
  4 0.63 0.55–0.74
a
Information from Subramanyam et al 1985 for Prostephanus truncatus, Stemley 1962 for Rhyzopertha commonwealth of dominica, Richards 1947 for Sitophilus granarius, Sharifi and Mills 1971a for Sitophilus oryzae, and Sharifi and Mills 1971b for Sitophilus zeamais.
b
For Prostephanus truncatus, the distance between 2 sutures on the head also can exist used to determine instar.

Moth pupae are initially very pale and get darker as they age (Fig. ii.ten). The eyes darken first, then the overall cuticle, and finally the wing pads. The age of S. oryzae and Prostephanus truncatus females can be estimated based upon the size and darkness of the accumulation of egg chamber relics at the base of their ovaries (see recommended readings past Perez-Mendoza et al and by Scholz et al). For mated Sitophilus, the first relics were observed five days afterward they emerged from a wheat kernel, and by twenty-four hour period 10, some relic accumulations had visible gray spots. The accumulations of relics darken with age, and by day 40, the accumulation of relics was a nighttime chocolate-brown blackness.

Figure 2.ten. Variation of color of Plodia interpunctella pupae with time until developed eclosion. Days or hours before eclosion: a, six to seven days; b, five to half dozen days; c, three to four days; d, two to iii days; e, one to two days; f, one day; one thousand, xviii–20 hr; h, 12–15 hr.

 (Courtesy of D. L. Silhacek and 1000. P. Whitmer.) Smithwick and Brady 1971 depict the color changes over fourth dimension. Copyright © 1971

For mated P. truncatus insects, no relics were observed five days subsequently emergence from their pupal sleeping room. By day 10, all three levels of egg sleeping accommodation relic aggregating were observed, and the number of females for which the accumulation of relics had gray spots or was chocolate-brown black gradually increased up to thirty days. The spermatheca may need to be examined for sperm to plant whether a female has mated, because ovarian evolution is faster in mated females. Also, starvation tin can result in an accumulation of egg chamber relics due to egg resorption.

Characteristics such as wing fraying or mandible wear can provide some data about adult insect historic period, but these can also vary with the extent of flight activity, the environmental conditions, and the type of food eaten.

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Age Stratification

P. Uhlenberg , D. Dannefer , in Encyclopedia of Gerontology (Second Edition), 2007

Age Grading, Allotment, and Socialization

The population historic period construction refers to only one of the components of age stratification, the age-specific distribution of people. The age stratification framework also implies attention to the age-related aspects of the office structure of society and the problem of allocating or matching the available individuals with a finite number of available historic period-graded roles. When roles are rigidly age graded (as in the case of mandatory schooling for children, military conscription, or mandatory retirement), bug of mismatch or 'strain' tin can occur.

Historic period is built into the role structure of order when age is a criterion for occupying, entering, or relinquishing certain roles. Further, age tin can regulate how individuals are expected to perform their roles: the advisable behavior in a office and rewards (or punishments) for performance may vary depending on the age of the person occupying the part. The nigh obvious apply of age in social structures occurs when chronological historic period criteria are written into constabulary, regulations, or contracts. For example, in contemporary United states of america society, age regulates when information technology is legal for one to marry, drive a car, leave schoolhouse, drink alcohol, vote, and get president. Further, chronological age is a criterion for receiving Medicare insurance, pension benefits, and selected taxation benefits. In that location also are breezy norms that use age to indicate what behavior is or is not acceptable, such every bit when one is judged as too old to go a foster parent, to enter a graduate programme, or to participate in certain sporting events. As with all norms, age norms are sometimes violated and can alter over time. Nevertheless, the age stratification perspective calls attention to the importance of social definitions of age as forces that shape behavior and the crumbling of individuals.

The final component of the age stratification model deals with the processes by which the individuals in an age stratum are matched with the appropriate historic period roles in social structures. Allocation processes are used to assign people to historic period-advisable roles and to continually reassign them every bit they age into unlike socially recognized phases of the life form. The mechanisms for allocating may be individuals in roles designed for this purpose (due east.g., personnel managers or admission directors) or policies (e.g., pension plans or schoolhouse omnipresence regulations).

This general phenomenon of allocation is closely related to several fundamental theoretical ideas and research questions. For example, according to the Easterlin effect, the members of small cohorts accept a broad-based reward in that members of such cohorts volition experience less contest for the finite number of age-graded roles as they enter particular historic period strata (eastward.yard., admissions slots to elite colleges or pick entry-level jobs), whereas members of large cohorts volition face greater competition. These differentials of advantages can carry on through the life course. In any pyramidal organizational structure (which describes non simply corporations but as well armed services, ecclesiastical, and educational organizations), the adventure to exist promoted to i of a few high-level managerial or executive slots volition be enhanced if 1 has fewer competitors. On the other paw, it has also been suggested that nether some conditions, individuals in an age stratum may benefit from being members of a relatively big cohort; for instance, this might have applied to the male Infant Boomers who were in the draft lottery in the early 1970s. Information technology has also been hypothesized that those retiring in the early twenty-first century may derive political advantage because they will comprise a larger relative size of the electorate.

Riley used the outcome of the person–role mismatch to call for social change. She adult a disquisitional assay of inelastic, age-graded social arrangements that outcome in humanly destructive consequences. This critique led to the development of the concept of structural lag (discussed later).

The age stratification perspective too recognized that the concomitant process of socialization operates constantly, in parallel with allocation. That is, in everyday life experience, individuals are continuously internalizing the social practices and learning the skills that are integral to the roles that they occupy in the larger social system. The concept of socialization has been widely and effectively critiqued because of a number of conceptual and theoretical limitations that it imposes on the kinds of questions i would enquire as a researcher. Nevertheless, the powerful processes through which individuals are shaped by the roles they occupy are a central feature of the reality that the age stratification model seeks to represent.

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Falls lukunani, Cichla cataractae (Sabaj, López-Fernández, Willis, Hemraj, Taphorn & Winemiller 2020)

Kirk O. Winemiller , ... Carmen G. Montaña , in Peacock Bass, 2021

Population abundance and construction

Reports containing abundance or size and age structure information have not been published for this species, but the falls lukunani ( C. cataractae) appears to be less abundant than the pond lukunani (C. ocellaris) in rivers where the two co-occur. Withal, when fishing around rocky shoals in appropriate river reaches, the falls lukunani seems to exist most common, whereas a few C. ocellaris may exist caught almost the shoreline or from habitat patches well sheltered from water current.

Unlabelled Image

Professor Donald Taphorn with a falls lukunani captured in a gillnet from the Essequibo River.

 Photograph: D. Taphorn.

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Fisheries Management

Due south.J.D. Martell , in Encyclopedia of Ecology, 2008

Compositional Information

Equally previously mentioned, compositional information (age-structure or size-structure information) form very valuable demographic data for making inferences about full mortality rates. Compositional information has also been used to make inferences about the relative cohort strengths, and more recently, information on the relative abundances of juvenile fish is at present being used to improve the short-term forecasts of stock abundance. Other potentially useful types of compositional information include mean body weight, mean length, or mean age data. These simple measures of population composition are usually easier to obtain and are more cost-constructive in terms of the information they provide relative to the cost of obtaining detailed age composition information.

Most oft, composition information is obtained by randomly sampling the take hold of from commercial or recreational fisheries. Individual fish are then measured using hard bony structures (fin rays and more normally otoliths or earbones). These aging structures lay down annual growth rings (annuli) much like the rings in a tree and the fish can be aged by simply counting the number of rings. Age composition can also be inferred directly from size composition data, where a length–frequency distribution is converted to an age–frequency distribution using an age–length central.

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Crime and Age

E.Due east. Flynn , in Encyclopedia of Gerontology (Second Edition), 2007

Age Structure and Crime

Because criminal offense varies with historic period, changes in the age structure of lodge exert an important impact on the criminal offence charge per unit independent of the other known factors, such equally dysfunctional families, schools, peers, and neighborhoods. The Baby Boom after World State of war 2 is well known and documented. The twin promises of peace and prosperity accelerated the nation's marriage and nativity rates with highly anticipated consequences. When the Baby Nail generation reached its nigh law-breaking-prone years during the 1960s, the country's crime charge per unit rose precipitously. By 1980, the criminal offence rate peaked at 5950 per 100  000 in the population and declined. A decade later, index crimes were downwardly, along with the proportion of juveniles in the total population. Since then, alphabetize crimes have been falling, with minor fluctuations. There take been farther small decreases in the national crime rate since 1990. However, recent offense rates conceal two highly divergent and troubling trends: although adult offense rates are declining equally the Baby Nail generation ages, juvenile violent law-breaking has increased rapidly. An examination of the nation's homicide rate, calculated per 100   000 inhabitants, illuminates the trouble. Since 1985, the homicide rate for adults aged 25 and over has steadily declined from 8 to 5.2% in 1993. During the same time, the homicide rate for young adults aged 18 to 24 has increased from xvi to 26%. Worst of all, for juveniles aged xiv to 17, the homicide charge per unit has more than doubled from vii to most nineteen%. Because the fact that the nation's adolescent population will aggrandize to 23% by 2005, the problem of rapidly rising serious, violent juvenile crime volition simply be compounded.

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