The Population Age Structure of Spotted Knapweed (Centaurea maculosa) in Montana

Weed Science ◽  
1987 ◽  
Vol 35 (2) ◽  
pp. 194-198 ◽  
Author(s):  
Keith W. Boggs ◽  
Jim M. Story
Keyword(s):  
High Mortality ◽  
Age Structure ◽  
Secondary Xylem ◽  
Older Age ◽  
Centaurea Maculosa ◽  
Early Age ◽  
Spotted Knapweed ◽  
Age Classes ◽  
Population Age Structure ◽  
The Relationship

Spotted knapweed (Centaurea maculosa Lam. # CENMA) communities were sampled to determine the relationship between age and the number of root rings, and the population age structure. Spotted knapweed taproots add one ring of secondary xylem annually. In 1984, populations were expanding with high densities of individuals in the early age classes, followed by a steady decline in the older classes. In 1985, the majority of the individuals in knapweed populations were in the older age classes. This change in the population age structure was attributed to high mortality among the young age classes due to a drought in 1985. The maximum age class at the sites ranged from 5 to 9 yr. The percentage of plants with floral stalks increased with age to a peak of 75% in the fifth year in 1984 and in the seventh year in 1985.

The age structure of a striped maple population

1979 ◽  
Vol 9 (4) ◽  
pp. 504-508 ◽  
Author(s):  
David E. Hibbs
Keyword(s):  
Structure Analysis ◽  
High Mortality ◽  
Age Structure ◽  
Mortality Rates ◽  
Population Age Structure ◽  
Survivorship Curve ◽  
Age Dependent ◽  
Gap Phase ◽  
Annual Mortality

Cohort and population age structure analysis showed that, after the initially high mortality rates of the 1st year (87.5%), striped maple seedlings (Acerpensylvanicum L.) underwent practically no mortality until the age of 15. Annual mortality was up (3.8%) between the ages of 16 and 40, then dropped to a lower level (1.6%). Mortality was age dependent and generally density independent. The survivorship curve agrees well with a pattern that could be expected of a species whose strategy is gap phase replacement.

Données préliminaires sur la taille, la croissance et la longévité du varan du Nil (Varanus niloticus) dans la région du lac Tchad

1994 ◽  
Vol 72 (2) ◽  
pp. 262-273 ◽  
Author(s):  
Vivian de Buffrénil ◽  
Claire Chabanet ◽  
Jaques Castanet
Keyword(s):  
Growth Rate ◽  
Age Structure ◽  
General Model ◽  
Tail Length ◽  
Large Species ◽  
Age Classes ◽  
Total Length ◽  
Asymptotic Size ◽  
The Difference ◽  
The Relationship

A sample of 288 Nile varanids, including only adults and subadults (153 males and 135 females), was collected in the Tchadian part of Lake Tchad where the species is regularly exploited. Each animal was measured (L, total length; MC, snout–vent length) and weighed, and its age was determined by the skeletochronological technique. No information of this sort, collected on a wide sample, was hitherto available. For the age-classes studied, the most representative sizes in the population (the medians being considered) were close to 155 cm for males and 134 cm for females, with respective masses of about 5 and 3 kg. The difference between sexes was highly significant. Conversely, age structure in the samples were not significantly different among sexes (except for one age-class: 4 years). The longevity of these lizards is about 8 years in the Lake Tchad region. The relationship between tail length and snout–vent length shows similar tendencies in both sexes (Q = 1.06MC + 21.48). The tail becomes proportionally shorter with growth. Both sexes also display similar tendencies for the relationship between total length and mass (M = 8.131E − 9L3.992 − 8.131E − 9(213..992) + 0.034). Body growth in the Nile varanids corresponds to a model derived from Von Bertalanffy's general model: L = K(1 − e−b(age)) + a. Growth of males is faster and steadier than that of females. Males reach their asymptotic size (207 cm) at a later age (9 years) than the females (154.8 cm reached at age 6 years). Though comparative data are very scarce, the growth rate in the animals examined seems high compared with that of other large species of varanids, especially Varanus komodoensis.

scholarly journals When does selection favor learning from the old? Social Learning in age-structured populations

2020 ◽  
Author(s):  
Dominik_Deffner ◽  
Richard McElreath
Keyword(s):  
Social Learning ◽  
Adaptive Behavior ◽  
Age Structure ◽  
Cultural Transmission ◽  
Empirical Work ◽  
Structured Populations ◽  
Older Age ◽  
Age Classes ◽  
Demographic Processes ◽  
Age Structured

Culture and demography jointly facilitate flexible human adaptation, yet it still remains unclear how social learning operates in populations with age structure. Specifically, how do demographic processes affect the adaptive value of culture, cultural adaptation and population growth and when does selection favor copying the behavior of older vs. younger individuals? Here, we develop and analyze a mathematical model of the evolution of social learning in a population with different age classes. We find that adding age structure alone does not resolve Rogers' paradox, i.e. the finding that social learning can evolve without increasing population fitness. Cultural transmission in combination with demographic filtering, however, can lead to much higher adaptation levels. This is because by increasing proportions of adaptive behavior in older age classes, demographic filtering constitutes an additional adaptive force that social learners can benefit from. Moreover, older age classes tend to have higher proportions of adaptive behavior when the environment is relatively stable and adaptive behavior is hard to acquire but confers large survival advantages. Through individual-based simulations comparing temporal and spatial variability in the environment, we find a ``copy older over younger models''-strategy only evolves readily when social learning is erroneous. The opposite ``copy the younger''-strategy is adaptive when the environment fluctuates frequently but still maintains large proportions of social learners. Our results demonstrate that age structure can substantially alter cultural dynamics and should be addressed in further theoretical and empirical work.

scholarly journals Modeling schistosomiasis transmission: the importance of snail population structure

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Larissa C. Anderson ◽  
Eric S. Loker ◽  
Helen J. Wearing
Keyword(s):  
Age Structure ◽  
Human Infection ◽  
Infection Prevalence ◽  
Snail Population ◽  
Snail Infection ◽  
Deterministic Models ◽  
Population Age Structure ◽  
Force Of Infection ◽  
The Impact ◽  
The Relationship

Abstract Background Schistosomiasis is a neglected tropical disease endemic in 54 countries. A major Schistosoma species, Schistosoma mansoni, is sustained via a life cycle that includes both human and snail hosts. Mathematical models of S. mansoni transmission, used to elucidate the complexities of the transmission cycle and estimate the impact of intervention efforts, often focus primarily on the human host. However, S. mansoni incurs physiological costs in snails that vary with the age of the snail when first infected. Snail demography and the age of snail infection could thus affect the force of infection experienced by humans, which is frequently used to predict the impact of various control strategies. Methods To address how these snail host and parasite interactions influence model predictions, we developed deterministic models of schistosomiasis transmission that include varying complexity in the snail population age structure. Specifically, we examined how model outputs, such as schistosome prevalence in human and snail populations, respond to the inclusion of snail age structure. Results Our models suggest that snail population age structure modifies the force of infection experienced by humans and the relationship between snail infection prevalence and corresponding human infection prevalence. There are significant differences in estimated snail infection, cercarial density and mean worm burden between models without snail population dynamics and those with snail populations, and between models with a homogeneous snail population and those with age stratification. The variation between finely age-stratified snail populations and those grouped into only juvenile and adult life stages is, however, minimal. Conclusions These results indicate that including snails and snail age structure in a schistosomiasis transmission model alters the relationship between snail and human infection prevalence. This highlights the importance of accounting for a heterogeneous intermediate host population in models of schistosomiasis transmission where the impact of proposed control measures is being considered.

scholarly journals MODELING THE DYNAMICS OF THE PREDATOR- PREY COMMUNITY WITH THE PREY AGE STRUCTURE AND THE WITHDRAWAL

2021 ◽  
Vol 24 (2-3) ◽  
pp. 209-212
Author(s):  
O.L. Revutskaya
Keyword(s):  
Population Size ◽  
Discrete Time ◽  
Age Structure ◽  
Older Age ◽  
Predator Population ◽  
Age Classes ◽  
Time Model ◽  
Predator Prey ◽  
Discrete Time Model ◽  
Interacting Species

The paper studies the dynamic modes of the predator-prey community discrete-time model taking into account the prey age structure and the withdrawal. The investigated system is a modification of the Nicholson-Bailey model. The author has considered the cases of withdrawal from the prey younger or older age class, or from the prey population of two- age classes, or from the predator population. It is studied conditions of stable coexistence of interacting species and scenarios of the population size oscillatory modes occurrence.

scholarly journals Polarized nature of the COVID-19 pandemic in Japan: associations with population age structure and behaviours

2021 ◽  
Vol 49 (1) ◽  
Author(s):  
Junko Okumura
Keyword(s):  
Age Structure ◽  
Public Transportation ◽  
Perceived Risk ◽  
Online Survey ◽  
Preventive Measures ◽  
Age Groups ◽  
Cumulative Number ◽  
Population Age Structure ◽  
Major Factors ◽  
Drinking Places

Abstract Background Although the scale of the coronavirus disease (COVID-19) pandemic was relatively small in Japan compared with the rest of the world, the polarisation of areas into high- and low-COVID-19-incidence areas was observed among the 47 prefectures. The aims of this study were not only identifying the factors associated with the polarised COVID-19 pandemic in Japan but also discussing effective preventive measures. Methods This was an ecological study using online survey data which was cross-sectionally conducted by the author. A total of 6000 respondents who resided in 10 low- and 10 high-COVID-19 incidence prefectures, with a wide gap in terms of COVID-19 incidence, in Japan were recruited. Data on COVID-19 cases and geodemographic information were obtained from official government sites. Statistical analyses were conducted to compare variables between the two areas and age groups. Results This study revealed that that age influenced people’s behaviours and perceptions, except one behaviour of ‘wearing facemasks’. The major factors significantly associated with the cumulative number of COVID-19 cases per 100,000 people were ‘commuting by private automobile’ (adjusted odds ratio [AOR], 0.444; 95% confidence interval [CI], 0.394–0.501), ‘commuting by public transportation’ (AOR, 6.813; 95% CI, 5.567–8.336), ‘washing hands’ (AOR, 1.233; 95% CI, 1.005–1.511), ‘opening windows regularly’ (AOR, 1.248; 95% CI, 1.104–1.412), ‘avoiding crowded places (AOR, 0.757; 95% CI, 0.641–0.893), ‘non-scheduled visits to drinking places’ (AOR, 1.212; 95% CI, 1.054–1.392) and ‘perceived risk of contracting COVID-19’ (AOR, 1.380; 95% CI, 1.180–1.612). These factors were strongly associated with age groups. Conclusions Effective preventive measures for COVID-19 transmission can be developed by understanding the characteristics of populated areas, such as public transportation infrastructure and younger people’s movements and behaviours in relation to the population age structure to contain the current epidemic and protect the most vulnerable elderly people.

The Welsh Eating Disorder Service Review 2018, Scottish Eating Disorder Service Review 2021 and recommendations of best practice in comorbid eating disorders and diabetes

2021 ◽  
pp. 135910452110138
Author(s):  
Jacinta Tan ◽  
Gemma Johns
Keyword(s):  
Eating Disorders ◽  
United Kingdom ◽  
Eating Disorder ◽  
High Mortality ◽  
Best Practice ◽  
Service Development ◽  
The United Kingdom ◽  
Scottish Government ◽  
The Relationship ◽  
Service Change

Background: Diabetes and eating disorders are frequently comorbid. This particular comorbidity is not only often poorly recognised, but is difficult to treat and has a high mortality. Method: In this article, we will briefly review the relationship between diabetes and eating disorders. We will review the current NICE and other guidance and reports concerning both diabetes and eating disorders in the United Kingdom. We will then describe the recommendations of the 2018 Welsh Government Eating Disorder Service Review and the 2021 the Scottish Government Eating Disorder Service Review regarding diabetes and eating disorders, which will lead to service change. Conclusions: We conclude that this is a relatively underdeveloped but important area where there needs to be further service development and more collaboration between diabetes and eating disorder services.

Automatization and Basic Fact Performance of Normal and Learning Disabled Children

1983 ◽  
Vol 6 (2) ◽  
pp. 223-230 ◽  
Author(s):  
Katherine Garnett ◽  
Jeannette E. Fleischner
Keyword(s):  
Learning Disabled ◽  
Academic Skills ◽  
Older Age ◽  
Basic Fact ◽  
Disabled Children ◽  
Rapid Automatic Naming ◽  
The Relationship ◽  
Naming Test

The relationship between automatization ability, as measured by the Rapid Automatic Naming Test (RAN), and proficiency in arithmetic basic fact computation was investigated. Subjects included 120 learning disabled and 120 nondisabled children between 8 and 13 years of age; 60 subjects in each group were designated as either younger or older. Significant correlations were obtained between RAN performance and basic fact proficiency for both the learning disabled and nondisabled groups. In addition, learning disabled subjects were found to be less proficient in basic fact computation and slower on RAN than their nondisabled peers at both younger and older age levels. Correlations were substantial enough to further inquire whether LD youngsters' lack of proficient basic fact skills may be due, in part at least, to weak automatization. The construct of automatization, or automaticity, has applicability to academic skills beyond those previously investigated.

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