scholarly journals Empirical Evidence for Various Evolutionary Hypotheses on Species Demonstrating Increasing Mortality with Increasing Chronological Age in the Wild

2008 ◽  
Vol 8 ◽  
pp. 182-193 ◽  
Author(s):  
Giacinto Libertini
Keyword(s):  
Empirical Evidence ◽  
Inverse Correlation ◽  
The Other ◽  
Chronological Age ◽  
Extrinsic Mortality ◽  
In The Wild ◽  
Negligible Senescence ◽  
Genetically Determined ◽  
Intrinsic Mortality ◽  
Cell Functionality

Many species show a significant increase in mortality with increasing chronological age in the wild. For this phenomenon, three possible general hypotheses are proposed, namely that: (1) it has no adaptive meaning; (2) it has an adaptive meaning; (3) the ancestry is the pivotal determinant. These hypotheses are evaluated according to their consistency with the empirical evidence. In particular, (1) the existence of many species with a constant, or almost constant, mortality rate, especially the so-called “animals with negligible senescence”; (2) the inverse correlation, observed in mammals and birds in the wild, between extrinsic mortality and the proportion of deaths due to intrinsic mortality; (3) the existence of highly sophisticated, genetically determined, and regulated mechanisms that limit and modulate cell duplication capacities and overall cell functionality. On the whole, the hypothesis of an adaptive meaning appears to be consistent with the empirical evidence, while the other two hypotheses hardly appear compatible.

scholarly journals Evolutionary Explanations of the “Actuarial Senescence in the Wild” and of the “State of Senility”

2006 ◽  
Vol 6 ◽  
pp. 1086-1108 ◽  
Author(s):  
Giacinto Libertini
Keyword(s):  
Inverse Correlation ◽  
Mutation Accumulation ◽  
The State ◽  
Chronological Age ◽  
Large Set ◽  
Age Changes ◽  
Extrinsic Mortality ◽  
Associated Diseases ◽  
In The Wild ◽  
Genetically Determined

A large set of data suggests that progressive reduction of fitness and senile decay in vertebrates are in correlation with the decline of cell replication capacities. However, the limits in such capacities are hardly explained in evolutionarily terms by current gerontological theories that rule out fitness decline as something genetically determined and regulated, and therefore somehow favored by natural selection.Four theories are tested as possible explanations of the “increasing mortality with increasing chronological age in populations in the wild” (“IMICAW”[1]), alias “actuarial senescence in the wild”[2], and of the observed negative correlation between extrinsic mortality and the ratio between deaths due to intrinsic mortality and deaths due to extrinsic mortality. Only the theory attributing an adaptive value to IMICAW allows an evolutionary explanation for it and for the aforesaid inverse correlation, while the other three theories (“mutation accumulation”, “antagonistic pleiotropy”, and “disposable soma” th.) even predict a positive correlation.Afterwards, the same theories are tested as possible explanations for the “state of senility”[3], namely the deteriorated state of individuals in artificially protected conditions (captivity, civilization, etc.) at ages rarely or never observable in the wild. With the distinction between “damage resulting from intrinsic living processes”[4], alias “age changes”[5], and “age-associated diseases”[4,5], the same theory explaining IMICAW allows a rational interpretation of the first category of phenomena while another theory, the “mutation accumulation” hypothesis, gives an immediate interpretation for the second category.The current gerontological paradigm explaining the increasing mortality with increasing chronological age as consequence of insufficient selection should be restricted to the “age-associated diseases”. For IMICAW, it should be substituted with the concept of a physiologic phenomenon genetically determined by a balance of opposite selective pressures — strictly in terms of kin selection — and, for “age changes”, with the action of the same IMICAW-causing mechanisms at ages when selection becomes ineffective.

Senescence in field crickets (Orthoptera; Gryllidae): examining the effects of sex and a sex-biased parasitoid

2000 ◽  
Vol 78 (1) ◽  
pp. 140-143 ◽  
Author(s):  
David A Gray ◽  
William H Cade
Keyword(s):  
Field Cricket ◽  
Gryllus Pennsylvanicus ◽  
Extrinsic Mortality ◽  
Field Crickets ◽  
Younger Age ◽  
In The Wild ◽  
Theory Of Aging ◽  
Male Calling ◽  
Intrinsic Mortality ◽  
Gryllus Integer

The evolutionary theory of aging proposes that senescence is related to decreased selection against deleterious mutations acting late in life. Senescence, i.e., an increase in intrinsic mortality with age, should reflect levels of extrinsic mortality early in life. We tested these predictions using two species of field cricket, Gryllus integer and Gryllus pennsylvanicus. Gryllus integer males are host to a sex-biased parasitoid fly, which orients to the male calling song. As a result, males have reduced life expectancy compared with females in the field. In contrast, G. pennsylvanicus males and females appear to have similar life expectancies in the wild. Thus, we predicted that there would be a significant species × sex interaction, with G. integer males having the shortest life-span. In two replicates, we found that males of both species died at a significantly younger age than females. However, no evidence of a species × sex interaction was found: in the first replicate, G. integer males died earliest, in the second replicate, G. pennsylvanicus males died earliest.

Minimising waste through bioenergetically and behaviourally based feeding strategies

1995 ◽  
Vol 31 (10) ◽  
pp. 29-40 ◽  
Author(s):  
J. E. Thorpe ◽  
C. Young Cho
Keyword(s):  
Feeding Activity ◽  
Activity Patterns ◽  
Growth Efficiency ◽  
Wild Food ◽  
Feeding Strategies ◽  
Physico Chemical ◽  
Evolutionary Features ◽  
Feeding Regimes ◽  
In The Wild ◽  
Genetically Determined

Most species in aquaculture are new to cultivation and so behave like wild animals. They are products of evolution, with adaptations to specific habitat conditions. In the wild, food is not available uniformly throughout the day or the year, or in space, and rarely exceeds the fishes needs. Competition is energetically expensive, reducing growth efficiency. Consequently, feeding activity patterns have evolved, implying internal appetite rhythms, which optimise food intake under these various constraints. Salmonids can adapt quickly to short term variation in food availability, but show seasonal genetically determined anorexia. Rational feeding regimes in culture should take all such features into account. When appetite is high naturally, food should be presented so that it is economically indefensible - where every individual can eat, and where fighting does not pay. At periods of anorexia it will be prudent to offer no food. Manufacturers' feed tables are usually regimes devised to meet the bioenergetic needs of fishes, as they are understood in a physico-chemical sense. While useful first approximations, they do not take into account these evolutionary features of the fishes, and can lead to waste. Methods of presentation are described which allow the fish to determine when food shall be available, and in ways which, by diminishing the advantages of social dominance, ensure relatively even opportunities to feed for all individuals in the population. Allowing the fish to set the time-table reduces the likelihood of waste.

The Ecology of the Western Swamp Tortoise Pseudemydura Umbrina (Testudines: Chelidae).

1981 ◽  
Vol 8 (1) ◽  
pp. 203 ◽  
Author(s):  
AA Burbidge
Keyword(s):  
Water Temperature ◽  
Aquatic Organisms ◽  
The Other ◽  
Restricted Range ◽  
Monotypic Genus ◽  
Insect Larvae ◽  
Relict Species ◽  
Desiccation Rate ◽  
In The Wild ◽  
Growth Activity

Western swamp tortoise (Pseudemydura umbrina) was rediscovered in Western Australia in 1954. It is a relict species of a monotypic genus, of very restricted range and specialized habitat. Population was estimated to be 13 to 45 and decreasing at 1 of its 2 native reserves and to be 10 to 45 and static at the other reserve. It does not use permanent water, but lives and feeds in ephemeral winter swamps and spends the other 6 to 9 months of the year in refuges in leaf litter, under fallen branches or in holes in the ground, in contact with the soil. The tortoise is carnivorous and in the wild takes only live aquatic organisms. Captive adults will not take meat until they have starved for many months. Stomach of 1 female (Edward, pers. commun.) had aquatic crustaceans, chiefly Eulimnadia sp., with insects and insect larvae, mainly Coleoptera and Diptera. Study of faeces confirmed that observation had shown that small tadpoles and an aquatic earthworm (Eodrilus cornigravei) were eaten also. Reproduction, growth, activity relative to body and water temperature, and desiccation rate, were noted. One adult female tortoise was eaten by a fox. Foxes and bandicoots (Isoodon obesulus) eat eggs of other tortoises and would eat those of P. umbrina. Hatchlings may be eaten by large wading birds such as straw-necked ibis (Threskiornis spinicollis) and white-faced heron (Notophoyx novaehollandiae).

scholarly journals Predators as Agents of Selection and Diversification

Diversity ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 415
Author(s):  
Jerald B. Johnson ◽  
Mark C. Belk
Keyword(s):  
Natural Selection ◽  
Empirical Evidence ◽  
Mortality Rates ◽  
Predator Species ◽  
Natural Systems ◽  
Evolutionary Diversification ◽  
Multiple Predator Species ◽  
In The Wild ◽  
Taxonomic Groups ◽  
Future Work

Predation is ubiquitous in nature and can be an important component of both ecological and evolutionary interactions. One of the most striking features of predators is how often they cause evolutionary diversification in natural systems. Here, we review several ways that this can occur, exploring empirical evidence and suggesting promising areas for future work. We also introduce several papers recently accepted in Diversity that demonstrate just how important and varied predation can be as an agent of natural selection. We conclude that there is still much to be done in this field, especially in areas where multiple predator species prey upon common prey, in certain taxonomic groups where we still know very little, and in an overall effort to actually quantify mortality rates and the strength of natural selection in the wild.

scholarly journals Symptom shift in 200 patients with H63D syndrome associated with abnormal TCS findings in substantia nigra

2021 ◽  
Author(s):  
Dr. Carolina Diamandis ◽  
David Seideman ◽  
Jacob S Adams ◽  
Riku Honda ◽  
Marianne Kaufmann ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Substantia Nigra ◽  
Patient Population ◽  
Inverse Correlation ◽  
Transcranial Sonography ◽  
The Other ◽  
Significant Finding ◽  
Other Hand ◽  
Parallel Increase ◽  
The One

In a study on the prevention of injury in patients with H63D syndrome and cataplexy, statistical analysis revealed an unexpected but clinically highly significant finding. Apparently, in this patient population, an inverse correlation exists between the severity of tic symptomatology on the one hand and narcolepsy with cataplexy on the other hand, as well as a parallel increase in the typical signs of degeneration observed in transcranial sonography of the substantia nigra. This finding has clinically far-reaching implications.

scholarly journals EFFECTS OF CHRONIC EXCESS SALT INGESTION

1967 ◽  
Vol 126 (4) ◽  
pp. 687-699 ◽  
Author(s):  
Lewis K. Dahl ◽  
Knud D. Knudsen ◽  
Martha Heine ◽  
George Leitl
Keyword(s):  
Blood Pressure ◽  
Blood Pressure Response ◽  
Pressure Response ◽  
Sensitive Strain ◽  
The Other ◽  
Experimental Hypertension ◽  
Highly Sensitive ◽  
Blood Pressures ◽  
Genetically Determined ◽  
Resistant Animal

Parabiosis has been found to modify the expected blood pressure response of rats from two strains with opposite genetic propensities for experimental hypertension. When a member from one strain was united in parabiosis with a member from the other and both were maintained on high NaCl diet, the rat from the strain ordinarily resistant to it rapidly developed hypertension, in contrast to appropriate controls from this strain. The development of hypertension in this resistant animal preceded that in its mate from the strain highly sensitive to hypertension. In the latter, both the level of hypertension and mortality were significantly less than in its control. It seems likely that the hypertension observed is the resistant parabiont was initiated in its partner from the sensitive strain. This modification in blood pressures was not observed in the absence of a high NaCl diet. Parabiosis between animals from the same strain did not alter their response. Thus, as in earlier experiences (1–4) the interaction of a nongenetic factor (NaCl) with the appropriate genetic substrate appeared to be necessary for the development of hypertension. The findings are interpreted as evidence that a transmittable humoral influence plays an important role in the pathogenesis of rat hypertension. The presence of this agent is genetically determined but, under the conditions of these experiments, it took the added stimulus of dietary NaCl to demonstrate its existence.

Transfer Pricing and Location of Intangibles - Spillover and Tax Avoidance through Profit Shifting

2020 ◽  
Author(s):  
Rebecca Reineke ◽  
Katrin Weiskirchner-Merten
Keyword(s):  
Empirical Evidence ◽  
Transfer Pricing ◽  
Home Bias ◽  
Tax Avoidance ◽  
Optimal Location ◽  
The Other ◽  
Profit Shifting ◽  
Tax Rate ◽  
Length Range ◽  
A Company

This study examines how spillovers affect a multinational company's choice of an intangible's location and the corresponding transfer price for using this intangible. Our model uses a company with a domestic division in a high-tax country and a foreign division in a low-tax country, where each division's activities generate spillovers on the other division's income. In contrast to previous studies, our analysis incorporates an intangible's optimal location when the company trades off tax minimization and efficient activities. By locating the intangible abroad, the company reduces its tax liability, whereas locating the intangible domestically yields more efficient domestic division activities. For a high spillover of the domestic division, the company locates the intangible domestically. Our model supports empirical evidence regarding intangibles' location that is interpreted as "home bias". Additionally, we show how variations in regulatory parameters-arm's length range and tax rate differential-affect the divisions' activities and the intangible's location.

Impact of Risk Assessment Models on Risk Factors

2018 ◽  
pp. 134-153
Author(s):  
K. Madhu Kishore Raghunath ◽  
S. L. Tulasi Devi ◽  
Chandra Sekhar Patro
Keyword(s):  
Risk Factors ◽  
Risk Assessment ◽  
Risk Management ◽  
Empirical Evidence ◽  
The Other ◽  
Risk Models ◽  
Public And Private ◽  
Risk Assessment Models ◽  
General Business ◽  
The Given

World is vicinity full of opportunities given the amount of economic and non-economic transactions taking place every moment. With ubiquitous opportunities all around, businesses can assume inherent risk everywhere in one or the other way. In this chapter, the authors have deliberated the general business scenario to prove the given inferences. The readers will come across why the risk management is gaining so much gravity and across risk strategy of top business players. The chapter will bring into light the various risk factors in business and study the various risk assessment models present to fortify the negativity of these risk factors. Simultaneously, the authors will draw empirical evidence on the effectiveness, qualitative and quantitative risk models have on risk factors in public and private business organisations.

The Economic and Social Value of Financial Literacy

2021 ◽  
pp. 416-436
Author(s):  
José Manuel Sánchez Santos
Keyword(s):  
Social Welfare ◽  
Empirical Evidence ◽  
National Economy ◽  
Financial Literacy ◽  
Social Value ◽  
The Other ◽  
Financial Instability ◽  
Allocation Of Resources ◽  
Financial Decisions ◽  
The One

The main objective of this chapter is to provide new insights into the economic and social value that financial literacy has for individuals and societies. Financial literacy has implications that are relevant both at a micro (especially for households) and macro-level (for the financial system and for the national economy as a whole). On the one hand, a lack of financial literacy put households a risk from making sub-optimal financial decisions and prevent them to maximize their wellbeing. On the other hand, financial literacy favors a better allocation of resources, reduces the risks associated with episodes of financial instability, and therefore, contributes to the increase of social welfare. The analysis and the empirical evidence showing the benefits (costs) of financial literacy (illiteracy) allows to conclude that policymakers have a key role to play implementing initiatives aiming to improve financial literacy of the population at all stages of life.

Sign in / Sign up

Export Citation Format

Share Document