scholarly journals Periodic Fluctuations in the Numbers of Animals: Their Causes and Effects

1924 ◽  
Vol 2 (1) ◽  
pp. 119-163 ◽  
Author(s):  
C. S. ELTON
Keyword(s):  
Natural Selection ◽  
Rapid Expansion ◽  
The Other ◽  
The Arctic ◽  
Arctic Regions ◽  
Biological Phenomena ◽  
Short Period ◽  
Periodic Fluctuations ◽  
Selection Of ◽  
New Mutations

I. Four main points are dealt with :-- (a) The widespread existence of fluctuations in the numbers of animals. (b) The existence, in many birds and mammals, of periodic fluctuations (p.f.). (c) The cause of the latter, which must be some periodic climatic change acting over wide areas. (d) The effects of fluctuations in general, and in particular of the p.f., on the method of evolution and other biological phenomena. 2. A short sketch is given of what is known about short- period climatic cycles (2 to 20 years), and their causes. 3. P.f. of lemmings have an average period of about 3½ years. The maxima in numbers occur synchronously in North America and Europe, and probably all round the arctic regions. The varying hare in Canada has a period of 10 to 11 years. 5. The only regular periods shown by the animals dealt with are the short one of 3½ years and the longer one of 10 to 11 years. The former is probably more marked in the arctic and the other further south. 6. The sandgrouse p.f. point to the existence of an 11-year climatic cycle in the deserts of Central Asia. 7. The effects of these p.f. on evolution must be very great, although at present problematical; but the following suggestions are made :-- (a) Natural selection of some characters must be periodic. (b) There will be different types of natural selection at the maxima and minima of numbers. (c) The struggle for existence, and therefore natural selection, tend to cease temporarily during the rapid expansion in numbers from a minimum, and new mutations have then a chance to get established and spread, i.e. without the aid of natural selection. This might happen only rarely. (d) This would explain the origin and survival of non adaptive characters in a species. (e) On the other hand periodic reduction in numbers will act as an important factor causing uniformity in the species. (f) The opposing factors (c) and (e) will vary much in different species, and the problem will require the combined attentions of mathematicians, and of ecologists working on the methods of regulation of the numbers of animals. (g) This mechanical uniformity factor, since it acts independently of natural selection, explains how a particular structure or habit may evolve, when it only has a general adaptive significance.

Polar Lows and Their Implications on Marine Operations: Survivability Criteria

2013 ◽  
Author(s):  
Meric Pakkan ◽  
David Heng ◽  
Ove Tobias Gudmestad
Keyword(s):  
Weather Forecast ◽  
Weather Conditions ◽  
The Arctic ◽  
Return Periods ◽  
Polar Lows ◽  
Wind Speeds ◽  
The North ◽  
Arctic Regions ◽  
Short Period ◽  
Polar Low

The oil resource potential in the Arctic/sub-Arctic regions is estimated to be as high as that 25% of the world’s yet-to-be-found. Nevertheless, operating in above-mentioned regions is more complicated and expensive than the ones in the North Sea. One of the most important aspects to consider in operating in these Arctic regions is the presence of polar lows and arctic fronts and storms. These extreme events and implications of them on the marine operations were the main focus of this study. While the maximum polar low-sourced wind speeds for 10-, 20- and 100-year return periods are estimated to be 55.37, 60.93 and 73.52 knots, the maximum polar low-sourced wave heights for 10-, 20- and 100-year return periods are calculated as 5.71, 6.66 and 8.82 meters, respectively. It is found out that polar lows weather conditions do not normally represent design values (survival conditions); however, they represent operational limitations. • We conclude that operations lasting longer than 72 hours shall be designed for a rougher weather than the polar lows lead to (survival mode). • For operations of duration less than 72 hours, the weather forecast is crucial and it must also be possible to abort the operation within a short period if one is close to a polar weather front as a polar low may appear very quickly.

scholarly journals Does habitat partitioning by sympatric plovers affect nest survival?

The Auk ◽  
2020 ◽  
Vol 137 (3) ◽  
Author(s):  
Kelly S Overduijn ◽  
Colleen M Handel ◽  
Abby N Powell
Keyword(s):  
Nest Survival ◽  
Elevational Gradient ◽  
Nest Site Selection ◽  
Breeding Habitat ◽  
Rapid Expansion ◽  
The Arctic ◽  
Nesting Habitat ◽  
Habitat Features ◽  
Nest Sites ◽  
Selection Of

Abstract The vertical structure and composition of vegetation can influence the quantity and quality of potential nesting sites for birds. Interspecific competition for high-quality nesting habitat may force some individuals into suboptimal habitat and lead to reduced reproductive success, eventually leading to changes in distribution or abundance. Large climate-mediated shifts in vegetation, including the rapid expansion of shrubs onto tundra, are occurring in the Arctic across important breeding grounds of many shorebird species of conservation concern. We investigated effects of vegetation structure and composition on nest-site selection and nest success of sympatrically breeding American Golden-Plovers (Pluvialis dominica) and Pacific Golden-Plovers (P. fulva), which nest along an elevational gradient ranging from coastal tundra meadows to alpine tundra. Both species strongly selected nest sites with less cover of tall shrubs and other tall vegetation than available at random sites within their territories. American Golden-Plovers selected territories and nest sites that were higher in elevation and had more rocky substrates and less graminoid vegetation than those selected by Pacific Golden-Plovers. The daily nest survival rate was equivalent in the 2 species (0.966, 95% CI: 0.955, 0.975) and similar to that found in other Arctic-breeding shorebirds; however, contrary to predictions, nest survival was not associated with habitat features selected for nest sites for either species. Strong selection of open habitat for nest sites suggests that continued climate-related shrub expansion may reduce the amount of suitable breeding habitat for both species, but partitioning along the elevational gradient and differences in body size suggest that impacts may be more severe for Pacific Golden-Plovers. Additional research is needed to determine if differential selection of nesting habitat is related to survival of the adults or their young.

Gesture–speech unity

2014 ◽  
Vol 5 (2) ◽  
pp. 137-184 ◽  
Author(s):  
David McNeill
Keyword(s):  
Prefrontal Cortex ◽  
Natural Selection ◽  
Language Evolution ◽  
The Other ◽  
Shared Intentionality ◽  
Origin Of Language ◽  
Child Speech ◽  
The Brain ◽  
Shed Light ◽  
Selection Of

This paper outlines an argument for how development in child speech and gesture could shed light on language evolution: child acquisition can be thought of as two types of acquisition, one of which goes extinct (gesture-first, Acquisition 1) and is replaced by another (gesture–speech unity, Acquisition 2). For ontogenesis, this implies that children acquire two languages, one of which is extinct, and which again goes extinct in ontogenesis (it continues as “gestures of silence” rather than as gestures of speech). There is no way to get from Acquisition 1 to Acquisition 2. They are on different tracks. Even when they converge in the same sentence, as they sometimes do, they alternate and do not combine. I propose that the 3~4 year timing of Acquisition 2 relates to the natural selection of a kind of gestural self–response I call “Mead’s Loop”, which took place in a certain psychological milieu at the origin of language. This milieu emerges now in ontogenesis at 3~4 years and with it Mead’s Loop. It is self-aware agency, on which a self-response depends. Other developments, such as theory of mind and shared intentionality, likewise depend on it and also emerge around the same time. The prefrontal cortex, anchoring a ring of language centers in the brain, matures at that point as well, another factor influencing the late timing. On the other hand, a third acquisition, speech evoking adult attachment, begins at (or even before) birth, as shown by a number of studies, and provides continuity through the two acquisitions and extinction.

Rights Over the Arctic

1930 ◽  
Vol 24 (4) ◽  
pp. 703-717 ◽  
Author(s):  
W. Lakhtine
Keyword(s):  
North America ◽  
Arctic Ocean ◽  
Far East ◽  
The Other ◽  
The Arctic ◽  
The North ◽  
Arctic Regions ◽  
The Far East ◽  
The Arctic Ocean ◽  
The One

The transarctic flights of 1926 and 1928 demonstrate the possibility of establishing communication by air across the Arctic regions between Europe, on the one side, and North America and the Far East on the other. Quite aside from the saving of time owing to shorter distance, the establishment of such communication presents considerably less diiSculty than air communication over the Atlantic: a conclusion derived from the transatlantic flights of the last three years. The experience of the airship Italia in May, 1928, does not at all nullify this conclusion. It serves merely to show that the organization of transarctic communication requires special prearrangements, such aa wireless stations, meteorological stations, landing-places, air-bases, the construction of which on the shores, islands, and even on the ice of the Arctic Ocean, appears to be quite feasible. The necessity for such stations has aroused in the governments of the North countries an increased interest in the Arctic regions which heretofore has been restricted to scientific circles.

scholarly journals Updating Darwin: Information and entropy drive the evolution of life

F1000Research ◽  
2016 ◽  
Vol 5 ◽  
pp. 2808 ◽  
Author(s):  
Irun R. Cohen
Keyword(s):  
Natural Selection ◽  
The Other ◽  
Evolution Of Complexity ◽  
Programmed Death ◽  
Evolution Of Life ◽  
The One ◽  
Survival Of The Fittest ◽  
Darwinian Paradigm ◽  
Physical Principles ◽  
Selection Of

The evolution of species, according to Darwin, is driven by struggle – by competition between variant autonomous individuals for survival of the fittest and reproductive advantage; the outcome of this struggle for survival is natural selection. The Neo-Darwinians reframed natural selection in terms of DNA: inherited genotypes directly encode expressed phenotypes; a fit phenotype means a fit genotype – thus the evolution of species is the evolution of selfish, reproducing individual genotypes.  Four general characteristics of advanced forms of life are not easily explained by this Neo-Darwinian paradigm: 1) Dependence on cooperation rather than on struggle, manifested by the microbiome, ecosystems and altruism; 2) The pursuit of diversity rather than optimal fitness, manifested by sexual reproduction; 3) Life’s investment in programmed death, rather then in open-ended survival; and 4) The acceleration of complexity, despite its intrinsic fragility.   Here I discuss two mechanisms that can resolve these paradoxical features; both mechanisms arise from viewing life as the evolution of information. Information has two inevitable outcomes; it increases by autocatalyis and it is destroyed by entropy. On the one hand, the autocalalysis of information inexorably drives the evolution of complexity, irrespective of its fragility. On the other hand, only those strategic arrangements that accommodate the destructive forces of entropy survive – cooperation, diversification, and programmed death result from the entropic selection of evolving species. Physical principles of information and entropy thus fashion the evolution of life.

Metric variations in populations of Carcinus moenas

1941 ◽  
Vol 25 (2) ◽  
pp. 261-281 ◽  
Author(s):  
G. Williams ◽  
A. E. Needham
Keyword(s):  
Body Size ◽  
Natural Selection ◽  
Carapace Length ◽  
Rate Of Change ◽  
The Other ◽  
Differential Growth ◽  
Moderate Amount ◽  
The Individual ◽  
Striking Fact ◽  
Selection Of

1. Measurements of Carcinus, comparable to those taken by Weldon at Plymouth 40 years ago, have been made on material from three Irish localities, the observations in each area extending over three years. The three localities afford different environments, one having no silt, one a moderate amount and the other much silt.2. The results support the view that the change in the ratio frontal width/ carapace length with increase in body size is due to differential growth in the individual and is not caused, as Weldon supposed, by the continuous removal through natural selection of those crabs with a relatively wide frontal aperture. Measurement on the growth of individuals confirms this view.3. A striking fact which emerged from Weldon's work was that the ratio mentioned above showed a successive diminution in each of the three years covered by the observations. A precisely similar diminution has been found at each of the Irish localities, and it is shown that the annual differences are mathematically significant.4. The results disprove Weldon's hypothesis that the change in the ratio is correlated with the slow accumulation of silt in Plymouth Sound. The Irish locality with most silt has the widest frontal aperture and the intermediate locality the narrowest. It is also shown that the yearly trend towards a lower value for the ratio cannot be continuous, for the rate of change is too rapid to be maintained indefinitely, and the values obtained in the Irish localities overlap those at Plymouth 40 years earlier. Possible explanations of the changes are discussed.5. The differences between populations from the three localities in any year are much less marked than the annual differences at one locality, and are not generally significant. Though small, however, they do show a consistent sequence among the three localities (but not corresponding to the order for siltiness).

scholarly journals Framing the Arctic: Reconsidering Roald Amundsen’s Gjøa Expedition Imagery

Nordlit ◽  
2015 ◽  
pp. 137
Author(s):  
Ingeborg Høvik
Keyword(s):  
Contact Zone ◽  
Dynamic Contact ◽  
The Other ◽  
The Arctic ◽  
Northwest Passage ◽  
Close Interaction ◽  
Extensive Body ◽  
Formed Part ◽  
The One ◽  
Selection Of

<p align="left">In 1906 Roald Amundsen’s Gjøa Expedition returned to Norway after three years in the Arctic. The first to complete a Northwest Passage by sea, the expedition also brought back a substantial amount of ethnographic material concerning the Netsilik Inuit, with whom Amundsen and his crew had been in sustained contact during their stay on King William Island in Nunavut between 1903 and 1905. This material included a large number of photographs, forty-two of which were included as illustrations in his expedition narrative, titled <span style="font-family: TimesNewRomanPSMT;"><em><span style="font-family: TimesNewRomanPS-ItalicMT;">Nordvest-passagen </span></em><span style="font-family: TimesNewRomanPSMT;">and first released in </span></span>Norwegian in 1907. Focusing on a selection of published and unpublished photographs from Amundsen’s voyage and their interrelationships, this article examines the degree to which the Gjøa Expedition’s use of photography formed part of a planned project that intersected with anthropological concerns and practices of its time. My purpose is further to demonstrate that there is a discernible change in the representation of indigeneity that occurs when particular photographs were selected and then contextually reframed as illustrations in <span style="font-family: TimesNewRomanPSMT;"><em><span style="font-family: TimesNewRomanPS-ItalicMT;">Nordvest-passagen</span></em><span style="font-family: TimesNewRomanPSMT;">. </span></span>On the one hand, the extensive body of photographs taken in the field elaborates the close interaction between crew and Inuit recorded in Amundsen’s personal diary and published narrative, testifying to the existence of an active and dynamic contact zone. In this regard, the original photographs could arguably be read as a dialogic portrayal of the unique individuals Amundsen’s crew met while in the Arctic. On the other hand, a peculiar distancing seems to have taken place as the Gjøa Expedition’s photographs were selected and reproduced as illustrations for Amundsen’s expedition narrative. Likely connected to a desire to match his expedition narrative to existing scientific visual and literary conventions, this shift suggests Amundsen’s attempts through textual and visual means to deny the Netsilik Inuit’s coevalness.</p>

scholarly journals Processes and patterns of interaction as units of selection: An introduction to ITSNTS thinking

2018 ◽  
Vol 115 (16) ◽  
pp. 4006-4014 ◽  
Author(s):  
W. Ford Doolittle ◽  
S. Andrew Inkpen
Keyword(s):  
Natural Selection ◽  
Biogeochemical Cycles ◽  
The Other ◽  
Units Of Selection ◽  
Biological Hierarchy ◽  
Global Biogeochemical Cycles ◽  
Evolution By Natural Selection ◽  
Definition Of ◽  
Patterns Of Interaction ◽  
Selection Of

Many practicing biologists accept that nothing in their discipline makes sense except in the light of evolution, and that natural selection is evolution’s principal sense-maker. But what natural selection actually is (a force or a statistical outcome, for example) and the levels of the biological hierarchy (genes, organisms, species, or even ecosystems) at which it operates directly are still actively disputed among philosophers and theoretical biologists. Most formulations of evolution by natural selection emphasize the differential reproduction of entities at one or the other of these levels. Some also recognize differential persistence, but in either case the focus is on lineages of material things: even species can be thought of as spatiotemporally restricted, if dispersed, physical beings. Few consider—as “units of selection” in their own right—the processes implemented by genes, cells, species, or communities. “It’s the song not the singer” (ITSNTS) theory does that, also claiming that evolution by natural selection of processes is more easily understood and explained as differential persistence than as differential reproduction. ITSNTS was formulated as a response to the observation that the collective functions of microbial communities (the songs) are more stably conserved and ecologically relevant than are the taxa that implement them (the singers). It aims to serve as a useful corrective to claims that “holobionts” (microbes and their animal or plant hosts) are aggregate “units of selection,” claims that often conflate meanings of that latter term. But ITSNS also seems broadly applicable, for example, to the evolution of global biogeochemical cycles and the definition of ecosystem function.

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

Sign in / Sign up

Export Citation Format

Share Document