Evolutie. Deel XIV

quote:

Op maandag 3 september 2007 16:44 schreef Autodidact het volgende:
Walking With Cavemen

Iemand deze al gezien? Ziet er wel leuk uit.

quote:

Op maandag 10 september 2007 13:40 schreef Rasing het volgende:
Een bijdrage van rapper Baas B aan het evolutiedebat: in een interview in het Veronica-magazine was de vraag: God of Darwin?

'Ik geloof wel in een God, maar ik geloof ook dat er buitenaardse wezens zijn. God of Darwin... het zijn voor mij allebei buitenaardse wezens.'

Ali_Kannibali en consorten: er zijn mensen met nóg minder verstand van evolutie.

quote:

Op maandag 10 september 2007 14:37 schreef Monolith het volgende:
Laat die jongen het maar bij rappen houden, daar heeft hij tenminste wel verstand va..oh nee, toch niet.

quote:

Op maandag 10 september 2007 14:39 schreef Rasing het volgende:

[..]

Zelfs dat kan hij niet Misschien doet de natuurlijke selectie zijn werk wel, en hebben we over honderd jaar in ieder geval geen last van zijn nazaten.

quote:

Op maandag 10 september 2007 15:11 schreef Autodidact het volgende:

[..]

Mensen van zijn subspeciës zijn toch vrij goed in het voortplanten? Zo wordt de evolutietheorie als meme er door de natuurlijke selectie uitgefilterd....

quote:

Scientists say velociraptor had feathers

WASHINGTON - Velociraptor, the terrifying predator made famous in the movie "Jurassic Park," appears to have had feathers in real life.

ADVERTISEMENT

A close study of a velociraptor forearm found in Mongolia shows the presence of quill knobs, bumps on the bone where the feathers anchor, researchers report in Friday's edition of the journal Science.

Dinosaurs are believed to be ancestors to modern birds. Evidence of feathered dinosaurs has been found in recent years, and now velociraptor can be added to that list.

"Finding quill knobs on velociraptor ... means that it definitely had feathers. This is something we'd long suspected, but no one had been able to prove," Alan Turner, lead author on the study and a graduate student of paleontology at the American Museum of Natural History and at Columbia University in New York, said in a statement.

The velociraptor the researchers studied was about three feet tall and weighed about 30 pounds. The size of these animals was exaggerated in the movie.

It had short forelimbs, compared to a modern bird, the researchers said, indicating it would not have been able to fly, even though it had feathers.

The feathers may have been useful for display, to shield nests, for temperature control or to help it maneuver while running, they said.

___

quote:

20-09-2007


Deze schedel van de Keniaanse Homo Erectus (foto Reuters)

In Georgië zijn op de beroemde vindplaats Dmanisi veel skeletdelen van Homo erectus gevonden, 1,77 miljoen jaar oud. Ze wijzen uit dat Homo erectus in deze vroege tijd nog veel primitieve kenmerken had.

Tot nu toe gold de Keniase Nariokotomejongen als het typische Homo erectus-skelet. Sinds die vondst in 1984 van dat uitzonderlijk goed bewaard skelet van een tienjarige (gedateerd op 1,55 miljoen jaar geleden) geldt erectus als bijna modern: erg lang, met rechte ribbenkast en met alleen een kleiner brein dan tegenwoordig. Maar in het tijdschrift Nature van vandaag schetst een team van maar liefst achttien archeologen onder leiding van de Georgiër David Lordkipanidze (Nationaal Museum, Tiblisi) een ander beeld. De nu gevonden skeletdelen tonen een aantal duidelijke primitieve kenmerken heeft, die lijken op Australopithecus, de voorganger van Homo. Er zijn uit de evolutie van de mens vrij veel schedels gevonden, maar weinig ander botmateriaal.

Dmanisi stond al bekend om de vondst van relatief kleine H. erectus-schedels. Die worden soms toegewezen aan een aparte soort Homo georgicus, maar vrij algemeen wordt deze als nauw verwant of identiek aan H. erectus gezien. Een toewijzing van Homo georgicus aan de veel primitievere voorganger Homo habilis (ca 2 tot 1,5 miljoen jaar oud) heeft tot nu toe niet veel steun gekregen, al zullen de nu gevonden kenmerken die discussie weer aanwakkeren.

De lange onderbenen van de Dmanisi-mensen lijken op die van moderne mensen: heel geschikt om veel en ver mee te lopen. Maar hun bovenarmen vertonen duidelijk primitieve kenmerken. Wel is onduidelijk welke functie die minder gedraaide vorm van het bovenarmbeen heeft. Ook blijkt uit een Dmanisis-dijbeen dat de Georgische erectus iets korter was: een geschatte lengte van 145 tot 166 cm – tegen een geschatte (volwassen) lengte van de Nariokotome-erectus van 150 tot 169 cm.

(nrc)

quote:

Santos et al.

Genetic isolation through time: allochronic differentiation of a phenologically atypical population of the pine processionary moth

Proceedings of the Royal Society B, Vol 274 No. 1612, pp. 935-941 (7 April 2007)

Allochronic speciation refers to a mode of sympatric speciation in which the differentiation of populations is primarily due to a phenological shift without habitat or host change. However, it has been so far rarely documented. The present paper reports on a plausible case of allochronic differentiation between sympatric populations of the pine processionary moth (PPM), Thaumetopoea pityocampa. The PPM is a Mediterranean insect with winter larval development. A phenologically atypical population with early adult activity and summer larval development was detected 10 years ago in Portugal. Mitochondrial and nuclear sequences strongly suggest that the ‘summer’ individuals are closely related to the sympatric winter population, while microsatellite data show a reduction in allelic richness, a distortion of allelic frequencies and significant genetic differentiation. Moreover, monitoring of adult flights suggests that reproductive activity does not overlap between the summer and winter populations. We postulate that the summer population appeared after a sudden phenological shift of some individuals of the sympatric winter population, leading to a founder effect and complete reproductive isolation. Given that the individuals showing this new phenology are subject to different selection pressures, the observed allochronic differentiation may rapidly lead to deeper divergence.

quote:

Sparkman et al.

An empirical test of evolutionary theories for reproductive senescence and reproductive effort in the garter snake Thamnophis elegans

Proceedings of the Royal Society B, Vol 274 No. 1612, pp. 943-950 (7 April 2007)

Evolutionary theory predicts that differential reproductive effort and rate of reproductive senescence will evolve under different rates of external mortality. We examine the evolutionary divergence of age-specific reproduction in two life-history ecotypes of the western terrestrial garter snake, Thamnophis elegans. We test for the signature of reproductive senescence (decreasing fecundity with age) and increasing reproductive effort with age (increasing reproductive productivity per gram female) in replicate populations of two life-history ecotypes: snakes that grow fast, mature young and have shorter lifespans, and snakes that grow slow, mature late and have long lives. The difference between life-history ecotypes is due to genetic divergence in growth rate. We find reproductive success (live litter mass) increases with age in both ecotypes, but does so more rapidly in the fast-growth ecotype, (ii) reproductive failure increases with age in both ecotypes, but the proportion of reproductive failure to total reproductive output remains invariant, and (iii) reproductive effort remains constant in fast-growth individuals with age, but declines in slow-growth individuals. This illustration of increasing fecundity with age, even at the latest ages, deviates from standard expectations for reproductive senescence, as does the lack of increases in reproductive effort. We discuss our findings in light of recent theories regarding the phenomenon of increased reproduction throughout life in organisms with indeterminate growth and its potential to offset theoretical expectations for the ubiquity of senescence.

quote:

Bragg and Wagner

Protein carbon content evolves in response to carbon availability and may influence the fate of duplicated genes

Proceedings of the Royal Society B, Vol 274 No. 1613, pp. 1063-1070 (22 April 2007)

Natural selection can influence even the lowest level of biological organization, the atomic composition of biological macromolecules. In analysing genome-scale gene expression data, we find that ancestral yeast strains preferentially express proteins with low carbon content during carbon limitation, relative to strains selected in the laboratory under carbon limitation. The likely reason is that the artificially selected strains acquire adaptations that refine their response to the limitation or partly circumvent the limiting condition. This finding extends previous work which shows that natural selection can act on the atomic costs of proteins. We also show that genes with high carbon and nitrogen content are less likely to have duplicates, indicating that atomic composition also plays a role in evolution by gene duplication. Taken together, our results contribute to the emerging view that protein atomic composition influences genome and transcriptome evolution.

quote:

Op donderdag 4 oktober 2007 12:44 schreef Triggershot het volgende:
FOK! wiki/evolutie is ook behoorlijk outdated, als iemand van jullie daar naar wil kijken. [afbeelding]

quote:

Op donderdag 4 oktober 2007 17:16 schreef Triggershot het volgende:

[..]

Niet de inhoudelijkheid, maar laatste keer dat er aan gewerkt is.

quote:

Op donderdag 4 oktober 2007 17:51 schreef Triggershot het volgende:

[..]



Als de user en auteur daarmee content zijn, mij best

quote:

For generations medical orthodoxy has maintained that the appendix is useless, warranting attention only for its tendency to become painfully inflamed and requiring swift removal. But now the reputation of this cul-de-sac in the human gut has been rehabilitated by a theory from a team of immunologists .

The US scientists found that the appendix acted as a "good safe house" for bacteria essential for healthy digestion, in effect re-booting the digestive system after the host has contracted diseases such as amoebic dysentery or cholera, which kill off helpful germs and purge the gut.
Quote:
The theory, developed by a team from Duke University Medical School, North Carolina, and published in the Journal of Theoretical Biology, has sent ripples through the scientific community. It "seems by far the most likely" explanation for the function of the appendix and "makes evolutionary sense", said Douglas Theobald, a professor of biochemistry at Brandeis University in Boston.

quote:

Op dinsdag 9 oktober 2007 11:35 schreef Monolith het volgende:
De blinde darm is misschien toch niet helemaal zo nutteloos als gedacht:
[..]

bron

quote:

Writing this week in the journal Nature, Erez Lieberman, Jean-Baptiste Michel, and colleagues in Harvard's Program for Evolutionary Dynamics, led by Martin A. Nowak, conceive of linguistic development as an essentially evolutionary scheme: Just as genes and organisms undergo natural selection, words -- specifically, irregular verbs that do not take an "-ed" ending in the past tense -- are subject to powerful pressure to "regularize" as the language develops.

"Mathematical analysis of this linguistic evolution reveals that irregular verb conjugations behave in an extremely regular way -- one that can yield predictions and insights into the future stages of a verb's evolutionary trajectory," says Lieberman, a graduate student in applied mathematics in Harvard's School of Engineering and Applied Sciences and in the Harvard-MIT Division of Health Sciences and Technology, and an affiliate of Harvard's Program for Evolutionary Dynamics. "We measured something no one really thought could be measured, and got a striking and beautiful result."

http://www.sciencecodex.c(...)re_of_the_past_tense