Phylogenomics and the rise of the angiosperms

Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods1,2. A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome3,4. Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5,6,7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade

Student attitudes to the nuclear arms race (1984 survey). Research Report

This is a study of students' knowledge, attitudes, expectations and fears about the nuclear arms race. It was conducted during October 1984 on a sample of 659 upper high school and first year University students in Western Australia. The results indicate a high degree of concern about the nuclear arms race, with females expressing more concern than males. Tertiary students expressed greater anxiety and pessimism about the arms race than high school students. The most common reactions were expressed in terms of fear, anger and frustration. Some students indicated that fears about nuclear war had affected their career and family plans. There was overwhelming support for the proposition that the Government should supply more information about the effects of nuclear war. The level of knowledge of the students about nuclear weapons was adequate only on the non-technical aspects. The survey did not indicate any correlation between increased knowledge about nuclear weapons and increased anxiety. Amongst all groups there was strong support for the nuclear freeze as an initial step towards nuclear disarmament. Many students advocate political action such as marches, demonstrations and lobbying campaigns to reduce the threat of nuclear war. The authors conclude that students are very worried about nuclear war and that they want more information about nuclear weapons. The results indicate that this information is unlikely to have an adverse psychological impact on the students

Thermodynamic assessment of the Pb–Zn system

International audienc

Comparative Yolk Cholesterol Content in Four Spanish Breeds of Hens, an F2 Cross, and a White Leghorn Population

Yolk cholesterol content (milligrams per gram of yolk and milligrams per egg) was studied in eggs of four Spanish breeds of hens (Castellana, Buff Prat, Vasca, and Villafranquina), an F2 from a cross between Castellana and Buff Prat (C x BP-F2), and a White Leghorn population. Birds were tested at 30 wk of age. There were differences among breeds (P < .001), cholesterol concentration being significantly lower in the C x BP-F2 (13.14 +/- .26 mg/g yolk) than in the other breeds. Villafranquina and Buff Prat showed significantly lower cholesterol (14.54 +/- .26 and 14.56 +/- .26 mg/g yolk, respectively) than the White Leghorn (16.30 +/- .26 mg/g yolk). Eggs from the Vasca breed contained significantly more cholesterol (19.09 +/- .26 mg/g yolk) than did eggs laid by the other breeds, whereas no differences were found between Leghorn and Castellana. A negative heterosis percentage of -13% was found in the C x BP-F2 when compared with the parental breed means. The reduction in cholesterol concentration per egg observed in the C x BP-F2 (220.49 mg per egg) was not related to breed differences in egg weight or to the proportion of yolk per egg. Eggs from the Vasca breed, with the lightest yolk and smallest yolk albumen ratio (P < .05), contained the highest amount of cholesterol (304.29 mg per egg). Eggs from the White Leghorn containing the second highest amount of cholesterol (275.63 mg per egg). Thus, the variation in cholesterol content per egg was not attributable to differences in the proportion of yolk