Bayesian quantification of ecological determinants of outcrossing in natural plant populations: Computer simulations and the case study of biparental inbreeding in English yew

Abstract Background and Aims Ultraviolet-B radiation (UV-B) radiation damages the DNA, cells and photosynthetic apparatus of plants. Plants commonly prevent this damage by synthetizing UV-B-protective compounds. Recent laboratory experiments in Arabidopsis and cucumber have indicated that plants can also respond to UV-B stress with endopolyploidy. Here we test the generality of this response in natural plant populations, considering their monocentric or holocentric chromosomal structure. Methods We measured the endopolyploidy index (flow cytometry) and the concentration of UV-B-protective compounds in leaves of 12 herbaceous species (1007 individuals) from forest interiors and neighbouring clearings where they were exposed to increased UV-B radiation (103 forest + clearing populations). We then analysed the data using phylogenetic mixed models. Key Results The concentration of UV-B protectives increased with UV-B doses estimated from hemispheric photographs of the sky above sample collection sites, but the increase was more rapid in species with monocentric chromosomes. Endopolyploidy index increased with UV-B doses and with concentrations of UV-B-absorbing compounds only in species with monocentric chromosomes, while holocentric species responded negligibly. Conclusions Endopolyploidy seems to be a common response to increased UV-B in monocentric plants. Low sensitivity to UV-B in holocentric species might relate to their success in high-UV-stressed habitats and corroborates the hypothesized role of holocentric chromosomes in plant terrestrialization.

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Emergence of Analogies in Collaboratively Conducted Computer Simulations

Cognitive Effects of Multimedia Learning ◽

10.4018/978-1-60566-158-2.ch018 ◽

2009 ◽

pp. 340-361

Author(s):

Wolff-Michael Roth

Keyword(s):

Computer Simulations ◽

Teaching Strategies ◽

Real World ◽

Relevant Information ◽

Multimedia Application ◽

The Real ◽

Physics Course

To learn by means of analogies, students have to see surface and deep structures in both source and target domains. Educators generally assume that students, presented with images, texts, video, or demonstrations, see what the curriculum designer intends them to see, that is, pick out and integrate information into their existing understanding. However, there is evidence that students do not see what they are supposed to see, which precisely inhibits them to learn what they are supposed to learn. In this extended case study, which exemplifies a successful multimedia application, 3 classroom episodes are used (a) to show how students in an advanced physics course do not see relevant information on the computer monitor; (b) to exemplify teaching strategies designed to allow relevant structures to become salient in students’ perception, allowing them to generate analogies and thereby learn; and (c) to exemplify how a teacher might assist students in bridging from the multimedia context to the real world.

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