Known as 'polyandry' among scientists, the phenomenon of females having multiple mates is shared across most animal species, from insects to mammals. This study suggests that polyandry reduces the risk of populations becoming extinct because of all-female broods being born. This can sometimes occur as a result of a sex-ratio distortion (SR) chromosome, which results in all of the Y chromosome 'male' sperm being killed before fertilisation. The all-female offspring will carry the SR chromosome, which will be passed on to their sons in turn resulting in more all-female broods. Eventually there will be no males and the population will die out.
For this study, the scientists worked with the fruitfly Drosophila pseudoobscura. They gave some populations the opportunity to mate naturally, meaning that the females had multiple partners. The others were restricted to having one mate each. They bred several generations of these populations, so they could see how each fared over time.
Over fifteen generations, five of the twelve populations that had been monogamous became extinct as a result of males dying out. The SR chromosome was far less prevalent in the populations in which females had the opportunity to have multiple mates and none of these populations became extinct.
The study shows how having multiple mates can suppress the spread of the SR chromosome, making all-female broods a rarity. This is because males that carry the SR chromosome produce only half as many sperm as normal males. When a female mates with multiple males, their sperm will compete to fertilise her eggs. The few sperm produced by males carrying the SR chromosome are out-competed by the sperm from normal males, and the SR chromosome cannot spread.
thinkahol * on 20 Aug 11Educational researchers at the Technical University of Munich (TUM) have found that schoolchildren can independently develop strategies for solving complex mathematical tasks, with weaker students proving just as capable as their stronger classmates. Researchers in mathematics education worked with approximately 1600 8th grade high-school students in various German states. Following an introduction to the general topic by their teachers, the school children were given a workbook of geometric tasks that they had to solve on paper and using a computer over four school periods. Calculating the surface area of Gran Canaria was one of the real-world, free-form assignments the students had to tackle. The workbook material included explanations and examples of various problem-solving approaches. The teachers took a back seat during the session but were on hand to answer questions from the children, who worked in pairs. After testing the students' skills before and after the session, the researchers recorded a significant improvement in their capabilities. The students learned to apply mathematics more effectively, the researchers said. The students were also able to call on these skills in a further test three months later. "We expected students who were weaker at math to benefit more from a greater degree of guidance through the module," said professor Kristina Reiss. "But we didn't see a significant difference between these and stronger students." The researchers also found that there were also no differences between boys and girls. "We now know that students - also those who are weaker in math - have the skills to master even very complex subject matters at their own pace," said Reiss. Topics: Cognitive Science/Neuroscience
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