How evolution shapes the geometries of life

Why does a mouse’s heart beat about the same number of times in its lifetime as an elephant’s, although the mouse lives about a year, while an elephant sees 70 winters come and go? Why do small plants and animals mature faster than large ones? Why has nature chosen such radically different forms as the loose-limbed beauty of a flowering tree and the fearful symmetry of a tiger?These questions have puzzled life scientists since ancient times. Now an interdisciplinary team of researchers from the University of Maryland and the University of Padua in Italy propose a thought-provoking answer based on a famous mathematical formula that has been accepted as true for generations, but never fully understood. In a paper published the week of Feb. 17, 2014 in the Proceedings of the National Academy of Sciences, the team offers a re-thinking of the formula known as Kleiber’s Law. Seeing this formula as a mathematical expression of an evolutionary fact, the team suggests that plants’ and animals’ widely different forms evolved in parallel, as ideal ways to solve the problem of how to use energy efficiently.If you studied biology in high school or college, odds are you memorized Kleiber’s Law: metabolism equals mass to the three-quarter power. This formula, one of the few widely held tenets in biology, shows that as living things get larger, their metabolisms and their life spans increase at predictable rates. Named after the Swiss biologist Max Kleiber who formulated it in the 1930s, the law fits observations on everything from animals’ energy intake to the number of young they bear. It’s used to calculate the correct human dosage of a medicine tested on mice, among many other things.But why does Kleiber’s Law hold true? …

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Capturing brain activity with sculpted light

Sep. 9, 2013 — A major aim of today’s neuroscience is to understand how an organism’s nervous system processes sensory input and generates behavior. To achieve this goal, scientists must obtain detailed maps of how the nerve cells are wired up in the brain, as well as information on how these networks interact in real time.The organism many neuroscientists turn to in order to study brain function is a tiny, transparent worm found in rotting soil. The simple nematode C. elegans is equipped with just 302 neurons that are connected by roughly 8000 synapses. It is the only animal for which a complete nervous system has been anatomically mapped.Researchers have so far focused on studying the activity of single neurons and small networks in the worm, but have not been able to establish a functional map of the entire nervous system. This is mainly due to limitations in the imaging-techniques they employ: the activity of single cells can be resolved with high precision, but simultaneously looking at the function of all neurons that comprise entire brains has been a major challenge. Thus, there was always a trade-off between spatial or temporal accuracy and the size of brain regions that could be studied.Scientists at Vienna’s Research Institute of Molecular Pathology (IMP), the Max Perutz Laboratories (MFPL), and the Research Platform Quantum Phenomena & Nanoscale Biological Systems (QuNaBioS) of the University of Vienna have now closed this gap and developed a high speed imaging technique with single neuron resolution that bypasses these limitations. In a paper published online in Nature Methods, the teams of Alipasha Vaziri and Manuel Zimmer describe the technique which is based on their ability to “sculpt” the three-dimensional distribution of light in the sample. With this new kind of microscopy, they are able to record the activity of 70% of the nerve cells in a worm’s head with high spatial and temporal resolution.”Previously, we would have to scan the focused light by the microscope in all three dimensions,” says quantum physicist Robert Prevedel. …

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Study relies on twins and their parents to understand height-IQ connection

Aug. 27, 2013 — The fact that taller people also tend to be slightly smarter is due in roughly equal parts to two phenomena — the same genes affect both traits and taller people are more likely than average to mate with smarter people and vice versa — according to a study led by the University of Colorado Boulder.The study did not find that environmental factors contributed to the connection between being taller and being smarter, both traits that people tend to find attractive.The modest correlation between height and IQ has been documented in multiple studies stretching back to the 1970s. But the reasons for the relationship between the two traits has not been well understood.The technique developed by the researchers at CU-Boulder to tease out those reasons may open the door for scientists to better understand why other sexually selected traits — characteristics that individuals find desirable in mates — tend to be linked. People who are attractive because of one trait tend to have other attractive traits as well.”Not just in humans but also in animals, you see that traits that are sexually attractive tend to be correlated,” said Matthew Keller, assistant professor of psychology and neuroscience at CU-Boulder and lead author of the study appearing in the journal PLOS Genetics. “So if you have animals that are high on one sexually selected trait they are often high on other ones, too. And the question has always been, ‘What’s the cause of that?’ And it has always been very difficult to tease apart the two potential genetic reasons that those could be related.”The key to the technique developed by Keller, also a fellow at CU-Boulder’s Institute for Behavioral Genetics, and his colleagues is using data collected about fraternal twins, identical twins and, importantly, their parents.It has been common in the past to use information about identical twins and fraternal twins to determine whether a particular trait is inherited, caused by environmental factors or affected by some combination of both. This kind of twin study assumes that each twin grows up with the same environmental factors as his or her sibling.If a trait that’s present in one twin is just as often present in the other — regardless of whether the twins are fraternal or identical — then the trait is likely caused by environmental conditions. On the other hand, if a trait is generally found in both identical twins but only in one of a set of fraternal twins, it’s likely that the trait is inherited, since identical twins have the same genetic material but fraternal twins do not.Similar studies also can be done for linked traits, such as height and IQ. But while scientists could determine that a pair of traits is passed down genetically, they could not further resolve whether inherited traits were linked due to the same genes influencing both traits, called “pleiotropy,” or because people who have those traits are more likely to mate with each other, known as “assortative mating.”The new CU-Boulder study solves this problem by including the parents of twins in its analysis. While this has occasionally been done in the past for single traits, information on parents has not previously been used to shed light on why two traits are genetically correlated. …

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