Month: September 2022

IMMORTAL CELLS. "Indeed, it is well-known that primitive organisms (e.g. bacteria, algae, protozoids, ...) are in a sense immortal. That is, when they reproduce (by mere splitting of cells) there is no difference between "parent" and "offspring": both splitted cells continue to survive, and undergo further splits, without any apparent aging or senescence." http://pespmc1.vub.ac.be/evolage.html View in LinkedIn

MEIOSIS. "Our own process of reproduction (meiosis) is merely a more complicated version of this, in which just a few cells (sex-cells or germ-line cells) can indefinitely reproduce, while the other cells die after a while." http://pespmc1.vub.ac.be/evolage.html View in LinkedIn

INDEFINITE REPAIR? "Even the increase of thermodynamic entropy can be counteracted indefinitely in an open system with a constant input of neguentropy. So there is no a priori reason why living systems would not be able to indefinitely maintain and repair their structural organization." http://pespmc1.vub.ac.be/evolage.html View in LinkedIn

TRANSITIONS TO COLONIES. “We develop a conceptual framework in which three fundamental processes (growth, division, and splitting) are the scaffold for unicellular and multicellular life cycles alike. We demonstrate how changes in the regulation of three fundamental aspects of colonial form (cell size, colony size, and colony cell number) could lead unicellular life cycles to evolve into primitive multicellular life cycles with group properties.” http://www.sciencedirect.com/science/article/pii/S0040580915000222 View in LinkedIn

COLONY CONSTRAINTS. “One interesting prediction of the model is that selection generally favors cycles with group level properties when intermediate body size is associated with lowest mortality. That is, a universal requirement for the evolution of group cycles in the model is that the size-mortality curve be U-shaped. Furthermore, growth must decelerate with size.” http://www.sciencedirect.com/science/article/pii/S0040580915000222 View in LinkedIn

BIRTH AND DEATH. “Beginnings are often difficult to pinpoint, particularly in life cycles, for life is continuous. Life does not tolerate a break (at most a transitory standstill in a stage of quiescence). Life is a continuing process that started some billions of years ago below the level of multicellularity and will end with the death of the last living being. Nevertheless, each individual life that is based on sexual reproduction has two discrete boundaries: fertilization and death.” https://lnkd.in/d6G9geU View in LinkedIn

DEATH ANTAGONISTS. "Peter Thiel, the billionaire co-founder of PayPal, plans to live to be 120. Compared with some other tech billionaires, he doesn’t seem particularly ambitious. Dmitry Itskov, the “godfather” of the Russian Internet, says his goal is to live to 10,000; Larry Ellison, co-founder of Oracle, finds the notion of accepting mortality “incomprehensible,” and Sergey Brin, co-founder of Google, hopes to someday “cure death.” http://www.newsweek.com/2015/03/13/silicon-valley-trying-make-humans-immortal-and-finding-some-success-311402.html View in LinkedIn

THIS IS THE END of this long section on the biology of death. The subject is far from over, and the transition is purely artificial. I hope that this series of perspectives from a biological viewpoint, nested in observations and experiments across the living world has been insightful. View in LinkedIn

FRAGMENT FROM NATURE contemplates for this and next weekend, jumping genes (more correctly, transposons or mobile genetic elements) that are generated by viruses. These semi-autonomous simple strands of DNA including genes defy our ideas of life. Just strings of chemicals, they hop around host genome ecosystems as free-living parasites and symbionts, and also have had an enormous impact on evolution across taxa. These curious entities are truly extraordinary, and we still know so little about them. View in LinkedIn

SAD AND COMMON POSITION. “The question whether or not “viruses are alive” is not a scientific question.” https://www.sciencedirect.com/science/article/pii/S1369848616300103 View in LinkedIn