How Microgravity Affects the Biology of Living Systems

Gravity has constantly influenced both physical and biological phenomena throughout Earth's history. The gravitational field has played a major role in shaping evolution when life moved from water to land, even if, for a while, it has been generally deemed to influence natural selection only by limiting the range of acceptable body sizes, according to Galilei's principle. Indeed, to counteract gravity, living organisms would need to develop systems to provide cell membrane rigidity, fluid flow regulation, and appropriate structural support for locomotion. However, gravity may influence in a more deep and subtle fashion the way the cells behave and build themselves.