Natural selection, which includes sexual selection, is the fact that some traits make it more likely for an organism to survive and reproduce. Population genetics describes natural selection by defining fitness as a propensity or probability of survival and reproduction in a particular environment. The fitness is normally given by the symbol w=1-s where s is the selection coefficient.
Atrial fibrillation with RVR (Rapid Ventricular Response) is a heart condition caused by irregular electrical activity that results in irregular contractions of the heart walls and its chambers. The heart (atrium), shakes with a rapid tremulous movement or makes fine irregular twitching movements, generally referred to as fibrillating.
Featured Diseases and Treatments. Atrial Fibrillation and MAZE Procedure for Treatment of Atrial Fibrillation. Atrial fibrillation (also called AF or A Fib) is an arrhythmia characterized as irregular, disorganized, electrical activity of the upper chambers (atria) of the heart.