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.
atrial fibrillation (AF) a cardiac arrhythmia characterized by disorganized electrical activity in the atria accompanied by an irregular ventricular response that is usually rapid. The atria quiver instead of pumping in an organized fashion, resulting in compromised ventricular filling and reduced stroke volume.