Editing Natural selection (section)

===By life cycle stage===

Another option is to classify selection by the [[Biological life cycle|life cycle]] stage at which it acts. Some biologists recognise just two types: [[Natural selection#Types of selection|viability (or survival) selection]], which acts to increase an organism's probability of survival, and fecundity (or fertility or reproductive) selection, which acts to increase the rate of reproduction, given survival. Others split the life cycle into further components of selection. Thus viability and survival selection may be defined separately and respectively as acting to improve the probability of survival before and after reproductive age is reached, while fecundity selection may be split into additional sub-components including sexual selection, gametic selection, acting on [[gamete]] survival, and compatibility selection, acting on [[zygote]] formation.<ref name=Christiansen1984>{{harvnb|Christiansen|1984|pp=65–79}}</ref>