Answer: catastrophic events.
Explanation:
Several factors besides Natural Selection, such as gene flow, mutations, and genetic drift promote the evolution of populations, but only Natural Selection results in adaptations. Natural selection can explain the adaptation and specialization of living beings and depends on the existence of reproduction, heritable phenotypic variation, to some degree, and especially the difference of fitness among individuals. Reproductive differential and/or mortality favors certain genotypes over generations and may lead to loss or fixation of alleles over time within populations. Natural selection can act in different ways, depending on the variants phenotypic phenomena and the adaptive values associated with them, which may be disruptive, directional or stabilizing. Based in this, we can affim the catastrophic events are not required for natural selction to occur.
