Adrastic short-term reduction of population size caused by natural disasters, disease, or predators is called:

A drastic short-term reduction of population size caused by natural disasters, disease or predators is called a bottleneck event. A bottleneck event or also known as genetic bottleneck results in the reduction of the gene pool of the population, making the current population have a low genetic diversity and high genetic deviation. Because of low genetic variation, the new population will become distinct from the original.

Since a female is both xx chromosome and the male passes down the x chromosome, than the offspring would be female since a female is xx.