How can karyotypes be used to see if species can successfully reproduce?

Answer 1

Using Karyotypes to Predict Genetic Disorders:
http://learn.genetics.utah.edu/units/disorders/karyotype/karyotypeinfo.cfm

A karyotype is an organized profile of a person's chromosomes. In a karyotype, chromosomes are arranged and numbered by size, from largest to smallest. This arrangement helps scientists quickly identify chromosomal alterations that may result in a genetic disorder.

To make a karyotype, scientists take a picture of someone's chromosomes, cut them out and match them up using size, banding pattern and centromere position.