The pennsylvania amish population has an increased rate of dwarfism due to one of the original members of this small population carrying the dwarfism allele. this is due to a type of genetic drift called the (2 words).

The correct answer is a founder effect.  

In population genetics, the founder effect refers to the loss of genetic variation that takes place when a new population is developed by a very small amount of individuals from a bigger population.  

As a consequence of the loss of genetic modification, the new population may be characteristically different, both phenotypically and genotypically, from the parent population from which it is obtained. In extreme situations, the founder effect is considered to result in subsequent evolution and speciation of new species.  

thermogram is the first one