Aspecies is defined as organisms capable of interbreeding and producing fertile offspring. diane dodd examined the idea of speciation in fruit flies. she took fruit flies from a single population and divided them into separate populations living in different cages, each receiving different food sources. one group was given maltose-based foods and the other, starch-based foods. after many generations, the flies were tested to see which flies they preferred to mate with. dodd found that "maltose flies" preferred other "maltose flies.” in this case, what lead to speciation?

The separation of the single population (allopatric speciation) led to speciation.

Explanation:

"Speciation" refers to the evolutionary process of organisms in order to become a "distinct" species. There are several factors affecting speciation and these are: Genetic Drift, Natural Selection, Mutation and Geographic Isolation.

The situation above is an example of the factor called "Geographic Isolation."  This type of isolation is reproductive in nature. This happens when organisms are separated or divided by a barrier. In the case above, the fruit flies were divided into different cages. One cage was for fruit flies who  fed on maltose-based foods, while the other cage was for fruit flies who fed on starch-based foods.

More specifically, this case may also be referred to as "allopatric speciation." It happens when a single population is divided. Thus, over time the separated species acquire genetic differences. These differences prevent them from breeding with each other once they are reunited. This is the reason why the maltose-based flies prefer to mate only maltose-based flies as well.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.