What are some of the things that could happened if a predator is introduced in an existing food wed?

Look at the following answer choices and determine which belongs in the both category. testable, can be disproven explains natural phenomena, has evidence to support it prediction, tentative, one or more scientists working together well established, many different scientists working independently, highly reliable

The idea of spontaneous generation was disproved by in a experiment involving jars of meat

Why has two different alleles for the same trait?