The answer to the question of whether evolution is a theory or fact is "both," and the answer to the question of whether extinction of the dinosaurs affected other species is "yes." Another question is whether the evolutionary process ever makes mistakes. The answer is "maybe."
As of 2015, the debate about whether evolution is a theory or a fact continues. In science, a theory is defined as an explanation supported by overwhelming evidence. A fact is a scientific explanation that has been thoroughly tested and confirmed so many times that no new outcomes are expected. So much evidence exists that evolution did occur that the process is accepted, in the scientific community, as fact.
When the dinosaurs died off, fish populations started showing more diversity. Scientists turned to fossils of ray-finned fish because they have bony spines supporting their fins. What they found was that roughly 66 million years ago, when the dinosaurs and most marine reptiles went extinct, ray-finned fish started biologically diversifying. Nearly 95 percent of the fish species on the planet are in the ray-finned family.
In human evolution, questions sometimes come up about why certain aspects of the human body seem odd. For example, the appendix might have had a function at one time, but today it's usually not noticed until it requires surgical removal. Wisdom teeth usually require extraction because the jaws of most modern humans are too small. These could be mistakes, or evolutionary changes still in process.