How do you feel about the use of animals for scientific research? Does the type of animal make a difference in your answer (e.g., a dog versus a cat...

This is
definitely a matter of opinion, but I can give you a few different ways of thinking about it.
The first thing that comes to mind is that "scientific research" is a pretty vague
term. Certain types of scientific research are purely observational and dont require any
interferencefield studies, mainly.

Assuming you want to focus on experiments
in a lab setting, its even more a matter of opinion. Some people believe that humane treatment
of lab animals is impossible (because they are out of their natural environment) and that any
kind of animal research is wrong. (However, replicating the animals environment as closely as
possible is often a crucial aspect of setting up the experiment.)

Others
believe that animal research is a necessity for scientific progress and that, as long as the
animals are treated well, theres not really an ethical dilemma. Nowadays, there are laws in
place to protect animals and to give precise definitions of what constitutes humane treatment.
Institutions (such as universities) will often have committees that evaluate proposed
experiments involving animals and determine whether those experiments will be allowed.

The type of animal might make a difference to you. Insects (such as fruit flies) are
often used in research because they breed quickly and are relatively easy to care for. This
question, as well as your third question, depends on your point of view.

The
last question seems very similar to the first oneyoull find people on both sides of the debate.
Medical research can be more invasive, but the essence of the issue is still the same, and my
original points still stand.