I've been told that there are a lot of ethics involved when dealing with animals that are invertebrates. Otherwise, when a person is working with invertebrates, such as bugs, snails, etc., then there are not so many ethical controls and a person can work with them without too much constraint, paperwork, and ethics committees.

 

First, about when did such a system develop?

Why did such a system develop?

Should the system develop to also consider invertebrates as precious as vertebrates?

You might want to edit your first sentence for clarity "animals that are invertebrates"

 

I think the system developed along the lines of "we are vertebrates therefore..." Its a question of arbitrary line drawing in the end; our fellow man, other primates, mammals, vertebrates...single-celled thingies - at some point we decide that care and supervision is necessary. We try to make this a rational objective decision based on the test subjects potential for feeling pain, anxiety, stress etc - but let's face it we are far from being to quantify this within ourselves let alone a species with whom we cannot properly communicate.