Which method developed at the end of 1980 lead to a major change in how scientists categorized organisms

Polymerase Chain Reaction (PCR) technique

Explanation:

The Polymerase Chain Reaction (PCR) technique was developed by Kary Mullis in 1984.  This technique exploits the ability of the DNA polymerase to amplify a specific DNA sequence (template), which is then observed as a band by traditional electrophoresis. Since PCR is highly specific and sensitive, it has enabled the detection of genetic variation among different DNA samples, and thereby this technique can be used to identify new species. One of the molecular markers most widely used to identify new species is the Citochormoe Oxidase I (COI) gene, which is amplified by PCR in order to detect genetic variation useful to classify species.

evidence and logical support is essential for a scientist to do in order to maintain credibility. this is because no one can believe without any logic and without any evidence.hence a scientist can maintain credibility by proving himself and by answering logically so experiments prove very beneficial. logical hypothesis give conclusion which is acceptable. therefore, there are two main factors to maintain credibility by a scientist is evidence and logical support.