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.

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.

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