A neurologist noticed that in one patient, damage to brain structure A resulted in a major disruption in speech production, but left hearing ability intact. However, in another patient,
damage to structure B left major hearing impairment, but did not affect speech production.
This scenario is an example of...

Wernicke's aphasia.

a double dissociation.

Broca's aphasia.

a single dissociation.

a double dissociation.

Explanation:

Double dissociation is a psychological term used to describe a scenario whereby two mentally concerned processes are independent in function i.e they work specifically for different functions. In double dissociation, damage to one neurological (brain) area affects only one of two functions and have no effect on the other.

This is the case in this question where a neurologist noticed that damage to brain structure A of a patient resulted in a major disruption in speech production, but left hearing ability intact while a damage to structure B in another patient left major hearing impairment, but did not affect speech production. This example portrays what DOUBLE DISSOCIATION explains.

not sure if this is what you'r looking for eubacteria and archaebacteria

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".