Final answer:
The answer for which system cannot be used for in vivo studies is 'd. cell cultures,' as in vivo implies studying living organisms, while cell cultures are grown outside their natural environment in labs.
Step-by-step explanation:
Experiments utilizing in vivo systems are designed to study the effects of treatments, conditions, and biological processes within living organisms. Such systems can involve a variety of test subjects, including humans, rats, and guinea pigs. However, when it comes to studying living organisms in their natural biological context, cell cultures do not qualify as an in vivo system since they are isolated cells grown in an artificial environment. Therefore, the correct answer to the question 'Experiments utilizing in vivo systems could use all of the following in the study except:' is d. cell cultures.
Ethical Considerations in Animal Research
Animal research has played a critical role in medical advances, including the understanding of the human immune system, development of vaccines, diagnostics, therapies, and translation medicine. Rodents, such as mice and rats, are the most commonly used species in these studies because of their biological similarities to humans and lower costs. Despite this, there is an ongoing ethical debate regarding the necessity and morality of using animals for medical research, driving the development and validation of alternatives like in vitro methods and computer models.