Final answer:
Julio's conclusion is not valid because association does not imply causation. He would need to conduct controlled experiments to rule out other factors and more definitively establish a cause-and-effect relationship between butterfly presence and bird activity. Therefore correct option is D
Step-by-step explanation:
No, Julio's conclusion is not valid because association does not imply causation. A weak, negative association indicates that there is a relationship in which one variable slightly decreases as another increases; however, this does not prove that one variable is causing the other to change. To prove causation, Julio would need to conduct experiments that control for other variables that could affect bird activity, or find more evidence that rules out other explanations.
For instance, in laboratory experiments, if yellow buntings exhibit fleeing behavior more frequently when encountering butterflies with eyespots versus without, this could support the claim that predation (bird behavior) is affecting the evolution of butterflies (natural selection against eyespots). The inverse would apply to a negative correlation, where yellow buntings might flee less from butterflies without eyespots, also affecting selection pressures.
In observational studies, correlation can be observed but it does not necessarily establish causation. For example, the correlation between smoking and cancer, while strong and intuitively suggestive of a causal relationship, initially could not definitively prove causation without more rigorous testing that excluded other variables.