Final answer:
The introduction of new diseases to indigenous populations was the most significant change resulting from European exploration, leading to high mortality rates among Native Americans and reshaping the demographics of the Americas.
Step-by-step explanation:
The most significant change that happened when Europeans began to explore the world was the introduction of new diseases to indigenous populations. The arrival of Europeans in the New World and their encounters with indigenous peoples led to devastating consequences, especially through the spread of diseases to which native populations had no immunity. This catastrophic impact, often referred to as a form of "biological warfare," resulted in mortality rates as high as 90 percent among Native American communities, significantly altering the demographic landscape of the Americas. The European expansion also sparked extensive cultural exchange, the establishment of global trade routes, and the spread of European hegemony.
The so-called Columbian Exchange entailed a two-way transfer of plants, animals, technology, and diseases between the Americas and the Old World. This exchange had profound effects on every aspect of life, reshaping societies, economies, and environments on both sides of the Atlantic. Moreover, European nations experienced economic growth due to global trade, which included the trafficking of enslaved people, while the conquests and colonization efforts brought about significant shifts in global power dynamics and cultural influences.