Final answer:
The Columbian Exchange was a positive result of contact between Europeans and Americans, leading to the sharing of crops and foods. Conversely, a major negative impact was the spread of European diseases to the Native American population, causing severe population declines.
Step-by-step explanation:
One positive result of contact between Europeans and Americans during the period between 1491 and 1607 was the Columbian Exchange, which led to the extensive exchange of plants, animals, and foods that enriched both the European and American diets and economies. For instance, Europe benefited by incorporating crops like potatoes and corn, which significantly improved their food security and diversity.
However, one negative consequence of this contact was the spread of European diseases to the Native American population, who had no immunity to these illnesses, leading to catastrophic population declines and the disruption of their societies. The introduction of smallpox, influenza, and measles, among others, caused widespread devastation, which is estimated to have wiped out anywhere from 50% to 90% of the native populations.