Describe the Columbian Exchange -- the transfer of plants, animals, and disease between the Eastern and Western Hemispheres after 1492 -- and explain why disease caused catastrophic loss of life among Native peoples.
After 1492, ships crossing the Atlantic carried far more than people -- they carried plants, animals, and diseases between two hemispheres that had been separate for thousands of years, a massive swap historians call the Columbian Exchange. From the Americas, foods like corn, potatoes, tomatoes, beans, squash, and cacao (used to make chocolate) traveled to Europe, Africa, and Asia, where they eventually changed diets so completely that it is hard to imagine Italian cooking without tomatoes or Irish cooking without potatoes. In the other direction, Europeans brought wheat, rice, sugar cane, and animals including horses, cattle, and pigs to the Americas, changing farming and transportation there forever.
The deadliest part of the exchange, by far, was disease. Illnesses like smallpox, measles, and influenza had existed in Europe, Asia, and Africa for centuries, so people there had built up some natural resistance over many generations. Native peoples in the Americas had never been exposed to these diseases before, so they had no such resistance, and the results were catastrophic: in many regions, disease killed the large majority of the Native population within a century or two of contact -- one of the greatest losses of human life in recorded history. Disease often spread from nation to nation faster than any European colonizer could travel on foot, meaning some communities were struck by devastating illness even before they ever met a single European in person.
Mastery looks like: They can describe at least one item exchanged in each direction and explain why disease was the deadliest part of contact.
Common stumbles: Thinking the exchange was only about food; assuming all disease deaths were intentional rather than resulting mainly from a total lack of prior exposure.