Final answer:
The major difference between ancestral teosinte and modern corn is the amount of resources allocated to seed production. Ancestral teosinte has a small number of fruits encased in rigid structures, while modern corn has larger ears and seeds that are easily removed. The difference in seed production is one of the key factors that differentiate the two plants.
Step-by-step explanation:
The major difference between ancestral teosinte and modern corn is the amount of resources allocated to seed production. Ancestral teosinte, the wild grass that is the ancestor of corn, has a small number of fruits encased in rigid structures, making it less likely to be domesticated. On the other hand, modern corn has larger ears and seeds that are easily removed, allowing for easier access to the edible structure. The difference in the allocation of resources to seed production is one of the key factors that differentiate ancestral teosinte from modern corn.