Why can't the world's food supply be grown out of this flower pot? My students have tons of fun answering that question and applying it to the law of diminishing marginal returns. Lessons 25 and 26 in the Morton workbook will help reinforce this concept.
It is critically important for students to understand the relationship between marginal product and average product as well as the mirror image of those curves with the marginal cost and average variable cost curves! The calculus students normally have an easier time of understanding the derivative nature of marginal product, cost, and revenue yet all students must have this concept mastered in order to fully analyze the theory of the firm models.
Also, students will need to understand that marginal revenue is the slope of the total revenue curve and that the same applies with the marginal cost and total cost and total variable cost curves. I always use examples about test averages and batting averages to explain the relationship between marginal and average calculations. These lessons are some of my favorite ones to teach. Have fun with these curves!