Final answer:
Joe's pond has higher species richness and greater biodiversity with 5 different species of frogs, while Amy's pond has only 2 different types of frogs.
Step-by-step explanation:
When comparing Amy's pond, which has only 2 different types of frogs but has hundreds of each, to Joe's pond, which has about 20 frogs of each species but has 5 different species of frogs, we focus on the concept of biodiversity, specifically species richness. Species richness is a measure of the number of different species present in an ecosystem. Since Joe's pond has 5 different species of frogs compared to Amy's 2, Joe's pond has a greater species richness and, thus, more biodiversity. This is because biodiversity is not merely a count of individuals but mainly the variety of different species within an environment.