Final answer:
The ideas about the evolution of tetrapods were considered a hypothesis and not a theory because they were still in the early stages and lacked substantial evidence. Hypotheses can evolve into theories as more evidence accumulates.
Step-by-step explanation:
In the context of tetrapod evolution, the ideas were considered a hypothesis and not a theory because a hypothesis is a proposed explanation based on limited evidence or assumptions, while a theory is a well-supported and widely accepted explanation based on substantial evidence from multiple sources.
At the time when the ideas about the evolution of tetrapods were being developed, they were still in the early stages and lacked the extensive body of evidence required to classify them as a theory.
It is important to note that hypotheses can evolve into theories as more evidence accumulates.