Question

explain why a mouse (an endotherm) would probably have wider bone rings than a similarly sized lizard (an ectotherm).

Answer 1

Write in your own words:

"Since the mouse is an endotherm, it probably has a higher metabolic rate, and thus a faster growth rate, than the lizard (an ectotherm of similar size) does. If the mouse has a faster growth rate, its bones would grow more between each ring, resulting in wider bone rings."

: )

and remember that a mouse is a endotherm because it generates metabolic heat to maintain internal body temperature.