Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
--------
Question: Ectothermic vertebrates control body temperature to just a limited extent from the outside by changing behavior.

Answer: What type of vertebrates control body temperature to just a limited extent from the outside by changing behavior?


Question: Sporopollenin protects the pollen of seed plants and spores of seedless plants.

Answer: What protects the pollen of seed plants and spores of seedless plants?


Question: Supernovas are the source of elements heavier than iron.

Answer:
What celestial events are the source of elements heavier than iron?