instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Zinc reacting with hydrochloric acid produces bubbles of hydrogen gas. Answer: hydrogen
answer:
Zinc reacting with hydrochloric acid produces bubbles of which gas?

question:
Passage: Carbon moves through ecosystems in two cycles that overlap. In the biotic cycle, it moves between living things and the air. In the abiotic cycle, it moves between the air, ground, and oceans. By burning fossil fuels, humans have increased the amount of carbon dioxide in the air. Answer: biotic cycle
answer:
In what part of the carbon cycle does carbon move between living things and the air?

question:
Passage: The first vertebrates evolved about 550 million years ago. The evolution of amphibians, reptiles, mammals, and birds occurred over the next 400 million years. The first vertebrates were ectotherms; endothermy evolved later. Modern fish, amphibians, and reptiles are ectotherms. Modern birds and mammals are endotherms. Answer: backbone or a spinal column
answer:
Vertebrates differ from invertebrates because they lack this?