Given a scientific passage and an answer, generate a question for the given answer.

Passage: Neurons that innervate the muscles of the respiratory system are responsible for controlling and regulating pulmonary ventilation. The major brain centers involved in pulmonary ventilation are the medulla oblongata and the pontine respiratory group (Figure 22.20). Answer: neurons
What basic structures of the nervous system innervate the muscles of the respiratory system and are responsible for controlling and regulating pulmonary ventilation?

Passage: Bacteria called cyanobacteria are very important. They are bluish green in color (see Figure below ) because they contain chlorophyll. They make food through photosynthesis and release oxygen into the air. These bacteria were probably responsible for adding oxygen to the air on early Earth. This changed the planet's atmosphere. It also changed the direction of evolution. Ancient cyanobacteria also may have evolved into the chloroplasts of plant cells. Answer: chlorophyll
Cyanobacteria are bluish green in color because they contain what?

Passage: Pollen is a tiny male gametophyte enclosed in a tough capsule. Pollen carries sperm to an ovule while preventing the sperm from drying out. Pollen grains can't swim, but they are very light, so the wind can carry them. Therefore, they can travel through air instead of water. Answer: pollen
What is the tiny male gametophyte enclosed in a tough capsule?