Joe Student is looking through a microscope at a sample of planktonic life filtered from the Gulf of Mexico. He discovers a single-celled organism with no pigmentation, but with a glassy-looking and porous shell or skeleton. Through the pores, tiny extensions of cytoplasm extend out in all directions, stiffened by thin rods. Joe is correct in thinking he is observing a member of the .

Drag each tile to the correct box. the body monitors the levels of oxygen in the blood to regulate breathing. isabel is running in a marathon and is near the finish line. she feels out of breath. how will her nervous system work to generate a reaction? arrange the tiles in chronological order. isabel's breathing rate increases. sensory receptors in the arteries detect low oxygen levels. the brain sends signals through motor neurons. sensory neurons generate an impulse. the central nervous system relays an impulse to certain brain regions.