Final answer:
Multicellular organisms have specialized systems because each system performs different functions that are necessary for life.
Step-by-step explanation:
Multicellular organisms have specialized systems because each system performs different functions that are necessary for life. Specialization allows cells to become more efficient at performing specific tasks. For example, the circulatory system brings nutrients and removes waste, while the respiratory system provides oxygen and removes carbon dioxide. The different organ systems in multicellular organisms work together to coordinate body functions and ensure the organism's survival.