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* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Answer Key REINFORCING KEY CONCEPTS 1. a. nitrogen; b. oxygen; c. argon, carbon dioxide, and other gases. Why we need it: protects Earth from radiation, keeps Earth warm, transports energy. 2. Carbon cycle: Animals inhale air and exhale carbon dioxide. Plants take in carbon dioxide and release oxygen into the air. Nitrogen cycle: Tiny organisms remove nitrogen gas from the air and change it into solid chemicals that enter the soil. Plants and animals use nitrogen, which is returned to the soil when they die and decay. Nitrogen is returned to the air from the soil. Water cycle: Water in oceans and lakes changes into gas and enters the atmosphere. Plants release water vapor from their leaves. Water falls from the atmosphere as precipitation.