Ontario Grade 9 Science Class Practice Exam

Nitrogen travels through its cycle by constantly moving between the Earth's atmosphere, the soil, and living organisms. It starts in the atmosphere, where bacteria in the soil convert it into a form that can be absorbed by plants. The plants then use nitrogen to build proteins and other essential molecules. Animals then obtain nitrogen by consuming plants or other animals. When plants and animals die, decomposers such as fungi break down their tissues and release nitrogen back into the soil. From there, some nitrogen is absorbed by plants again, while the rest is converted by bacteria into a gas and released back into the atmosphere. Options B, C, and D are incorrect because they do not include one or more parts of the nitrogen cycle. There is no mention of the atmosphere in option B, and option C includes only plants, animals, and fungi without accounting for the role of bacteria in the cycle. Option D