I'll give you a question, please answer with step-by-step reasoning process. Animals make up a large part of the?
Options:
- carrying cargo
- favorite
- ecosystem
- nature
- ecology

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
The ecosystem is of ecological units comprising living organisms and their interaction with the environment. Animals make up a large part of all ecological units.
The answer: ecosystem.